What a great, very informative video. Thanks!! Just got a M1078 A0 (which i believe is what you have) and trying to learn as much as possible about it. I'm more a visual learner so this is great! Thanks again!
AWESOME AND INFORMATIVE VIDEO ! . Im trying to buy a non running 1998 gmc with the 3116 , is 324k miles to much for this motor ???, what can i expect in miles left for a well cared for engine ? I havent heard it run , but runs well when it did ,, seller suspects fuel problems . He says it runs if bottle fed with an aerosol can . I believe him and trust his word and a tire shop owner i know confirms that. . . im hoping its an ipc or gummed up fuel system or something simple . I have become fascinated by diesel engines, after purchasing and wrenching on a 6.0 diesel f250.Want to learn as much as possible about all diesels , although im a very good gas engine shade tree mechanic . ideas and advice is greatly appreciated . thanks for selflessly sharing youre knowledge. all input is greatly appreciated . P S, based on the backstory , im ruling out injector issues ,
When you say aerosol bottle are you referring to starting fluid? Too much of that can do damage... if it runs that way it obviously has compression which is good. You need the fuel gallery in the head full of fuel, and the run solenoid on the governor to be energized which will allow the injectors to inject fuel. The run solenoid are the only wires connected to the governor. With your hand on it, you should be able to feel it go clunk when power is applied to its terminals. Yours may or may not have a hand primer, but it won’t have one like in my video as these are unique to the LMTV/military. Disconnect the line coming out of the pressure regulator on top of the governor. Pump the primer if fitted or crank the engine. You need fuel coming out of that line on the regulator to insure the head is full of fuel. A common problem is a small leak on the suction line from tank up to lift pump and the lift pump(in the governor) cannot lift fuel and sucks air instead. Once running the best judge of engine condition is blow-by coming from the crankcase vent on top of the main fuel filter... 324K is quite a few miles...
excellent video, i'm from Brazil and i have gmc 12170 with a 3116 engine and don't want to start you have any technical literature on the fuel system of this engine?
Valter P Not really. It is a pretty simple system though. If you remove the return line where it comes out of the pressure regulator block(above the governor, shown in the video) and crank the engine you should get fuel flow. If you don’t have flow out of that return port/regulator, you have a lift pump problem(on the governor) or a filter or clog problem or a real bad leak on the line back to the tank that is sucking in air instead of pulling fuel from the tank. If you are getting fuel out of the regulator block, then more than likely there is some issue with the run solenoid located on the rear of the governor. It receives power when the ignition is turned on. If you put your hand on it when you turn the key on, it should go clunk and you should be able to feel it energize. If it does not, either it is not getting power or it has failed which is keeping the fuel rack closed and preventing the injectors from spraying fuel. If it doesn’t energize you can unscrew it and remove it from the governor and the engine should start. You will need to push something in the hole where the solenoid was located to shut the engine down though... Good Luck.
Question. i think my lift pump has failed but not 100% sure. i have fuel from tank to Inlet of pump. i removed metal pipe off the exit of lift pump and have no fuel. i put 5psi air pressure into fuel tank and get nothing,even while cranking with pressure in tank i see nothing. i did this with ignition on. i can hear/feel the shut off solenoid click when ignition is turned on. if it is the lift pump, is it serviceable?
Yes the lift pump is serviceable. So with 5psi on the rank if you crack open the line entering the lift pump you get fuel coming out there? Just want to make sure there are no obstructions between tank and pump. The run solenoid in the governor has no effect on primary fuel. When power is removed, the solenoid allows the fuel control rod to pull the rack/injectors to the zero fuel point…
I have a 3116 7000.gmc and we are getting fuel to the inspection pump but fuel is coming out of the inspection pump we changed pump still getting the same issue but the fuel shut off solenoid is working what is your recommendation on my next step?
So is the truck not starting and running? Are you calling a primer pump the “inspection pump”? Being able to suck fuel from the tank with the primer pump is a good thing. The fuel comes from the tank, thru a primary filter, past the primer pump to the governor lift pump, thru the main fuel filter thru the head, past the pressure reg and back to the tank. If you pump the hand pump you should be able to see fuel at the tank return line. If so, great. Now crank the engine. You should also see fuel being pumped by the governor lift pump all the way back thru the return line to the tank. A lot of fuel… The run solenoid when de-energized keeps the injectors from spraying, but it has nothing to do with the lift pump and fuel flow. if the crank is turning, the lift pump should be pumping fuel. In the video, I show a t fitting between the governor and the main fuel filter. Connecting a pressure gauge there will show you if you are making primary pressure. No primary pressure, no run. Even if it is pumping fuel, too much air being sucked in will keep it from running. At that T you should have 10PSI cranking 20PSI at idle and ramping up to 60 PSI at ~ peak torque/1550 RPM… one of my other videos I show primary fuel pressure and what an air leak on the suction side looks like…
Well it has a Electric pump on it by the fuel tank come to find out no fuel is even going from the tank to the fuel filter so I think it's something in the tank
@@isaacwillis8892 ok, the cat 3116 doesn’t have an injection pump. It uses 6 mechanical unit injectors(pump,and injector in one, powered by the camshaft) The governor controls the fuel rack on those unit injectors that compress and spray the fuel at up to 33,000 PSI. These trucks don’t have a pump at the fuel tank, the lift pump is in the governor. It works with the pressure regulator to create the 20-60PSI of fuel pressure in the gallery. A pump installed at the tank is usually someones half assed attempt to deal with air leaks on the fuel line from tank to governor or a failing lift pump. The problem is an electric pump at the tank is usually only good for 5-7 PSI, and unless they flow enough fuel(probably not) the gallery will have problems reaching its proper running pressures I mentioned above. Running at the wrong/insufficient pressure can damage the MUI injectors… so yea you have something wrong at the tank, a,pump that doesn’t belong there, probably some air leaks in the lift line, and perhaps a problem with the lift pump in the governor…
is there a built in air bleed in the system? for example on MB's I've dealt with any small air leaks in fuel lines etc. is less troublesome cause said air is shunted out the top of the fuel filter housing thru a check valve and routed into the fuel return to tank line where it gets vented out via tanks vent.
@@rronmar thanks for mentioning hairline cracks.. I would like to ask you a question ?? on the primary filter with a rubber press pump, is that aftermarket?? I don't have that on my 3116... I don't think I have a primer pump on my engine ?? Next comment: There is a larger fuel line with a bracket along with two bolts that hold it to the top most fwd area of cylinder head... just forward of that point is the engine removal piece that has a large hole a chain will fit for lifting...fwd of that is the heavy bracket held by six bolts that supports fan clutch and fan assembly.... My thinking along with you're pointing out a hairline fracture might exist..?? the area of the right bolt ( 1 of 2 Looking from front of eng..) that secure the return fuel line flange to the cylinder head.... So happens that the top right bolt Of the bracket supporting fan and Clutch bracket taps and threads into the same vacinity of cylinder head.....very close!!!! Might be a weak spot?? Maybe you could share with me what I
Fuel in coolant or coolant in fuel means there is probably a bad injector cup, or a crack in the head. This series of Cat engines(3114,3116,3126, C7) and the ford power-stroke, use a copper cup that is press fit into the head. The injectors in turn are inserted into this cup with Oring seals. The coolant galleries and fuel galleries are separated by these cups, and when they have a problem fuel or coolant can change places between their respective systems. Since the primary fuel pressure in the gallery is up to 60 PSI when running, it is most likely that you will find fuel in the coolant, but some have found coolant in the fuel tank as the cooling system remains pressurized after shutdown until the engine cools…
Hello,got a nice,clean low mileage cat 3116,1993.Its been great,then overnight sitting it tends to act like there is a fuel system bleed down making it hard to start in the morning.?It will start,just a lot harder than it should,What about fuel check valves?thx
Well there is a check valve at the lift pump, I don’t think I would want one anywhere else. If the system is intact/sealed, you should have no drain back. You actually want this as a warning, because if it leaks enough to drain back, it IS sucking air while running. Air while running interferes with primary fuel pressure. I show what a air leak looks like when running in one of my other videos using a primary pressure gauge. I also show how to connect a inexpensive mechanical pressure gauge between governor and main fuel filter(pinch plastic gauge hose to dampen needle pulsations) to check primary pressure. These unit injectors need proper primary fuel pressure. Problems there can kill injectors if not corrected. The problem with lift side leaks as there is no pressure, they very rarely show any outward signs that there is a leak. Could be a loose fitting, could be a bad filter seal, could be a bad hose. The engine in the video is a military vehicle, so that primer and primary filter are unique to it. I don’t know what is between the tank and the governor lift pump on yours, but it could be any fitting or component between tank and governor. Do you have a hand primer pump? One way to test this is to start and run it so the system is full of fuel, then shutdown. At the tank disconnect and cap the return line. Then disconnect the supply line, and connect a low pressure regulator and gauge, and pressurize the supply line/engine fuel system plumbing to 15PSI. Then start searching the system looking for where fuel pressure is forcing fuel out. I had the same issue you describe, hard start and rough initial idle after setting. I could pump the primer and fill the system and it would start and idle great. Checked filters and fittings, no sign of an issue. Pressurized the system hoses and plumbing like I just described and found fuel dripping off of that primary filter after letting it set under pressure for a while. The water separator bowl on the bottom had a hairline crack in it. It wouldn’t leak fuel as there was no pressure, but it would suck air all day long when the lift pump puts it under vacuum to lift fuel from the tank…
Couldn’t say for certain, I never use the stuff. If the engine needs an overhaul, I do an overhaul. The HEUI uses a variable hydraulic pump to boost engine oil as high as 3000PSI to actuate the injectors which are controlled electronically thru hydraulic spool valves. The 7:1 injector piston ratio boosts the injected fuel pressure as high as 21,000PSI. Because if this more care must be taken with the engine oil or it will foul the close tolerances of the pressure pump, regulator and spool valves on the injectors. The MUI injectors are driven by a rocker arm off of the cam, so it is not really any different than any other engine and might not have any issue with this stuff. It does have a mechanical governor though that uses oil for lube, so only cat can reliably answer this question...
Thanks for the reply there's alot of confusion with this engine in this year of lmtv most people thinks its a HEUI engine & ive only owned my 98 1078 for about 2 months my engine doesn't need a rebuild mainly i wanted to know is my oil system is hyper critical & you have answered that. 👍 big thanks
julian botnick Sadly, yes there is. The fuel flows thru the gallery in the head past each injector. The injectors are imbedded in copper cup seals that seal the injector from the cylinder, and also from coolant which flows around the cups to help keep the injector temps under control. These will sometimes start leaking and can also lead to coolant in the fuel or fuel in the coolant... Disconnect the return line, and run it into a clear line or into a bucket. A small bubble in the line occasionally is OK, but a steady stream means an air leak or combustion gasses getting added to the fuel...
This was my fear. I had a cup fail on my 7.3 and had diesel in my coolant. Replacing the cups was fairly straight forward. However I hear with this engine you need a special tool to install them, and if not done perfectly they will leak. Have you done them before?
nicholas clinger: Serpentine pulley? What engine? On the 3116 the fuel enters the head at the rear and exits at the front to the pressure reg. There is an elbow, a pipe union and a hardline at the front so a loose fitting or cracked/damaged hardline at the front of the head would cause fuel where you describe. On the 3126 or C7 the fuel enters at the front and exits at the back, but same basic fittings/components
@@rronmar thanks so much for for information... Before I start tearing it apart I'll clean and check torque on the two bolts that hold the largest of the 2 fuel lines in the same area... I'll let you know...thanks again, nick
@@coachgeo thanks for mentioning hairline cracks.. I would like to ask you a question ?? on the primary filter with a rubber press pump, is that aftermarket?? I don't have that on my 3116... I don't think I have a primer pump on my engine ?? Next comment: There is a larger fuel line with a bracket along with two bolts that hold it to the top most fwd area of cylinder head... just forward of that point is the engine removal piece that has a large hole a chain will fit for lifting...fwd of that is the heavy bracket held by six bolts that supports fan clutch and fan assembly.... My thinking along with you're pointing out a hairline fracture might exist..?? the area of the right bolt ( 1 of 2 Looking from front of eng..) that secure the return fuel line flange to the cylinder head.... So happens that the top right bolt Of the bracket supporting fan and Clutch bracket taps and threads into the same vacinity of cylinder head.....very close!!!! Might be a weak spot?? Maybe you could share with me what I would see, if I were to removed the six bolts that support fan and clutch along with the engine lift piece that's behind it ..????????
The 3116 uses mechanical unit injectors that are both injector pump and spraynozzle, and they squirt at up to 33,000 PSI. Whatever you run thru them really should flow into the fuel gallery at near the same viscosity as diesel…
My 3116 has a running issue I've replaced the fuel tank and lines from tank to pump and the 2 fuel filters it will run fine with a mr.gasket in line pump till the pump get hot and shut off any help
Whats your baseline fuel pressure? I show how to hook up a gauge just after 4:30 in the video. With the engine running you should have about 20PSI at idle and up to 60PSI at higher RPM. If you don’t have that, you either have a regulator problem(block on top of governor) or a lift pump problem(inside top-right side of governor)… system is sealed and primed, it should not need a elect4ic lift pump…
You can set injector timing(injector height) with a vernier caliper that has a probe for measuring depth(most have this) as it is an absolute measurement. Like setting the valve lash, you install a bolt in the flywheel timing hole(down by starter) and rotate the flywheel up against the bolt/pin(see valve adjust procedure in tech manual) . With a timing pin installed you can adjust half of the valves and half of the injector heights. Using the depth pin you can measure the height from the top of the spring collar to the injector base. The timing measurement spec is on the data sticker on top of the valve cover(see injector sync/timing procedure in tech manual). When you get half of the valves/injectors set, you pull the timing pin, bar the engine over with a wrench(see valve adjust procedure ) and adjust the other half. You should be able to do the injector sync with a simple dial indicator and mag or clamp base IF you remove the intake manifold/plenum). With the manifold removed you gain access to the top deck of the cylinder head and the individual injector racks. cat tools make the job easier and you don’t have to pull the manifold, but they are not necessary., just decent quality measurement tools as the adjustment tolerance is well within the accuracy of even low end dial indicators. All the sync measurements are comparative/relative so you setup on each injector rack, zero in a particular set position and observe the movement as you shift the control rod from A to B. You will also need some blocks of known thickness to hold the main fuel rod in a particular position(see inj sync procedure in manual).
Yes, but you will need to make a wedge with a slot in it to go down between the side of the head and the governor. This wedge is used to pull the rack linkage pin to its full rack reference point. And of course all this is in the fuel setup procedure in the manual...
What a great, very informative video. Thanks!! Just got a M1078 A0 (which i believe is what you have) and trying to learn as much as possible about it. I'm more a visual learner so this is great! Thanks again!
This was very helpful, thanks Ron!
Amazing video, thank you. Learn a lot from it.
Please do more videos for LMTV.
Well explained thanks
AWESOME AND INFORMATIVE VIDEO ! . Im trying to buy a non running 1998 gmc with the 3116 , is 324k miles to much for this motor ???, what can i expect in miles left for a well cared for engine ? I havent heard it run , but runs well when it did ,, seller suspects fuel problems . He says it runs if bottle fed with an aerosol can . I believe him and trust his word and a tire shop owner i know confirms that. . . im hoping its an ipc or gummed up fuel system or something simple . I have become fascinated by diesel engines, after purchasing and wrenching on a 6.0 diesel f250.Want to learn as much as possible about all diesels , although im a very good gas engine shade tree mechanic . ideas and advice is greatly appreciated . thanks for selflessly sharing youre knowledge. all input is greatly appreciated . P S, based on the backstory , im ruling out injector issues ,
When you say aerosol bottle are you referring to starting fluid? Too much of that can do damage... if it runs that way it obviously has compression which is good. You need the fuel gallery in the head full of fuel, and the run solenoid on the governor to be energized which will allow the injectors to inject fuel. The run solenoid are the only wires connected to the governor. With your hand on it, you should be able to feel it go clunk when power is applied to its terminals. Yours may or may not have a hand primer, but it won’t have one like in my video as these are unique to the LMTV/military. Disconnect the line coming out of the pressure regulator on top of the governor. Pump the primer if fitted or crank the engine. You need fuel coming out of that line on the regulator to insure the head is full of fuel. A common problem is a small leak on the suction line from tank up to lift pump and the lift pump(in the governor) cannot lift fuel and sucks air instead. Once running the best judge of engine condition is blow-by coming from the crankcase vent on top of the main fuel filter... 324K is quite a few miles...
excellent video, i'm from Brazil and i have gmc 12170 with a 3116 engine and don't want to start you have any technical literature on the fuel system of this engine?
Valter P Not really. It is a pretty simple system though. If you remove the return line where it comes out of the pressure regulator block(above the governor, shown in the video) and crank the engine you should get fuel flow. If you don’t have flow out of that return port/regulator, you have a lift pump problem(on the governor) or a filter or clog problem or a real bad leak on the line back to the tank that is sucking in air instead of pulling fuel from the tank. If you are getting fuel out of the regulator block, then more than likely there is some issue with the run solenoid located on the rear of the governor. It receives power when the ignition is turned on. If you put your hand on it when you turn the key on, it should go clunk and you should be able to feel it energize. If it does not, either it is not getting power or it has failed which is keeping the fuel rack closed and preventing the injectors from spraying fuel. If it doesn’t energize you can unscrew it and remove it from the governor and the engine should start. You will need to push something in the hole where the solenoid was located to shut the engine down though... Good Luck.
@@rronmar thank you very much, I will do this procedure
Question.
i think my lift pump has failed but not 100% sure. i have fuel from tank to Inlet of pump. i removed metal pipe off the exit of lift pump and have no fuel. i put 5psi air pressure into fuel tank and get nothing,even while cranking with pressure in tank i see nothing. i did this with ignition on. i can hear/feel the shut off solenoid click when ignition is turned on.
if it is the lift pump, is it serviceable?
Yes the lift pump is serviceable. So with 5psi on the rank if you crack open the line entering the lift pump you get fuel coming out there? Just want to make sure there are no obstructions between tank and pump. The run solenoid in the governor has no effect on primary fuel. When power is removed, the solenoid allows the fuel control rod to pull the rack/injectors to the zero fuel point…
I have a 3116 7000.gmc and we are getting fuel to the inspection pump but fuel is coming out of the inspection pump we changed pump still getting the same issue but the fuel shut off solenoid is working what is your recommendation on my next step?
So is the truck not starting and running? Are you calling a primer pump the “inspection pump”? Being able to suck fuel from the tank with the primer pump is a good thing. The fuel comes from the tank, thru a primary filter, past the primer pump to the governor lift pump, thru the main fuel filter thru the head, past the pressure reg and back to the tank. If you pump the hand pump you should be able to see fuel at the tank return line. If so, great. Now crank the engine. You should also see fuel being pumped by the governor lift pump all the way back thru the return line to the tank. A lot of fuel… The run solenoid when de-energized keeps the injectors from spraying, but it has nothing to do with the lift pump and fuel flow. if the crank is turning, the lift pump should be pumping fuel. In the video, I show a t fitting between the governor and the main fuel filter. Connecting a pressure gauge there will show you if you are making primary pressure. No primary pressure, no run. Even if it is pumping fuel, too much air being sucked in will keep it from running. At that T you should have 10PSI cranking 20PSI at idle and ramping up to 60 PSI at ~ peak torque/1550 RPM… one of my other videos I show primary fuel pressure and what an air leak on the suction side looks like…
Well it has a Electric pump on it by the fuel tank come to find out no fuel is even going from the tank to the fuel filter so I think it's something in the tank
@@rronmar sorry injection pump not inspection pump lol
@@isaacwillis8892 ok, the cat 3116 doesn’t have an injection pump. It uses 6 mechanical unit injectors(pump,and injector in one, powered by the camshaft) The governor controls the fuel rack on those unit injectors that compress and spray the fuel at up to 33,000 PSI. These trucks don’t have a pump at the fuel tank, the lift pump is in the governor. It works with the pressure regulator to create the 20-60PSI of fuel pressure in the gallery. A pump installed at the tank is usually someones half assed attempt to deal with air leaks on the fuel line from tank to governor or a failing lift pump. The problem is an electric pump at the tank is usually only good for 5-7 PSI, and unless they flow enough fuel(probably not) the gallery will have problems reaching its proper running pressures I mentioned above. Running at the wrong/insufficient pressure can damage the MUI injectors… so yea you have something wrong at the tank, a,pump that doesn’t belong there, probably some air leaks in the lift line, and perhaps a problem with the lift pump in the governor…
is there a built in air bleed in the system? for example on MB's I've dealt with any small air leaks in fuel lines etc. is less troublesome cause said air is shunted out the top of the fuel filter housing thru a check valve and routed into the fuel return to tank line where it gets vented out via tanks vent.
coachgeo Just the plug you can loosen that I pointed out on top of the secondary filter, nothing automatic...
@@rronmar thanks for the info..
I'm not understanding all that you said ??
Ok got it..!
Just had to view your vision again...thanks
nicholas clinger I just did another video on how to check that the primer is functioning properly
@@rronmar thanks for mentioning hairline cracks..
I would like to ask you a question ?? on the primary filter with a rubber press pump, is that aftermarket?? I don't have that on my 3116... I don't think I have a primer pump on my engine ??
Next comment:
There is a larger fuel line with a bracket along with two bolts that hold it to the top most fwd area of cylinder head... just forward of that point is the engine removal piece that has a large hole a chain will fit for lifting...fwd of that is the heavy bracket held by six bolts that supports fan clutch and fan assembly....
My thinking along with you're pointing out a hairline fracture might exist..?? the area of the right bolt ( 1 of 2
Looking from front of eng..) that secure the return fuel line flange to the cylinder head....
So happens that the top right bolt
Of the bracket supporting fan and
Clutch bracket taps and threads into the same vacinity of cylinder head.....very close!!!! Might be a weak spot??
Maybe you could share with me what I
What causes the 3116 cat engine to bring diesel to the radiator?
Fuel in coolant or coolant in fuel means there is probably a bad injector cup, or a crack in the head. This series of Cat engines(3114,3116,3126, C7) and the ford power-stroke, use a copper cup that is press fit into the head. The injectors in turn are inserted into this cup with Oring seals. The coolant galleries and fuel galleries are separated by these cups, and when they have a problem fuel or coolant can change places between their respective systems. Since the primary fuel pressure in the gallery is up to 60 PSI when running, it is most likely that you will find fuel in the coolant, but some have found coolant in the fuel tank as the cooling system remains pressurized after shutdown until the engine cools…
Hello,got a nice,clean low mileage cat 3116,1993.Its been great,then overnight sitting it tends to act like there is a fuel system bleed down making it hard to start in the morning.?It will start,just a lot harder than it should,What about fuel check valves?thx
Well there is a check valve at the lift pump, I don’t think I would want one anywhere else. If the system is intact/sealed, you should have no drain back. You actually want this as a warning, because if it leaks enough to drain back, it IS sucking air while running. Air while running interferes with primary fuel pressure. I show what a air leak looks like when running in one of my other videos using a primary pressure gauge. I also show how to connect a inexpensive mechanical pressure gauge between governor and main fuel filter(pinch plastic gauge hose to dampen needle pulsations) to check primary pressure. These unit injectors need proper primary fuel pressure. Problems there can kill injectors if not corrected. The problem with lift side leaks as there is no pressure, they very rarely show any outward signs that there is a leak. Could be a loose fitting, could be a bad filter seal, could be a bad hose.
The engine in the video is a military vehicle, so that primer and primary filter are unique to it. I don’t know what is between the tank and the governor lift pump on yours, but it could be any fitting or component between tank and governor. Do you have a hand primer pump?
One way to test this is to start and run it so the system is full of fuel, then shutdown. At the tank disconnect and cap the return line. Then disconnect the supply line, and connect a low pressure regulator and gauge, and pressurize the supply line/engine fuel system plumbing to 15PSI. Then start searching the system looking for where fuel pressure is forcing fuel out.
I had the same issue you describe, hard start and rough initial idle after setting. I could pump the primer and fill the system and it would start and idle great. Checked filters and fittings, no sign of an issue. Pressurized the system hoses and plumbing like I just described and found fuel dripping off of that primary filter after letting it set under pressure for a while. The water separator bowl on the bottom had a hairline crack in it. It wouldn’t leak fuel as there was no pressure, but it would suck air all day long when the lift pump puts it under vacuum to lift fuel from the tank…
@@rronmar Thankyou,Im in the midst of troubleshooting different things now.
Do you know if engine restore will hurt this MUI 3116 engine like it will on a HEUI 3126?
Couldn’t say for certain, I never use the stuff. If the engine needs an overhaul, I do an overhaul. The HEUI uses a variable hydraulic pump to boost engine oil as high as 3000PSI to actuate the injectors which are controlled electronically thru hydraulic spool valves. The 7:1 injector piston ratio boosts the injected fuel pressure as high as 21,000PSI. Because if this more care must be taken with the engine oil or it will foul the close tolerances of the pressure pump, regulator and spool valves on the injectors.
The MUI injectors are driven by a rocker arm off of the cam, so it is not really any different than any other engine and might not have any issue with this stuff. It does have a mechanical governor though that uses oil for lube, so only cat can reliably answer this question...
Thanks for the reply there's alot of confusion with this engine in this year of lmtv most people thinks its a HEUI engine & ive only owned my 98 1078 for about 2 months my engine doesn't need a rebuild mainly i wanted to know is my oil system is hyper critical & you have answered that. 👍 big thanks
I have what looks like exhaust expelling from my diesel tank. Is there any way for exhaust to enter into that return line?
julian botnick Sadly, yes there is. The fuel flows thru the gallery in the head past each injector. The injectors are imbedded in copper cup seals that seal the injector from the cylinder, and also from coolant which flows around the cups to help keep the injector temps under control. These will sometimes start leaking and can also lead to coolant in the fuel or fuel in the coolant... Disconnect the return line, and run it into a clear line or into a bucket. A small bubble in the line occasionally is OK, but a steady stream means an air leak or combustion gasses getting added to the fuel...
This was my fear. I had a cup fail on my 7.3 and had diesel in my coolant. Replacing the cups was fairly straight forward. However I hear with this engine you need a special tool to install them, and if not done perfectly they will leak. Have you done them before?
julian botnick not on a cat....
Why would fuel be leaking from front and top area of cylinder head just aft of fan surpentine pulley???
nicholas clinger: Serpentine pulley? What engine? On the 3116 the fuel enters the head at the rear and exits at the front to the pressure reg. There is an elbow, a pipe union and a hardline at the front so a loose fitting or cracked/damaged hardline at the front of the head would cause fuel where you describe. On the 3126 or C7 the fuel enters at the front and exits at the back, but same basic fittings/components
@@rronmar thanks so much for for information...
Before I start tearing it apart I'll clean and check torque on the two bolts that hold the largest of the 2 fuel lines in the same area...
I'll let you know...thanks again, nick
@@nicholasclinger1737 others have found hairline crack in hardlines on this engine. do not recall if it was this hardline or not
@@coachgeo thanks for mentioning hairline cracks..
I would like to ask you a question ?? on the primary filter with a rubber press pump, is that aftermarket?? I don't have that on my 3116... I don't think I have a primer pump on my engine ??
Next comment:
There is a larger fuel line with a bracket along with two bolts that hold it to the top most fwd area of cylinder head... just forward of that point is the engine removal piece that has a large hole a chain will fit for lifting...fwd of that is the heavy bracket held by six bolts that supports fan clutch and fan assembly....
My thinking along with you're pointing out a hairline fracture might exist..?? the area of the right bolt ( 1 of 2
Looking from front of eng..) that secure the return fuel line flange to the cylinder head....
So happens that the top right bolt
Of the bracket supporting fan and
Clutch bracket taps and threads into the same vacinity of cylinder head.....very close!!!! Might be a weak spot??
Maybe you could share with me what I would see, if I were to removed the six bolts that support fan and clutch along with the engine lift piece that's behind it ..????????
Thank You!!
Can the 3116 run on waist oil
The 3116 uses mechanical unit injectors that are both injector pump and spraynozzle, and they squirt at up to 33,000 PSI. Whatever you run thru them really should flow into the fuel gallery at near the same viscosity as diesel…
My 3116 has a running issue I've replaced the fuel tank and lines from tank to pump and the 2 fuel filters it will run fine with a mr.gasket in line pump till the pump get hot and shut off any help
Whats your baseline fuel pressure? I show how to hook up a gauge just after 4:30 in the video. With the engine running you should have about 20PSI at idle and up to 60PSI at higher RPM. If you don’t have that, you either have a regulator problem(block on top of governor) or a lift pump problem(inside top-right side of governor)… system is sealed and primed, it should not need a elect4ic lift pump…
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How do you set injector sync in these with a caliper?
You can set injector timing(injector height) with a vernier caliper that has a probe for measuring depth(most have this) as it is an absolute measurement. Like setting the valve lash, you install a bolt in the flywheel timing hole(down by starter) and rotate the flywheel up against the bolt/pin(see valve adjust procedure in tech manual) . With a timing pin installed you can adjust half of the valves and half of the injector heights. Using the depth pin you can measure the height from the top of the spring collar to the injector base. The timing measurement spec is on the data sticker on top of the valve cover(see injector sync/timing procedure in tech manual). When you get half of the valves/injectors set, you pull the timing pin, bar the engine over with a wrench(see valve adjust procedure ) and adjust the other half. You should be able to do the injector sync with a simple dial indicator and mag or clamp base IF you remove the intake manifold/plenum). With the manifold removed you gain access to the top deck of the cylinder head and the individual injector racks. cat tools make the job easier and you don’t have to pull the manifold, but they are not necessary., just decent quality measurement tools as the adjustment tolerance is well within the accuracy of even low end dial indicators. All the sync measurements are comparative/relative so you setup on each injector rack, zero in a particular set position and observe the movement as you shift the control rod from A to B. You will also need some blocks of known thickness to hold the main fuel rod in a particular position(see inj sync procedure in manual).
@@rronmar thanks man! Can you use this same procedure to set the fuel?
Yes, but you will need to make a wedge with a slot in it to go down between the side of the head and the governor. This wedge is used to pull the rack linkage pin to its full rack reference point. And of course all this is in the fuel setup procedure in the manual...
@@rronmar thank you for sharing your knowledge, I greatly appreciate this!