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Bleeding the HEMTT fuel system

K

Karl kostman

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Hey guys I have a question. I fired up my M977 HEMTT the other day first start in 3 years and it fired right up like I started it yesterday the problem came in when I went to shut it off, the fuel cut off switch would not shut the fuel off I later found the nutt had backed of the fuel shut off solenoid so it would not pull the shut off lever far enough to kill the fuel supply. SO in not thinking very well about how to shut off the engine I drained the sediment bowl and ran the engine out of fuel that way, yes I now realize BAD idea! So no after fixing the problem I filled the sediment/filter assembly with fuel and took the fuel filter off the engine and filled that with fuel and I also tried cranking the engine over with the valve open by the engine fuel filter and got no fuel out of that. can you tell me what I am forgetting to bleed in the fuel system because it sure seems like I have air in the system that need to be bled out, both the sediment bowl and the on engine fuel filters are full I filled them both before trying to start the truck. What am I forgetting ???

Thanks much guys!!
 
Guyfang

Guyfang

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We used a spare fuel tank cap that we drilled and tapped a hole for a fitting. Applied a LITTLE air pressure. Just a little bit. Since you probably dont have a spare cap, it just going to take a bit longer. Go as far up the system as you can, and have someone crank it over while you crack the fuel system. Its a pain.
 
WillWagner

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Same principle as Guyfang, just get a mess of rags, stick the air nozzle into the filler neck and pack tightly with the rags. Hold your hand over the wad of rags or they will blow out. AND a little will do ya, really, 2 psi maybe. If you have a full tank, S L O W L Y release the pressure or you will get a bath! 2 people works the best, one to feed air and the other to crank
 
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Guyfang

Guyfang

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The bath part is why I did not mention that possibility. I once saw, twice in one day, the plastic fuel bowl go "POP", when too much pressure was applied. . And in 1985, getting a replacement was reallllll tough!
 
Mullaney

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Karl kostman said:
Hey guys I have a question. I fired up my M977 HEMTT the other day first start in 3 years and it fired right up like I started it yesterday the problem came in when I went to shut it off, the fuel cut off switch would not shut the fuel off I later found the nutt had backed of the fuel shut off solenoid so it would not pull the shut off lever far enough to kill the fuel supply. SO in not thinking very well about how to shut off the engine I drained the sediment bowl and ran the engine out of fuel that way, yes I now realize BAD idea! So no after fixing the problem I filled the sediment/filter assembly with fuel and took the fuel filter off the engine and filled that with fuel and I also tried cranking the engine over with the valve open by the engine fuel filter and got no fuel out of that. can you tell me what I am forgetting to bleed in the fuel system because it sure seems like I have air in the system that need to be bled out, both the sediment bowl and the on engine fuel filters are full I filled them both before trying to start the truck. What am I forgetting ???

Thanks much guys!!
Click to expand...
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On top of the suggestions from @Guyfang and @WillWagner , if you do happen to have two sets of hands - one to hold the air in the tank with rags - and the other cranking - maybe postpone the cranking for a few minutes.

You might try cracking open a fuel line leading into the IP, then on an injector to force (allow) air to escape. When you start confirming that there is fuel going beyond the sediment bowl you might be golden...
 
WillWagner

WillWagner

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HEMTT, I believe it is an 8V92 driptroit, no fuel lines to crack. It is a common rail type of system. A positive displacement gear pump directly feeds passages in the heads. Maybe crack the discharge line out of the gear pump, but it should fire fine with a bit of help from the pressurized tank.
 
G744

G744

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Detroits self-prime easily. Are you sure you got a good seal on the bowl gasket?

Most Jimmys use two steel canister or spin-on filters, primary B4 the transfer pump, secondary after.

After checking the gasket, I'd open the fuel link into the head and crank.

DG
 
K

Karl kostman

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Thanks very much for your help guys you have given me many areas to look into and I will get this engine fired up later this week!
Thanks again!
Karl
 
fuzzytoaster

fuzzytoaster

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I had this issue with my "new to me" HEMTT 2 weeks ago. I drilled a tapped a gas cap with a schrader valve and put 5 psi to the tank. Cracked the output side of the fuel filter. When the bubbles were gone I gave her 3 cranks and she fired up.
 
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