hemtt won't start, fuel issue

[builderboy]

Hello all!! my 977 has been running great with no problems until lately, fuel issue! It will not even fake wanting to start. I've pulled of a rubber hose about 6" around and hit it with either and boom! It's ready to run. Now since I'm not a diesel expert and a guy that helps me with my diesel problems is out of town for work, I thought I'd give it a shot. I asked a couple of other guys and was told to not undo any fuel lines because they could have some high pressure in them and I might do more harm than good. Tank is 1/2 full, checked the electric shut off and it appears to be in the correct position, Fuel filter looks old, could it be full of water somewhere? This thing has always fired right up, then on day I go to move it and it won't. I'm hoping its something simple and not an injection pump. Any one have any ideas? I have the basic understanding of diesel's just stumped on what it might be?

Thanks !!

 

[Coffey1]

Explain the 6" thing a little bit more.

 

[builderboy]

intake pipe coming in from the air cleaner, there is a rubber section that can be taken loose easily

 

[Jericho]

Builder boy, STOP, working on that HEMMIT immediately, (ill come down and get it , save you all the turmoil, ) Lucky guy to have one, suspect they are going to get a s rare as hens teeth real soon. good luck on your trouble shooting, !

 

[builderboy]

Its a military truck, can a person ever really "stop" working on them??? LOL !!

 

[wreckerman893]

If it lost prime you will need to slightly pressurize the system to get it to crank. Detroits are notoriously hard to start after being ran dry. Check your fuel cap and see if a Schrader valve has been installed. You don't need a lot of pressure.

You need to find the underlying cause before you try to prime it.

 

[98G]

Clogged fuel filter...

 

[155mm]

my guess, broken quill shaft in the blower.

 

[WillWagner]

^^Good guess! Are the filters dry? Tap on them with a wrench, if they "ting" no go juice. If they "thunk", they are full.

 

[wreckerman893]

Are the filters dry? Tap on them with a wrench, if they "ting" no go juice. If they "thunk", they are full.

Are "ting" and "thunk" terms out of the Technical Manual?

 

[snowtrac nome]

check filters are tight the pump sits about 6 feet above the fuel tank and is fed with a half inch hose detroits use positive displacement gear pump to provide the mechanical unit injectors fuel. the first sign of a pump going bad is the loss of prime. I have run into this in the past I have also seen rotten hoses and leaking fuel fittings. follow the trouble shooting guide if all is well replace the fuel pump and yes the pump will need to be primed as it wont lift fuel dry. the best way to do this is with compressed air don't exceed 2 psi or you could damage the tank.

 

[Floridianson]

I like this for any priming or filter change. I have one and I leave it hooked up on one of the cranes for quick priming as the Detroit sits a lot. Bought it back in 1980 when I was running Detroit's in dump trucks. If I had Hemtt I would install one and leave it on the machine so any fuel priming or filter change is made easer at home or in the field. I don't assume I will always have air available.

 

[WillWagner]

Are "ting" and "thunk" terms out of the Technical Manual?

Yup. I keep my TMs right next to the books that tell me how to fix maters and taters for grub

 

[builderboy]

thanks for all the info! I will start at the tank and work my way up, very possible filters are clogged, hose has a hole, etc. It will be a couple days till I can get back on this project. I will keep everyone posted, plus I like the idea of installing the priming thing. the 5 ton has one, great idea.

thanks

 

[Floridianson]

Yea most of the old International's Harvesters have them and some import diesels have them as part of the IP. Don't know why they are not standard on all machines.

 

[JDToumanian]

I've never tried pressurizing the fuel tank, but I'm sure it would work and probably not do any damage as long as you're careful. The brass hand pump James posted is the method of priming described in the HEMTT manuals as well as Detroit manuals... There's a pipe plug on the secondary fuel filter housing, you remove it and screw in a hose barb, and connect the pump with hose (with more hose barb fittings screwed into the pump). Pump into a coffee can or whatever, until you get bubble-free fuel. I can understand why people so often use the pressurization method, especially on a HEMTT, as I think you'd have to lower the spare tire to connect the pump... But maybe you could reach it though the wheel well? I dunno, I'm not going outside right now, LOL.

Jon

 

[builderboy]

Got it started!! Drained and cleaned fuel separator, put in new primary and secondary filters, pressured the tank purged the lines... Started right up. And Holly Molly the filters looked terrible!!

 

[byrdman1312]

I have a HEMMIT cargo truck. We start it about once a week to let it run a while. Last week we started it, it ran a few minutes and it quit and wouldn't start back. It will turn over with either, but not continue to run. I also have a HEMMIT tanker that sat for several months and won't start. I talked to a NG warrant officer mechanic about the tanker (this was a few months ago, before the cargo truck stopped running. He said that there is a check valve in the fuel line just above the tank. He said that the check valve is to keep fuel from running back into the tank. If the check valve gets a little trash in it, it will not close and the fuel will drain back into the tank, after it sits a while. He said that to correct this, remove the return line back to the tank. Put the return line over a bucket to catch the fuel. Add air pressure to the tank via where the return line was removed. Slowly and carefully add air to the tank until you get a fuel flow from the return line. When this happens the system is primed, the engine will start.
I haven't tried this with either truck, but I plan to.
Anyone have any ideas? Many thanks!!
Keith

 

[74M35A2]

Detroits use a gear pump for fuel driven off the blower. I doubt it would free flow with pressure on the inlet? Air push could likely get the fuel to the pump, but not past it.