HMMWV Rough Idle, Surging now Dead no Restart.

[UserError]

Ive got a 87 6.2 in the hmmwv.

It was idling rough, but always started up. Today i started it and let it run and warm up. After about 5-10 minutes of running it started to stumble, then began surging. 15 seconds later or so it died, and won't restart.

Im assuming this is a fuel delivery problem of some time. Plugged filter, Bad injection pump. Maybe a bad shutdown solenoid?

My question is, what are the usual suspects/common failures?

After it died i opened the little valve on the bottom of the fuel filter housing, and diesel ran out. So i assume fuel is making it up to the filter. From there, I'm a bit clueless.

Any advice is greatly appreciated.

 

[Action]

what does it do when you try to start it now? dead batteries also cause a no start.

 

[orgnal]

Ive got a 87 6.2 in the hmmwv.

It was idling rough, but always started up. Today i started it and let it run and warm up. After about 5-10 minutes of running it started to stumble, then began surging. 15 seconds later or so it died, and won't restart.

Im assuming this is a fuel delivery problem of some time. Plugged filter, Bad injection pump. Maybe a bad shutdown solenoid?

My question is, what are the usual suspects/common failures?

After it died i opened the little valve on the bottom of the fuel filter housing, and diesel ran out. So i assume fuel is making it up to the filter. From there, I'm a bit clueless.

Any advice is greatly appreciated.

My guess would be clogged fuel injectors. One step before that would be to make sure fuel pump is good.

McReddy

 

[UserError]

Action - it cranks around fine. It has "new" civi batteries in it.

The filter housing has fuel in it. So i assume the lift pump from the tank is working. But you know what they say about assumptions.

Going out to mess with it now, will report back what i find.

 

[UserError]

ok so i went out and tried to start it. no start. cranks strong.

i opened the fuel sample/water drain valve thing from the bottom of the filter housing. Nothing came out.

i cranked the engine with the valve open, the housing seemed to them fill with fuel and start to pee out the sample valve. The engine stumbled briefly like it wanted to start then back to nothing.

The pedal is hard to press, like when my cummins runs out of fuel.

I have to assume at this point the pressure in the fuel lift system is low, or clog perhaps.

Is the in tank fuel pump electric? Should it start pumping once the key is "on", or does it wait to see crank rotation before it starts pumping?

 

[Action]

there is a mechanical pump on the lower, front, right side of the motor.
Is your wait light coming on and staying lit for about 7 seconds?
the sender for the gauge is in the tank.

 

[UserError]

I was using this guide to walk through, it had me assuming it was an electric pump. https://hummerhuren.files.wordpress.com/2013/01/hmmwv_test-diagnostics.pdf

I have realized it is a mechanical pump, similar to an old gasser of the side of the motor just as Action pointed out.

The mechanical pump seems to be working fine. I removed the filter housing and cranked the engine. It spurted out fuel.

Wait Light - i just walked out there and flipped the switch. the light lit for about 10 seconds, then went out. If i turn the switch off and right back on the wait light just flashes on. If i give it a minute and try again the light comes on for a second or two then goes out. Ambient temp is about 95 here today. Am i correct to assume the glow circuit is working correctly, and has some sort of temp sensing?

When the truck died, it had been running for several minutes. Then began to surge and died out. It wasn't able to restart.

The fuel filter seemed pretty disgusting on both sides. The mesh screen in the middle has crap stuck to it. Im assuming dirt was making it past the filter.

 

[UserError]

double post. sorry.

 

[UserError]

Is this the fuel return line i need to blow through and make sure its not blocked going back to the tank? Still trying to figure out where the return valve is I've heard can be trouble. {Learning Curve is Steep lol}

Can the fuel pressure transducer, if bad, cause a no start?


View attachment 651340

 

[dilvoy]

That nipple where the fuel return line you mention can be a problem. It has a glass plunger inside with a spring as well. It can get jammed with bits of deteriorating fuel return hose particles and if it is stuck closed, it keeps the mechanical advance parts in full retard. Might be the problem might not. I have broken the glass out and have had a vehicle come back to life and sometimes not, but the engine runs fine without the plunger.

 

[Action]

if you have lots of crud in the fuel filter, you may want to drainthe tank and put some fresh fuel in it. Maybe order a new tank plug first. 12340000

 

[UserError]

Ok i think I'm onto something here. I took the stock fuel filter housing out of the loop, replaced it with one of those generic see through lawn mower fuel filters.

If i connect the IP side fuel line, the filter will not fill up while cranking. When i take the IP side fuel line off there is an audible pop/hiss of built up air pressure and fuel squirts out of the tank side line.

If i leave the IP side {1/4"} fuel line disconnected and crank the engine, the little fuel filter fills up {with some seriously gross looking diesel}

Reconnected the IP fuel line to the little filter. Took the return line hose off the nipple on the IP. When i crank the engine a little bit of fuel dribbles from that nipple. But the inline filter still isn't filling

So either i have a clog, an air lock, or maybe the lift pump is just too weak? Im not sure what minimum system pressure is to function on this thing. Im going to try and rig a way to see how much pressure the stock mechanical pump is putting out. I don't know if i have a low pressure gauge though. I assume like a carbureted vehicle its in the 4-7psi range normally.

Maybe the IP is plugged up full of crap? Or? ...... I'm going to pull that valve thing off and see if maybe that isn't it. From there, i yield to you guys, the experts

I cracked an injector line, completely removed the "return nipple" and cranked it. No change, still an air lock between the IP and the filter.

Now the batteries need a charge. Back at it in the morning.

Thanks all! Keep the ideas coming

 

[1 Patriot-of-many]

Check to see if your solenoid on the IP is working. Pull the wire from the connector on the pump, turn your ignition switch on, replug the wire into the connector. You should hear a click. If you don't there's your problem.

 

[diesel dave]

Fuel injection systems need super clean fuel. If the "generic lawn mower type filters"were adequate,the engine manufacturers would not waste money installing larger more elaborate filtration systems. You need to get rid of that filter and go back to the factory or equivalent micron filter. From what you have said about the "nasty looking fuel",I'm afraid you have already plugged your injection pump and injectors and that could be your problem. For your sake,I hope I'm wrong. But you still need to get rid of that filter ASAP.

 

[Retiredwarhorses]

Start by draining your fuel tank. Add fresh fuel.
next, start from the fuel pump and move forward, easiest way is to disconnect the hose coming from the
fuel pump that terminates into the fuel filter inlet. Crank the truck....this hose should dump serious fuel out.
if not, you have one of 3 things wrong, clogged fuel line, bad pump, NO FUEL in tank if you didn't do the first thing I said.

if yes to fuel, reconnect 3/8 inlet hose and disconnect the 1/4in outlet hose that goes to injector pump.
now crank again...lots of fuel? Yes or no. If no...clogged filter, if yes...bad fuel cutoff solenoid, clogged pump.

the symptoms you described when the truck died are of a motor fuel starved, if the fuel cutoff solenoid just went bad, the truck would just die, no sputtering...nothing.

whats your fuel gauge say you have for fuel?


Also....replace your fuel filter.

 

[UserError]

Fuel gage says its full. The tank will be drained and cleaned today.

Lawnmower filter is just to give you a visual idea of what I'm doing. Its a paper element 10 micron filter with a window. Only being used as a diagnostic tool. No fuel has ever made it past this filter into the pump. So if the pump is clogged up, its not this filters fault. The failure occurred with the OEM filter and housing in place. {And its extremely nasty}

I ordered a replacement stock filter from one of those military surplus houses, but I'm awaiting its arrival. I would like to figure this out before it arrives.

How the heck they got it to run, i will never know. Im assuming the filter can was bottom fed, the truck started and once it ran dry that was it. Is the line from the tank forward rubber?

The standadyne manual has me thinking this is an air leak/fuel delivery and/or fuel quality issue. Possibly electrical {Use Test Light} is written on the windshield.

When i disconnect/reconnect wire 54a from the top of the IP with the Switch ON, the solenoid clicks. It also seems to trigger something in the dash, i hear a relay thunking i believe its triggering the glows when i put the 54a wire back on. I need to throw a test light on there and make sure the Fuel Shut Off is staying ON during cranking as well.

No idea what wire 56 does, it makes no sounds if connected/disconnected with the switch on. it also goes to the top of the IP right behind 54a. Ive got the TM's off this site open now, and trying to dig through them to find the information i need. But they keep referring to things that i don't have any clue what they are. Im assuming there is some sort of electronic diagnostic tool the military has, that i do not.

Im not at all well versed in how to prime this thing. On the cummins, there is a hand pump below the filter housing. When i run it out of fuel, i pump the plunger until i hear the relief valve in side the pump whine and then i know its ready to start. Im not finding the 6.2 to be quite as forgiving or user friendly. Learning curve is kicking my butt on this one.

 

[Retiredwarhorses]

Go back and read my post....if you follow it, this will isolate each component.

 

[UserError]

I am following along! i just posted the reply before i got started for the day. Every time i look sideways at this thing i end up SOAKED in diesel.....then the wife won't let me near the house till I've cooked off outside for a couple hours. I just dropped the boy at school so now its time to play! woot! lol. Tank draining commencing in 5, 4, 3, 2.............

 

[Retiredwarhorses]

Your going to need a new fuel tank plug...so don't get ahead of yourself. Those tank plugs are really one time use or they leak the next time around. Perform the steps I outlined above first before the tank draining.
you can check the fuel level in the tank with a good flash light, hold the light up against it and shake the tank and see if you can get a level. That is of pyrite tanks not painted black like a lot of them. It's easy on new tanks...not so on old tanks.
the idea here to see if you have a bad pump or clog, there is a strainer in the tank on the end of the pickup tube. Only acceible if you drop the tank.

 

[UserError]

Can i drop a stick down the filler neck worse case for a fuel level check? I have zero faith in these military fuel senders.