Hmmwv fuel delivery run issue

infinitymotors · Mar 19, 2020

over the last 2 years I picked up 3 humvees from GovPlanet. I had no isssues with the first 2. My third is a having fuel delivery issues. This unit had been thru a rebuild. Practically all new under the body. Rebuilt engine ect.,all new 50 miles since the rebuild 8 years ago. The engine will start and run well for 3-10 minutes at idle. I have not driven it on the road just into the shop. It runs until it runs out of fuel. You can start it back up again and it does the same thing. Things I have checked. (Mike Vaden has been coaching me thru some trouble shooting, great guy. ) I have remove the check valves in the fuel line near the tank. I have replaced the fuel filter. The mechanical lift pump seems to be putting out tons of fuel. This is what blows my mind. I have traced the fuel system up to the ip. I bypassed the water fuel separator to a small clear fuel filter for testing. So at this point. I crank the engine. Get the little glass filter full of fuel. It runs for a few minutes and the glass filter slowing runs out of fuel. This is what gets me. If I disconnect the fuel line from the filter going to the injection pump fuel comes rushing into the filter like there was air pressure keeping fuel from filling the filter. Could the IP be pushing air back towards the fuel pump? The fuel return line on top of the IP is tribbling fuel our when running. The hard return line is clear blow thru it back to the tank. Do I need to bleed the air out down by the injectors?

Welder1 · Mar 19, 2020

infinitymotors said:
over the last 2 years I picked up 3 humvees from GovPlanet. I had no isssues with the first 2. My third is a having fuel delivery issues. This unit had been thru a rebuild. Practically all new under the body. Rebuilt engine ect.,all new 50 miles since the rebuild 8 years ago. The engine will start and run well for 3-10 minutes at idle. I have not driven it on the road just into the shop. It runs until it runs out of fuel. You can start it back up again and it does the same thing. Things I have checked. (Mike Vaden has been coaching me thru some trouble shooting, great guy. ) I have remove the check valves in the fuel line near the tank. I have replaced the fuel filter. The mechanical lift pump seems to be putting out tons of fuel. This is what blows my mind. I have traced the fuel system up to the ip. I bypassed the water fuel separator to a small clear fuel filter for testing. So at this point. I crank the engine. Get the little glass filter full of fuel. It runs for a few minutes and the glass filter slowing runs out of fuel. This is what gets me. If I disconnect the fuel line from the filter going to the injection pump fuel comes rushing into the filter like there was air pressure keeping fuel from filling the filter. Could the IP be pushing air back towards the fuel pump? The fuel return line on top of the IP is tribbling fuel our when running. The hard return line is clear blow thru it back to the tank. Do I need to bleed the air out down by the injectors?

Just a thought check the tank venting. Sounds like the fuel tank maybe coming under vacuum.

infinitymotors · Mar 19, 2020

I agree. It seemed clear. Running with cap off would bypass that issue, correct? The vacuum is after the lift pump.

Sent from my iPhone using Tapatalk

Mogman · Mar 19, 2020

I think this is a Rosa Master IP, what GM seems to like using, they are notorious for the rubber coupling (inside the IP) shedding pieces and plugging the return check valve, it is mounted in the pump and is part of the return fitting, If you unscrew the fitting there should be a small glass check ball in there, if you see black then there is a piece of rubber stuck in the valve and that will cause the symptoms you describe.
IF so you can drill out the check valve and test, (I have never been successful at clearing the check valve, just replace it when you get the pump rebuilt) it will run with no back pressure but that will not fix the underlying issue in the IP

The check valve is #13

Bulldogger · Mar 19, 2020

The IP may be the culprit, especially since it's a known failure item.

Before I read that explanation, my thoughts were blocked lines. Easy enough to blow them out with low pressure compressed air. A line can have partial blockage and still pass fuel briefly in good quantity form that stored in the unblocked portion of the line downstream of the blockage, but be unable to supply continuous due to the partial blockage. Did you check your fuel pump screen in the tank? Granted I wouldn't want to drop the tank to inspect until I'd tried everything else...

Bulldogger

infinitymotors · Mar 19, 2020

I did remove the check valve #13. The ball did seem stiff and I couldn’t blow thru it. I poked the spring loaded ball and got it moving. I replaced it with one from my other running hmmwv. I had the same results, but maybe it’s clogged again. The ball seems like it’s made of glass. Can that be removed and will the pump still function properly? How much fuel flow should you see from That hose?

Sent from my iPhone using Tapatalk

infinitymotors · Mar 19, 2020

One other question. This is my first post. Did I post this question in the correct thread?

Sent from my iPhone using Tapatalk

Mogman · Mar 19, 2020

There should be a good steady flow from the hose, basically it is bypassing all the diesel the IP is not using with a little back pressure, I have made it home a couple times after drilling out the valve back in my 5.7L days, I have run my JD310 backhoe and 350 dozer for several months without the valve before having the pump rebuilt.
As stated above it could also be a plugged return line.
EDIT yes this is the correct forum

Mogman · Mar 19, 2020

OK I looked it up and GM went to a Stanadyne IP, looks like and probably acts the same as a Rosa Master

infinitymotors · Mar 19, 2020

Yes it’s a standyne

Sent from my iPhone using Tapatalk

gem1410 · Mar 19, 2020

I had a similar problem--the fuel return line to the tank was clogged-- had to replace the line and it then ran well

infinitymotors · Mar 19, 2020

Gem1410 were you able to blow thru the return
Line with air before the issue or was it completely clogged?

Sent from my iPhone using Tapatalk

gem1410 · Mar 19, 2020

600 mile truck-- completely clogged --600 mile truck--inside of return line was rusty and the diesel turned to sludge--disconnect your fuel return metal line and run the return line from the injector pump into a 5 gal pail--see how it runs--

infinitymotors · Mar 20, 2020

Why I blow in the upper part of the line where the injection pump inputs I can hear gurgling in the tank.

Sent from my iPhone using Tapatalk

infinitymotors · Mar 20, 2020

Do you think I need to bleed the pump at all injectors?

Sent from my iPhone using Tapatalk

Mogman · Mar 20, 2020

I have never seen the issue you are describing caused by the need to bleed, usually hard starting, rough running are the symptoms of air in the injector lines.
So you say it starts, runs smoothly for 5-10min at idle and then just falls dead? Then how long do you have to wait until it will start again?
Have you tried running a line from the IP return into a bucket?

infinitymotors · Mar 20, 2020

It will start right back up in a few minutes. You have to give it half throttle to get it started. Yes the diesel dribbles out of the hose at idle.

Sent from my iPhone using Tapatalk

Mogman · Mar 20, 2020

Does the "dribble" change just before it dies?

Bulldogger · Mar 20, 2020

If you blew through the line (and that was worth checking), you definitely should bleed the injectors now.
BDGR

Mogman · Mar 20, 2020

Bulldogger said:
If you blew through the line (and that was worth checking), you definitely should bleed the injectors now.
BDGR

He blew through the return line

Hmmwv fuel delivery run issue

Member

Active member

Member

Moderator

Well-known member

Member

Member

Moderator

Moderator

Member

Active member

Member

Active member

Member

Member

Moderator

Member

Moderator

Well-known member

Moderator