M998 stalling at highway speeds

[FFesco]

I’ve had one of my m999 HMMWV’s running great, but the other night it stalled as I was driving on the highway. If I keep it below 30mph on the street, it is fine. If I take it up to 60mph, it will eventually shutoff and roll to a halt, power steering eventually goes as well. I’ll wait a few min and start right back up. Seems like a fuel issue. Any thoughts??

 

[Dock Rocker]

Sounds like a fuel restriction. Have you changed the fuel filter cartridge?


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[FFesco]

I haven’t changed it but did remove it, inspected it. Clean as can be. No visible defects either.

 

[porkysplace]

I haven’t changed it but did remove it, inspected it. Clean as can be. No visible defects either.

So you can tell it is spot less under the expanded metal and no water swelling the paper element ?
When was the last time it was changed?

 

[Action]

Once the engine stops, you should only have one good easy application of the brakes.

 

[papakb]

My recommendation is to change the fuel pump. Here's a link to a perfectly good pump that I've installed in several vehicles without any problems: https://www.carid.com/spectra-premium/mechanical-fuel-pump-mpn-sp1143mp.html?singleid=78059414 Before you start this job pick up the fuel pump mounting plate gasket: http://www.jegs.com/i/Fel-Pro/375/5182/10002/-1 it'll make the job infinitely easier if you remove the plate, remove the pump actuator rod and coat it with bearing grease to hold it up into the block before you put the new pump in. It also helps to remove the right side splash panel so that you can see what your working on.

Unless the filter is really crapped up it shouldn't be the cause of your stalling but if you pull it for inspection and it is filthy you might want to drain the tank and see what comes out. There are a couple of threads on priming the fuel system you should brush up in before starting the job too.

 

[tage]

Fuel pump is mechanical. One would do a flow and pressure test before replacement.
Replace the fuel filter and report back....


Have you been running a winter blend of bio diesel/reg diesel? That will clog a previously clean filter rather quick

 

[155mm]

My guess is the pickup in the tank or something in the tank sucking up against the pickup. If the new fuel filter, and the fuel pump test ok, nest easy test is in tank.

 

[Action]

I will guess fuel pump or clogged intake sock in tank.

 

[FFesco]

I will have to work on this next week, will let you know how I make out. Thanks for all the help everyone!

 

[911joeblow]

Sounds definitely like a bad or floating fuel pump. Floaters are where the pump shaft binds in the bore or the pump return is not working well. Either case needs at least the pump removed to take a look.

 

[Dock Rocker]

My guess is the pickup in the tank or something in the tank sucking up against the pickup. If the new fuel filter, and the fuel pump test ok, nest easy test is in tank.

I remember there being a rash of guys getting a piece of the sock from the fuel float assembly in the pickup tube. The symptoms were similar to the OP’s issue.

The test was to pull the fuel line loose at the block mounted pump and blow compressed air into the fuel line to blow the obstruction out and see how it ran.


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[papakb]

Just as a fast addendum you might want to look at the fuel lines themselves to make sure you don't have a cracked line sucking air. There are lines on the top of the tank and more up around the filter.

 

[FFesco]

Ok, I’ve figured it out! I swapped out the mechanical pump that feeds fuel to the injector pump. The one I bought was a Carter M73105. I also some air in my lines along with blocked injectors, so I cleaned those out as well and made sure I had fuel running through. I did a few small things, such as new clamps around my hose lines to assure the fuel system is air tight.

I hope my problem helps someone out there. Thanks for all your input. My truck sounds great now!


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