M998 Cranks but Quits Quickly

[Phoenix77]

I have a 1986 M998 with "87k" miles on it. Ran great at first, but then lost power and quit.
I replaced the fuel filter (looked like someone wiped their butt with it), changed oil, changed transmission fluid, complete coolant system flush, new batteries.

It has fuel, and it Cranks but shuts off immediately. Might get a few yards.

Fuel pump?

 

[Bulldogger]

Did you bleed the injectors? Might be full of air from the fuel filter change. Seems unlikely to cause stalling, but could be part of it.
BDGR

 

[Phoenix77]

I will try bleeding an injector; thanks.

I am moving forward with a fuel pump replacement (already ordered it, have it on hand), it is just a matter of finding time.

 

[Retiredwarhorses]

I have a 1986 M998 with "87k" miles on it. Ran great at first, but then lost power and quit.
I replaced the fuel filter (looked like someone wiped their butt with it), changed oil, changed transmission fluid, complete coolant system flush, new batteries.

It has fuel, and it Cranks but shuts off immediately. Might get a few yards.

Fuel pump?

Immediate shutoff is usually a bad connection or bad fuel cutoff solenoid. Also make sure the 2 wires aren’t reversed, one is a cold advance switch and will turn off 24v as soon as the engine gets above 120 degrees.
the plug for the cold advance has ribs on the rubber plug

 

[Phoenix77]

I read about someone else having that issues with the wires reversed, but my HMMWV ran great until it just didn't, so I doubt it is that.

I'll check the connection; simplest is usually best. If it sits for a few days, I can generally go a few hundred yards before it cuts off.

 

[Phoenix77]

Sitting in my dead m998; it fired up, I drove it to the back of our property, gunned it, it only got to about 35 MPH then seemed to hit the ceiling. I slowed down a bit and then it cut off.

Turned ignition all the way off then it fired back up. Nursing it back at 5 mph, but it cut off again. There is hesitation right before it cuts off.

 

[Phoenix77]

Fixed

Replaced fuel pump, ran better, but still stalled out.

I drained the fuel tank (it had 1/2 tank when I picked it up), kicking the tank to stir up sediment as it drained; saw some opaque fuel and sketchy streaks. Filled her back up and she runs great.

 

[papakb]

I had the same start stop problem a few years back and found that the engine fuel pump was not pumping. The tank pump will supply fuel to the filter but the engine mounted pump is needed to make sure the IP gets a continuous flow of fuel to keep the engine running. Here's a link to the pump I used that's a whole lot cheaper than buying a "HMMWV" pump:https://www.carid.com/spectra-premium/mechanical-fuel-pump-mpn-sp1143mp.html?singleid=78059414

I just did this job on a friends HMMWV and there's no good way to push the fuel pump actuator pin back up into the block without removing the mounting plate. The gaskets are readily available and fit 1955 thru 1995 GM engines and only cost a few bucks so bite the bullet and remove the plate. I used wheel bearing grease to hold the pin up in the block when I remounted the plate and it washes out after the engine warms up so it won't cause any problems down the line. Use a touch of Permatex Hi-Tack to hold the gaskets in place. A word of advice when you do this job, remove the right splash panel and have a long extension with either a 3/8 swivel socket or a universal with a 3/8 socket to put things back together. This allows you to tighten everything up reaching in over the frame rather than busting your knuckles on all the solid stuff in the neighborhood.

Fuel pump: https://www.carid.com/spectra-premiu...gleid=78059414

Gasket:http://www.jegs.com/i/Fel-Pro/375/5182/10002/-1

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