Hmmwv runs great then dies

[capnstinky]

Hi all! I have an 86 m998 that I have mostly brought back from the dead. Bad head and head gasket had it off the road. These things are replaced and I went to fire it up after bleeding the lines and vroom. Happy day. I was letting it warm up and checking for leaks etc when after about 3 minutes it stopped like I turned it to the off position on the ignition switch. There is fuel in the filter housing as I turned the bleeder valve and now have a mess to clean up. Poked around for a bit and ate lunch and thought what the heck, try again. It ran for about 1 minute and then shut off in the same manner as before. It seems to get mad with heat. I fed it a spray of ether and it tried to kick over which tells me this is a fuel issue. I checked the wires on the top of the injection pump and both have juice 23.5v to one and .5 to the other. Could I have crossed the wires? 54A was one wire and I have forgotten the numbers of the other wire. I am wondering if I have a bad fuel shut off switch. Any ideas? I have an old injection pump from a parts engine I picked up. I was thinking of just robbing the top cover off of it with the switch and see what happens. It's condition is unknown so it is a crap shoot. Thanks for the help/tips/tricks. On a side note, fuel is fresh and tank was drained. I did NOT change the fuel filter however and it is on my list of things to do, I just want to drive this thing around the block without pushing it 1/3 of the way.

 

[Chief_919]

I'll bet you have the wires on the top of the IP swapped. One is your shut off and the other controls the fast idle that is only powered when the engine is cold.

swap them and see what happens.

 

[capnstinky]

Before I go there, do you know the wire number that goes to the front (radiator side) for the pump? Thanks again!

 

[Chief_919]

Before I go there, do you know the wire number that goes to the front (radiator side) for the pump? Thanks again!

Not off the top of my head. Schematic in the TM will tell you.

i can almost guarantee you swapped them. We used to intentionally swap them to create a problem for new mechanics to troubleshoot in training and that is exactly what it did.

 

[capnstinky]

The TM shows 54a being the forward ip wire and 569b being from the cold advance system plugging into the rear of the ip. I will give it a try tomorrow and hope for the best!

 

[dilvoy]

One of those two connections has a special shape to it that is found nowhere else on the Humvee. It has a high low shape to the rubber connectors so you should be able to tell at a glance if they are mixed up.

 

[Retiredwarhorses]

One of those two connections has a special shape to it that is found nowhere else on the Humvee. It has a high low shape to the rubber connectors so you should be able to tell at a glance if they are mixed up.

One is ribbed and one is smooth..
if they were backwards, once the engine warms up the voltage to the cold advance would disappear and kill the motor.
NEVER use starting fluid on these motors...you could also still have air in the system that has not been purged.
pull the drain back line of the front of the pump when it's running, that will purge any air in the top of the pump and fuel will flow...better to run a tube into a bottle to do this.

 

[capnstinky]

Crossed wires for 1000 Alex. Thanks guys for your help. Now to diag all of the other little stuff, like the kick down not working, crappy acceleration and lots of black smoke at WOT. This thing rolls some coal, maybe that is normal with these?

 

[ryanruck]

Crossed wires for 1000 Alex. Thanks guys for your help. Now to diag all of the other little stuff, like the kick down not working, crappy acceleration and lots of black smoke at WOT. This thing rolls some coal, maybe that is normal with these?

Nope. I've turned up my injection pump 1/6th a turn and still don't have black smoke under acceleration.

 

[MrLucky7137]

The TM shows 54a being the forward ip wire and 569b being from the cold advance system plugging into the rear of the ip. I will give it a try tomorrow and hope for the best!

What voltage is required at 569b ?

 

[Mogman]

What voltage is required at 569b ?

Jumping threads is not going to help, the cold advance is not the problem, if it would start then immediately die maybe but not going to be your problem in AZ in the summertime.
But to answer the question it should have 24V when stone cold in the run position.

 

[MrLucky7137]

I'll bet you have the wires on the top of the IP swapped. One is your shut off and the other controls the fast idle that is only powered when the engine is cold.

swap them and see what happens.

I tried this, and mine will not run at all with them reversed. It will crank forever, but it won’t start. Is this a sign of something because I’m having the same problem, where mine only runs for about a minute, and then surges and dies.