1994 M1123 won’t start. Please help!

[Mullaney]

Ok so I got it running after having the IP rebuilt. I replaced the fuel pump on the block as well, started right up and ran great. This morning it started right up and idled for 20 minutes No problem. Now it starts after cranking for about 20 seconds runs for about 20 seconds and dies every time. Please help

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I can't swear to it, but it sounds like you have some sort of air leak. Sucking air when it shouldn't be. Maybe go through the fuel lines and make sure that you didn't leave something loose or maybe something vibrated loose on that 20 minute run... Maybe?

 

[MrLucky7137]

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I can't swear to it, but it sounds like you have some sort of air leak. Sucking air when it shouldn't be. Maybe go through the fuel lines and make sure that you didn't leave something loose or maybe something vibrated loose on that 20 minute run... Maybe?

thank you. I just went to my sons baseball game came home. It started up after cranking for about 10 seconds and ran fine for about 10 minutes until it got warm then died.

 

[Mogman]

thank you. I just went to my sons baseball game came home. It started up after cranking for about 10 seconds and ran fine for about 10 minutes until it got warm then died.

Remove your fuel cap and try it again.

 

[MrLucky7137]

Remove your fuel cap and try it again.

I just did and got the exact same result

 

[MrLucky7137]

Every wire has an aluminum tag on it, the one going to the fuel solenoid on the IP is 54A, the one that excites the alternator is 5A, just look for the tag numbers.

good morning. Any idea why my 98 m1123 6.5 would die as soon as it warms up?

 

[MrLucky7137]

This link should help. Pages 1 and scroll down and some Scotch Tape >https://hmmwvsystems.com/hmmwv-wiring/

5A is the "SENSE" lead from the control box to the alternator. 24 Volts in the RUN position. Some might call it the exciter or field.

Sticky subject. And there's the TM's too, CAMO

View attachment 881732

good morning. Any idea why my 98 m1123 6.5 will start when it’s cold but dies as soon as it gets up to temp?

 

[MrLucky7137]

Do you have fuel coming up? While cranking open the fuel filter drain located on the driver fender well. It should flow pretty good with a working pump. Follow the fuel hose leaving the bottom of the filter to its terminus. Should have a little elbow valve on it.

good morning. Any idea why my 98 m1123 6.5 will start when it’s cold but dies as soon as it gets up to temp?

 

[Mogman]

I suppose it is possible you have the cold advance wire and the run wire reversed on the IP so when it does warm up it shuts off power the the cold advance (which if reversed actually shuts off power to the run solenoid)
The run wire, 54A should be connected to the most forward connector on the IP

 

[MrLucky7137]

I suppose it is possible you have the cold advance wire and the run wire reversed on the IP so when it does warm up it shuts off power the the cold advance (which if reversed actually shuts off power to the run solenoid)
The run wire, 54A should be connected to the most forward connector on the IP

Thank you. I believe I have them right on the IP. I went off a different thread on here someone posted a pic of the diagram .

 

[Mogman]

Well then there is only two things that it could be, lack of power to the IP run solenoid or you are loosing fuel.
Again, have you replaced the fuel filter, all the rubber fuel lines and removed the check valves in front of the fuel tank?

 

[Mogman]

It likely has nothing to do with actual heat, the engine cannot get overheated in 10 minuits as long as it is full of water, it takes a long time to actually warm up.

 

[Mogman]

Does it surge or rev up a little just before it dies or is it just like shutting off the switch?

 

[MrLucky7137]

I suppose it is possible you have the cold advance wire and the run wire reversed on the IP so when it does warm up it shuts off power the the cold advance (which if reversed actually shuts off power to the run solenoid)
The run wire, 54A should be connected to the most forward connector on the IP

I just switched em and now it won’t start at all.

 

[MrLucky7137]

Well then there is only two things that it could be, lack of power to the IP run solenoid or you are loosing fuel.
Again, have you replaced the fuel filter, all the rubber fuel lines and removed the check valves in front of the fuel tank?

I did replace the filter and all of the fuel lines. Didn’t know about the check valves

 

[Mogman]

Again does it surge or rev up a little just before it dies or is it just like shutting the run switch off.

 

[MrLucky7137]

Again does it surge or rev up a little just before it dies or is it just like shutting the run switch off.

It definitely surges several seconds before dying

 

[Mogman]

Then it is definitely a fuel issue, you are not getting a good fuel supply to the IP.

 

[Mogman]

Some issues can be, plugged fuel screen in the tank, the for-mentioned check valves, bad fuel pump, plugged fuel filter, leaking (sucking air) fuel lines (would be before the fuel pump)
If you do not have some flow from the fuel filter drain while cranking or running it is no bueno

 

[Mogman]

When you replaced the fuel pump did you remove the plate behind the pump, remove and grease the push rod so it would stay up in the block before installing the new pump?

 

[MrLucky7137]

Again does it surge or rev up a little just before it dies or is it just like shutting the run switch off.

I’m starting to think it’s the new lift pump is bad. I started it this morning and it only ran for a couple of minutes before it sputtered and died.