1994 M1123 won’t start. Please help!

[Mogman]

how about the fuel control module? I am told that most guys relocate it, because when it heats up it causes similar symptoms.

HMMWV has a pure mechanical IP, no control module or any electronics, sorry.
AGAIN if it surges before it dies it is starving for fuel, simple as that, have you done any flow testing from the lift pump or the return line??????

 

[MrLucky7137]

HMMWV has a pure mechanical IP, no control module or any electronics, sorry.
AGAIN if it surges before it dies it is starving for fuel, simple as that, have you done any flow testing from the lift pump or the return line??????

Copy that. I have, I’m getting good flow from the lift pump . I’m starting to think more and more that this is a timing issue since I didn’t know about the witness marks, and just put the pump back on without adjusting it at all. Side question, would you recommend using thread tape on these? I have a lot of small leaks.

 

[Mogman]

It is a little frustrating to try and help someone that does not answer any question asked, it seems all you have done is search the internet for possible causes including civy engines that have completely different electronically controlled IPs

Copy that. I have, I’m getting good flow from the lift pump . I’m starting to think more and more that this is a timing issue since I didn’t know about the witness marks, and just put the pump back on without adjusting it at all. Side question, would you recommend using thread tape on these? I have a lot of small leaks.

If it starts and runs it is not a timing issue, the timing could be off but that will not cause it to run then die.,
If you are positive you have good flow ALL the way to the IP then start looking at the return line, that is the only thing left that could possibly cause the kind of issues you have, if that checks out then you have a defective IP
ALL the IP needs is a good fuel supply, a good clear return line and return check valve, 24V to the shutdown solenoid and an engine to turn the IP that is all, if you have all of those things the IP is bad.

Since you have proven fuel flow the next step would be to pull the return line off the top of the IP and connect a hose to it going into a container so you can see if there is any fuel coming out of the return fitting.

 

[Mogman]

Copy that. I have, I’m getting good flow from the lift pump . I’m starting to think more and more that this is a timing issue since I didn’t know about the witness marks, and just put the pump back on without adjusting it at all. Side question, would you recommend using thread tape on these? I have a lot of small leaks.

You re-installed the injection pump without witness marks? the factory usually does not put a witness mark on the engine side of the IP flange, there is a witness mark on the IP, if you pull the IP you must copy the witness mark over to the engine side of the IP flange BEFORE removing the IP or you are going to have to have a professional diesel mechanic time the engine.
Having said that you would still have to have it WAY off to cause any big trouble running the engine static (sitting there with the hood open) it still would not just surge and die.
I thought all you replaced was the lift pump..
And no there is no place I would use Teflon tape except on water pipe, there are only a few places, the return fitting in the top of the IP being one, that have tapered threads, on tapered threads I use a small amount of thread sealing compound.
The lift pump only has one fitting with tapered threads and that is the suction side so it should not be leaking, where are the fuel leaks?

 

[Coug]

Have you checked fuel flow again right as it is dying/immediately after it dies? There's always the chance it's a failing fuel line or something similar causing a blockage after fuel has flowed for a bit

It's probably already been mentioned, but if the vent system for the fuel tank gets plugged up, the engine will run for a while then die from fuel starvation due to vacuum in the tank preventing fuel flow. Way to test that is run it with the filler cap off.

 

[MrLucky7137]

You re-installed the injection pump without witness marks? the factory usually does not put a witness mark on the engine side of the IP flange, there is a witness mark on the IP, if you pull the IP you must copy the witness mark over to the engine side of the IP flange BEFORE removing the IP or you are going to have to have a professional diesel mechanic time the engine.
Having said that you would still have to have it WAY off to cause any big trouble running the engine static (sitting there with the hood open) it still would not just surge and die.
I thought all you replaced was the lift pump..
And no there is no place I would use Teflon tape except on water pipe, there are only a few places, the return fitting in the top of the IP being one, that have tapered threads, on tapered threads I use a small amount of thread sealing compound.
The lift pump only has one fitting with tapered threads and that is the suction side so it should not be leaking, where are the fuel leaks?

Most of the fittings from the back of the IP leak, so diesel just sits in the valley and where the injection lines connect to the injectors also leak number eight cylinder I had to tighten more than I wanted to to get it to stop leaking.

 

[Mogman]

If any of the 8 injector lines leak they were ether cross threaded, not tight enough or there is a crack in the line, no type of sealing tape/compound should ever be used there, the only other line is the fuel feed, it is a flair fitting and rubber hose so again nothing need or should be used to try and seal it

 

[Mogman]

I went back and re-read everything and see you did replace the IP, if there is no witness mark on the block side where the IP is bolted up you will have to get a pro to time it, but still not likely your issue at this time, just get it done before driving it.

 

[Mogman]

The next step is to witness the fuel flow out of the IP return fitting, that will confirm you have a good flow to the IP, and if the return line is plugged it will continue to run as long as it is connected to a container.

 

[MrLucky7137]

I went back and re-read everything and see you did replace the IP, if there is no witness mark on the block side where the IP is bolted up you will have to get a pro to time it, but still not likely your issue at this time, just get it done before driving it.

ok so after replacing the lift pump twice (correctly) new injectors, fuel line, drained the tank and put new fuel, new glow plugs, and a brand new injection pump from the hummer parts guy I’m still having the same issue. It runs for 60 seconds surges and dies. Please help

 

[Mogman]

You still have not said if you removed the check valves, and also if you have monitored the out flow from the IP return fitting to make sure it is flowing and remains flowing until the engine dies, that is a pretty simple thing to do.

 

[MrLucky7137]

You still have not said if you removed the check valves, and also if you have monitored the out flow from the IP return fitting to make sure it is flowing and remains flowing until the engine dies, that is a pretty simple thing to do.

I don’t remember the check valves. How do I do that? I did monitor the out flow of the new injection pump by putting a fuel line into a bucket and it had a slow steady flow while the motor is running.

 

[Mogman]

I don’t remember the check valves. How do I do that? I did monitor the out flow of the new injection pump by putting a fuel line into a bucket and it had a slow steady flow while the motor is running.

And the flow stayed steady until just when it died? if so there is no fuel supply issue, if it quits before it dies then you still have a fuel supply issue.

 

[MrLucky7137]

And the flow stayed steady until just when it died? if so there is no fuel supply issue, if it quits before it dies then you still have a fuel supply issue.

and the check valves?

 

[Mogman]

and the check valves?

They are in front of the fuel tank inline with the fuel feed and return hoses, if you are getting flow out of the injection pump into a jar etc, until the moment it dies that is not likely the issue,
You need to run the engine with the return line in a jar etc. and monitor it until it dies to see if the flow continues until it dies or stops sometime before it dies.
This will answer the question of fuel supply.

 

[TNDRIVER]

They are in front of the fuel tank inline with the fuel feed and return hoses, if you are getting flow out of the injection pump into a jar etc, until the moment it dies that is not likely the issue,
You need to run the engine with the return line in a jar etc. and monitor it until it dies to see if the flow continues until it dies or stops sometime before it dies.
This will answer the question of fuel supply.

OR............ 2 very clean 5 gallon pails and several feet of fuel line........ one pail with CLEAN FUEL and a line to the back of the pump..... the other pail with a line from the filter into the pail........ crank it up and wait........... runs ok needs a complete fuel system clean up, tank and all.... like in remove and pressure wash the tank and replace anything rusty, all the lines and either replace , remove or clean the one way valves, remove and clean the filter housing (crud in the bottom) new hoses and "good' clamps on the fuel line(think stainless steel) Did I mention CLEAN pails and fuel....... My two cents.

 

[MrLucky7137]

and the check valves?

It was the check valves. Having fuel pressure at the valve on the driver side wheel well is NOT a good indication of whether or not the check valves are restricting flow. Runs great now