Mechanical/Lift Pump Issues M1043A2

[diseasewithnocure]

Hi Everyone,

First time posting but have searched myself blue through every post here trying to find a relevant post without bothering everyone with new thread…but here I am.

GovPlanet M1043A2 delivered to me with “78” miles (I know, could be anything—underside is INSANELY clean however with virtually all factory paint underneath in tact).
Did all the fluids front to back (except hubs for now), filters, etc. It started immediately always (faster than my 2011 Lexus LOL) without issue…drove it on my “test track” (100 acre back yard) one evening and parked it in the garage. Next morning…nothing, crank, crank, crank - won’t show any signs of life.

I use the technical manuals and own intuition to check fuel first—nothing getting to the filter. Suspect lifter pump internals are shot — order a new fuel pump. Install … still nothing. Blew air through lines (from fuel filter down to lift pump outlet)…and pushed fuel (using compressed air) from tank to lift pump inlet..ensuring gas is getting TO and theoretically FROM the lift pump.

After 3X removals/reinstall of the lift pump now (including removing the plate and grease sticking the lift pump rod in place) I finally got a helper to turn over the motor while I put my thumb on the outlet to feel for pressure…nothing.

I removed the whole setup again and measured the rod. It measures 5.25” (measured quickly with a tape measure, not a caliper/micrometer).

In further searching ( https://www.steelsoldiers.com/threads/hmmwv-fuel-lift-pump.195226/) I learn Dorman 03875 is a compatible rod…and is 5.75” long according to the Internet..so 1/2” longer than current one in my 6.5L truck, which is exactly what it sort of feels like —meaning the pump isn’t being engaged while cranking.

Should the HMMWV push rod be 5.25” or 5.75” in length? Could it be too short to actually push/engage the mechanical arm on the lift pump?


Is this a possibility? I HIGHLY doubt something on the lobe of the cam is gone or damaged (but open to consideration if someone thinks it’s a possibility)…otherwise I’m getting somewhat dumbfounded (and frustrated) how this seemingly simple, mechanical pump mechanism isn’t working to deliver fuel up to my HPIJ.

As to how/why it ran before (and now not) with the same rod (but old pump) in place — my only guess is that the HPIJ was pulling it up, but that’s just a (relatively uneducated) guess.

Open and appreciative of all suggestions or ideas at this point -thabj

 

[Action]

I had installed an auto parts store pump. It didnt work. Found out that the pump lever moved about 1/2” freely. I found an ac delco that had no freeplay on lever. Put in and works great.
Did you rotate the engine before each install to nake sure the rod was all the way up?

 

[diseasewithnocure]

I had installed an auto parts store pump. It didnt work. Found out that the pump lever moved about 1/2” freely. I found an ac delco that had no freeplay on lever. Put in and works great.
Did you rotate the engine before each install to nake sure the rod was all the way up?

Pump was sourced from Midwest Military Equipment, so I assumed it’s the right one.

I did not rotate the engine to any particular point before aligning — is that something I do on the crank (manually) or is there a better/different way?

 

[Milcommoguy]

Might be some info in this thread title, back a couple of days> Find and read to the end.
Fuel pump part number
With rod fully depressed up in bore on flat of cam... just a little pre-load to be felt. Has in slight to too none. Good point on the pump by ACTION. Pump arm fully extended and Its all one can do to actuate it while holding. Well, I can't do it. Very strong spring. No slop in action. Didn't mean it that way, LOL

Don't have the length handy on the rod. If it worked before??? I don't see how it could have shrunk a 1/2 LOL That extra 1/2 is a lot. So no help here.

One doesn't have extra parts??? and snapped it into two ??

These pumps are starting to be a problem, CAMO

 

[diseasewithnocure]

Might be some info in this thread title, back a couple of days> Find and read to the end.
Fuel pump part number
With rod fully depressed up in bore on flat of cam... just a little pre-load to be felt. Has in slight to too none. Good point on the pump by ACTION. Pump arm fully extended and Its all one can do to actuate it while holding. Well, I can't do it. Very strong spring. No slop in action. Didn't mean it that way, LOL

Don't have the length handy on the rod. If it worked before??? I don't see how it could have shrunk a 1/2 LOL That extra 1/2 is a lot. So no help here.

One doesn't have extra parts??? and snapped it into two ??

These pumps are starting to be a problem, CAMO

Thanks for the link to that CAMO - I will give it a shot when I can get another set of hands…the wife is less than amused sitting there trying to battle a 2-year old from touching everything in sight, all while waiting for my “crank!” signal…helps to know it does indeed have a position it needs to hit.

In terms of length, I wasn’t insinuating that it shrunk or anything like that. The ends are nice and smooth (machined finish) so I’m happy/confident it didn’t break off or anything. I was more asking in case the wrong one was installed at some point (not by me, but by USMC) that was 1/2” shorter than the Dorman part #…and it essentially isn’t long enough to make contact to engage the pump — and the reason it worked before was that the HPIP was doing all the work beforehand with a dead (lifter) pump…

All guesses and speculations —I’ll try aligning that pump rod into position first next and checking that first.

 

[diseasewithnocure]

Might be some info in this thread title, back a couple of days> Find and read to the end.
Fuel pump part number
With rod fully depressed up in bore on flat of cam... just a little pre-load to be felt. Has in slight to too none. Good point on the pump by ACTION. Pump arm fully extended and Its all one can do to actuate it while holding. Well, I can't do it. Very strong spring. No slop in action. Didn't mean it that way, LOL

Don't have the length handy on the rod. If it worked before??? I don't see how it could have shrunk a 1/2 LOL That extra 1/2 is a lot. So no help here.

One doesn't have extra parts??? and snapped it into two ??

These pumps are starting to be a problem, CAMO

Thanks for the link to that CAMO - I will give it a shot when I can get another set of hands…the wife is less than amused sitting there trying to battle a 2-year old from touching everything in sight, all while waiting for my “crank!” signal…helps to know it does indeed have a position it needs to hit.

In terms of length, I wasn’t insinuating that it shrunk or anything like that. The ends are nice and smooth (machined finish) so I’m happy/confident it didn’t break off or anything. I was more asking in case the wrong one was installed at some point (not by me, but by USMC) that was 1/2” shorter than the Dorman part #…and it essentially isn’t long enough to make contact to engage the pump — and the reason it worked before was that the HPIP was doing all the work beforehand with a dead (lifter) pump…

All guesses and speculations —I’ll try aligning that pump rod into position first next and checking that first.

 

[Retiredwarhorses]

do you have fuel in the tank? Have you verified you don’t have a problem at the fuel tank and not the pump itself?
if it ran and now not getting fuel, Yes…it could be a bad pump, but the rod if not broken, is not the issue.
I would remove the 2 anti-siphon valves on the fuel tank lines and just put in 1/4 and 3/8 fuel hose, the valves are notoriously bad from old fuel sitting in them for 11yrs and getting algae in them.

 

[diseasewithnocure]

do you have fuel in the tank? Have you verified you don’t have a problem at the fuel tank and not the pump itself?
if it ran and now not getting fuel, Yes…it could be a bad pump, but the rod if not broken, is not the issue.
I would remove the 2 anti-siphon valves on the fuel tank lines and just put in 1/4 and 3/8 fuel hose, the valves are notoriously bad from old fuel sitting in them for 11yrs and getting algae in them.

Great questions and points - a little under 10 gallons of fuel in the tank just recently added.

You reminded me that shortly before my test drives I added diesel fuel injector cleaner to the system. I put probably 20 or so miles on it with that active in the system; parked it at ~10pm and the next day by 10AM it would not start…might have something to do with it?

I AM able to get fuel to run out of the inlet hose (to the fuel pump) with some pressure on the tank - but understanding that is obviously far more pressure on the line than the pump creates in vacuum (from a pounds per square inch perspective).

I’ll work on getting those valves removed and report back.

Thanks much - I hope in all of this I didn’t ruin or have a bad HPIP now ($$$).

 

[papakb]

Something that caught me by surprise was the gasket on the fuel seperator housing split and the system was sucking air. After changing the fuel pump I've always used a small vacuum pump to precharge the system by drawing a vacuum on the petcock outlet of the water seperator down in the drivers wheelwell. I also add a piece of fuel line so that the outlet of the petcock drains on the ground instead of the drivers foot panel. This makes sure that you have clean fuel at least to that point.

 

[diseasewithnocure]

Something that caught me by surprise was the gasket on the fuel seperator housing split and the system was sucking air. After changing the fuel pump I've always used a small vacuum pump to precharge the system by drawing a vacuum on the petcock outlet of the water seperator down in the drivers wheelwell. I also add a piece of fuel line so that the outlet of the petcock drains on the ground instead of the drivers foot panel. This makes sure that you have clean fuel at least to that point.

Great point and something I will need to keep an eye out for — unfortunately I’m not even that far “up” in the line/system yet and can’t even get fuel to come out of the outlet side of the mechanical fuel pump.

Removed the 2x anti-siphon valves, but have not replaced the lines tonight — not a fun job!

 

[diseasewithnocure]

Great point and something I will need to keep an eye out for — unfortunately I’m not even that far “up” in the line/system yet and can’t even get fuel to come out of the outlet side of the mechanical fuel pump.

Removed the 2x anti-siphon valves, but have not replaced the lines tonight — not a fun job!

Hi everyone,

Happy to report she is back up and running again. It was indeed the clogged anti-siphon valves (2x) near the tank that was causing it not to run.

Curiosity remains if that’s all it was, but at $50 replacing the mechanical lifter pump was good insurance anyways.

Issue/topic closed — for all those reading this a month, a year, or a decade from now hunting the Internet for answers…unless the shaft is broken, it’s long enough.

Also, check and replace those anti siphon valves with straight tubing (thanks Retiredwarhorses)

 

[Action]

In a pinch, you can just remove the insides of the valves and put back on truck. There is a snap ring inside holding it together.
if you determined they are clogged by blowing through them...that wont work. I could not blow through a new supply line valve. Yes. I know they are one-way.
take them apart on a paper towel and see what is in them.
Have you checked the sock at the end of tank pick up tube?

 

[McSpeed]

I don't have a solution - but wanted to feel your pain a bit - I replaced my pump as it was leaky...It is a PAIN to do. There just isn't much room to work there.