Hmmwv fuel system issue

[Milcommoguy]

Make or buy a 3-way wire. male one end. female another end. whatever for the third end. hook the male and female to the truck. Hook your multimeter to the third end.

I may have con-fused you guy's... I read that like he knew how and was pointing to the syntex error in the TM. and not the first time for crazy instructions.

You can measure the current flow easily. Pull the 54A lead, set the meter to measure DC current, positive lead to the 58A lead and negative to the IP pump connection post down in the rubber "Packard" boot. DO NOT miss and touch the pump body or any ground. Have one of the PVT's standing around turn the IGN sw to RUN and measure. Engine doesn't need to be running. Should be about 1/2 Amp. Not a lot.

What the history on this rig. That could add to the story. Maybe a picture too.

Guessing time.....
Solenoid maybe ??? Pop the top off the pump and poke around... Good time to bench check both solenoids and the electrical feed through with 24 Volt and wires, hardware. Check the "glass" check ball feeding the return line. There is small input filter too. My guess is leaning to bad IP or fuel cut-off mechanicals... busted, bent, rusted crudded up or just plain worn out. Take care on slipping in back into place. Little tricky with a wiggle wiggle.

Free guess with a shorted brain cell, CAMO

Manual >> https://radionerds.com/images/f/f4/Stanadyne_db2_operation_and_instructions_manuals.pdf

 

[Action]

........Also I pulled the fuel return line at IP, I then tried to crank. It cranked strong, nothing coming out of that fuel return line and where the return line was connected to IP it was spitting fuel a little bit. But it never cracked so not sure if this test works if foes not run.........

When you disconnect the return line from the injection pump, nothing will come out of the HOSE while running. It just connects to the fuel tank.

 

[Phoenix77]

@NCarolinadawg

Drop your fuel tank out and clean it out.

My 1986 M998 from Bragg would do the same thing. I replaced all kinds of stuff, but still had the issue. Definitely pull your fuel filter and replace it, but drop that tank, clean it, and flush the lines.

I took mine to a local shop and they charged me $400, which I don't mind because it completely fixed the issue. You're driving along fine, but then crap gets stirred up in the tank and goes into the fuel line / engine and you're dead in the water.

They told me the "sock" to catch particulate where the diesel comes in was jammed full of mess and there was water and sediment in the tank.

Get it cleaned out and you'll have a happy, new HMMWV.

 

[NCarolinadawg]

@NCarolinadawg

Drop your fuel tank out and clean it out.

My 1986 M998 from Bragg would do the same thing. I replaced all kinds of stuff, but still had the issue. Definitely pull your fuel filter and replace it, but drop that tank, clean it, and flush the lines.

I took mine to a local shop and they charged me $400, which I don't mind because it completely fixed the issue. You're driving along fine, but then crap gets stirred up in the tank and goes into the fuel line / engine and you're dead in the water.

They told me the "sock" to catch particulate where the diesel comes in was jammed full of mess and there was water and sediment in the tank.

Get it cleaned out and you'll have a happy, new HMMWV.

Fuel filter/separator has been replace, housing cleaned. Instead of dropping the full tank to "see" can I just unhook fuel pump inlet from tank, bypass tank and drop a new line into a 5 gal clean diesel can and see if will stay cranked? As stated, take fuel tank out of the equation.

Because some have asked again, It is a 1989 M998 6.2 3 speed. Had 2.5 years and no issues until this.

 

[TNDRIVER]

Fuel filter/separator has been replace, housing cleaned. Instead of dropping the full tank to "see" can I just unhook fuel pump inlet from tank, bypass tank and drop a new line into a 5 gal clean diesel can and see if will stay cranked? As stated, take fuel tank out of the equation.

Because some have asked again, It is a 1989 M998 6.2 3 speed. Had 2.5 years and no issues until this.

You can bypass the fuel tank to eliminate it with a piece of 3/8 inch fuel line , one end on the pickup side of the fuel pump and the other in a jug of clean fuel. (You can even drive around with this setup, jug in the pass. floor hose taped to the side of the truck. Don't tell anyone) If you have the removable panel over the fuel tank( 4 screws in the bed, passenger side) you can pull the fuel sender and get a good look inside the tank for yourself. Otherwise removing the tank is not a bad idea. 2 trucks both tanks had to be removed and cleaned, just saying. Good luck.

 

[NCarolinadawg]

You can bypass the fuel tank to eliminate it with a piece of 3/8 inch fuel line , one end on the pickup side of the fuel pump and the other in a jug of clean fuel. (You can even drive around with this setup, jug in the pass. floor hose taped to the side of the truck. Don't tell anyone) If you have the removable panel over the fuel tank( 4 screws in the bed, passenger side) you can pull the fuel sender and get a good look inside the tank for yourself. Otherwise removing the tank is not a bad idea. 2 trucks both tanks had to be removed and cleaned, just saying. Good luck.

So that's a question. I have seen some notes on forums here that with the fuel tank access cover you can NOT pull base plate out. HOWEVER, in the army cartoon drawings of access cover as attached it states that the Gasket can be replaced via access cover which would mean base plate can be removed. If base plate can be removed then you should be able to clean tank and do everything from access cover.

 

[Mullaney]

Fuel filter/separator has been replace, housing cleaned. Instead of dropping the full tank to "see" can I just unhook fuel pump inlet from tank, bypass tank and drop a new line into a 5 gal clean diesel can and see if will stay cranked? As stated, take fuel tank out of the equation.

Because some have asked again, It is a 1989 M998 6.2 3 speed. Had 2.5 years and no issues until this.

.
Everybody has a pressure washer. What they DON'T have is a steam heater pressure washer... Dropping the tank, cleaning out what you can, then with really hot water and pressure you will knock loose any "splooge" that might be in the tank. Again HOT, REALLY HOT water. Then dump it wearing gloves to keep from burning your hands. When you dump the water, it should come out clean. If not, refer to your shampoo bottle where is says "rinse & repeat".

If you want to try it at home, a hose from the bottom of your water heater might work.

Heat helps dry the tank. A little bit water isn't going to be awful.

 

[Action]

So that's a question. I have seen some notes on forums here that with the fuel tank access cover you can NOT pull base plate out. HOWEVER, in the army cartoon drawings of access cover as attached it states that the Gasket can be replaced via access cover which would mean base plate can be removed. If base plate can be removed then you should be able to clean tank and do everything from access cover.

You may be able to remove the top plate if nothing was attached to it, it was turned sideways and pulled out at an angle. And, all the nuts holding it to the tank would need to not be there. You can't reach the nuts.

 

[TNDRIVER]

So that's a question. I have seen some notes on forums here that with the fuel tank access cover you can NOT pull base plate out. HOWEVER, in the army cartoon drawings of access cover as attached it states that the Gasket can be replaced via access cover which would mean base plate can be removed. If base plate can be removed then you should be able to clean tank and do everything from access cover.

My opinion is the gasket under the metal plate could not be replaced thru the bed...... just my opinion. If you remove the fuel sender you can get a good look in the tank. At that point I believe you will opt to remove it. If you are in a nice neighborhood with gutters down the street flushing it is probably not an option. If you are on a farm and have an equipment wash area it is a possibility you could stick a pressure washer in thru the fuel sender hole and eventually flush the tank. (replace the drain plug with a NEW one.) Right now it appears you need an eyeball inside the tank. I think you will be amazed at what you see! Good luck, it's awfully hot to be mechanicing.

 

[Mullaney]

My opinion is the gasket under the metal plate could not be replaced thru the bed...... just my opinion. If you remove the fuel sender you can get a good look in the tank. At that point I believe you will opt to remove it. If you are in a nice neighborhood with gutters down the street flushing it is probably not an option. If you are on a farm and have an equipment wash area it is a possibility you could stick a pressure washer in thru the fuel sender hole and eventually flush the tank. (replace the drain plug with a NEW one.) Right now it appears you need an eyeball inside the tank. I think you will be amazed at what you see! Good luck, it's awfully hot to be mechanicing.

.
IDEA: What about a USB camera that would plug into your cell phone?
Quick search calls it a USB Camera Scope.
Like an endoscope or borescope

That would give you a set of eyes on the end of your mobile phone...

 

[TNDRIVER]

.
IDEA: What about a USB camera that would plug into your cell phone?
Quick search calls it a USB Camera Scope.
Like an endoscope or borescope

That would give you a set of eyes on the end of your mobile phone...

I own a bore scope. If you remove the fuel sender it's not needed. It might work down the filler tube but you have to disassemble part of the filler tube . Gets you further along the path to removing the tank. Diesel fuel and gasoline are two different animals in a fuel tank. STUFF grows in diesel fuel. I have a fuel polisher and three hours of it circulating fuel didn't clean up the tank . Tank had to be removed. (google "fuel polisher" and "bio kleen")

 

[Action]

Or pull the plug on the bottom of the tank and stick your finger in to see what you pull out...
You can only pull the sender and look in, if your hmmwv has the access hole in the bed.

 

[TNDRIVER]

Or pull the plug on the bottom of the tank and stick your finger in to see what you pull out...
You can only pull the sender and look in, if your hmmwv has the access hole in the bed.

YUP, works. And he will likely have to cut the plug in two and push the remainder into the tank. Once they are in there for a few years they seem to be near permanent.

 

[Action]

There is a one-way valve stuck in the fuel filter housing, on the input hose.
I had the lift pump diaphragm fail. Pieces of it got stuck in the valve. After replacing the filter and pump, the flow still was not good. I looked in the tank from the access hole. It and the sock were clean. I pulled the valve apart and found junk in it. All good now.

 

[badger_610889]

Hi there,
I’ve experienced the same symptoms with my M1123 for the past couple days. Before investigating tomorrow, I was researching on the forum and found this useful thread (as always!)

I suspect that mine will be straight forward (the truck has been running great since I reworked it 18 months ago) but I’m curious to know what the issue with your truck was?

And happy new year!