Fuel pump issue -- can't get fuel rod back in block

[M998 NYC]

(go to underlined below to skip earlier details)


Where to begin… Last summer I was having some fuel delivery issues on my M998. Basically it would run out of fuel on a full tank while driving. Not a convenient issue to have.

Problem seemed related to the fuel pump so I swapped it with a refurbished and the issue persisted. Ended up working with a local mechanic who suggested swapping it for an electric pump, so I got a 24v pump with 5.6.5psi (meant for a Hitachi excavator). It worked great for 6 months then the issues started again … driving along and then the truck suddenly sputters and turns off. Cranking and nothing.

ANYWAY, didn’t get too far with the TM and there’s not much online about humvees with electric fuel pumps, so I got another mechanical fuel pump and had to get a new push rod since I misplaced the one I had thinking I wouldn’t need it again. Both are original parts from Midwest Military but so the next issue has me kind of baffled.


I can’t get the fuel rod back into the block. The original slid right out, and the replacement is an original part so can’t wrap my head around it. There’s nothing I found online about others having trouble getting it to slide back in (vs. STAYING in while fitting gasket) .. Is there something obvious I’m missing here? Again, don't have the original I took out to compare to the one I bought, which I have no other reason to believe isn't original.

After inserting it into the block by about an inch I can feel it slide into the right place for about another half inch, then it won't budge further. I can’t find posts about others having this issue so makes it more likely we're overlooking the obvious.

What could prevent the block from taking the rod? Could the bushings be damaged? Corrosion? Should I just hammer it in hoping it can slide once in? Sand down the rod?
Any suggestions on that or my larger fuel delivery issue would be greatly appreciated.

 

[Maxjeep1]

(go to underlined below to skip earlier details)


Where to begin… Last summer I was having some fuel delivery issues on my M998. Basically it would run out of fuel on a full tank while driving. Not a convenient issue to have.

Problem seemed related to the fuel pump so I swapped it with a refurbished and the issue persisted. Ended up working with a local mechanic who suggested swapping it for an electric pump, so I got a 24v pump with 5.6.5psi (meant for a Hitachi excavator). It worked great for 6 months then the issues started again … driving along and then the truck suddenly sputters and turns off. Cranking and nothing.

ANYWAY, didn’t get too far with the TM and there’s not much online about humvees with electric fuel pumps, so I got another mechanical fuel pump and had to get a new push rod since I misplaced the one I had thinking I wouldn’t need it again. Both are original parts from Midwest Military but so the next issue has me kind of baffled.


I can’t get the fuel rod back into the block. The original slid right out, and the replacement is an original part so can’t wrap my head around it. There’s nothing I found online about others having trouble getting it to slide back in (vs. STAYING in while fitting gasket) .. Is there something obvious I’m missing here? Again, don't have the original I took out to compare to the one I bought, which I have no other reason to believe isn't original.

After inserting it into the block by about an inch I can feel it slide into the right place for about another half inch, then it won't budge further. I can’t find posts about others having this issue so makes it more likely we're overlooking the obvious.

What could prevent the block from taking the rod? Could the bushings be damaged? Corrosion? Should I just hammer it in hoping it can slide once in? Sand down the rod?
Any suggestions on that or my larger fuel delivery issue would be greatly appreciated.

You need to take that plate off to get the rod back in. I just did mine and rod slide out and against the plate and that tells me the angle is wrong to get it in with plate on. Gasket needs replaced also.

 

[Maxjeep1]

Remove the 2 10mm bolts take plate off and see if rod slides right in.

 

[M998 NYC]

Remove the 2 10mm bolts take plate off and see if rod slides right in.

What a dummy (me) -- thanks for the quick reply correcting the error of my ways before I hammer the damn thing at the wrong angle. Duh, plate needs to come off. Thanks again, Maxjeep1
-Max

 

[Mullaney]

(go to underlined below to skip earlier details)


Where to begin… Last summer I was having some fuel delivery issues on my M998. Basically it would run out of fuel on a full tank while driving. Not a convenient issue to have.

Problem seemed related to the fuel pump so I swapped it with a refurbished and the issue persisted. Ended up working with a local mechanic who suggested swapping it for an electric pump, so I got a 24v pump with 5.6.5psi (meant for a Hitachi excavator). It worked great for 6 months then the issues started again … driving along and then the truck suddenly sputters and turns off. Cranking and nothing.

ANYWAY, didn’t get too far with the TM and there’s not much online about humvees with electric fuel pumps, so I got another mechanical fuel pump and had to get a new push rod since I misplaced the one I had thinking I wouldn’t need it again. Both are original parts from Midwest Military but so the next issue has me kind of baffled.


I can’t get the fuel rod back into the block. The original slid right out, and the replacement is an original part so can’t wrap my head around it. There’s nothing I found online about others having trouble getting it to slide back in (vs. STAYING in while fitting gasket) .. Is there something obvious I’m missing here? Again, don't have the original I took out to compare to the one I bought, which I have no other reason to believe isn't original.

After inserting it into the block by about an inch I can feel it slide into the right place for about another half inch, then it won't budge further. I can’t find posts about others having this issue so makes it more likely we're overlooking the obvious.

What could prevent the block from taking the rod? Could the bushings be damaged? Corrosion? Should I just hammer it in hoping it can slide once in? Sand down the rod?
Any suggestions on that or my larger fuel delivery issue would be greatly appreciated.

.
I agree with @Maxjeep1 . Take the plate off, get that rod in place with lots of red grease to hold it in place. It should stay overnight even... Whatever you do, don't hammer it in place! It should slide.

 

[Maxjeep1]

I covered the end of rod with grease to hold it in while I took forever to get the plate and pump on. I had about 1/2” of rod sticking out of block and that was in far enough for me to get pump on. I also started the metal fuel line to help hold pump up

 

[Maxjeep1]

I used gasket maker to hold gasket to plate and gasket on the pump. I didn’t want it on the block and I figured I would be trashing the pump if I changed it again. I would only have to clean it off of one side of plate that comes off. Not a lot of room in there and I could only get one hand

 

[Action]

And you may need to turn the motor to get it all the way up.
Just curious...,How does a refurbished lift pump compare in price to a new one? Arent new pumps under $50?
A dead lift pump will not cause the engine to die.

 

[Maxjeep1]

I ordered my new pump from Mac Motors and it was a much better quality than the one Melton used. Old pump had a lot of travel before it was solid. I was reading on HPG and it said the spring shouldn’t show on the right pump. I did notice that spring showed on old pump but not on new. I don’t know if It makes any difference, I’m just throwing it out there

 

[M998 NYC]

And you may need to turn the motor to get it all the way up.
Just curious...,How does a refurbished lift pump compare in price to a new one? Arent new pumps under $50?
A dead lift pump will not cause the engine to die.

Thanks for the bit on turning the motor, I'll report back.

I don't remember what I paid for the refurbished fuel pump but funny enough Midwest Military Equipment currently has a new OEM pump for $55 and a "replacement" version, non OEM, for $60. When I asked why they replied with, "All of our pricing just comes down to what we pay for items we stock. OEM is cheaper at the moment "

 

[M998 NYC]

I ordered my new pump from Mac Motors and it was a much better quality than the one Melton used. Old pump had a lot of travel before it was solid. I was reading on HPG and it said the spring shouldn’t show on the right pump. I did notice that spring showed on old pump but not on new. I don’t know if It makes any difference, I’m just throwing it out there

Good to know, I'll check it out when I'm back at the garage

 

[papakb]

Spectra Premiun SP1143MP fuel pumps for the HMMWV currently run between $20 and $40.

https://herko.com/Retail/spectra-pr...sp1143mp-for-am-general-hummer-1993-1993.html

SPECTRA PREMIUM SP1143MP Fuel Pump | Shop Now at RockAuto

SPECTRA PREMIUM Fuel & Air Parts and More for Your Vehicle at Reliably Low Prices. Fast Online Catalog. DIY-Easy. Your Choice of Quality. Full Manufacturer Warranty.

www.rockauto.com

 

[Mogman]

You probably have more issues than just a pump, have you removed the troublesome check valves?, cleaned the fuel tank and replaced the pickup sock?

 

[blutow]

It seems you are running into the same issue w multiple lift pumps. I would consider the possibility that it’s something else. I’d look on the supply side of the pump, particularly the fuel tank and filter sock in the tank. Sounds like it’s working for a while and eventually getting plugged up, which sounds like junk in the fuel system building up somewhere.

 

[blutow]

You probably have more issues than just a pump, have you removed the troublesome check valves?, cleaned the fuel tank and replaced the pickup sock?

You beat me to it, exactly my thoughts.

 

[TNDRIVER]

(go to underlined below to skip earlier details)


Where to begin… Last summer I was having some fuel delivery issues on my M998. Basically it would run out of fuel on a full tank while driving. Not a convenient issue to have.

Problem seemed related to the fuel pump so I swapped it with a refurbished and the issue persisted. Ended up working with a local mechanic who suggested swapping it for an electric pump, so I got a 24v pump with 5.6.5psi (meant for a Hitachi excavator). It worked great for 6 months then the issues started again … driving along and then the truck suddenly sputters and turns off. Cranking and nothing.

ANYWAY, didn’t get too far with the TM and there’s not much online about humvees with electric fuel pumps, so I got another mechanical fuel pump and had to get a new push rod since I misplaced the one I had thinking I wouldn’t need it again. Both are original parts from Midwest Military but so the next issue has me kind of baffled.


I can’t get the fuel rod back into the block. The original slid right out, and the replacement is an original part so can’t wrap my head around it. There’s nothing I found online about others having trouble getting it to slide back in (vs. STAYING in while fitting gasket) .. Is there something obvious I’m missing here? Again, don't have the original I took out to compare to the one I bought, which I have no other reason to believe isn't original.

After inserting it into the block by about an inch I can feel it slide into the right place for about another half inch, then it won't budge further. I can’t find posts about others having this issue so makes it more likely we're overlooking the obvious.

What could prevent the block from taking the rod? Could the bushings be damaged? Corrosion? Should I just hammer it in hoping it can slide once in? Sand down the rod?
Any suggestions on that or my larger fuel delivery issue would be greatly appreciated.

When you get through with the pump I would suggest that you check the fuel system for BIO contamination. REMOVE and inspect the fuel filter, LOOK at the inside of the fuel tank for contamination that could stop up the sock on the fuel pickup. Just my 2 cents.

 

[Milcommoguy]

Free information and observations. NOT directed at anyone, anytime, anywhere or any HMMWV. Just burning bandwidth. CAMO

Depending on the fuel pick up filter... factory or a hack replacement, there maybe a flow by-pass valve on the end that even if it filter get clogged it can open and pull crap fuel AND crud right up the lines.

Something to read on this related issue. Some info may apply > https://www.dieselhub.com/maintenance/6.5-diesel-fuel-tank-sock.html

Seems like more and more of the same old problems showing up here. Lately fuel or electrical (Not looking to be that old crank) Yes, the HMMWV is a driving experience. IMO the BIGGER experience is not in the drivers seat, but on a creeper riding around under the rig or under the hood. LOL Not as much fun (can be) but not doing it, getting to "know the workings" and the TM's... or down the road it will BITE one in the BUTT.

As a side note... Be careful dropping it off at the "dealer" Ask lot of question first. Like the sign says in the shop " First question free. Additional $1 each one, till I get one right that you like" DUH... I don't know what that means BUT go with a experienced, reputable shop. No time to start a training class on your dime. TM's are FREE.

This photo is OEM GM tank filter as found in my HMMWV tank. Common filter in this application. Shown full size to see the valve.


Knowledge is power and money in the wallet for HMMWV owners, CAMO

 

[M998 NYC]

You probably have more issues than just a pump, have you removed the troublesome check valves?, cleaned the fuel tank and replaced the pickup sock?

It seems you are running into the same issue w multiple lift pumps. I would consider the possibility that it’s something else. I’d look on the supply side of the pump, particularly the fuel tank and filter sock in the tank. Sounds like it’s working for a while and eventually getting plugged up, which sounds like junk in the fuel system building up somewhere.

Yep we dropped the tank last year to troubleshoot the sender and the tank was surprisingly clean. Tank sock looked pretty clean too but I regret not doing a closer inspection considering the current situation.
Planning to check to the fuel injector next. Any and all suggestions appreciated, thanks for your time and help!

 

[M998 NYC]

When you get through with the pump I would suggest that you check the fuel system for BIO contamination. REMOVE and inspect the fuel filter, LOOK at the inside of the fuel tank for contamination that could stop up the sock on the fuel pickup. Just my 2 cents.

I replaced the filter only about a year ago but a good idea to check. Hoping to not have to drop the tank again for a closer inspection of the sock but one thing at a time! Thanks for your input here

 

[M998 NYC]

Free information and observations. NOT directed at anyone, anytime, anywhere or any HMMWV. Just burning bandwidth. CAMO

Depending on the fuel pick up filter... factory or a hack replacement, there maybe a flow by-pass valve on the end that even if it filter get clogged it can open and pull crap fuel AND crud right up the lines.

Something to read on this related issue. Some info may apply > https://www.dieselhub.com/maintenance/6.5-diesel-fuel-tank-sock.html

Seems like more and more of the same old problems showing up here. Lately fuel or electrical (Not looking to be that old crank) Yes, the HMMWV is a driving experience. IMO the BIGGER experience is not in the drivers seat, but on a creeper riding around under the rig or under the hood. LOL Not as much fun (can be) but not doing it, getting to "know the workings" and the TM's... or down the road it will BITE one in the BUTT.

As a side note... Be careful dropping it off at the "dealer" Ask lot of question first. Like the sign says in the shop " First question free. Additional $1 each one, till I get one right that you like" DUH... I don't know what that means BUT go with a experienced, reputable shop. No time to start a training class on your dime. TM's are FREE.

This photo is OEM GM tank filter as found in my HMMWV tank. Common filter in this application. Shown full size to see the valve.
View attachment 869046

Knowledge is power and money in the wallet for HMMWV owners, CAMO

Free information and observations that are greatly appreciated....
I haven't replaced the tank sock but inspected it last year and seemed fine.
The DieselHub.com resource is great, thanks for your help and advice.