Fuel system trouble

[04mustang]

My city just received 2 1990 6.2 M998's. We have been going through them and getting everything up to par but keep having an issue.

On both trucks when they are running and accelerator is pressed and let off suddenly (like you would do coming up to a stop sign) the trucks die and must be restarted.
We put clean fuel in them, changed fuel filters (didn't look bad), bled the fuel lines at the injectors (some air but not really any to amount to anything), and the last step was putting a new lift pump on. None of this really changed anything.

My thoughts now are revolving around the IP and swapping or rebuilding it. Does anyone have any other advice or suggestions? or a place to get a replacement IP that doesn't cost $2000.

Thank you,
Corey

 

[Wire Fox]

I had the same issue in my HMMWV and it was resolved with an IP rebuild. I made use of DieselCare (based in Tennessee). You can use their main website http://dieselcare.us, or you can find them on eBay and pay less than $300 for the rebuild service, which includes shipping both ways. To be on the safe side, make sure you send them a note that you're sending them a 24V military pump. Caveat: if they need to replace components beyond the standard service, they will charge accordingly. So a new rotor, solenoids, or the like will be extra; however, seals, filters, engine block mating gasket, and connectors would be included. If you don't want your engine hanging open for two weeks while you wait for them to receive your pump, rebuild it, and ship it back, then buy a used core from a member on here or on an auction site and send that in instead, which should only be an extra $50-100.

Edit: Just wanted to note... they don't try to act like a retail establishment, just a wholesale parts house. They're not going to help you diagnose any odd issues with your engine beyond the parts that they've sold you, but they will rebuild your pump and rebuild it right...and if you can show that they did their job wrong, they'll make it right. That said, they did a very professional job on mine. Everything was clean, calibrated, well-assembled, sealed for storage, and they even went to the detail of engraving their own tag and riveting it in-place of the old tag, showing the correct model information for how the pump was built and tuned (I had them build it differently than what was sent).

 

[04mustang]

Thank you wire fox for the info.
I wanted ask about the IP's though. I see that the parts TM has separate listings for 6.2 and 6.5 which is understandable but it lists 2 different IP's and part numbers for the 6.2 for before and after 1990 year model engines. would this come into play here? I see on their website that they list the 6.2 IP for 1982-88 only.

 

[Wire Fox]

Thank you wire fox for the info.
I wanted ask about the IP's though. I see that the parts TM has separate listings for 6.2 and 6.5 which is understandable but it lists 2 different IP's and part numbers for the 6.2 for before and after 1990 year model engines. would this come into play here? I see on their website that they list the 6.2 IP for 1982-88 only.

The Diesel Care website listing doesn't matter so much. They're just listing years based upon the common application, as most vehicle moved to an electronic control after that year, though the military remained mechanical with only two solenoids. They can rebuild any of them and should know what to do based upon the tag that's riveted to the pump (and actually, you can look at that yourself and see what's installed on your own engine, too). Even though your trucks are 1990 M998s, they may have had a new engine installed in them at some point, particularly they may have received a de-tuned 6.5L GEP engine. You can follow this guide to help identify which engine you have installed: https://halfmastpsmag.wordpress.com...ween-the-hmmwv-6-2l-and-6-5l-detuned-engines/ As well, the tag on the injection pump will help confirm what you find, but it is entirely possible that someone switched it and installed the wrong pump.

A thing you may want to consider only if you have a de-tuned 6.5L engine: it may be worth having them re-build your pump to the metering spec of a DB2831-5149 pump intended for a 6.5L engine...that will give you a teensy bit more power over a 6.2L/detuned 6.5L, and the engine should be able to handle everything just fine as the only real difference for power production is the pump is turned down (Yes, the injectors should be the same on all naturally aspirated 6.5L block engines). It also shouldn't cost anything extra for that, as it's just a different tuning spec on the bench for them. The only fitment difference between a true DB2831-5149 and a detuned DB2831-5209 will be the throttle lever. On the DB2831-5149, it has a slot on the right-hand side for mounting a throttle position sensor instead of a linkage for a kick-down switch featured on the 5209/all 6.2L HMMWV pump builds. So, in summary...you would ask for them to tune that 5209 as a 5149, keeping the original throttle lever as-is; all of this is moot if you have a true 6.2L block.