Surging, stumble and stall

[Ajax MD]

I have a *very* intermittent problem that is beginning to rear its head. (Engine is a 2005 6.5L installed in an early M998 paired up with the 3-speed).

Twice, when cold, my truck has exhibited a surge. One of those times, in the driveway, it actually revved up and stalled. I simply cranked it for a bit longer than normal and it started up just fine.
I thought perhaps the problem was low fuel level in the tank, sucking air with the fuel pickup. The second surge/stumble incident, the gauge read 1/2 so I doubt that's the case.

This only occurred for a few minutes when the truck is stone cold (so far). The truck drove perfectly fine after that. I feel that this would be easier to troubleshoot if the problem were more frequent.

I'm aware that the fuel pump could be slowly failing but what else could I examine before defaulting to that?
Are there hard seals that could be allowing air to enter the system in cold temperatures?
Is it true that new fuel tanks won't fit in trucks with the early parking brake?

I appreciate any advice.

 

[Mullaney]

I have a *very* intermittent problem that is beginning to rear its head. (Engine is a 2005 6.5L installed in an early M998 paired up with the 3-speed).

Twice, when cold, my truck has exhibited a surge. One of those times, in the driveway, it actually revved up and stalled. I simply cranked it for a bit longer than normal and it started up just fine.
I thought perhaps the problem was low fuel level in the tank, sucking air with the fuel pickup. The second surge/stumble incident, the gauge read 1/2 so I doubt that's the case.

This only occurred for a few minutes when the truck is stone cold (so far). The truck drove perfectly fine after that. I feel that this would be easier to troubleshoot if the problem were more frequent.

I'm aware that the fuel pump could be slowly failing but what else could I examine before defaulting to that?
Are there hard seals that could be allowing air to enter the system in cold temperatures?
Is it true that new fuel tanks won't fit in trucks with the early parking brake?

I appreciate any advice.

.
Cheapest possible fix is to treat the fuel with additive.

There are more opinions on what to use than people, so a trip to Tractor Supply or somewhere similar and then go drive a half a tank of fuel out - and see if things got better. I had what I call oscillating that was about to drive me BS Crazy. Treated the fuel and the problem is gone and has stayed that way for over a year now...

 

[Retiredwarhorses]

Air in the fuel system, check all rubber lines, especially the water separator hose and all hose clamps.

 

[Ajax MD]

Air in the fuel system, check all rubber lines, especially the water separator hose and all hose clamps.

I'll get right on that. Thanks for giving me a good starting point.

I do put PS diesel fuel supplement in the fuel.

 

[Thumper580]

You probably have but new fuel filter and strainer and cut out the check valves in the supply and return lines under the truck, right side in front of the fuel tank. You'll need a foot each of 1/4" and 3/8" ID fuel line. A good diesel fuel additive/cleaner is always a good idea as well.

 

[Mogman]

The late fuel tank will not fit with the driveshaft mounted parking brake.

 

[Ajax MD]

The late fuel tank will not fit with the driveshaft mounted parking brake.

Can old style tanks still be had?

 

[Thumper580]

Can old style tanks still be had?

If I'm allowed to say so there is a NOS 998 one on ebay for $145.00. Type in: hmmwv fuel tank.

 

[Mogman]

By part number that is a late tank

 

[Ajax MD]

If I'm allowed to say so there is a NOS 998 one on ebay for $145.00. Type in: hmmwv fuel tank.

Also, what was the purpose of the check valves? Is there any consequence to removing them, such as loss of fording ability or anything?

 

[Ajax MD]

Looks like the old ones are still available:
Fuel Tank Shell for EARLY Humvee M998 A0/A1; 2910-01-263-3224 5582606 12338588 | eBay

I'll investigate upgrading the parking brake to the wheels before buying the old style tank though.

 

[Mogman]

Looks like the old ones are still available:
Fuel Tank Shell for EARLY Humvee M998 A0/A1; 2910-01-263-3224 5582606 12338588 | eBay

I'll investigate upgrading the parking brake to the wheels before buying the old style tank though.

That is very likely an import tank, there is no nomenclature or part numbers visible

 

[Mogman]

Unless you have a hole in your tank it can simply be cleaned out if needed.

 

[diesel dave]

I have a *very* intermittent problem that is beginning to rear its head. (Engine is a 2005 6.5L installed in an early M998 paired up with the 3-speed).

Twice, when cold, my truck has exhibited a surge. One of those times, in the driveway, it actually revved up and stalled. I simply cranked it for a bit longer than normal and it started up just fine.
I thought perhaps the problem was low fuel level in the tank, sucking air with the fuel pickup. The second surge/stumble incident, the gauge read 1/2 so I doubt that's the case.

This only occurred for a few minutes when the truck is stone cold (so far). The truck drove perfectly fine after that. I feel that this would be easier to troubleshoot if the problem were more frequent.

I'm aware that the fuel pump could be slowly failing but what else could I examine before defaulting to that?
Are there hard seals that could be allowing air to enter the system in cold temperatures?
Is it true that new fuel tanks won't fit in trucks with the early parking brake?

I appreciate any advice.

Years ago I had a Mack with similar issues. I finnaly called a heavy truck repair shop and was told I better get it in for repair ASAP. They recommended towing. Not wanting a big towing bill,I opted to have a driver take it to the shop. Big mistake. On the way,the IP went to WOT and trashed the engine. Maybe these little IP’s aren’t prone to this,but if it were mine,I’d talk to a IP specialist. My $.02.

 

[Ajax MD]

I think I've found the problem. I observed drips under the truck. Fuel is weeping from a pair of lines near the top of the tank, wicking over and dripping down off of the transfer case. It's definitely diesel and not ATF or any other fluid.

Looking at the diagram on p. 2-113 of the -280-20-1, these appear to go to the top of the tank. Either the hose clamps need tightening or the lines have chafed through. I can move the tank around a bit simply by shoving it around so it's entirely possible that road vibration chafed through something.

I'm assuming that the engine is sometimes drawing a bit of air when pulling from the tank, causing the stumbling.

 

[TOBASH]

Years ago I had a Mack with similar issues. I finnaly called a heavy truck repair shop and was told I better get it in for repair ASAP. They recommended towing. Not wanting a big towing bill,I opted to have a driver take it to the shop. Big mistake. On the way,the IP went to WOT and trashed the engine. Maybe these little IP’s aren’t prone to this,but if it were mine,I’d talk to a IP specialist. My $.02.

If your Mack was computer controlled then the PCM a went bad causing WOT. We do not have PCM with DB2 IP’s.

 

[diesel dave]

If your Mack was computer controlled then the PCM a went bad causing WOT. We do not have PCM with DB2 IP’s.

This Mack was/is old school. No pcm,computers,emissions crap. Still on the job in my former business. The problem was in the ip.