Looking For Some Answers - Or Not

[Bthrasher4]

I have an AM General M923 I recovered from Jefferson City, MO. The truck was completely rebuilt in November 2010 and since the last servicing in 2010 the truck was only driven 325 miles. During the recovery (on the road coming back to Northern VA) the voltage regulator took a dodo and first cooked the alternator and took out the control module (The black box on the firewall) just outside of Jeff City. I replaced the control module and the alternator. I was able to get the truck going again (go figure). So I drove for a number of hours with no issue, until I got just past St. Luis, MO. I started noticing that the truck would not accelerate and little by little I was unable to get going more that 15 or 20 MPH. I even had to shift the truck into 6x6 low to get over some of the peaks (on the highway). I drove back to VA like this (it took 36 hours) as I did not have anyone with me and very few tools. This recovery was a complete nightmare.

My local mechanic (pretty savvy guy on cars and commercial vehicles - does all the repairs on the country trucks) and I have checked and changed the fuel filter and the usual suspects (i.e. fuel jelling, changed all the fluids and filters on everything else), but cannot find any obvious problems. Just as a side note, Going in reverse the truck has the proper acceleration and everything seems to work right. In drive the truck will not accelerate or go up any type of incline. It has been suggested that some type of solenoids in or on the transmission might have gone out, but I cannot find anything in the TMs regarding this issue (OK, guys I am not much of a mechanic regarding trucks -my specialty WAS hotrod cars years ago). I really am trying though.

Any recommendations, advice or people here in the Western part of Northern VA that are military master mechanics for trucks that can provide some type of assistance...I am at a loss and super frustrated.


Bob Thrasher
703-728-6164
tsa_thrasher@comcast.net

 

[wheelspinner]

Wow Bob, sorry to hear you are still battling this. Really does sound like a tranny prob. Do you have the Allison book? I can send it to you.

 

[Bthrasher4]

I do not...If you have a PDF version that would be great...

 

[wheelspinner]

Its in your email. Its a start at least.

 

[rrrr]

Sounds like a fuel starvation problem. Did you make sure the manual shutoff is fully open ?

 

[GHall]

Does the truck start, run, idle and rev up like it should in neutral? Which motor are you runnin, turbo or natural?

 

[NDT]

Clearly a fuel problem. If the transmission or other power train component was to blame, it would be glowing red after absorbing 240 horsepower for hours.

 

[GHall]

Smell the tranny fluid, if its bad it would have a real burnt smell after a trip like that. Tranny fluid in those things is originally oil not dex so it's gonna be brown instead of red.. It's under a trap door in the cab on the passenger side floorboard.. But I'm withe the other fellas on the fuel deal. If not the stop lever on the IP then maybe a big ole air leak?

 

[Artisan]

I am a plumber so I am only guessing BUTSOMEHOWEVER...

If you fired stuff you prob fried the fuel shut off device, it has a manual override.

Open this valve as shown and if all is now well replace the valve.

IdahoMotorpool has them for 55 bux. I need a spare too.

 

[Artisan]

Here is the valve off the truck that might be fried.
I am told you only need to unscrew the 4 tiny screws
and replace that part of it vs replacing the whole thing.

Get another opinion please.

 

[WillWagner]

Does the pump look like the one in the above post or does it have a big housing on top of it with a second lever or shaft out the side at the rear?

Like this....

 

[Bthrasher4]

GHall and all

The M923 is a standard model and is running the Cummins 250 (No turbo)...The engin seems to run normal and rev fine in Nutrual...the truck runs perfect in Reverse...just has problems in Drive (forward)...When we first started looking at it, I figure the fuel filter was going to be the solution (but that did not change anything)...it looked clean and no gelled fuel in the tank or filter.

I will check (as you guys have recommended) the fuel shut off. Thank you all...these all make sense...It also seems likely that the fuel shut off valve fried when the voltage regulator took a doodie...

Artisan

Allthis looks like I need to review this as I have a funny feeling it is thr porblem..Thank you

 

[Bthrasher4]

WillWagner....not sure, but once the ice storm coming my way passes, you can bet I'll be looking.

Thanks guys.

 

[ranchhopper]

Its probably like was stated a fuel starvation when revving in reverse or neutral you are probably not running an extended period of time like going forward down the road which will use all the fuel in the system then it starves out pop open the air cleaner and check for obstructions or mouse nests air starvation will do the same thing. Also have someone look at the exhaust when it starts to act up usually a lot of exhaust smoke will give you a clue of air or fuel starvation.

 

[Bthrasher4]

Guys...all great recommendations...can't wait to get a chance to look all this over on the truck...I have ordered a new Fuel cut-off valve (solenoid) just to be sure...After sitting down and looking over all the symptoms, it totally makes sense regarding the fuel starvation (which I had a feeling it was), but I was looking in the wrong place (I looked at the carb and the fuel filter, as these are the common places for muscle cars). And I thought the new cars on the road were complicated...these military trucks have so many more "systems" onboard to maintain and check for problems...what ever happened to the simple vehicles of the 60s...

 

[MO MV man]

The fuel solenoid is an easy job.
It was inop on my M923 from Fort Leonard Wood.
Picked one up for $52 delivered from C&C.

Artisan's previous pictures and explanations of the manual shut-off and solenoid bypass thumbscrew are outstanding.
Great info.

Somewhere in the TM's I recall seeing a picture of a tiny metal-mesh filter that goes in from the top of the injection pump.
Anyone have any insight into that?

 

[pctrans]

You also need to disconnect the fuel line behind the filter head, and where it connects to the tank. Spray some brake parts cleaner in one end and blow the line out to make sure there is no algae buildup in the line.

 

[GHall]

Somewhere in the TM's I recall seeing a picture of a tiny metal-mesh filter that goes in from the top of the injection pump.
Anyone have any insight into that?

I saw that same filter and asked the same thing.. What I got in response was that many people have checked it many times and it always looked fine. What I was told is it's for when the IP goes bad, it's supposed to keep metal particles outta the system.

 

[Bthrasher4]

PCTRANS

Great idea...I was wondering about any type of buildup as Diesel does get and have live microbes in it. I purposely put a fuel stabilizer/algaecide in all my diesel powered vehicles/items.

Thanks you all

 

[GHall]

How's it lookin Bthrasher? Any updates?