m35a2c clogged fuel system

Just bought my first M35a2c from GL at Warner Robins AFB. Its a 86 Air Force truck. with 9k miles and 400 hours. I found that the fuel system was stopped up with crude. I took the tank off cleaned the pump screen and all slude off the bottom. changed all the fuel filters also. The problem is the truck will start when cold but rpm's climb to over 2000 and will slowly drop about 10 sec's later and then quits running. Will not start for a couple of hours only to repeat same problems. I have bled all the fuel filters and checked all of the cables and have run out of ideas!?!

are all the lines CLEANED out? or is fuel barely passing thru? Have you blown out the lines with air?

Just give it to me, it's totally broke.

Did you change 3 filters, and not just the 2 on the engine? You mean engine goes to 2000 without you pushing the pedal? Sounds like a fuel starvation issue, and maybe a broken return spring on the pump. could be other things, let us know.

Dennis

Thanks for the reply. No I didn't blow the lines out but after I cleaned the screen on the tank pump the fuel shoots out of the bleed valves. Think I still need to blow the lines?

Yes it goes almost to the red line without hitting the pedal. when the idle drops the throttle has no effect almost like its unhooked (but its not). I changed all three filters and put clean fuel in the tank....

Sounds like a stuck IP plunger

Can I take a look at the IP plunger with out take the whole pump off? (that looks like a job)

Ehh, I'd wait for more experianced guys to chime in. I thought about it, and it might just not run with a stuck plunger. I'd hate to put you through alot of work for nothing. There is a cover under the IP head, if you open that up, does that linkage move freely? I will be back in a min with a pic.

yes the linkage moves freely as well as the shut-off linkage....I mean the
external linkage

Pull off the cover and see if this moves freely:

Thanks...a picture is worth 10,000 words....I will check at first light. should it move fairly easy or have alot of tension? thanks again

Free as a bird. I had one truck that it siezed up in. No fun.

I just worked on the same problem. The fuel system had sludge in it. After
cleaning the tank, filters etc, I also had the 2000 rpm then dying problem

I suspected the IP timing was off, so I removed the IP pump. I wanted to make sure everything was installed correctly.

Remove the cover on the the fuel cutoff and check the movement of the linkage just like Gimpy showed you. The fuel cutoff is probably sticking shut. It should move freely.

Turned out that that my Fuel Control Rod was gummed up. You should remove the Hydralic Head and clean the fuel passages. The instructions are in the IP manual TM9-2910-226-34 and the LDS Troubleshooting manual. You can remove the head without removing the whole pump.

Also clean the Overflow valve on the injector pump and the bypass valve on the secondary/final fuel filters as they are problably gummed up as well.

If you have specific questions PM me.

Warthog

Thanks alot guys... I will get started in the morning. Hopefully my first retirement project will be running when I write back. DP

Man, wheres the the 3rd filter at ( the lil one thats supposed to be on the frame right )? Me and Woody have looked all under both are trucks and cant find that son of a gun! Not meaning to highjack!

Alredneck said:

Man, wheres the the 3rd filter at ( the lil one thats supposed to be on the frame right )? Me and Woody have looked all under both are trucks and cant find that son of a gun! Not meaning to highjack!

Click to expand...

The 3rd(is actually the 1st, it's the primary filter) is under the generator/alternator, mounted on the inside of the frame rail.




Dpsmith, did you change all 3 fuel filters? You need to to be sure they are not plugged. If you had gummed fuel in the tank, I would expect the filters to be the same. While you have them off, blow out your lines with compressed air. After doing all this, if it still has a problem, look at the ip for sticking.

Yes Sir I did change all three filters and you were right they all were varnished up inside. I went back this morning and blew out the lines I think they were ok but at least now I'm getting good clean fuel to the top. seems to have good pressure. I moving on now to the IP will let you know what I find. Cold outside today and I'm moving slow...Thanks for yall's help..

How's it run with the filters/lines cleaned out? You might not have to mess with the IP with some luck...

My luck was'nt so good. After blowing the fuel lines out I had all my fingers and toes crossed but the truck still did the same.