It Runs!!

but not for long.


After all the hard work the last month or so, we finally got to try to start the XM215 today. It last ran four or so years ago, before being parked in the junkyard.

After several tries cranking, with no firing, the problem was diagnosed as dirty points by Ron of MV R&R, (never mind the need for the ignition switch to be on, which I did figure out myself), the points were cleaned and it fired up.

However, due to an apparent air leak at the base of the carb, which is yet to be fixed, it wanted to run full throttle, so had to be shut off after ten or so seconds at a time.

However, It had good oil pressure, air pressure was building, and the batteries were charging. It sounded great, if a little loud due to an exhaust system that is full of holes, but that's another project.

Eric

Great news. The XM215 is very worthy of a restoration.

That's awesome Eric! Congrats. It is such a good feeling to hear a truck start up for the first time after so much hard work. Keep us posted!

Great job! Now get us some pics dammit!

Theres getting to be a nice accumulation of dumpers in this group of military truckers. Those early GMC's are easy to work on and they are good ole engines. Mine had a miss in it and I put new plugs, points and condenser in it and found one plug that had a broken electrode in it. Runs good now. I am looking forward to pictures and some history on your truck. Does it still dump? Have a winch?

Guys, Pictures can be seen here:

http://www.steelsoldiers.com/index.php?name=PNphpBB2&file=viewtopic&t=10011

It supposedly dumps, just have to get it running first.

Eric
It originally had a winch which was removed, however,thanks to cbvet, I do have a winch and all other pieces sitting in storage nearby.

Well, after removing the carb, and installing new gaskets, it appears as though that was not the problem.

As it turns out, the linkage seems to be worn enough that the gas pedal will only return to within all but a 1/4 inch of idle, so it revs way up.
Ron and I were going to attempt to make a new u-shaped bar that is a quarter inch longer to compensate for this.

First, I have a question before doing all that. Currently, the throttle cable on my truck is broken off, however, we do have one removed from a parts truck. My question is, if I hooked up the throttle cable, would it have enough tension to hold the throttle at idle? Hopefully one of you has some experience with this.

Thanks in advance.
Eric

The throttle cable is used to open the butterfly and has no positive action toward closing it.. For temporary use just put a screen door spring on the linkage to pull it shut..and adjust the idle speed screw accordingly. ACE

OK, still having problems with the linkage.

My linkage is the one which has two smaller springs alongside the carb by the engine. since one of these ended up broken anyway, I went and replaced them with springs that seem to be quite a bit stronger. Now when we went to fire it up after that, it didn't rev up so high, only twice that of idle or so.

Thinking that the problem might be the bracket mounted to the manifold, because it seemed to be wobbly, I swapped it with another one which seems to be less worn off a parts M135.

It only seemed to make it worse!! Once again, it wants to rev way up.

This is stumping us all, because all the linkage seems to be fine, and operating correctly, and all the idle screws and such are adjusted properly.

My only thinking now is that the problem involves the carb. As some of you are no doubt aware, with the linkage disconnected, the carb itself keeps the bracket down some, and this is all the further that my linkage will go. Is this the way its supposed to be?? Could this be an internal problem in the carb? I really hope that one of you with more experience could give me some advice.

Thanks so much.

Eric

I am not an expert , but I keep thinking that something is missing on the linkage at the carb? I mean it is flopping freely instead of being directly connected, although it looks connected? I will take a look at mine to see if I can help.If the throttle for example, doesnt firmly hols the carb open and something is spring loaded at the carb, possibly a small sping is missing at the carb? There is a governor on this engine, so there must be a way the governor can change engine rpms without it being restricted yet spring loaded? Hard for me to explain. Look at a engine the same as yours to compare.Let us know, we want to help you.

Eric, I took a good look, and There is a spring on the throttle bracket from the firewall to the linkage and a spring on the crossshaft that goes on top of the exhaust manifold, but even with one of them missing it should be o.k. Question: When it over revs, can you see any of the linkage move? My other guess is , possibly something disconnected inside the governor ? I noticed some kind of vacuum line to the governor, Is that intact? Any signs of anything being taken apart and possibly not reassembled correctly? If you still need halp maybe I can post a picture of mine for you?

I just mthought of another possibility. Because this truck had been sitting, possibly there is some corrosion or stickieness in the guts of the carb, due to non use? So when you gave it the increased rpms it didnt return to idle. You could try spraying "Gumout" in and maybe it would return to idle. I bet it is old gas tar deposits in the carb. Gee, I am getting obsessed with this. Try the gumout. Thats the easiest thing to do first.

Possible answer.

Well, in the half hour I had today, I tried out a few of pa rich's suggestions.

Actually, first I double checked the idle speed screw, cause you just never know

Next, I went to check/tighten the governor vacuum line. So, I put the wrench on, and it tightened! Odd, I thought, because I know I tightened it before. I disconnected the line, and found brass shavings on the end of the line!! As it turns out, the fitting was not only mostly stripped, but also loose where it goes into the governor.

I don't know if that's the answer or not, but its a good place to start, as I examined the carb with the top off, and with no springs attached, the butterflies are 90% closed on their own.

pa.rich, I think I might owe you a drink one of these days

Thanks
Eric

Holly carb

Hello Eric,
When I installed a NOS carb on my GMC it went to wide open when first started. Figured out the the linkage on the carb was backwards, holding the butterfly valve wide open. This carb is the same one used on the M35 gasser, but the linkage is reversed.
Don't know if this helps?
Karl

RE: Holly carb

Karl,

I belive the linkage appears correct now, as it seems to be doing what it should... Still I will doublecheck.
Thanks for your help.

Eric

RE: Holly carb

Eric , it is holding butterfly closed when not touching it? That is, when linkage connected, it shouldnt be wide open.Someone may have messed with this at some time and gave up on it and parked it. If you need pictures of something , let me know, I will get " my people right on it". [My camera savy wife] Also, This is hard to diagnose over the computer. Its gotta be something simple, I gave some suggestions, but something like this is probalbly some thing like a mouse in there stuffing up the carb? Gee when a vehicle has set idle those insects and small critters can get in there. Was the air filter on it when you recieved the truck?Mine had those mud dabber nests all over the engine compartment in the strangest places and the air filter canister on the firewall was full of mouse nest materials. When I took it apart, I was surprised it even ran. I cleaned and repainted it and refilled with new oil. That air filter is the nicest part on the truck

RE: Holly carb

yes, with no springs, the butterflies are nearly closed by themselves.

RE: Holly carb

You might have the springs pulling the wrong side of the little turn thingy. Are you sure they pull the butterfly closed?

RE: Holly carb

yes, the springs pull them nearly shut. I think that the stripped out fitting was causing a vacuum leak for the governor, which caused the governor to open the butterflies.

RE: Holly carb

The only springs on mine are on the cross shaft on the Exhaust manifold and the throttle brackt. at the firewall, are those still there on your truck?Mine doesnt have any other springs than that , no springs on the carb itself.