The Stovebolt Site Forums The Parking Lot Big Bolts coe wont stay running...

I just put a new carb on my 47 gmc and shes having issues, she did this before as well. When she does start, she runs a real high idle for about 5 seconds, then stumbles and unless you pump the pedal she'll die. Repeat high idle for about 5 seconds and stumble again...

Any ideas? She also doesnt like it with the choke all the way off but I havent gotten her to stay running long enough to push the choke in...

Gas line is clear, good spark. Do these updrafts typically run at a higher idle then the downdrafts?

Thanks, Jeff

Just a thought..have you checked the fuel pump for pressure????

Geoff

Alright, on a whim I swapped out the coil and she stays running now... Go figure...

She still has the high idle issue. Might be that its idleing alright and it just sounds that way cause she has 3' of exhaust pipe left :rolleyes:

Either high idle or no idle. So maybe these updrafts do idle higher???

Even if the fuel pump wasnt working the gas tank sits 6' off the ground so gravity would be more then adequate to fill the carb.

Hey Rusted,

Mine idles fine. So no updraft higher idles. I presume you've adjusted the idle screw? Should have one and should allow you to go below idle, in other words, I had to give mine a little of the idle screw or it won't run at all. I'm thinking intake leak? Is it possible on this type of truck? That would also account for it not liking the choke all the way in. If it's getting too much air, then it may want less intake from the "throat". Are the linkage shafts tight? no play? All the pieces back in place? Can the intake manifold have leak or crack?

i just checked out some pics of your COE and that is one bad ride....Metz Beer, what a cool truck and great patina, glad to hear you got your coil figured out

Tom I think If for some reason it was cracked Id hear it or notice (granted my square head dont fit underneath the floor to well!). Ive adjusted the idle, it just seems to like the high idle. You have the carter carb, this has a zenith but it still seems a little odd that she doesnt like idleing any lower. Im tinkering and she will run without the choke now, but stutters a little after 5-10 minutes and eventually dies.

I think to much rust and dirt covering it for an intake leak

All the connections, linkage and whatnot seems to be in working order, maybe Im having gas restriction issues but Im pretty doubtful as Ive cleaned most of the crap out of the tank and have a paper filter under the tank to catch the rest of the leftovers, plus Ive blown out all the lines and so on.

Thanks for the compliments vonguinness!

Along with the carb ajustment make sure that your timing is corect. Set the timing then the idle mixter and the idle last. You may find you have to go from the back and forth between the idle mixter and the ilde a couple of times they will afect each other.

One other thought ... could there be a vacuum issue? I'm reaching at straws, but who knows?

Hey rustednuts, I've had idle issues with my 235 also so will pass on what I've learned. It sounds to me like you have a vacuum leak and beaware that there are lots of places other than the intake manifold from which they come. Since you just put a new carb on it maybe the mounting gasket is leaking. I remember reading a post that the insulator should have gaskets too. Check your two speed if you've got one. Shift it from hi to low and see if that makes a difference. Also your hydrovac can leak too. Try pushing on the break pedal hard and hold it there to see if that makes any difference. Check the wiper motor. And don't forget the vacuum advance. Start at the main vaccum inlet on the intake, plug it and see if it makes a difference. Then just start eliminating possibilities. It dosen't take much of a leak, but if your compression and everything else checks out she should idle... good luck

give it some back pressure, is my vote.