Starter/Electric/Carb Problem 1985 GMC

[Harrycarry]

Hi All, This is a great site. I have a 1985 GMC 1 Ton with a 454 motor. When I turn the key nothing happens until I tap the starter which sparks around the solenoid then go back in the cab and it cranks. This also effects the headlights and other electrical items. Another unrelated problem is with the carb I believe. The other day the truck was running fine until suddenly it backfired thru the carb and barely ran at all unless I floored it but just barely ran. I changed the plugs, dist cap and rotor. No difference but when I tap around the carb it starts running pretty good then dies again. The carb is a Rochester Q-Jet which I don't believe is original because it's not electric choke. Any advice would be greatly appreciated. The truck has been sitting for a couple of years and I'm slowly getting back to working order.

[strokd 84]

Before I got my motor tuned right, I had some back fire issues. I was running a little more tempermental Holly Carb, but everytime it back fired, I had to replace the power valve in the carb. Power valves are pretty cheap and not hard to change. For your carb problem, I'd start there.

I'm not sure about the starter. They're pretty cheap to replace. I just bought one for $40. You might start there...

[Srubydo1986]

For the starter the wires might be loose or the starter is just going bad.

For the carb check the gascket around it to the mainfold. If it been sitting then it might have goon bad<also u you said when u tap it so it leads me to think its loose or bad gasket.

[84slopwaggin]

Yeah you could spray wd-40 around the base of the carb and see if the rpm's raise up or stay the same. If the rpm's raise, then the gasket is bad. Check the starter wires for looseness. If they're tight, then remove it and have it tested. Basically the samething Scrubydo said.

[Harrycarry]

Thanks for all the info guys, I'll be going out to the truck in a couple of days to check the things mentioned. Does a Rochester have a power valve or is that the same as power piston? Also why would starter wires have anything to do with headlights? Are the wires crossed or is this normal?

[Srubydo1986]

juice from the batter runs down to the starter from there is goes to a fuse block on the fire wall i think the juice from there runs power to most everything like us alot of juice so if one of those things are loose not enough power is brought or youll get an arking effect.

Hope that halps on the light question if that doesnt help the lights check the swith it maybe loose or going bad.

[lurch115]

just a little tip...Holley carbs. are the only ones with a power valve....what probably happened with your q-jet is that the back fire may have been strong enough to shift something inside the carb....i'd get a rebuild kit and rebuild the carb....those carbs. are easy to rebuild and the kit(and float) cost about $30 from a local parts store....as far as the starter. i'd say go to a local dealership and get a new one....you'll spend more than you would at a parts store, but you also won't be replacing it every 6 months

[Harrycarry]

Thanks for the advice everyone. I replaced the starter and that solved that problem. As for the carb, it turns out the pcv valve was bad even though it rattled when I shook it. I think there are still timing issues and carb issues to deal with but she's running pretty good now.

[scotto0609]

Where on L.I.?

[Harrycarry]

Huntington How about you?

[scotto0609]

Directly south, Babylon.