bigk40k

I just inherited a project truck with multiple issues. I can do a lot by myself but need some ideas of were to look and what to do, instrument panel did work at some point for previous owner, sat for awhile, and now nothing on it works, the speedo wire is partially melted cause someone ran it loose and let it rest on muffler, seems to be outer casing only but if I can get the fuel gauge and heat gauge to work I will know if thats bad.

Someone at one point had a stereo system in there and there are extra wires everywhere that are dead ends, also the old cylinder fuse has one or two wires wrapped around the cylinders that go to more fuse's?

390 with a electronic fuel pump, had a quadra jet carb on it, ran ok but quad was leaking fuel(previous owners statement) so his mechanic swapped it with a 2 barrel, not sure of brand, any specific area to look or is it pretty obvious?

And I guess it was ok for awhile but now when driving after less than 5 minutes of driving, it will start to chug like it wants to die, if you let it idle it's fine, but give it gas it chokes but not just completely die, but never revs up just continues to choke, but when driving it I noticed there is a sweet spot just off idle while barely pressing the pedal that it will go fine, any more pressure it starts to choke and you have to let off pedal and try again. Any ideas on were to start of what to try would be great TIA!

Manuellabour247

If I were you I'd go buy another QJ or similar 4 bbl. My old 75 had the 390 with a Carter 2 bbl on it and ran like you described after a while. I was told to either rebuild it or replace it. So I replaced it with a QJ 4 bbl. Ran a lot better.

As far as the wiring goes you can get wiring schematics online or in the forum there is a link. If it were me, I'd rerun all the wiring like it should be and loom it.....but that takes a while and a lot of patience. Haha. The dash wiring might be more tricky as the board may have a break in the connections that you can't see with the naked eye. Good luck and please post some pictures.

JayzDaddy

Your electrical is older than any i have messed with before so im out on explaining anything on that.

But your carb i might could help with. Change your fuel filter first, its 3 bucks and cant hurt trying. You need 3 things for an engine to run, fuel, spark, and air, it runs and idles so we know you have all 3. But think about what happens when you push the throttle, you add more fuel and air and change where the spark occurs (advance in distributor). So take a look at what you can see. Make sure choke opens when warm. When its warm look down in carb and check the fuel stream when you work the linkage . It shouldnt drip or see a heavy stream. Should be a nice thin mist looking pattern. Make sure your not getting air leaks at carb base. Spray carb cleaner around base and at vac lines and ports. If idle changes you found a air leak.

If neither of those help try adjusting the air/fuel mix. Screw the screws all the way in then back them out 1-1/2 turns. Start the truck. 1 at a time back the screws out until it hits its highest idle speed and begins to stumble. Then screw it back in 1/4 turn. Repeat for other screw. Then back and forth til its smooth as melted butter.

bigk40k

Ok after some investigating it's an auto lite carb, and the butterfly valve arm is missing a spring so it always stays wide open, also I'm at high altitude if it makes a difference to anyone posting, gonna replace that spring and go from there.

After more research it is the fast idle cam, it is not seated at all on the adjustment screw so that needs to be fixed but would that cause the choking issues while driving?

JayzDaddy

Its possible. I aint familiar with part names. If the butterfly dont open you aint gettin enough air youre in a sense flooding it everytime you give it gas.

bigk40k

So I fixed the fast idle adjusted the cam, first time but sounds good, ran a lot better than before but after a long drive it started the choking just a little bit and only at 50+mph and also it only seemed to happen going uphill? I live in mountains and go from 5000-7500 feet pretty regularly

JayzDaddy

50+ steady throttle or accelerating and pulling hills. That could be a filter clogging or you are running a bit rich in the mixture since youre not saying anything about knocking you shouldnt be lean and timing should be good. Check a random plug or 2 and make sure they are clean. If black or sooty they can confirm a rich setting.

bigk40k

ok speedo cable was junk, replaced that and now the speedo works but fuel and temp still dont? fuses look good, wiring looks good as far as i can tell. Also I adjusted the carb and got it running really nice, took it for a long drive and was good, took it for a drive the other day and it barely made it up the first hill choking the whole way up unless I barely touched the pedal, so back to square one? It had(befor I got it) a Quadrajet carb and electric fuel pump on it and the Qjet was cracked so a 2bbl was put on and now it does this?

Manuellabour247

I wouldn't think that your elevation would be that bad, but like I said before, I would get another old 4bbl and see what that does for you.

If you have a multimeter, I'd pull the cluster while it's on and test the connections using a good ground. Probably the easiest way to eliminate some things with electrical gremlins.

JayzDaddy

Is your 2bbl on a 4bbl intake?

Also there is like a ballast resistor on the back of the 80-86 guage clusters. If more than 1 guage quits working that would be my first suspect. Pull your cluster and look and smell (yes SMELL) for burnt areas. Test continuity one the cluster. If everything looks good ground the sensor for like the oil pressure. The the needle moves your guage is good the sensor is bad.