[ebrishnu]

just bought this truck a few weeks ago, every thing seemed good

i descided to do a little maintnence, and replaced plugs, wires, cap, button, and new fuel filter, and air filter, every thing ran great and smooth for the afternoon

then, things went wrong

everytime i took my foot off the gas, engine quits. started running very erratic, espescially at low rpms. I took it to a mechanic who checked all the easy stuff, and didn't seem to want to mess with it. my guess is that the carburater is sucking air through a bad gasket. anybody got any ideas before i start tearing things up?

 

[TNT]

just bought this truck a few weeks ago, every thing seemed good

i descided to do a little maintnence, and replaced plugs, wires, cap, button, and new fuel filter, and air filter, every thing ran great and smooth for the afternoon

then, things went wrong

everytime i took my foot off the gas, engine quits. started running very erratic, espescially at low rpms. I took it to a mechanic who checked all the easy stuff, and didn't seem to want to mess with it. my guess is that the carburater is sucking air through a bad gasket. anybody got any ideas before i start tearing things up?

as for looking for a air leak take your hand and float it over the top of the carb (relatively close.) if the engine smooths out you have a vaccum leak i may be wrong on that it has been a while since I last done it. Someone feel free to correctme if I am wrong Not sure if its any help or not.

 

[jlangdon]

It does sound like it could be a vacuum leak. The easiest thing to do is check that every hose is connected on both ends (obviously you want them conected to the right things). Make sure that there are no open ports on the intake or bottom of the carburetor. If there is one and there is no hose that looks like it goes there, then plug it. To check for a leak around the gasket where the carb and intake meet you can use starter fluid. (THIS CAN BE DANGEROUS BUT IT CAN BE EFFECTIVE PLEASE TAKE THE PROPER PERCAUTIONS). Have someone hold the throttle just enough to keep it running. While it is running spray a small amount of starting fluid around the base of the carb. Don't hose it down. If the engine tends to respond positively (i.e. revving up slightly or just sounding better all together, then there might be a leak around the gasket. You might also try to do this and see if it will idle using the staring fluid. Don't use too much starting fluid to prevent fires and also to prevent burning up valves.

If you can't find any vacuum leaks then your next best bet is to check all of the settings on the carburetor. The float level might be wrong or the choke might not be opening all of the way or the idle screw might not be set right. There is also a mix adjustment on some of these carburetors. The float level is easy to check. There is a sight-glass on the front of the carb (assuming it is the orginal Aisin carb). The fuel level should be centered in the sight-glass. If not the float should be adjusted. Also make sure the choke is opening up once the truck is warm. If the choke doesn't open once warm it can starve the engine for air and cause it not to idle.

If you can't find any of these obvious problems then it might simply be that your carb is ready for a rebuild. Usually no matter how good you are about changing fuel filters you will get some buildup of unwanted dirt and mischief in your fuel bowl. The idle circut in the carb may be clogged which would cause the truck not to idle. I have seen similar problem in many other carburetor applications. Assumming the truck runs good except for idling this might be the right fix.

I'm not an expert. This is just what i have seen from my experience with a lot of carbureted engines from an old mustang, a gto, an s-10, an old 8n tractor, to my 84 pickup.

There might be other things that i haven't mentioned such as the fuel cut solenoid, a choke pull-off valve, EGR (if applicable) to the signs of a failing fuel pump.

I hope some of this helps. These types of things can be frustrating.

Good luck.