I got the idle straighted out and now she purrs but every time I kick the heat on the whole truck shuts down, any ideas?

 

My guess would be vacuum related. All the hvac stuff is run off of vacuum. Could be a leak behind the dash or where the lines go through the firewall.

 

Does it shut down at speed or only at idle? Does it shut down slowly or like you just hit a kill switch?

 

it will run for about 15 seconds and then nothing. and at running speeds its about 10 seconds.

 

That tells me it is not vacuum. 91 is a TBI. Look down inside the throttle body and see if the fuel shuts off or slows down just before it shuts off. This should tell you if it is a fuel problem or electrical. Does it shut down slowly or like you just hit a kill switch? Does it restart immediately after it shuts off and if so is it hard to start or does it start right up?

 

I agree with all that, but it's odd how the heater would affect any of that. Maybe on a '91 it's different, but I didn't think there was anything electric, other than the blower motor, involved in operating the heater.

 

Im thinking a fuse might have blown. Ive been working alot with the electrical system and charging system since when I bought it the wire harness was a mess. Someone was using it for a plow truck and I have all kinds of splice jobs under the hood. I even found a piece of lamp cord under there. So Ive been trying to run back all the wiring and clean it a bit.

 

So i stripped everything down to the standard wire harness and re-grounded everything. I also checked all the fuses and all were fine. Anyone have any ideas?

 

And the only thing that causes it to die is turning the heat on?

 

seems that way, Im afraid to try anything else. But she runs in all gears pretty well and since the tune she has a bit more pep, but as soon as the heat goes on the truck goes off. I thought maybe a vacuum leak? But how to check that and where to look?