Truck Stalls At Night Help!

[88 GMC Truck]

Has anybody an opinion as to why my truck is stalling out only with a heavy electrical load on the system and only at night? I have replaced everything Engine, Trans, all sensors, 4 fuel pumps and relays, TBI Injectors etc. Could it be as simple as a bad ground and if so, where would be the most likely place to look? This is a 1988 GMC Sierra 3/4 ton C2500 extended cab truck. 5.7 TBI engine with AC.

 

Also - IT is an intermittent problem and happens only under an electrical load IE Head Lights, Radio, Heater fan. The alternator is brand new and charging correctly.

 

Thanks for any advice!

[BigJayDogg3]

Simple the truck doesn't like you. But it may be something with the temps dropping and making something shrink enough that contact isn't made or something like that. Just a shot in the dark.

[88 GMC Truck]

 

Ok here is the problem I found. The small wire that leads from the + side of the battery to the electrical junction box on the firewall (on the passenger side) that powers the sensors like the fuel pump relay and the other sensors on the intake manifold Etc., had rubbed on the frame rail where it was routed at the factory new. Over the past twenty years this wire was shorting out intemittently causing all sorts of mis-diagnosis with this truck. Solution, I replaced the wire and now it runs again. This has been a costly situation which many garages could not find. The four (New) fuel pumps must of ran untill they deteriorated and failed due to the resistance caused by the wire shorting out. At least it is finally fixed now Ill have to see if anything else shows up bad because of this wire. Time will tell!