88 Gmc Dies

[fearless]

my uncle has a 88 gmc 1500 with a 305. The truck has been having problems. It will run for unpredicted amounts of time and die and then it wont start. yesterday i played with it and found out it had a bad fuel pump so i replaced it and then the truck ran fine. for some reason i suspect that the computer is shutting fuel off to the TBI injectors. before the fuel pump i couldnt get the injectors to spray fuel unless i manually grounded them and powered them through the harness (its 12v all the time and i take it that the ground resistance goes down to allow a higher spray of fuel).

 

my uncle called me this morning and said he drove it around for an hour last night with no problems, went out this morning and it died after 15 - 30 seconds. any ideas?

 

Matt

[racerx55]

i ran into a similar situation on my 92 TBI, it ended up being a combination of the oil pressure / fuel pump switch and a bad connection on the plug that goes from the coil to the ign. module in the distributor.

[fearless]

suggest to me how to fix this please?

 

Matt

 

p.s. if i manually trigger the injectors it would inject fuel and run. so the oil pressure switch is shutting the fuel off in the system?

[ryank1]

The oil pressure switch will not allow the pump to continue to run after the prime if the pressure is low, also some truck have 2 switches, 1 for the fuel pump and 1 for the gauge. The switch will just unscrew out of the engine.

[tflessner]

I had the same problem in my '88, and it was the ignition module (in the distributor). So, if it's not the oil pressure switch, check the ignition module.

[fearless]

ok, new oil switch, fuel pump and it wont start unless i manually trigger the injectors. i have bypassed the fuel relay so the pump is running the whole time. good fuel pressure and flow. i get absolutly no ground on terminal b on the injectors when cranking and or any other time. if i ground it the injectors fire and the truck starts

 

Matt

[fearless]

new ign module and its running now.