Truck Repair: 1993 gmc sierra 1500 wont start, oil pressure switch, throttle body injection


Question
Son has had trouble starting it for several days. It would only start if he primed it first. 350, I believe fuel injected ( has two set of wires on top of carb each one has two wires going to it). We changed the fuel filter, but it still won't start. At a loss what to do now.

Answer
Hi Pam,
It IS fuel injected. Throttle body injection, to be exact.
Those wires go to the two injectors on top of the throttle body.
With the air cleaner off, look in the throttle body, just under those injectors, as someone cranks the engine over with the key.
You should be able to see a cone shaped spray of gas under each one.
The filter is a good first step, but testing the fuel pressure may be what is needed next.
Autozone.com will usually loan a test kit, or connect one and test the pressure for you.
It should have 13 PSI, while cranking and while running.
The fuel pump relay is a guess as to the problem, since it runs after priming. There is an oil pressure switch that supplies power to the fuel pump once oil pressure builds up, and it will run the pump even if the relay is bad. That sounds like what yours is doing. Starting on the prime, and building oil pressure.

Van

Van