I got roped into helping fix up an old GMC van that has a 350 TBI in it and its doing something really weird...

You can start it, it will run for a second then die. UNLESS you feather the throttle then it will run, all tho hesitantly....

New Spark plugs, wires, cap rotor, oil pressure sensor, coolant sensor, Air filter, fuel filter. Timing is dead on, its getting a strong spark to all cylinders , The compression is great and I can see fuel spraying from the injectors on the TBI unit, tho I have NO idea how to check the fuel pressure on this system.

Whats weird was it was running just fine then parked for the day, and came out to start it then this! It makes no sense at all.

Any ideas so I can get this ugly thing out of my driveway?

 

Check plug wire configuration. Check the connectors at the distributor.

 

I did, connections are clean and the wires are in the right firing order. No change.

 

I had a G20 that had a very similar issue.
Could be a couple of things, but what fixed my G20 was replacing the fuel pump and Fuel Pick-up "sock".
After all of the years on the road, the fuel pick-up finally clogged.

Check the amperage going to the electric fuel pump at the tank, excessive amps mean the pump is bad.
Also check the fuel pump relay and electrical connections going to the fuel pump, corrosion at these connections, or a relay going bad will prevent full fuel pressure.

There shound be a test port near the end of the the fuel supply line where the line connects to the TBI unit.
If memory serves, the fuel pressure should be 80 psi...

You have to drain and drop the fuel tank in order to gain access to the pump, which is why I replaced my pump and "sock" at the same time.
You need an extra long deep well socket to remove the tank straps with...

You should also check the resistance of the Throttle Position Sensor (TPS), as they can go bad and can give you the same problems as well...

 

Thank you

Tho Their is no test port near the TBI on this one (its a 92 so maybe thats why) And 80PSI seems WAY overkill for just 2 injectors... But I know for a fact its not even getting that.

Waiting now for a break in the rain so I can drop that tank.

 

The TBI system only runs 9-12 psi. It sounds like the fuel pump is on its way out.

 

At lest it didnt go out with a full tank....

 

Go figure, dropped the tank and pulled out the fuel pump and it turns out the rubber line between the pump and the hardline inside the tank blew up. So I replaced it and the pump anyways and now it runs!