hard starting 1990 suburban

[lou1990gmc]

I have a 1990 GMC Suburban 2500 4x4, wiht a 350. I am having a problem with starting the truck. When I can get it to turn over, it will only run for 10-15 seconds then shut off. I'v replaced the fuel pump 3 times. After the second time, the truck ran fine for about a week, then as I was making a turn it shut off. I tried to restart the truck it ran for about 5 seconds the shut off again. I thing it was running on the fuel left in the lines. Replaced the pump (while doing so found out that the ground wire from the pump was not securely connected, Fixed that problem). Before replacing the pump the 3rd time I had the same problem with the engine shutting down after 15 seconds. I have a new fuel filter. I know fuel is getting to the injectors, (unhooked fuel lines, and can see a even pattern of fuel from the injectors). I put on a new throttle position sensor, map sensor, O2 sensor, coolant temp sensor, cap, rotor, coil, and plug wires. If its near the throttle body its been replaced. I can remember the check engine light coming on with a running lean code. When I bought the truck (Aug 2002 w/130k miles) I replaced all the vaccum lines. At this point I am starting to think this problem may be electrical and not so much fuel. Is it possible that a relay is causing these problems? I'm sure this a easy fix, I just can't figure it out. Please help.

Thanks

[trickyricky123]

Lou

You may have found the problem by now in case you haven't, I had many of the same problems with my 90, like you replaced everything to no avail.
Took it to the dealership and was informed that I had a bad fuel pump, filter and coil,I replaced them and the same problems persisted. Like you I didn't think it had anything to do with fuel as it seemed the injectors were putting out a nice spray of fuel. To make a long story short, I replaced the fuel pressure regulator, my burb now runs like new. Good Luck

[horse482]

When you start having problems are you getting good power to the fuel pump? If not it could be that you have a bad fuel pump relay, or a short in the power line going to the pump. I had a gm pickup with simillar problems, found that someone had replaced the tranny when putting it back in they pinched the wires going to the pump between the frame and the cross member, any flex in the frame would create a direct short and the truck would stop running. Hope this helps.

[IFIXCARZ4U]

Another item to check is the connector inside the fuel sending unit. Sometimes the connection will get corroded where the wires pass through the top of the fuel sending unit. Another crazy thing i found was the pipe that the fuel pump connects to was loose from the top of the sending unit causing a poor ground to the pump because some pumps ground to the pipe itself.