98 gmc k3500 non start, no fuel

From: willybob To: rasmataz Posted: Sat Sep 22, 2007 10:05 pm Subject: 98 gmc k3500 non start, no fuel This has been posted on the general forum, but it seems you have answered some questions regarding jumpers and a Chevy Silverado, so here goes. Also, will look in daylight for grey wire to check for power. If no power is computer replacement indicated? My post: My vehicle suddenly quit, then ran again after sitting a few hours. It has become unreliable, and will starve and die. This usually occurs on startup, usually after running. I am convinced it is starving for fuel. It does have spark. The fuel pump (NAPA) has about 20,000 miles on it, pump relay has been replaced, all fuses are intact, contacts are clean. Fuel pressure test shows no pressure. Pump does not run when ignition is turned on. I will pursue by checking all connections, but, assuming good connections, I am uncertain how to follow this up. Is there a common problem to look at first? If an oil pressure sender can prevent operation, can a jumper be used to bypass, therefore, verify this failure? Having asked this, shouldn't the oil pressure sender shutoff be bypassed on start, therefore, the vehicle would start, then die? In addition, does the oil sender shutoff the injectors versus the fuel pump? It seems unlikely that a dirty filter would prevent pump operation. Can a fuel pressure regulator prevent all operation of the pump, given no fuel pressure? Can a jumper safely be used to operate the pump for testing purposes? If so, where to connect, starting at the relay (for What's the liter on this horse is it 4.3/5.0/5.7/6.5/7.4 Liter Okay my friend-The pump should come On when key is in On position for 2 secs. When it stops-there's no power to it-the computer de-energizes it-unless its being crank over and when it has enough oil pressure it will fire up, If its tied in with the OSU. See below

Thanks for your reply. It is a 7.4 engine. Once today the 2 sec operation of pump was heard. Pump is dead rest of the time. It would seem I could verify power if connected to proper lead during the 2 sec period, or when cranking. Will attempt eval tomorrow evening. Any other input appreciated.