Fuel Pump Relay Buzzing, No Start

[chrmar]

Hi all, I have a 1994 K1500 5.7L that I'm attempting to get running again. The truck has a bit of a hacked wiring harness due to someone installing a remote starter at some point. The wires from the firewall to the fuel pump have been replaced as well as the fuel pump itself with a known good unit and a number of the grounding straps. When the key is turned on to the "on" position, the service engine soon light comes on and the fuel pump relay on the passenger side of the firewall buzzes. The fuel pump does not sound like it is cycling on and the truck cranks but doesn't start, naturally.

Any thoughts on why this relay would be buzzing? Is it not getting enough power to be able to cycle the pump on?

 

[CrustyJunker]

That's a tough one, captain. I'd recommend checking the relay coil terminals (I believe terminals 85 and 86) to see what kind of voltage you're getting to it on key-on. You can also ohm check the circuit by disconnecting the connector from your ECM in your dash and check to ground. The ECM is what turns that relay on, so if you can't find any more wiring issues, you may wanna scout for a new computer or junkyard computer.

Good luck and I hope this helped.

 

[chrmar]

How compatible would the wiring be between this 94 K1500 and an 89 K1500? Both have a 5.7L, only difference between the two trucks is the 94 is an ECSB and the 89 is a RCLB. I know the instrument clusters and transmissions are different. The 89 is a retired plow truck and now is only a parts donor.

 

[CrustyJunker]

How compatible would the wiring be between this 94 K1500 and an 89 K1500? Both have a 5.7L, only difference between the two trucks is the 94 is an ECSB and the 89 is a RCLB. I know the instrument clusters and transmissions are different. The 89 is a retired plow truck and now is only a parts donor.

I think the wiring harness is the pretty close to the same on the engine side of it except for a couple of the TBI connectors. Your '94's got extra stuff for the transmission, though.