1987 GMC V1500 TBI crank but no start

[NateP350]

I have an 87 GMC with a TBI 350 that has been sitting for about 15 years. I put a known good engine in it that came with a throttle body. I have replaced almost everything in the fuel system, tanks, fuel pumps, lines, filter, relay, tank selector valve and switch. I went to start it and it cranks fine but will not start. I replaced the distributor cap, rotor and ignition module. I have spark at the plugs. I noticed my fuel pump wasn't turning on with they key so I made a connector and got the pump to run and then I had fuel at the throttle body. What would cause my fule pump to not run. Or does someone have schematics so I could test the wiring harness. I open to any ideas at this point.

Thank you

 

[YakkoWarner]

Will it run if you manually power the fuel pump to get fuel to the throttle body?

The pump is controlled by a relay with an oil pressure switch backup (relay should be up on the firewall). There are a lot of good wiring diagrams available right here on this site - just goto FORUMS at the top and look in Squarebody Reference Library. Pretty much everything to know about the fuel pump wiring will be in there....

 

[NateP350]

Ok thank you i will check those out. It would not run when The fuel pump was was powered manually. It was close but it just wouldn't take off.

 

[gmbellew]

If you get the fuel pump sorted, you might verify timing is right with rotor pointing at no 1 TDC and the wire firing order.

 

[NateP350]

Thanks will do. Started checking every wire at the relay. The orange wire has 12 volts, the black and white wire is a good ground and the green and white wire has voltage for about 2 seconds like it is supposed to from the ecm when the key is turned on. The tan and white wire runs to the tank selector switch and get the signal from the relay for 2 seconds when the key is turned on like it is supposed to. I ohmed out the wires from the tank selector switch to each of the fuel pump connectors and I have an open somewhere in between them. So I am starting to trace them wires back.

 

[NateP350]

I found a connector i missed on the driver's side firewall with a tan wire and a gray wire. It took me a while to find the other end because it was hidden between the main harness and the cruise control servo. That connector goes back to each fuel pump. I then had all the plug wires on the distributor one spot off so I rotated them all one spot counter clockwise and it fired right up. Thank you both for all the help.