PCM controlled fuel pump relay - Issues
PCM controlled fuel pump relay - Issues So I'm about ready to fire off my LQ9/4L80 swap in my 1969 C-10 SWB, but I'm having a little trouble with the fuel pump relay.
For whatever reason, the PCM control output for the pump relay is coming out as a ground. I have few sets of pin-outs and they all show plug C2, pin A7, Dark Green/White as the PCM output for primary fuel pump. I always understood this to be 12v for fuel pump, as opposed to ground for fans, etc....or are the truck harnesses different?
I'm using a 2003 LQ9 motor, harness, and computer. Fuel pump is a Walbro 255 in tank setup.
Any ideas?
Thanks
For whatever reason, the PCM control output for the pump relay is coming out as a ground. I have few sets of pin-outs and they all show plug C2, pin A7, Dark Green/White as the PCM output for primary fuel pump. I always understood this to be 12v for fuel pump, as opposed to ground for fans, etc....or are the truck harnesses different?
I'm using a 2003 LQ9 motor, harness, and computer. Fuel pump is a Walbro 255 in tank setup.
Any ideas?
Thanks
Joined: Nov 2001
Posts: 3,043
Likes: 0
From: Texas and Qatar
No that's right, it should ground the relay. If you are using a regular relay put the PCM control on pin 85, and a 12v ignition source on the opposite side pin 86. Then pin 87 can be your fused 12v in, and pin 30 the activated 12v fuel pump wire.
Having a hard time figuring things out. I have no 12v at coils, injectors aren't firing, no fuel pump activation signal. Have been searching, anyone have any troubleshooting suggestions?
Go back to check the grounds, and that your getting power at that power and ign power.
Do you have access to a scanner ?
I would make sure the ground are good to the back of the heads, frame, battery and body.. that the PCM grounds are good. Are you sure the ign 12+v lead doesn shut down as you crank ?
Let us know what you find..
are you able to crank it over, getting oil and fuel pressure ?..
Do you have access to a scanner ?
I would make sure the ground are good to the back of the heads, frame, battery and body.. that the PCM grounds are good. Are you sure the ign 12+v lead doesn shut down as you crank ?
Let us know what you find..
are you able to crank it over, getting oil and fuel pressure ?..
Thanks, I'm using a factory Silverado underhood fuse block. Somewhere along the line of wiring I lost a ground (b9 I think, on connector C2) at the fuse block...where I'm sure I had a solid ground earlier. Used a jumper wire and now the fuel pump runs its prime cycle and I've at least got 12v and ground at the coils. Need to go buy a spark plug and I'll see if she fires later tonight.
Stay tuned
Stay tuned
Teching In
Joined: Apr 2008
Posts: 21
Likes: 0
From: PA
do you have ign power at ECM coils and at injectors while cranking injectors and coils have their own fuses .I would look at the connector pin out and check out that i have all my powers and grounds to ecm. Also did you reprogram the ECM to get rid of the the VATS.If not it will shut the injector drive down.Usually a loss of pump relay signal is due to an input of power or ground to ecm
John
John
