Chevrolet Colorado & GMC Canyon Forum banner
1 - 10 of 10 Posts

·
Registered
Joined
·
30 Posts
Discussion Starter · #1 ·
I'm having an INSANE problem that I have spent 2 entire days trying to track down. My truck has sat for 2 years and I CANNOT get the fuel pump to prime. I took the pump out of the tank and it's fine. I do have the passlock logo on in the dash as well as the battery light. I can't get the battery light to turn off unfortunately even though the battery holds a charge fine and I've had my battery box on it for 3 days. I've tried leaving the key in the ON position for 30 mins, then off for 10 seconds, then ON for 30 minutes, then off for 10 seconds to try and trip the pass lock. But no dice. I ordered a new ignition switch but that won't get here for a couple days. Meanwhile I'd love to try and get the pump to turn on. Right now I get 12V to the right two pins with the key-on. Which pin do I jumper to on the left?

 

·
Premium Member
Joined
·
2,935 Posts
The relay usually has a diagram on it someplace, indicating which contacts are the switch and which contacts are control. You will want the switch contacts. The Service Manual doesn't show the relay terminals in the fuel pump schematic.
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #3 ·
The relay usually has a diagram on it someplace, indicating which contacts are the switch and which contacts are control. You will want the switch contacts. The Service Manual doesn't show the relay terminals in the fuel pump schematic.
You're right. 87 should be top right and 30 should be bottom left. I ran a wire between those and the pump doesn't prime. If I apply 12V to the bulkhead connector on the top of the assembly, it primes loud. I simply cannot get 12V to the assembly through the factory harness.

I even tried running 12V directly to fuse #13 and no luck. There are no burned wires whatsoever and the pump primed perfectly prior to being parked. Although, I did change the clock spring since we broke it when we replaced the steering wheel with a new leather unit and the airbag light was on in the dash. That being said, the clock spring is an OEM GM part and the airbag light is no longer on so I don't see how replacing the clock spring could cause the fuel pump not to prime?
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #5 ·
When the truck sat for two years, was it outside? Rodents like to chew wiring.
Yes it was outside but we don't really have rodents here in California. There's no evidence of chewed wiring anywhere.

A little update. I did get the fuel pump to prime by jumpering pins 30 and 87 with the key on. In case anyone needs to test in the fuel pump in the future, pin 87 is the upper right pin and pin 30 is the lower left pin, looking down on the fuse box from the driver's side fender.

That being said, I did recently have some keys made as I considered myself lucky to have found the key after 2 years so I think I need a new ignition switch. I've ordered that and will install it today and report back.
 

·
Premium Member
Joined
·
7 Posts
I have a 2012 and all constant hots for the relays are the two pins towards the back of the truck, or if you are standing on the driver side looking at the fuse box, constant hots are on the right. Keep in mind that these relays will work both directions, but not properly. Pin 30 goes into a constant hot. I think you have yours backwards. You can jump it, but you must have the ignition switch in the run position or else the relay will not stay closed. The fuel pump primes when the ignition switch is in run. If you want to jump the fuel pump relay it will be pin 30 to 87. Viewing the fuse box from the my stated perspective places them at the top right and bottom left, or the pin holes closest to the mega fuse.

Check all your grounds. These trucks are notorious for grounding issues.

I think I made a mistake somewhere, but I'll have to get back to it later.
 

Attachments

·
Registered
Joined
·
30 Posts
Discussion Starter · #7 ·
Hey man thanks for your post. I can definitely get the pump to turn on by jumping pin 87 and 30. And you're right, it's the top right and bottom left pin on the fuse box, looking down on it.

I still can't get the damn pump to turn on with the key, but I think that is my ignition switch/ passlock problem. I'm waiting on a new ignition switch to arrive.
 

·
Registered
Joined
·
30 Posts
Discussion Starter · #8 ·
Well I replaced the ignition switch and the problem persists. Given that pin 87 and 86 both have 12V when the key is on the on position, I can conclude that the BCM grounds the fuel pump relay when it decides to and decides not to. Evidently I have a BCM problem or some other ground issue (and I've thoroughly cleaned and checked both fender ground junctions to make sure there is good metal to metal contact).

I think I will bypass this stupid problem by tieing the ground for the fuel pump relay into another relay. Unfortunately, I can't think of any other relay that would get grounded by the PCM / engine computer. Everything else is stuff like wipers and headlights. Hmmm
 

·
Premium Member
Joined
·
7 Posts
Have you tried jumping 86 to 85? Those are the pins for the magnet that is energized by closing the ignition circuit. Have you swapped relays? You can pull a relay and put 12 volts directly to 86 and ground 85 on the relay itself. If you can't hear it click you can check continuity across 30 and 87 with the magnet energized. From the schematics it appears that the RAP, and IGN 3 are grounded through the BCM. ERLS and FSCM provide power to the fuel control module. Are both energized with the ignition "on"? Can you get any obd2 codes?
 

·
Registered
Joined
·
1 Posts
Have you tried jumping 86 to 85? Those are the pins for the magnet that is energized by closing the ignition circuit. Have you swapped relays? You can pull a relay and put 12 volts directly to 86 and ground 85 on the relay itself. If you can't hear it click you can check continuity across 30 and 87 with the magnet energized. From the schematics it appears that the RAP, and IGN 3 are grounded through the BCM. ERLS and FSCM provide power to the fuel control module. Are both energized with the ignition "on"? Can you get any obd2 codes?
 
1 - 10 of 10 Posts
Top