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2002 Z06 with racetronix firewire and KB BAP. I have a fuel pressure gauge in the dash.
Yesterday car drove normal to work in the AM, then into town at lunch. Kill it and go in the gym. Come back out and it fires up, but fuel pressure drops off and car sputters. Fuel pressure comes back intermittently, but it never fully dies while in the parking lot.
I can hear the relay for the BAP clicking on/off as its in the rear fenderwell right behind drivers seat.
I attempt to drive home. It sputters a few times, dies a couple times, but always restarts.
After a while, the BAP relay stops chattering and it runs fine the rest of the drive home. Until I hit a speed bump just before my neighborhood. Then it dies completely and will not restart, no fuel pressure.
Tow it 1.5 miles home and start doing testing on the fuel pump circuit. The problem is two fold. I figure out that switching relays on the fuse panel under the hood does nothing to fix the problem. So I jumper 30 to 87 to move on and troubleshoot the FW/BAP relay.
I noticed that i could touch the bottom of the FW/BAP relay and it would kick the fuel pump on and then go off as soon as i release it. So i pulled the FW/BAP relay and checked all the connections. I even put a new relay on the FW/BAP. Now the fuel pump runs continuously. So i fixed the first problem.
The second problem is that once I remove the jumper wire for the relay at the fuse panel, the fuel pump will no longer run with relay in place.
Around this same time, I noticed am also getting low oil level warning. So I start troubleshooting G105 (above the starter). Its tight and no corrosion or anything. Pulled it loose just to check, and put it back together. Mess with the wiring for the oil level and also added oil. It could have been low enough to trigger the switch. So Im not sure which "fix" worked.
Bolt G105 back up and then move on to SP122 (behind/below the battery tray). I mess with the wires to see if anything is loose. Put it all back together and hook the battery back up. The low oil level light is gone, however, the fuel pump still isn't working with the relay in place.
So what else could be causing it? I have power to the Fuel Pump fuse, which means its getting power from the PCM, correct? Which makes sense because I can jumper 30 to 87 and it works.
I checked voltage at the slots for the relay. 86 has 12V, 85 has 12V, 30 has 12V.
I checked continuity to ground (probe at each slot of relay on fuse panel, other probe on negative of battery). 86 has 0 Ohms, 85 has infinite (no continuity).
It looks like the problem is on the coil side of the relay, but I dont know what to check next? It doesnt make sense that 85 and 86 both have 12V. One of them should be to the controlled ground of the PCM, correct - which would be 86 because it had continuity? Or could I be reading voltage from the other circuits that go to ground there (O2 sensors, oil level switch, etc).
Im also confused about what was the initial cause. Was the chattering FW/BAP relay what caused the relay circuit at the fuse panel to go bad? Or vice versa? The fact that I hit a bump in the roadway and lost everything leads me to believe the problem was initially with the relay and circuit in the fuse panel and hitting that bump knocked something that was slightly loose completely loose.
I googled and found some others with similar issues, however, they all seemed to be fixed with G105 cleaning or SP122.
Answered my own question. I was looking at the wrong ground. I looked on the driver side of the car and the ground was loose. Put some dielectric grease on the connections, lock tite on the bolt and torqued it back down.
Everything works as as it should right now. More testing to follow.
I was jumpering 85 to 30 and the fuel pump worked.
I had 12V on 87, 86, and 85.
85 had no continuity to ground.
86 had continuity to ground.
i see you figured it out. but for future reference. 85 and 86 are the relay control circuits and should not be jumped over to anything else. they can't handle loads. 87 and 30 is the load side and can be jumped to check whatever component your trouble shooting.
i see you figured it out. but for future reference. 85 and 86 are the relay control circuits and should not be jumped over to anything else. they can't handle loads. 87 and 30 is the load side and can be jumped to check whatever component your trouble shooting.
Understand. That wasnt my intentions, i was trying to jumper 87 and 30, but was looking at the relay and thought that diagram was also showing the pin locations. WRONG!
Sorry to bring this back up but I am having a similar experience. However when I jump 85 to 30 I get nothing. Does the wire from 30 control the fuel pump?
You need to jump 87 to 30. 30 is the pin that goes to the fuel pump. 87 is battery voltage to power the pump.
85 and 86 are pins that go to the PCM and ground.
You need to jump 87 to 30. 30 is the pin that goes to the fuel pump. 87 is battery voltage to power the pump.
85 and 86 are pins that go to the PCM and ground.
Gary
How about if I go from the battery positive straight to the 30 shouldn't the pump turn on? Without the relay in place, even if the key is off?
My question is depending on how the relay is installed will change the wiring. From what I gather the forward inner socket is 30
Sorry to bring this back up but I am having a similar experience. However when I jump 85 to 30 I get nothing. Does the wire from 30 control the fuel pump?
You jump 87 and 30 colored white in the picture…87 should be hot with the key on !!..a video I did on the fuel pump circuit below…I have 86 and 85 swapped in the video…85 is control side feed !!
I’m having similar issues. Just replaced my fuel pump thinking it was the issue. Turns out, the wires powering the original fuel pump had broke inside the tank. I went ahead and installed the new pump and still no power to the pump. I am installing a Racetronix fuel pump wiring harness now, but does it still rely on the original relay to trigger the pump on/off? I was hoping to completely bypass the stock relay.
The Racetronix harness does need the factory trigger to turn the pump on. All the Racetronix harness is a larger gauge wire and 2nd relay to power their pump which pulls more power than the factory pump.
FYI, the ground on the drivers side of the block is where the relay that controls the fuel pump is connected.
07-19-2017, 09:13 AM
Help with Fuel Pump Relay Circuit
