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Topic: HELP! Fuel pump primes when headlights are turned on... (Read 6759 times) previous topic - next topic

HELP! Fuel pump primes when headlights are turned on...

This is on my 86 Cougar with a 2.3T engine.

I'm not exactly sure what is going on.  I turned the marker lights on to see if any bulbs were burned out in the cluster I installed.  A few of them were, so I pulled the cluster and replaced them.  Now the fuel pump primes when I turn the headlight switch on.  The fuel pump also primes with key turned to run.  The marker lights don't come on either, except while the starter is engaged.  Everything was working fine yesterday.  Any suggestions would be appreciated. 

Ed
1986 Mercury Cougar - 2.3T/T5 swap, TC brakes and suspension and rearend, 3" exhaust, 255 lph fuel pump, Stinger BOV, Gillis MBC @ 18 psi
2003 Chevy Suburban Z71 - Daily driver
2015 Chevy Volt - Wife's daily driver

HELP! Fuel pump primes when headlights are turned on...

Reply #1 –
how long was the car sitting? you in wichita now?  do a visual on the wiring and see if anything looks chewed or bare could of had a mouse...

HELP! Fuel pump primes when headlights are turned on...

Reply #2 –
The car has been sitting for a few years.  I just shipped it out to me in Las Vegas this week and am trying to get it finished up.  I am working on checking the wiring out now.  I know that there has been mice in the car but I haven't seen any damage from them yet.
1986 Mercury Cougar - 2.3T/T5 swap, TC brakes and suspension and rearend, 3" exhaust, 255 lph fuel pump, Stinger BOV, Gillis MBC @ 18 psi
2003 Chevy Suburban Z71 - Daily driver
2015 Chevy Volt - Wife's daily driver

HELP! Fuel pump primes when headlights are turned on...

Reply #3 –
Try disconnecting your new cluster and see if it still happens. I bet there is something different in the pinout feeding back through the new cluster light circuit.

I am not familiar with what you swapped in, but if you still have the old cluster look at the backs side-by-side and compare the circuitry. I bet they are different.
CoogarXR : 1985 Cougar XR-7

HELP! Fuel pump primes when headlights are turned on...

Reply #4 –
The car was originally a 5.0 but I removed the drivetrain and all wiring.  The cluster is the stock turbo cluster, as is all the wiring.  The fuel pump still primes when the lights are turned on even with the cluster removed.  Like I said, everything was working fine with the turbo cluster, and then it just started doing weird things.

Thanks for responses, keep em coming!
1986 Mercury Cougar - 2.3T/T5 swap, TC brakes and suspension and rearend, 3" exhaust, 255 lph fuel pump, Stinger BOV, Gillis MBC @ 18 psi
2003 Chevy Suburban Z71 - Daily driver
2015 Chevy Volt - Wife's daily driver

HELP! Fuel pump primes when headlights are turned on...

Reply #5 –
Did some more investigating.  I found that the plugging the cluster caused the fuel pump to prime (with the lights on) and unplugging it made it stop.  I used some test leads I made and tried applying 12v to the different wires in the cluster plug.  Pins #1 and #16 made the the fuel pump prime.  Now according to the pinouts on Coolcats, pin 1 is for "Brake, turbo, tach & speedo 12V+" and pin 16 is for "Tach in."  Any idea why these wires would cause these weird issues?  Thanks!
1986 Mercury Cougar - 2.3T/T5 swap, TC brakes and suspension and rearend, 3" exhaust, 255 lph fuel pump, Stinger BOV, Gillis MBC @ 18 psi
2003 Chevy Suburban Z71 - Daily driver
2015 Chevy Volt - Wife's daily driver

HELP! Fuel pump primes when headlights are turned on...

Reply #6 –
You could pull those wires out of the cluster connector one at a time and see which one is the culprit...
CoogarXR : 1985 Cougar XR-7

HELP! Fuel pump primes when headlights are turned on...

Reply #7 –
Well, I'm pretty sure the issue isnt in the cluster because it still primes the pump even with the cluster out of the car. I think I may have narrowed it down to the illumination circuit. I pulled the fuse from spot #13 in the fuse panel and it stopped priming the pump when the lights are on. Does anybody know if the light circuit and the fuel pump circuit share any common connections?
1986 Mercury Cougar - 2.3T/T5 swap, TC brakes and suspension and rearend, 3" exhaust, 255 lph fuel pump, Stinger BOV, Gillis MBC @ 18 psi
2003 Chevy Suburban Z71 - Daily driver
2015 Chevy Volt - Wife's daily driver

HELP! Fuel pump primes when headlights are turned on...

Reply #8 –
I am guessing that by priming the pump, you mean it turns on for a couple of seconds and then turns off.
If so, it means that somehow you are powering up the EEC when you turn on the lights.
You must be picking the EEC power relay.
Put your meter on the Batt side of the ignition coil. This is a W/LB wire if you have a 86 2.3 harness. This was a R/LG wire on the 5.0.
This wire should be hot with the ignition in start or run and is the same circuit that picks the EEC power relay.
See if you get voltage there when you turn the lights on.

HELP! Fuel pump primes when headlights are turned on...

Reply #9 –
Thanks for the reply, I could use all the help I can get on this.  Yeah, I tracked down the white with blue wire earlier and it lead me to a junction block with a few other wires.  They all had no power with the ignition off and had power with the lights on.  Not sure if it related, but I have a bundle of grounds in the center dash area that arennt ground, they are actually hot. 

The harness is an 86 2.3 harness.
1986 Mercury Cougar - 2.3T/T5 swap, TC brakes and suspension and rearend, 3" exhaust, 255 lph fuel pump, Stinger BOV, Gillis MBC @ 18 psi
2003 Chevy Suburban Z71 - Daily driver
2015 Chevy Volt - Wife's daily driver

HELP! Fuel pump primes when headlights are turned on...

Reply #10 –
Quote from: Loaded87IROC;319470
Thanks for the reply, I could use all the help I can get on this.  Yeah, I tracked down the white with blue wire earlier and it lead me to a junction block with a few other wires.  They all had no power with the ignition off and had power with the lights on.  Not sure if it related, but I have a bundle of grounds in the center dash area that arennt ground, they are actually hot. 

The harness is an 86 2.3 harness.

The W/LB wire being hot with the light switch is causing the pump to prime. This circuit should not be connected to the light switch.
Try pulling fuse 18 and see if you still have the problem.

HELP! Fuel pump primes when headlights are turned on...

Reply #11 –
I pulled fuse 13 earlier and that did stop it from happening.  I have been testing wires all day.
1986 Mercury Cougar - 2.3T/T5 swap, TC brakes and suspension and rearend, 3" exhaust, 255 lph fuel pump, Stinger BOV, Gillis MBC @ 18 psi
2003 Chevy Suburban Z71 - Daily driver
2015 Chevy Volt - Wife's daily driver

HELP! Fuel pump primes when headlights are turned on...

Reply #12 –
The fuse 18 circuit (hot in start or run) is R/Y wire and goes many places.
The headlight circuit from the main headlight switch is also a R/Y wire.
I see a potential confusion factor here.

HELP! Fuel pump primes when headlights are turned on...

Reply #13 –
Fuse 13 (LB/R) is fed from the dimmer control part of the headlight switch and goes to pin 13 of the big(18 pin ) connector on the IP cluster and to pin 12 of the small IP cluster connector.
Fuse 18 (R/Y) goes to pin 1 of the big connector and pin 2 of the little connector.

HELP! Fuel pump primes when headlights are turned on...

Reply #14 –
Quote from: Loaded87IROC;319375
Did some more investigating.  I found that the plugging the cluster caused the fuel pump to prime (with the lights on) and unplugging it made it stop.  I used some test leads I made and tried applying 12v to the different wires in the cluster plug.  Pins #1 and #16 made the the fuel pump prime.  Now according to the pinouts on Coolcats, pin 1 is for "Brake, turbo, tach & speedo 12V+" and pin 16 is for "Tach in."  Any idea why these wires would cause these weird issues?  Thanks!

Pin 1 is the "Hot in Start or Run" circuit and will pick the EEC power relay which will prime the pump.
Pin 16 goes to the Tach side of the coil. Hot in Start or Run is on the other side of the coil. You must have picked the EEC power relay by going through the coil.
Applying 12v to the connnector pins is risky. some of them go to ground through various sensors and switches. Pin 16 also goes to the TFI. Time will tell if you blew out the TFI or not.

Quote from: Loaded87IROC;319421
Well, I'm pretty sure the issue isnt in the cluster because it still primes the pump even with the cluster out of the car. I think I may have narrowed it down to the illumination circuit. I pulled the fuse from spot #13 in the fuse panel and it stopped priming the pump when the lights are on. Does anybody know if the light circuit and the fuel pump circuit share any common connections?

Somewhere the fuse 13 circuit is tied together with the Hot in Start or Run circuit. Pulling fuse 18 (with 13 back in) can rule in or out a big part of the Hot in S or R circuit.

Quote from: Loaded87IROC;319470
Thanks for the reply, I could use all the help I can get on this.  Yeah, I tracked down the white with blue wire earlier and it lead me to a junction block with a few other wires.  They all had no power with the ignition off and had power with the lights on.

Yes the W/LB wire goes to a 5 wire splice. BR/PK to ignition swt start, R/LG to ignition swt run, R/LG to voltage regulator S terminal and R/LG to the input side of fuse 18.
Quote
  Not sure if it related, but I have a bundle of grounds in the center dash area that arennt ground, they are actually hot.

This can be normal. If the ungrounded component has voltage applied to it, you will measure that voltage between the disconnected ground wire and ground.