Runs with Fuel Pump Relay pulled
Thread Starter
Safety Car
Joined: Nov 2008
Posts: 4,328
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From: Jacksonville FL
Runs with Fuel Pump Relay pulled
I thought the power to the fuel pump runs thru the relay and when you pull it the car will stop running when the gas is burned out of the fuel rails. My '85 continues to run. I have pulled both the FP and OD relays thinking I got them backwards with no luck. Has someone hacked into my wiring and added a power feed somewhere or am I not allowing the car enough time to run out of fuel? Ive let it run a good 30-45 seconds.
I was thinking that I need to replace my fuel pump as the car keeps missing and I have gotten a Code 54 a couple of times but if there is a wiring issue where someone has jumpered the power lead then I need to find that point first to see if its going bad.
Help!
I was thinking that I need to replace my fuel pump as the car keeps missing and I have gotten a Code 54 a couple of times but if there is a wiring issue where someone has jumpered the power lead then I need to find that point first to see if its going bad.
Help!
Melting Slicks
Joined: Mar 2008
Posts: 2,141
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From: Santa Maria, CA
I thought the power to the fuel pump runs thru the relay and when you pull it the car will stop running when the gas is burned out of the fuel rails. My '85 continues to run. I have pulled both the FP and OD relays thinking I got them backwards with no luck. Has someone hacked into my wiring and added a power feed somewhere or am I not allowing the car enough time to run out of fuel? Ive let it run a good 30-45 seconds.
I was thinking that I need to replace my fuel pump as the car keeps missing and I have gotten a Code 54 a couple of times but if there is a wiring issue where someone has jumpered the power lead then I need to find that point first to see if its going bad.
Help!
I was thinking that I need to replace my fuel pump as the car keeps missing and I have gotten a Code 54 a couple of times but if there is a wiring issue where someone has jumpered the power lead then I need to find that point first to see if its going bad.
Help!
Thread Starter
Safety Car
Joined: Nov 2008
Posts: 4,328
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From: Jacksonville FL
I am hoping this is the case. I understand both the FP and OD relays on the '85 are between the W/W motor and the brake booster. If the FP relay is somewhere else I need to find out.
Team Owner
Joined: Sep 2003
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Without looking and studying a wiring diagram I always thought the relay was a device to energize the circuit until oil pressure was established and the OPS over rides the circuit.
Unplug the oil pressure switch not the gauge sender and I doubt you'll have the problem.
Unplug the oil pressure switch not the gauge sender and I doubt you'll have the problem.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
I thought the power to the fuel pump runs thru the relay and when you pull it the car will stop running when the gas is burned out of the fuel rails. My '85 continues to run. I have pulled both the FP and OD relays thinking I got them backwards with no luck. Has someone hacked into my wiring and added a power feed somewhere or am I not allowing the car enough time to run out of fuel? Ive let it run a good 30-45 seconds.
I was thinking that I need to replace my fuel pump as the car keeps missing and I have gotten a Code 54 a couple of times but if there is a wiring issue where someone has jumpered the power lead then I need to find that point first to see if its going bad.
Help!
I was thinking that I need to replace my fuel pump as the car keeps missing and I have gotten a Code 54 a couple of times but if there is a wiring issue where someone has jumpered the power lead then I need to find that point first to see if its going bad.
Help!
Thread Starter
Safety Car
Joined: Nov 2008
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From: Jacksonville FL
Thank you Tom, Dave. I thought everything on this car went thru a relay including the output from the OP switch to the FP. I also thought that you could pull the relay and evac the gas from the fuel tail. Since the car had 4psi built up already, that was not the case. I was over at a friends house and didnt have my FSM with me to verify the circuit.
Thanks again fellers!!
Thanks again fellers!!
- 1986 Original Owner -
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Thank you Tom, Dave. I thought everything on this car went thru a relay including the output from the OP switch to the FP. I also thought that you could pull the relay and evac the gas from the fuel tail. Since the car had 4psi built up already, that was not the case. I was over at a friends house and didnt have my FSM with me to verify the circuit.
Thanks again fellers!!
Thanks again fellers!!
Team Owner
Joined: Sep 2003
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Yes Ray - that's certainly the simple solution for disabling the FP but I didn't know what the original intent was. I've never needed to do any code 54 diagnostics.
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I still don't know what the original intent was! But when he said:
Has someone hacked into my wiring and added a power feed somewhere or am I not allowing the car enough time to run out of fuel? Ive let it run a good 30-45 seconds.
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Safety Car
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From: Jacksonville FL
I was trying to depressurize the fuel line to replace the fuel pump. I have been chasing a miss for several months. All the ignition side is done with major improvements but I still have a miss. I repaired the FP relay harness. I need to check the OP switch and wiring as well.
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I was trying to depressurize the fuel line to replace the fuel pump. I have been chasing a miss for several months. All the ignition side is done with major improvements but I still have a miss. I repaired the FP relay harness. I need to check the OP switch and wiring as well.
Thread Starter
Safety Car
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From: Jacksonville FL
Another related question. Can I temporarily jumper around the OP switch to see if it is the issue? I dont think it is as when the Code 54 popped up, I was experiencing long crank time. The car finally kicked over when the OP side saw 4psi.
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From: Park City Utah
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Safety Car
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From: Jacksonville FL
I agree with you Tom. The problem with the long crank is rare and once the relay is out of the loop I still have the problem. I have had an OP switch on another vehicle fail and leave me stranded. This will leave the fuel pump and any wiring.
Thread Starter
Safety Car
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From: Jacksonville FL
I am still leaning to the fuel pump but I have had so many things that a simple visual search has revealed wiring issues that were easily (and cheaply) fixed.
The Code 54 is low voltage to the fuel pump so it has to be the relay, wiring, or the pump. Since that only pops up during the sporadic long start, I would agree with Tom, thats prolly the relay. At $16 I will replace it anyway for peace of mind.
Another thought since I do not get a constant 54, maybe the FP diaphragm is allowing too much fuel to return to the tank.
It amazes me that I had so many running issues at one time. Diagnosis of multiple simultaneous issues is a biotch. I thought I fixed it 3 times thinking I got it only to have another thing rear its ugly head.
Ahhh the joy of owning a 30 year old, high mileage sport car that no one ever replaced anything. Its getting newer one part at a time!
Team Owner
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From: Park City Utah
So in that situation, the relay was bad? Or removed? B/c it should have run on the relay.
Thread Starter
Safety Car
Joined: Nov 2008
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From: Jacksonville FL