HELP! FUEL PUMP RELAY

[ninety15.0]

I pulled the code for fuel pump relay circuit failure the other day and i dont know how to go about fixing this. my mechanic suggested that it may just be a ground fault and i should just check/rewire te relay. Its supposed to be under the drivers seat correct? Has anyone ever had a problem with this and if so...how did they fix it? should i just by a new relay (10$) and rewire everything? thanks in advance!

 

[jrichker]

What was the code? There are 3 different ones for fuel pump electrical problems, all with different causes and fixes.
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Code 87 – fuel pump primary circuit failure. check inertia switch, wiring to/from inertia switch, red wire going to inertia switch for +12volts. Check other side of inertia switch for +12 volts.

To help troubleshoot the 87 code, follow this link for a wiring diagram http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

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Code 95 - Possible bad fuel pump ground or open between fuel pump and pin 8 at PCM (Fuel Pump Monitor signal) - Power / Fuel Pump Circuits

To help troubleshoot the 95 code, follow this link for a wiring diagram http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Check the black wire that comes out of the tank; it is the fuel pump ground. It goes to a 2 wire connector and then ground to the chassis. If the connections get dirty or corroded, you will lose fuel pressure.

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Code 96 – KOEO- Fuel pump monitor circuit shows no power - Fuel pump relay or battery power feed was open - Power / Fuel Pump Circuits.

Look for a failing fuel pump relay, bad connections or broken wiring. The fuel pump relay is located under the Mass Air Meter on Fox bodied stangs built after 91. On earlier model cars is under the passenger seat.

To help troubleshoot the 96 code , follow this link for a wiring diagram http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Look for power at the fuel pump - the fuel pump has a connector at the rear of the car with a pink/black wire and a black wire that goes to the fuel pump. The pink/black wire should be hot when jumpered to the test position. . To trick the fuel pump into running, find the ECC test connector and jump the connector in the lower RH corner to ground. http://www.mustangworks.com/articles/electronics/eec-iv_codes.html for a description of the test connector. it. No voltage when jumpered, check the fuel pump relay and fuse links.

Using the diagram, check the red/black wire from the fuel pump relay: you should see 12 volts or so. If not, check the inertia switch: on a hatch it is on the drivers side by the taillight. Look for a black rubber plug that pops out: if you don't find it, then loosen up the plastic trim. Check for voltage on both sides of the switch. If there is voltage on both sides, then check the Pink/black wire on the fuel pump relay: it is the power feed to the fuel pump. Good voltage there, then the fuel pump is the likely culprit since it is getting power. No voltage there, check the Orange/Lt blue wire, it is the power feed to the fuel pump relay & has a fuse link in it. Good voltage there & at the Pink/black wire, swap the relay.

 

[tmoss]

Disconnect the battery for 20 minutes and see if the code comes up again. If it does, start by replacing the relay.

 

[ninety15.0]

Thanks for the response...you really seem to know your $hit when it comes to codes and troubleshooting. The code was 87, and i know my fuel pump has seen better days but its still pumping....or else the car wouldnt run...but it has been making a little extra noise lately. I will check all the stuff you recommended. I noticed from the first wiring diagram u gave me for the 87 code that your MAF, EGR, TAB are all on the same 12v...and when i pulled codes i got a code for each of those. There might be some connection....where is the ground for all of these things or are there individual grounds for each one? thanks for the time and help its very informative...i appreciate it

 

[87'GTstang]

When mine went, I rewired everything with your standard 4 prong bosch relay and converted it into a manual override switch on my ashtray switch panel. Not only did I get a little bit of a theft deterrant device but I also got $100 knocked off of my insurance also

If you go this route, by all means, don't bypass the fuel inertia switch on the left-hand trunk/hatch area.

 

[ninety15.0]

ooooh, i like that idea. i think for the short money it is to replace the relay i might just do that and wire it up right once and forget about it. I hate dealing with wiring....its by far my weakest area or cars. I think i have a ground problem somewhere causing my egr and Thermactiv air diverter and fuel pump relay to all fail. So somehow i need to find that ground for all of those and re-do them correctly. My car is driving like $hit right now. i HATE it. thanks for the info though

 

[Mizark347]

When i had to replace the fuel pump relay on my 89. My Fuel pump just wouldnt shut off and kept kiling my battery. I just chnge the fuel pump relay under the driver seat and it fixed the problem.

 

[jrichker]

I think i have a ground problem somewhere causing my egr and Thermactiv air diverter and fuel pump relay to all fail. So somehow i need to find that ground for all of those and re-do them correctly. My car is driving like $hit right now. i HATE it. thanks for the info though

All the devices are constantly hot, and the computer provides the ground to complete the circuit. Each device has a wire coming from the computer that switches to ground on computer command. That allows the current to flow from the power provided by a tap from the ECC relay, through the device and then through the computer to ground.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

 

[ninety15.0]

Ok awesome...so i finally understand those wiring diagrams...sorry bout this i am terrible at wiring $hit!!!! But i get it and from what i understand then...i should check the computer to ground first because the ground is completed through the computer?!? correct. If so where would i find that ground connection? If that doesnt work should i go about testing the grounds for all those seperate pieces? the diagram says that the EGRVPS, is grounded to a signal return wire back to the comp. but what about the fuel pump relay and the RH 02 sensor. (F*#@ING $hit, i hate this type of stuff) thank you soo much for your help with all this jrichker!