I am having a problem with my '91 Mustang, it won't start. I turn the key and I hear all the relays click but the Fuel Pump does not prime. I have already replaced the Fuel Pump Relay under the drivers seat and replaced the fuel filter about 5 months ago. I had a similar problem before and it turned out to be a clogged fuel filter. This time is different. Tomorrow I will be replacing the Ignition Switch to see if that will fix the problem. I am pretty sure the fuel pump is ok as it was working fine till the car just stalled, luckily I was at my destination. If the Ignition Switch does not fix the problem I was wondering how I would go about installing a manual switch to turn the Fuel Pump on and off but still have the Inertia Switch. I am not very good at electrical schematics. It looks like if I run a wire from a constant power supply to the red wire of the Inertia Switch it should then power the Fuel Pump bypassing all the relays. I am gettings tired of the witch hunt and just want to be able to drive my car back and forth from work. I have no problem turning a toggle switch on and off, in fact, I think it would be cool. Here is the schematic I used which is for an '89 Mustang:
On second review I may also have to run a wire from the R/Bk wire of the Inertia Switch to the PK/BK wire of the Fuel Pump. That way it totally bypasses all the Relays. If you guys could help me out a little or at least confirm my idea that would be great.
You have enlightened me. We wondered what that thing we unplugged under the driver's seat was...fuel pump relay:thumbsup. I know the car wouldn't start without it. I thought maybe something to do with the inertia switch or some type of safety feature. I don't guess you can hear the always noisy Ford fuel pump when you just switch the ignition on?
i had to sound negative, but im going to guess its the fuel pump. if you have replaced everything else, and it was all working before the car STALLED out (lack of fuel?) then i bet its the pump. things do just crap out man, thats what cars do.
however, in your manual, there is a section about the fuel pump. in the back of your car (hatch?) there is a small black grommet protecting a hole, inside that hole you can reach a reset button on your fuel pump. maybe give that a whirl?? i dont really know what it does ...
toggle switch would be kinda neat, i would hide it, then it would act like a security device because the car wont start without fuel. could drop a few bucks off of your insurance premium.
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Thanks for all the replies. I will try the reset button today on the fuel pump and also install a new ignition switch. If that does not work I will run 12v directly to the fuel pump to see if it will turn on. I would still like to pursue the manual fuel pump switch just for the future when whatever else decides to spontaniously die. Also, just a FYI, it is a '91 Convertible. If anyone else has any other ideas please post them.
Ok, I replaced the Ignition Switch and still no luck. I couldn't find the reset button for the Fuel Pump. I am running out of options. This is what I have replaced so far:
While browsing the forums I came accross a fwe other things that I will try. One person siad to replace the TFI Module on the Distributor. I will try that next. Someone posted a way to hook up a toggle switch to manually turn the fuel pump on and off but I need it in Layman's Terms. Anyone care to convert it for me. Here are the instructions.
"The Gree/Tan wire goes to the EEC and the EEC ground that wire to pick up the relay secondary curuit (coil) and turn on the pump (primary power circuit). Sounds like the solid state device in your computer that grounds the relay coil might be bad. You can fix this if you don't want to buy a new EEC just for that problem by running the Green/Tan wire through the primary circuit of a new relay and using an ignition "run" source to pick up the new relays secondary circuit. When the key is on the pump will be on and the inertia switch is still in the circuit for protection. Down side is the pump is on anytime the key is on. you could also wire a switch between the "run" power source and the secondary circuit of the new relay so that you could override the pump run in the key on position."
I guess I'm convinced it is the pump if your not hearing it whine when the ignition switch is on prior to starting the car. Even if the filter was clogged again, she would still whine.
Ok, I guess I will try the pump after the TFI Module. The TFI is much cheaper and easier than the fuel pump. Damn, I am flat out broke, guess I will be borrowing cars and riding my bike to work for a while. I am almost ready to go back to Chevy, this is my second Ford and I think I would rather have car payments instead of parts payments and spending my weekends under a car, and being left stranded. I got Gasoline in my ear last night while checking the fuel filter, Christ does that hurt. At least it is nice outside. Thanks again, I will keep ya posted of the progress.
I am looking at the Ford Racing High Flow Fuel Pump from Summit Racing. I am guessing that would be the easiest to install without having to modify the wiring harness.
It's hard to go wrong with a factory pump designed by the company that built the car. Afterall, your pump is probably the original (hmmm 1991, Pearl Jam, Nirvana, etc. get the point.) Mine is the original from the G&R "appetite for destruction" era (89) and still going abet whining. When you drop the tank, you might want to cut an access hole over the fuel pump in your trunk in case you need to do this again. Just find some sort of rubber grommet to plug the hole and you should be fine.
That is a good idea, I totally did not think of cutting a hole. I will be ording a new pump tonight. I think I am still going to splice in a seperate wire with a universal Inertia Switch and run it off of a toggle switch just in case I have a problem in the future I can at least throw the switch and keep the pump running as to get me home. My next car will be carburated, as much as a pain they are at least they will always get you home.
I ordered a new Walbro Fuel Pump, Accel TFI Module, and the EEC Power Relay, and the parts needed to do a direct line to the fuel pump. I will let you all know what it was.
Bypassing Fuel Pump Relay 
.) Mine is the original from the G&R "appetite for destruction" era (89) and still going abet whining. When you drop the tank, you might want to cut an access hole over the fuel pump in your trunk in case you need to do this again. Just find some sort of rubber grommet to plug the hole and you should be fine.
