Fuel Pump and Electrical Guru question Please Help!

[Black1987Stang]

I just finished up my lifter install earlier today, i starter her up drove her around to get her to operating temp and I come back in the driveway (slight incline) while shes idling for maybe 20 seconds i am playing with the timing and all of a sudden she dies I figured I ran out of gas since I was low and i was also on an incline) The wierd thing i found out is i was turning the dizzy clockwise (with the engine off) and I heard a click and when i turned it the other way I heard a funny buzzing sound cycling on (also heard a few beeps too). I found out it was the fuel pump but it wasnt the normal buuzzzzzzzzzzz, it was very weak and was dying, it sounded like it had a weak battery or something. I grounded the fuel pump terminal to check for any fuel pressure and its not making any Also my battery went bad, it will start perfect and if i turn it off it wont even start back up without jumping up. I put in a friends battery and it cranks everytime but the fuel pump still has a dead sound to it. Im pretty confused on why when I turn the dizzy a little bit it turns on the fuel pump or makes a clicking sound if i turn it the other way? My other question is how could my pump make good pressure one second then like die the next? Anybody have some good articles or tips on changing a fuel pump? Do I need any special tools like a fuel disconnect tool or something lol Im thinking about a 255lph since ill be going boost some day.

 

[old_blue]

Nothing special for the fuel pump exchange. The new one should come with new clips that almost always get ruined/destroyed when taking them out. just make sure you don't destroy the housing of the clips. As for your dizzy question, I have no frkn clue. sry

 

[HISSIN50]

Turning the dizzy does fire the injectors (you are triggering the stator).

I would want to make sure the FP electrical side is square before R/R'ing the pump.

You can probe the FP relay under the driver seat to ensure you have what you need. Make sure something dumb like the inertia switch did not trigger.

David (5 spd gt) has a great FP R/R article that he posts occasionally. It should help ya out.

Good luck.

 

[jrichker]

Fuel Pump Troubleshooting for 86-90 Mustangs

Clue – listen for the fuel pump to prime when you first turn the ignition switch on. It should run for 5-20 seconds and shut off. To trick the fuel pump into running, find the ECC test connector and jump the connector in the lower RH corner to ground. See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html for a description of the test connector. If the relay & inertia switch are OK, you will have power to the pump. Check fuel pressure – remove the cap from the schrader valve behind the alternator and depress the core. Fuel should squirt out, catch it in a rag. A tire pressure gauge can also be used if you have one - look for 37-40 PSI. Beware of fire hazard when you do this.

No fuel pressure, possible failed items in order of their probability:
A.) Tripped inertia switch – press reset button on the inertia switch. The hatch cars hide it under the plastic trim covering the driver's side taillight. Use the voltmeter or test light to make sure you have power to both sides of the switch
B.) Fuel pump power relay – located under the driver’s seat in most stangs built before 92. On 92 and later model cars it is located below the Mass Air Flow meter.
C.) Clogged fuel filter
D.) Failed fuel pump
E.) Blown fuse link in wiring harness.
F.) Fuel pressure regulator failed. Remove vacuum line from regulator and inspect for fuel escaping while pump is running.

The electrical circuit for the fuel pump has two paths, a control path and a power path.

The control path consists of the inertia switch, the computer, and the fuel pump relay coil. It turns the fuel pump relay on or off under computer control. The switched power (red wire) from the ECC relay goes to the inertia switch (red/black wire) then from the inertia switch to the relay coil and then from the relay coil to the computer (tan/ Lt green wire). The computer provides the ground path to complete the circuit. This ground causes the relay coil to energize and close the contacts for the power path. Keep in mind that you can have voltage to all the right places, but the computer must provide a ground. If there is no ground, the relay will not close the power contacts.

The power path picks up from a fuse link near the starter relay. Fuse links are like fuses, except they are pieces of wire and are made right into the wiring harness. The feed wire from the fuse link (orange/ light blue wire) goes to the fuel pump relay contacts. When the contacts close because the relay energizes, the power flows through the contacts to the fuel pump (light pink/black wire). The fuel pump has a black wire that supplies the ground to complete the circuit.

Remember that the computer does not source any power to actuators, relays or injectors, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.

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

http://www.veryuseful.com/mustang/t...witchWiring.gif

http://www.veryuseful.com/mustang/t...inks-ign-ac.gif

http://www.veryuseful.com/mustang/t...91eecPinout.gif

Now that you have the theory of how it works, it’s time to go digging.

Look for 12 volts at the Orange/Lt. Blue wire (power source for fuel pump relay). No voltage or low voltage, bad fuse link, bad wiring, bad ignition switch or ignition switch wiring or connections. There is a mystery connector somewhere under the driver’s side kick panel, between the fuel pump relay and the fuse link.

Turn on the key and jumper the fuel pump test connector to ground as previously described. Look for 12 volts at the Light Pink/Black wire (relay controlled power for the fuel pump). No voltage there means that the relay has failed, or there is a broken wire in the relay control circuit.

Check the Red/black wire, it should have 12 volts. No 12 volts there, either the inertia switch is open or has no power to it. Check both sides of the inertia switch: there should be power on the Red wire and Red/Black wire. Power on the Red wire and not on the Red/Black wire means the inertia switch is open.

The Tan/Lt Green wire provides a ground path for the relay power. With the test connector jumpered to ground, there should be less than .75 volts. Use a test lamp with one side connected to battery power and the other side to the Tan/Lt Green wire. The test light should glow brightly. No glow and you have a broken wire or bad connection between the test connector and the relay. To test the wiring from the computer, remove the passenger side kick panel and disconnect the computer connector. It has a 10 MM bolt that holds it in place. With the test lamp connected to power, jumper pin 22 to ground and the test lamp should glow. No glow and the wiring between the computer and the fuel pump relay is bad.

If all of the checks have worked OK to this point, then the computer is bad. The computers are very reliable and not prone to failure unless there has been significant electrical trauma to the car. Things like lightning strikes and putting the battery in backwards or connecting jumper cables backwards are about the only thing that kills the computer.

 

[JB66]

Both my Mustangs had problems with disintegrating connectors on the fuel pump itself, one twice. Of course, you have to drop the tank to check it. You can also disconnect the 4 pin connector at the rear of the tank by the rear bumper which goes to the sending unit and the fuel pump. I believe the Y/W is the feed for the fuel sending unit and the PK/BK is the feed for the pump.

 

[ss93cobra]

The distributor acts as a ground as well. The hold down needs to be snug at least and the hold down area needs to be clean and free of sludge too. Try cleaning the area and snugging down the dist. hold down first. By rotating the dist. you're making a decent ground and that's why you're hearing some clicking and buzzing. For example, try removing the nut (before you clean it), pull up on the dist. a bit, and try jumping the solenoid first to see what I mean.

 

[jrichker]

Both my Mustangs had problems with disintegrating connectors on the fuel pump itself, one twice. Of course, you have to drop the tank to check it. You can also disconnect the 4 pin connector at the rear of the tank by the rear bumper which goes to the sending unit and the fuel pump. I believe the Y/W is the feed for the fuel sending unit and the PK/BK is the feed for the pump.

I know what you mean - I have seen the crimp on splice connectors discolor from the heat. I have even seen the spagetti insulator tubing over the splices looking very deteriorated. Just let those two wires get together and spark - big bang and no more Mustang...

 

[Black1987Stang]

The distributor acts as a ground as well. The hold down needs to be snug at least and the hold down area needs to be clean and free of sludge too. Try cleaning the area and snugging down the dist. hold down first. By rotating the dist. you're making a decent ground and that's why you're hearing some clicking and buzzing. For example, try removing the nut (before you clean it), pull up on the dist. a bit, and try jumping the solenoid first to see what I mean.

I dont get what ur saying. and it has a ground? Hissin just said the clicking and pump priming was from me moving the stator (ignition on). Hissin, I also heard a beeping sound too, what is this beeping sound? ive heard it on other occasions also. this is normal then right, if not if the dizzys bad it might have something to do with my crazy timing probelm.
ss93cobra-the block is free of any grease and all and has a great connection between the dizzy and the block.

Anyways I pulled the tank anyways and put in a Holley 255lph pump, even if it wasnt bad i was still running the stock pump and wanted to upgrade. The tank is going back up tomorrow

 

[xkuntrycowboyx]

For a 95, you need the fuel disconnect tool (plastic things) that they sell at any automotive store. It was like $10 for the set for me, and included several sizes for different hose sizes. ...if u need one, ask a store and you'll understand how to use it when ya see it... no biggy. ...but u may not... i don't know bout the Fox's