Fuel pump diagnosis

[Bert]

A pin connector (one of 4) within the fuel pump harness at the gas tank gave out/melted recently. The pump has been replaced as has been the plug-able short section of harness (between the gas tank and the car body) but the pump still refuses to run. Pump is functional when it's jumped from a battery. There is a pulse signal coming thorough these wires (from the ECU?) but otherwise nothing. OEM manual says nothing about pumps (inertia switch was not tripped by the way, and was reset just in case) and the Haynes manual says to check the fuse and the fuel pump relay. VAF is also involved as I understand it but the fuel pump test circuit (green/red wire and a black wire on a dead end stub near the firewall) also are live.
I cannot identify nor find a fuse location for the fuel pump nor can I find 'the' pump relay. Sure, there are Aspire pictures of connectors and fuses in the Haynes manual but nothing relevant to EFI (90-93) Festys. Anyone out there have any experience and/or advice in this matter? Would be very much appreciated.

[bravekozak]

Fuel pump relay is located right beside where the antenna enters the side panel under the dash. It should have a six terminal yellow connector. The red wire at the fuel pump provides juice for the sender. The black/white stripe provides juice for the pump motor. Black is ground. Imertia switch only breaks the circuit on impact. Power to the fuel pump relay comes from the main relay near the L/H headlamp. In order for the fuel pump relay to work, the Vane Air Flow must be grounded (air flowing).

I cheated and just put a temporary jumper so that it runs continuously in RUN. Until I replace my relay with a fuel pump safety relay that gives me three seconds to prime my carbs and then monitors my tach signal. I don't have a VAF.

[bravekozak]

No fuse. MAIN fusible link to ignition and EGI fusible link to main relay.
The solenoid on the main relay is protected by the ENGINE fuse.
Bert, what color wire melted?
Does anyone know what the draw is for a fuel pump motor? Is it 10.1A ?

[nitrofarm]

Bert does the pump run when you jump the "Test" connector now?

[tooldude]

That pulsing you mention is interesting, how did you do the test for voltage at the fuel pump? If you did it by cranking the engine, it sounds like the VAF vane could have been pulsing with intake strokes. It's a simple circuit, it's just a matter of where the supply voltage stops.

[gotrootdude]

Sorry to hijack this thread but I'm also having a problem getting my car started due to a fuel pump issue. I used to have to knock on the rear seat in order to crank the car, so I figured the pump was the problem and replaced it. Also, before the pump was replaced it would occasionally shut off while driving.

Since replacing the pump, the car has started up a few times but mostly refuses to crank and I know next to nothing about cars..
Where's the test connector for the fuel pump and how would I jump it? Would that maybe allow me to start my car?

[bravekozak]

The fuel pump self test connector is located between the brake fluid reservoir and the ignition coil. I would suggest opening up your VAF meter behind your right headlamp and checking for smooth operation of your vane. The check also includes making sure there is no corrosion on any of the electrical terminals inside your VAF connectors.

The green/red stripe wire that goes to the VAF also goes first to the fuel test connector. If you jump that connector to ground and you can start the car, then the problem is your VAF. The VAF must be fixed and don't leave the jumper wire in the test connector. This is for safety shut off of the fuel pump in case of key in RUN, engine not running and fuel pump pumping.

[Bert]

Haven't been out yet to check the car (it is in a heated garage a few miles down the road) yet but am printing off all of your advice for when I do. Thanks guys! I must say I look longingly at pre-electronic vehicles because diagnosis is so wonderfully simple on them.

[tooldude]

If you crank the engine and get no voltage at the fuel pump, then the FP relay is most likely faulty because the relay is supposed to be activated while cranking. This is a separate circuit from the VAF switch which maintains a connection only with air flow. If you do get voltage at the pump while cranking, then most likely there is loss of continuity through the inertia cutoff switch to ground. If it's neither of these it must be a wiring/connector problem.

[nitrofarm]

You can use the test circuit to tell you everything is good EXCEPT the micro switch in the VAF which completes the ground.

[tooldude]

Yes, like nitrofarm said above. Bert, going from what you posted above it sounds like you have only the Haynes book. Therefore I was trying to give you an idea of what the circuit is doing if you don't have that information. This is a simple circuit but has multiple possibilities of why it failed; and I can see at least 3 ways you may have checked voltage at the fuel pump which would prove different parts of the circuit as good. From a troubleshooting perspective out here, this is complicated by the fact that you had a terminal meltdown which could indicate a very high current draw. Lack of information causes assumptions and I'm assuming that's why you changed the pump. The pump may be good though, as resistance from corrosion there can cause that much heat. Most failures are simple and singular and most likely it's a bad FP relay. With the ignition on, there should be 12V from the main relay (Y/BK) to the FP connector (Y/BK) and 12V through the relay contacts (GN/Y) to the pump. You could jump the Y/BK to GN/Y for a quick test (key on) if you don't have a relay. You have proven at least one ground is good by jumping 12V directly to the pump.

[gotrootdude]

Update on mine. Literally I just tapped on the top of the VAF and she fired right up. VAF it is, will be cleaning it out.

[Bert]

You diligent folks on here certainly gave me valuable advice. I can see that the Haynes manual has several shortcomings with regard to Festy fuel pump circuits. One of which is that the wiring diagram colour codes don't jive with what I've got. However I did find the fuel pump relay (thank you bravekozak) and have been busy testing circuits. Car has not fired up yet and I am lucky to have access to spare parts and a spare car!
I pulled the fuel pump from a spare car only to discover that the in-tank filter on it had completely disintegrated; plastic mesh covering plus the cloth bag had fallen apart. This set-up was only 3 years old. Makes me wonder if pre-ethanol gas cars are susceptible to much more than softening seals and gaskets.

[nitrofarm]

Bert are you aware there are Ford Service Tech schematics on this forum? Just wondering because you said you are using Haynes...

[Bert]

Up date. The car is functional again thanks to valuable input from forum members, especially bravekozak nitrofarm and tooldude. Thank you very much gentlemen!
Turns out there were two primary issues; poor contact at the EGI loop fuse in the engine compartment Fuse Box and a melted/eroded connector at the gas tank. Meanwhile I did thoroughly re-acquaint myself with the VAF, alternator, fuel pump, pump relay and a collection of coloured wires. Perhaps I should have taken pictures of the jury-rig that was made to make and install a fuel strainer on the new fuel pump because none of my parts-bin pumps yielded anything of use. What is a joy about the new SPI pump is that I am longer party to the sound of a 'hive of bees' behind the back seat such as was the case during the past 2 years with a Delphi pump adaptation.
By the way nitrofarm it was the black/white wire connection in the short gas tank harness that eroded/overheated and failed.