Fuel Pump Problem

Stage-manager · #1 05-20-2010, 01:45 PM

our 95 SVX has been in the shop for a few days now, after it just stopped. the mechanic can get the fuel pump to work when he uses his testers directly into the pump, but when he connects the connector and tries to use his tester it will not work.
Does anyone know what wires go to where? such as a color code?
Thanks
Jeff

svxfiles · #2 05-20-2010, 03:02 PM

Has he looked at the fuel pump modulator and resistor?
http://www.subaru-svx.net/photos/use...svxfiles|23919

Stage-manager · #3 05-21-2010, 10:28 AM

Here is a little more info to see if any one has a solution.
My son was driving it home from work when it stopped. He started it up and it ran for a few minutes, then stopped again, tried it again, and the same thing. Then it would not start at all. That was when we had it towed to our mechanic.

When the mechanic has the fuel pump disconnected(unplugged) and puts his testers on lead 1 blue hot, and lead 3 black ground, the fuel pump works, when he reconnects the pump and puts his testers on the same leads it will not work! any ideas?
his questions are-

1. What colored wires go to what?

2. what is #4 G/W wire? he gets a 12v reading from that one!

I can furnish the shop number to anyone who might be interested in talking to
him.

Tom- I am not sure he looked at the fuel pump modulator or resistor. I will ask him today when I talk to him.

Thanks
Jeff Johnson

Manarius · #4 05-21-2010, 10:40 AM

Have you checked the plug under the rear seat? (I'm pretty sure there's one there)

On the Legacy's of that era, that plug had a tendency to melt.

svxfiles · #5 05-21-2010, 05:37 PM

Quote:

Originally Posted by Stage-manager

Here is a little more info to see if any one has a solution.
My son was driving it home from work when it stopped. He started it up and it ran for a few minutes, then stopped again, tried it again, and the same thing. Then it would not start at all. That was when we had it towed to our mechanic.

You know that other things can cause this behavior.
A car with a bad MAF/cam sensor/crankshaft sensor/WATER TEMP SENSOR

can just shut off, stop while driving, and restart fine.

Stage-manager · #6 05-21-2010, 05:51 PM

Quote:

Originally Posted by svxfiles

You know that other things can cause this behavior.
A car with a bad MAF/cam sensor/crankshaft sensor/WATER TEMP SENSOR

can just shut off, stop while driving, and restart fine.

I will pass this on to my mechanic. but what about the fuel pump not working when its plugged in? even when he puts power to it?
could it be a short?
Thanks for all the info.
Jeff

SoCal LS-L · #7 05-21-2010, 06:39 PM

Quote:

Originally Posted by Stage-manager

I will pass this on to my mechanic. but what about the fuel pump not working when its plugged in? even when he puts power to it?
could it be a short?
Thanks for all the info.
Jeff

From what you describe, it almost sounds like a lead inside the harness may have broken, making an intermittent connection. A simple way to check is to use a multimeter and check the continuity between the tip of the lead and the corresponding wire, while wiggling it. Otherwise it sounds like a possible ground issue.

Trevor · #8 05-21-2010, 08:38 PM

Quote:

Originally Posted by Stage-manager

Here is a little more info to see if any one has a solution.
My son was driving it home from work when it stopped. He started it up and it ran for a few minutes, then stopped again, tried it again, and the same thing. Then it would not start at all. That was when we had it towed to our mechanic.

When the mechanic has the fuel pump disconnected(unplugged) and puts his testers on lead 1 blue hot, and lead 3 black ground, the fuel pump works,

One must assume that works means runs, and this "tester" is a means of applying a voltage. In which case this proves the pump is OK.

Quote:

when he reconnects the pump and puts his testers on the same leads it will not work! any ideas?

Your mechanic does not know what he is doing. He has applied a reverse voltage voltage to a control circuit. You indicate that he has been unable to identify the polarity of the wiring involved. If he has applied reversed polarity he may have damaged the fuel pump modulator.

Keep fingers crossed.

The obvious test is to check for voltage at the pump connections, the fact that this was not his first check proves a lack of ability. The positive supply to the pump via the blue lead, is switched via the fuel pump relay, located under the dash, drivers side. The negative (black, changing to a yellow at a connector) is controlled via the fuel pump modulator.

The resistor, black and yellow connecting wires, grounds the pump for slow running. The modulator bridges the resistor so as to provide a solid ground when full pump speed is required.

Someone with a clue or two, should be able to identify which circuit is faulty. Hopefully the problem will involve the relay which can be easily be replaced at no great cost.[/QUOTE]

Quote:

his questions are-

1. What colored wires go to what?

2. what is #4 G/W wire? he gets a 12v reading from that one!

The official manual does not show a green white wire.

Stage-manager · #9 05-22-2010, 08:11 AM

thanks for all the info, I will pass these onto my mechanic.
Jeff

SoCal LS-L · #10 05-22-2010, 10:28 AM

Quote:

Originally Posted by Stage-manager

thanks for all the info, I will pass these onto my mechanic.
Jeff

Especially stress these points

Quote:

Originally Posted by Trevor

Your mechanic does not know what he is doing.
The obvious test is to check for voltage at the pump connections, the fact that this was not his first check proves a lack of ability.