I replaced my fuel pump but it still won't start. The new fuel pump won't run at all because I can't hear it in a quiet garage. All fuses are good, relay it clicks when the key is turned on, but no go. Does anyone have any ideas? It has to be a either a short or a power issue.

 

The only wires that are hot at the pump are the yellow and one of the greens when the key is turned on (there's a blue, black two greens, and a yellow for a total of 5 wires). I'm not sure if this is normal or not. All wires are dead at the pump with the key off. I checked the wires in the rear of the trunk including the modulator, resistor and ground wires. All looks good as far as I can tell.

 

Could a bad relay still click but be bad? I think I'm aiming towards this. All these problems occurred after I had disconnected the battery and reconnected it trying to clear ECU codes.

 

Thanks in advance.

Edited July 29, 201213 yr by DavieGravy

Could this be the problem?

 

Looks like the wire to the knock sensor. That would not cause a no start condition.

 

What are we working on?

It's a 92 SVX

 

The car was also flashing the power light and giving a code 21 for duty solenoid C. This was replaced at the mechanic, but the light still flashes. Wonder if the 2 problems are related.

 

The car was hit in the rear passenger side by a tractor trailor. I'm wondering if this didn't cause some kind of issue. Also, some exhaust work was done. Could a ground have been left loose?

Edited July 29, 201213 yr by DavieGravy

Is there any sort of alarm/security system with fuel shut-off?

There's a factory alarm, but this can be disabled with the security button on the dash which I have done. As far as I know, there's no fuel shutoff mechanism. It just causes the horn to beep until you turn the key on. Good thinking though...

 

I wonder if the ECU itself is bad. Or an ECU ground was disturbed.

Edited July 29, 201213 yr by DavieGravy

Try this:

"Have you put a meter across the connector to the fuel pump? Very often on the Impreza when the ECU senses nofuel the car will not restart. It will need an ECU reset. The easiest way of doing this is to disconnect the battery for half an hour. The ECU has capacitors in it that retain a charge. By cutting the current supply the charge in the capacitors leaks away and any stored fault codes will be wiped."

http://www.fixya.com/cars/t1708583-fuel_pump_not_working

Not your car model but you never know and hell, go watch the Olympics while the battery is disconnected for a while.

You did say it started when you first disconnected the battery but perhaps there is a sequence to get it going AFTER you did your work like when turning on a router after a modem etc... just sayin'.

Edited July 29, 201213 yr by brus brother

Cougar is the go to guy here on USMB for electrical gremlins. I don't receive any fee for this endorsement ;-)

I've left the battery disconnected for days but the issue continues. I assume the ECU was reset during that time.

Yes, a relay can click, and still be bad. A single pole, single throw relay consists of an electromagnet, which closes the contracts when it is engergized, and the contacts themselves. The "click" you hear is the electromagnet energizing, but the contacts could be worn or misaligned.

 

But FIRST, I would try to find a wiring diagram for the fuel pump. You have know the purpose of all the wires running to the fuel pump to be able to troubleshoot effectively. Troubleshoot using a wiring diagram and a voltmeter whenever you can, parts substitution can be a very expensive way to solve a problem.

Here's a link to pdf of wiring 92 svx:

http://home.arcor.de/klaushoffnau/SVX_Historie/WIRING_DIAGRAMS.pdf

see page 4 area C-7 for fuel pump

Edited July 30, 201213 yr by brus brother

Are you sure it isn't getting fuel?

 

Generally you'll have 3-4 wires at the sender and the two largest ones will be power and ground for the pump.

The fuel pump definitely isn't turning on because you can't hear it run at all.

 

I unplugged the connector from the relay and tested the wires there.

 

Yellow - hot with key on, dead with key off

All the rest - dead with the key off

 

The red and one of the other wires peg the volt meter to the negative (opposite direction) with the key on. I'm using the 50 volt DC scale on the volt meter.

 

Is this indicative of a short somewhere between the engine compartment and the relay under the steering wheel?

Does anyone know where the ground wire is to the fuel pump?

Does anyone know where the ground wire is to the fuel pump?

 

I'm assuming that you know how use a voltmeter, and that you know enough about basic electricity to keep yourself out of trouble. Don't do any electrical testing if you have pulled the fuel pump out of the gas tank. Electrical sparks and gas, especially gas fumes, do not mix.

 

There's a fuselink, no.2, that supplies 12VDC to one of the contacts in the fuel pump realy. Have you checked that fuselink?

 

I'm using the schematic provided by Brus Brother. It looks like there's a two pin electrical connector coming off the fuel pump. I'm assuming that connector is inside the car interior and NOT inside the fuel tank. THE BEST WAY TO TEST. Leave the connector connected. See if you can get your test lead probes into the backside of the connector. You need to be touching the metal wire crimp inside the connector with your probes. You want the red test probe on the blue wire. You want the black test probe on the black wire. Energize the fuel pump relay. You should have about 12VDC. If you have about 12VDC and the fuel pump is not pumping then the fuel pump is bad.

 

If the fuel pump connector is not convenient, you might be able to put your red test probe on the blue wire where it is connected to the fuel pump relay. You can put your black test probe on any piece of metal that is connected to ground.

 

If you don't have about 12VDC on the blue wire when the fuel pump relay is energized just post and we'll trace the circuit back.

Edited July 31, 201213 yr by The Dude

The fuel pump definitely isn't turning on because you can't hear it run at all.

It can be difficult to hear a pump run. Have you verified that no fuel is being pumped? Either with a pressure gauge or by sticking the supply line into a bottle.

The red and one of the other wires peg the volt meter to the negative (opposite direction) with the key on. I'm using the 50 volt DC scale on the volt meter.

 

Is this indicative of a short somewhere between the engine compartment and the relay under the steering wheel?

No, usually means the polarity is reversed, or it could mean you are testing incorrectly (meter on the wrong setting or the circuit can't be tested in such manner).

 

If the wire diagram is right you are testing the red/yellow wire for the modulator, which feeds back to the ECU. That is probably ECU reference. Would need a pinout of the ECU to be sure though, but that's how it looks in the diagram.

 

Blk/wht wire going into the relay is 12V from fuse 16 in the dash panel. Green/blk is ground through the ECU. If the relay clicks w/key ON the ECU is grounding it, you should then have 12V output on the Blue wire which goes to the pump. I don't know where the fuel pump modulator is, but it controls ground for the pump.

 

At the pump: W/key ON you should have 12V at the pump on the Blue wire, and should see continuity to ground on the black wire.

 

There is a resistor inline straight to ground so resistance may be high, but should still see cont. to ground w/ key OFF.

Key ON should show low resistance Cont. to ground if the Modulator is working properly.

There's a fuselink, no.2, that supplies 12VDC to one of the contacts in the fuel pump realy. Have you checked that fuselink?

I did see that on the diagram. Is this a 30 amp fuse as opposed to a wire fuse link? I gathered it was. If not, then I have no idea where it's located.

If the fuel pump connector is not convenient, you might be able to put your red test probe on the blue wire where it is connected to the fuel pump relay. You can put your black test probe on any piece of metal that is connected to ground.

I could not get my probes in the connector at the fuel pump with it plugged in so I tested the connector at the relay, with it plugged into the relay.

 

When I first turn on the key, I get 1 volt on the blue. Then I hear a click (the relay?) in the dash and the volt meter pegs negative as far as the needle will go. I'm using the 50 volt DC scale, but just to be sure I tried all the scales and they all pegged negative as soon as that relay kicked on.

 

At the relay with the connecter disconnected from the fuel pump, the blue is dead.

Edited August 1, 201213 yr by DavieGravy

It can be difficult to hear a pump run. Have you verified that no fuel is being pumped? Either with a pressure gauge or by sticking the supply line into a bottle.

I have. I disconnected the In line to the filter and no fuel squirts out when I turn the starter or leave the key in the on position.

If the relay clicks w/key ON the ECU is grounding it, you should then have 12V output on the Blue wire which goes to the pump. I don't know where the fuel pump modulator is, but it controls ground for the pump.

The relay clicks immediately when the key is turned on, then once more about 3 seconds later. Not sure if this means anything.

Edited August 1, 201213 yr by DavieGravy

That means the ECU is cutting the ground to the relay as it should after the prime test is done. That is normal operation.

Did you check the blk/wht wire for 12v w/ key ON?

Did you check the blk/wht wire for 12v w/ key ON?

 

Sorry for my misunderstanding The blk/wht wire tests at 12v against the green/black (ground). When the relay clicks it goes to 0

Edited August 1, 201213 yr by DavieGravy

Understanding now the green/black is ground, at the pump, the yellow and green/white test hot with the key on. With the key off, all dead. Including the blue.

Both the blue and the black are at 12v until the relay clicks, then the black goes to 0 and the blue pegs negative at the relay. So the blue is not staying live it seems. This is using green/black as ground.

Ok, the Grn/blk wire is the ground to the ECU. Since voltage goes to 0 when the ground is open (ECU opens/closes the circuit to allow 12v to pass through the relay) that shows the ECU is grounding the circuit properly, at least during the prime test (builds pressure in the lines for starting)

You should also have 12V w/ key ON at the Yellow wire to the relay. This should show 12V when grounded to chassis ground.

 

If the relay is working properly you should be getting 12V on the blue wire for the ~3 seconds or so during the prime test. Put the negative probe on a clean chassis ground point somewhere under the dash when checking this. Pretty much any clean metal part or bolt head should work.

 

At the pump, if you disconnect the connector and test the blue wire during the prime test (you'll need to connect the meter and then go turn the key while watching it. Again, ground the meter negative to the chassis, even if it's just the floor pan of the car, don't ground to other wires) you should see 12V.

 

If you have 12V at the relay blue wire during prime test, but not at the pump blue wire there is an open in the circuit somewhere between the relay and pump. Then check for continuity across the blue wire by connecting the meter to each end. You may need to string a wire across the car if your test leads aren't long enough to reach.

 

If 12V at relay AND pump on blue wires during prime test, the pump modulator (which I still haven't found a location for) is probably faulty.

 

 

The Green/white, Green /yellow, and Orange wires at the pump are for the level sender unit. No need to mess with those.

Thanks for this. I'll check the blues tomorrow (at both ends during prime test grounding to the chasis) and post back. I'm starting to lean toward a faulty modulator since it's in the trunk and the car was slammed from behind.

 

The modulator is in the top of the trunk underneath the trim. I've removed the trim and it's in full exposure.

Edited August 1, 201213 yr by DavieGravy

That's great you know where it is! You can check some wires there as well then.

 

The modulator is what grounds the pump, check the black wire at the pump for continuity to chassis ground with the key ON. As I said before, there should be low or no resistance there with key ON. High or infinite resistance could indicate an open circuit which would mean the ground wire is damaged or the mod. is bad.

 

Should be 4 wires on the modulator, Yellow, Black, Blue, and Red/yellow.

Yellow is the pump ground. Continuity from the black at the pump to the yellow at the modulator. Should be low or 0 ohm resistance. Should also show continuity to chassis ground with key ON. This may only show during prime test. High or infinite resistance would likely mean the modulator is bad.

 

Black wire on the modulator is the ground. This should show continuity to chassis ground at all times.

Should also show some resistance between there and the black wire at the pump. They are connected but there is a resistor in the way.

 

Blue wire to the Modulator. Same blue wire that feeds 12V to the pump. That should also be 12V w/key ON during the prime test.

If you get 0V, check for continuity from the blue wire at the relay to the blue at the modulator. Should show very low or 0 ohm.

 

Red/yellow goes to the ECU. I said this may be 5V reference before, but it could be ground to turn the modulator on/off. Hard to say, but it can be tested. Connector unplugged, Check for DCV at the red/yellow w/ key ON. If no voltage present check for cont. to ground. This may only show during the prime test, since the ECU controls this circuit.