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.

There is continuity between the black wire at the pump (with the connector disconnected) and the chassis of the car with the key on, meaning the ohm meter pegs all the way forward.

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.

With the key on, the connector disconnected at the pump and the connector plugged in at the modulator, there is continuity between the yellow at the mod and black at the pump. There is also continuity between the yellow at the mod and the chassis. (the ohm meter pegs all the way forward on the ohm scale)

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

It does.

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.

I don't see any resistance between the black at the pump and the black at the modulator.

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.

It is.

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.

The red/yellow does not show any voltage during prime test or any other time. There's continuity with some resistance. on the 1k ohm scale the needle goes about half way.

Edited August 2, 201213 yr by DavieGravy

I am also getting 12 volts at the blue wire at the pump (with ground to chassis) during prime test until the relay clicks.

 

I'm stumped. Could it be a problem with the resistor? The pump is new and should be coming on.

I am also getting 12 volts at the blue wire at the pump (with ground to chassis) during prime test until the relay clicks.

 

I'm stumped. Could it be a problem with the resistor? The pump is new and should be coming on.

 

You need to things to run a DC motor like the fuel pump. You need a voltage, in this case 12VDC on the blue wire, and you also need ground.

 

When you turn the key to "on" the fuel pump relay supplies 12VDC to the pump on the blue wire. After a few seconds the CPU signals the modulator to remove ground from the pump. Pin 1 at the modulator, the yellow wire, switches from ground to 12VDC. At this point there is 12VDC on the blue wire, and 12VDC on the yellow wire. Both these wires go directly to the fuel pump. With 12VDC on both wires supplying the fuel pump there is no voltage difference across the pump, no current will flow, and the fuel pump will not work. The resistor is in the circuit so that when pin 1 on the modualtor switches to 12VDC it does not short directly to ground.

 

I know how to read a schmetic diagram, but I am not experienced on your particular model. So, wait for Fairtax4me to comment before trying my suggestion.

 

I am wondering if you could just remove the connector from the modulator? With the modulator out of the circuit, the fuel pump should continue to run with the key in "on". There is a return fuel line, so I don't think it will hurt anything, but I am not certain.

 

If you remove the modulator from the circuit and the fuel pump runs, you can be fairly certain that the modulator is the problem.

Edited August 2, 201213 yr by The Dude

I cant view the diagram right now (on the mobile) but what I remember from it I THINK The Dudes suggestion should work.

 

You could run a jumper wire straight to ground from the pump (modulator unhooked) and turn the key on to see if the pump runs.

 

There's still no guarantee that the new pump isn't just DOA.

Well, unfortunately my battery is now dead, so I'll have to try it and post back after I charge it back up. Where exactly should I run the jumper wire to on the pump?

 

Thanks

Well, unfortunately my battery is now dead, so I'll have to try it and post back after I charge it back up. Where exactly should I run the jumper wire to on the pump?

 

Thanks

 

 

Once you pull the connector off the modulator you can run a jumper wire from the yellow wire to ground. Running a jumper without first removing the connector from the modulator will probably destroy the modulator.

 

However, you shouldn't need to run a jumper. Just remove the connector from the modulator, that will take it out of the circiut. Without the modulator, the fuel pump should run as long as the key is in the "run" position. Only power the pump for as long as it takes to test it.

 

If the pump still doesn't run with the modulator out of the circuit, you can leave the connector disconnected and run the jumper from the yellow wire to ground. At this point you should have 12VDC on the blue wire, and a good ground on the yellow wire. If the fuel pump still doesn't run, brand new or not, you have a dead pump.

I tried just unplugging the modulator connector and also unplugging the connector and grounding the yellow to the chassis. The car would not start. It "puffed" a few times while the starter was going as if it could almost start, but never did. I assume this is just from residual gas in the engine.

 

Thanks for all the help.

Edited August 4, 201213 yr by DavieGravy

I don't think I did, but what would happen if I mixed up the pos and neg connectors on the pump?

I would think it should spin backwards, but it may have a diode in it to prevent it from spinning if the polarity is wrong.

Could this be the source of the problem? I recall, it was like this before I removed the old pump. It looks like the connector is burned. This connector goes underneath the fuel tank lid thingy that all the hoses connect to. This connector supplies the wires that go to the pump. It's burned through on both sides and looks like it might have been arching.

 

Edited August 5, 201213 yr by DavieGravy

Could this be the source of the problem? I recall, it was like this before I removed the old pump. It looks like the connector is burned. This connector goes underneath the fuel tank lid thingy that all the hoses connect to. This connector supplies the wires that go to the pump.

 

 

Well yeah, Davie, the condition of that connector is key to your problem with the new pump. It's unfortunate that you didn't disclose this vital piece of information at the beginning of this thread. That connector is VERY badly burnt, it is likely that it will no longer conduct electical current. That connector must be replaced. My guess is that your old pump started drawing a huge of amount of excessive current, more current than the rating for the connector. BTW, while we're at it, what does the other side of the connector look like? Any wiring burnt, or badly discolored?

No offense intended, but do you feel experienced enough to handle this repair yourself? There is no margin for error where gasoline and electricty are concerned. I do 90% of the mechanical work on my Subaru myself. That remaining 10% I gladly pay a professional, full time mechanic to handle. I like to think that I'm pretty good at mechanics, but I know, and respect, my limits.

Well yeah, Davie, the condition of that connector is key to your problem with the new pump. It's unfortunate that you didn't disclose this vital piece of information at the beginning of this thread. That connector is VERY badly burnt, it is likely that it will no longer conduct electical current. That connector must be replaced. My guess is that your old pump started drawing a huge of amount of excessive current, more current than the rating for the connector. BTW, while we're at it, what does the other side of the connector look like? Any wiring burnt, or badly discolored?

No offense intended, but do you feel experienced enough to handle this repair yourself? There is no margin for error where gasoline and electricty are concerned. I do 90% of the mechanical work on my Subaru myself. That remaining 10% I gladly pay a professional, full time mechanic to handle. I like to think that I'm pretty good at mechanics, but I know, and respect, my greatly limits.

No offense taken and I apologize, but I will say that I didn't notice it was burned through when I removed the old pump. The holes that burned through the connector likely happened while the new pump was in. What I did noticed while removing the original pump was a little bit of blackness in the hole. I should have clarified this in my last post.

 

I do feel experienced enough now to replace this connector and get it all hooked back up.

 

I do realize a lot of nice folks here spend some time helping me out and I greatly appreciate it.

Yep you need a new connector there. Is that inside the tank?

It is. I'm definitely going to replace it. Although there is continuity between the connector and the other end of the wire. So it had to have been working.

This may still have a plot twist.

Let us know how the movie ends.

It may have continuity but the reason they burn like that is usually because the female connector doesn't grip the male connector tightly enough.

 

The loose fit causes high resistance and subsequently high heat and arcing.

Is there any way you can cut the plug out entirely and connect the wires with crimp connectors? I would use the high quality double jacketed type that cost twice as much. But they'll work better.

I ended up just getting another connector from the junk yard. It's the same on the legacies, but much shorter. Due to the long wires on the fuel pump this wasn't an issue.

 

I took extreme care putting it all back together and double checked everything, but I'm nervous as hell about trying to start it. Is there any possibility of an explosion?

Sweet, I now have a running SVX. Thank you fairtax4me, the dude brus brother, and all the others who helped.

Edited August 5, 201213 yr by DavieGravy

I ended up just getting another connector from the junk yard. It's the same on the legacies, but much shorter. Due to the long wires on the fuel pump this wasn't an issue.

 

I took extreme care putting it all back together and double checked everything, but I'm nervous as hell about trying to start it. Is there any possibility of an explosion?

 

As long as you didn't put a spark plug in the tank, no.

Funny thing about gas. It's extremely flammable in the right vapor concentration, called the stoichiometric ratio. That's the mixture of fuel to air ratio. Mix the right amount of fuel and air, plus a spark/flame/etc., you get a big bang. But inside a closed fuel tank, there's very little air. It's mostly fuel vapor, and without enough oxygen it doesn't combust. So you can get small sparks/ arcing without it relocating your trunk.

 

 

Glad to hear you got it going!

There is a fuel pump relay under the dash by the ecm. There is also a fuel pump resistor under the rear deck lid... need to see where power is lost

 

Tom

Sweet, I now have a running SVX. Thank you fairtax4me, the dude brus brother, and all the others who helped.

 

Excellent!