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Old 03-20-2022, 08:55 AM
Black88GTA's Avatar
Black88GTA Black88GTA is offline
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Join Date: Jan 2009
Location: Huntington, NY
Posts: 249
Question Pinout for fuel pump connector?

My SVX (92, 123k miles) has been sitting pretty much since November, since it was getting too cold to work on it outside. At the time, it was running fine. I went to move it yesterday, and it wouldn't start. The battery has been on a trickle charger inside, and is fully topped up. It cranks strong, but seems to not be getting fuel.

Further investigation showed that the fuel hoses didn't seem to be pressurized, and I can't hear a hum from the pump when I turn the ignition on. I did some basic checking at the connector (going to do more today) but I feel like I'm flying blind without knowledge of what some of these wires are for.

Does anyone have a diagram of the fuel pump connector showing the function of each wire? I have searched, but can't seem to find anything. I did find the wiring diagram, but it doesn't seem to correspond to the plug? So far I have the following:

Blue: +12v ~5 sec after key on, then goes to 0v
Green w/ yellow stripe: ???
Orange: ???
Black: Ground
Green w/ white stripe: ???

I think the behavior of the blue wire indicates that the FP relay under the dash is working properly (?), and the ground / fuse is good. I tested the blue wire both with a chassis ground, and again using the black wire in the plug, with the same result.

I found information on the fuel pump resistor and modulator under the rear parcel shelf, and read that one of these acting up can cause problems. So I tried messing with those, with the following results:

Resistor / Modulator both plugged in (normal): no start
Resistor unplugged: no start
Modulator unplugged: no start
Both unplugged: no start

Based on this, I don't think either one of these are my problem. I'm pretty sure my fuel pump is original, and looked pretty crusty when I had it out last year, so I'm leaning toward that being it but would like to do more tests at the connector to rule out as much as I can before replacing it.

In the event I do have to replace it, what is the current consensus on a quality pump to use? I've read Walbro is the go-to, but is there a specific model / part number to look for? Are any of the offerings on Rock Auto worthwhile as an alternative? Also, I've read that the 92-93 cars used a different pump than the 94-97s? I took some pics / got some information off of my current pump when I had it out (just in case )

Pic:


The pump measures approx 2" diameter, and uses two screw terminals for wiring connections (as opposed to a plug). It has the following identifiers on it:
A42-650040
JECS
1529C

Thanks in advance for any help!
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Ebony/Gray '92 LS-L, @123k - bought 01/17/2010, parked for 10 years. Getting back on the road.

Last edited by Black88GTA; 03-20-2022 at 09:03 AM. Reason: Added crusty pump pic
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Old 03-20-2022, 11:59 AM
Black88GTA's Avatar
Black88GTA Black88GTA is offline
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Join Date: Jan 2009
Location: Huntington, NY
Posts: 249
Re: Pinout for fuel pump connector?

OK, I went out and did a bit more checking. I looked for voltage and resistance on each pin relative to ground, both with key on and in ignition / run position. Findings are below. All of them have some sort of signal (either in voltage or resistance) in one of the key positions, so my thoughts are that my wiring / relays / modules are all good, and so, I'm almost sure it's the pump. If anyone sees anything abnormal about the readings below, I'd love to hear it

Voltage (key OFF): All 0

Voltage (key ON):
Blue: +12v (5s after ign on) 0v after that
Grn/Yel: 0v
Orange: +6v
Grn/Wht: +11.5v

Resistance (key OFF):
Blue: 77.7 ohms
Grn/Yel: 5.0 ohms
Orange: 83.6 ohms
Grn/Wht: 29.1 ohms

Resistance (key ON):
Blue: 85.8 ohms
Grn/Yel: 39.7 ohms
Orange: open
Grn/Wht: open
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