Bad fuel pump?

[doug7x]

OK, folks...almost got my '91 XFI running. (well, actually it DOES run if I keep pouring gas down the TBI). Now, it's been sitting for 8 yrs, so I figured I'd put fresh gas in (appx 7 gal) to start it, so the LAST thing I want to do now is drop the tank to change the fuel pump. (the pump & gas guage were working fine when I parked it in 2000). Fuel pump relay works- not getting gas to TBI...also, gas guage is reading 1/4 tank, & not moving, with 8+ gal's. In my Chilton's book, the schematic shows that both the pump & guage share the black (ground) wire at the tank. When I bypass the relay & jump 12v+ to the pink wire at the relay block, nothing happens. When I ring it out, it reads infinity (open) pink to ground. However, when I check voltage between the pink & my + bat. terminal, I'm seeing 10 vdc. (term to term across the bat is 12vdc). Could I have lost the pump & gas guage at the same time, or am I looking at a bad ground? BTW, same results with a charger hooked up @ 13.5vdc. I REALLY hope you tell me I don't have to drop the tank & wear 7-8 gal's of 4.00 per gal. gas all over my sorry self. Thanks

[91Caprice9c1]

Originally Posted by doug7x

In my Chilton's book, the schematic shows that both the pump & guage share the black (ground) wire at the tank. When I bypass the relay & jump 12v+ to the pink wire at the relay block, nothing happens. When I ring it out, it reads infinity (open) pink to ground.
However, when I check voltage between the pink & my + bat. terminal, I'm seeing 10 vdc. (term to term across the bat is 12vdc).

Look for a burned fuel pump connector beneath the rear bench seat. Then determine continuity between the relay block and the FP connector, and between the FP connector and ground. Also look for continuity across the fuel pump itself.

Next, backprobe the fuel pump connector pink wire, and jump the opposite end of the pink wire at the fuse block, and look for voltage drop between the relay block and the connector.

Then, keeping the pink wire energised, backprobe the pink and black wires at the FP connector and look for voltage drop, and again between the fuel pump connector black wire and chassis ground.

The closer to zero, the better. This will tell you exactly between which two points in the circuit the electricity is being kept from doing it's job: Supply, load and ground. In order to back probe you must have thin enough probes to slide in to the connector, with it still connected. Or if you have sharp probes, you can stab insulator around the wire, and repair it with electrical tape later.

-MechanicMatt

[doug7x]

thanks, Matt...I'll try that in the AM...easier to pull the seat than the tank...thanx again....Doug

[doug7x]

Well, Matt...the connector was OK, but I cut it out anyway...the wire for the gas guage was pinched bad, so I cut it out & spliced it...gas guage now works. As far as the pump goes:
12vdc+ at the connector on the pink. (& to the pump)
Black rings to ground (both sides of the plug under the seat)
Pump does not run...when I ring JUST the pump, it's showing open. I think I should see SOME kind of continuity thru the pump, but I'm getting zip.
When I ring the pink to the pump to ground, it rings.( 0 ohms) (plug is disconnected) Am I gonna be taking a bath in my gas? (bad pump?) Thanks again...Doug

[91Caprice9c1]

Pump should not be open-circuited. You're bathing your way toward a working Metro.

A good friend and a floor jack are in order.


-MechanicMatt

[doug7x]

Well, I guess I know what I'll be doing next weekend. Where's the best place (cheapest) to order a pump from. I figure I'll ask here first, before I go to NAPA. Thanks again...Doug

[W00dy]

I got a bosch from Carquest for $116 and the strainer was $16.

[doug2060]

Check out ebay too. Very cheap there...

[doug7x]

Looks like ebay is the best deal (35.00, I think)...only problem...these pumps are listed as being for '95 & newer...will it work on my '91? (if so, I'll just use the one out of my '96 Swift parts car, (if I can get it to run on the bench)...Thanks again...Doug

[doug2060]

I'm not sure. Contact the ebay seller for further details. I'm sure someone on ebay has it cheao for that year model. Some of the sellers there only list the years they know it fits even when there are more.