Here's what happened:

This past spring my Jimmy sprung a fuel leak in the fuel lines. I parked it with it running roughly but was able to move it. About a month ago I replaced the lines, sending unit and fuel tank figuring it would fire back up. That didn't happen. I then replaced the fuel pressure regulator and spark plugs (I replaced the spider and fuel pump about 3 years ago.). I checked the coil and rotor which tested fine. I checked the pump and confirmed I was getting fuel at the plenum when my wife turned the key on using a glass jar to catch the fuel in. I then sprayed starting fluid into the plenum and it tries to start till the fluid burns out.

Now, when I checked the voltage I got 12.2 volts at the battery, 11.6 volts at the fuel pump relay but only 8.4 volts at the pigtail that connects to the pump. I looked at the pigtail as best I could but didn't see any corrosion, but again, as best as I could tell. It's way up in there on top of the tank. As I understand it, if the fuel pump isn't getting enough voltage the pump won't supply the proper pressure.

Does this indicate a short and how do you test for that?

Thanks for any help on this.

 

You shouldn't be seeing that kind of voltage drop with no load on the circuit. I bet that if you were to test the fuel pressure, there still wouldn't be enough pressure (>55psi) at the intake plenum.

To narrow down the source of the problem, you can test the quality of both the +12V and the ground at the pump by extending a jumper wire from the battery back to the pump. While testing the +12V feed to the pump, connect the jumper wire to the negative terminal on the battery and record the voltage at the pump connector while probing the +12V pin. When testing the ground, connect the jumper wire to the positive post and record the voltage at the pump connector while probing the ground pin.

You should see near the same value at both and they both should be relatively close to battery voltage.

 

I'm not sure I'm understanding you. I tested the pigtail on the relay side, not the pump side. Which connection should I test using the jumper wire; the connection on the relay side or the connection on the pump side. And just so we're on the same page, this is the connectors at the pump/sending unit. Thanks again.

 

I thought I was fairly clear... Using a jumper wire will allow you to isolate the individual wires and not bring uncertainty of ground points, etc into the equation especially if you do your battery test using the jumper wire

You can also take the relay out of the equation by making a fused jumper wire to provide power to the pump at the relay connector.

 

ok. I'm not very experienced with wiring problems and wasn't sure what you meant. Thanks. I'll let you know how things went.

 

alright. 1st thing I did was swap the relays in the glove box. They looked identicle with the same number. Voltage was exactly the same...8.4 volts. Then I ran the jumper. Got 8.4 volts through the feed wire and 11.7 through the ground wire. So I'm guessing the feed wire is the problem. I'm going to start looking for corrosion from the jimmy sitting all summer. I'll be back. Thanks.

 

I've been looking on the internet and saw GM had an issue with the connector. Is there a way to check that without cutting the wires? I can't see anything just looking at it. Or should I just replace the connector since that's what some recommend?

 

Turns out the spider failed. The spider was only about 2-3 years old but I let the Jimmy sit for the summer without starting it. The fuel lines sprung a leak so I finally got around to fixing them. I replaced them but it wouldn't fire, but it start would with ether. I changed the sending unit, fuel pump, filter, regulator. I checked the oil sending unit which seemed to be fine as well as the relay. Still wouldn't go. I finally pulled one of the poppits and put it in a glass jar and tried to turn the engine over. Nothing came out, no gas, not even a drop. I tried 2 more with the same result. So reluctcnly I sent out for a new spider (I didn't want to spend any more money on this but did.) And voila, she fired right up.

I was getting 60 lbs. of pressure, the noid light was flashing, etc.. But apparently you can't let these things sit. I dissected the spider but couldn't figure out why a fairly new unit would fail.