No power to new fuel pump

I recently installed a new fuel pump into a 1997 jeep grand cherokee laredo and it is not getting any power to the fuel pump. When the pump is disconnected the connector reads 11 volts......when the pump IS connected...........it gets grounded and reads nothing. Switched around the relays thinking it was that but none of them worked. I didn't install a new assembly with the fuel pump........but I don't think thats the problem. Any thoughts?

Reply to
gloeliger
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Three things needed: (1) Accurate schematic for (specific to) the vehicle (FSM or www.allldata subscription), (2) Multimeter, (3) Someone who knows how to use items (1) and (2) for torubleshooting.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Reply to
Bill Putney

My neighbor is a mechanic and he did all these things and is completely stumped too. We use a voltage meter on the connection by the fuel pump..........and it was getting sufficient power while the pump was unplugged but when the pump is plugged in..............no more power.

Reply to
gloeliger

When you run electrical wires beside each other you can see a "ghost" on a wire that is not connected to anything. Your meter pulls so little power that it won't bleed off the ghost voltage so it looks like you are seeing the voltage needed to run the pump. Once you connect the pump it bleeds off the ghost voltage which is why it looks like the power goes away when you plug in the pump.

You need to trace the power circuit to the pump to find out where the problem is. You will need to get a wiring diagram for the vehicle or have someone who is knowledgeable with electrical troubleshooting.

Steve B.

Reply to
Steve B.

Hi...

Not a mechanic, just an old retired electrical guy - forewarned is forearmed! :)

I agree with Steve in part, suspect that the 12 volts you're seeing is being delivered inadvertently in series with something else, so that there's virtually no current available.

Quick and dirty test that you and your neighbor can do to verify this, before you spend the big bucks at the dealer...

Remove the positive connection from the pump, connect it to a light bulb that wants a fair bit of current like a parking light bulb. Connect the other side of the bulb to ground. If it doesn't light, then our guess is correct.

If that's the case - check the fuse, not visually but by replacing it with another, or by testing it with your meter.

While you're in there, check all the fuses just for the heck of it. Last summer my neighbor's wife was distressed that her (GM car) power door locks had quit. The fuse marked "courtesy lights" was the culprit :)

If that's not it go back to the relay. Don't swap it again, just remove and re-insert it half a dozen times - kinda wipe the contacts.

I *think* the asd relay removes power to the fuel pump, check that by swapping it, and perhaps the wiping trick.

If none of those does the trick, do the old bend the wire trick on the fuel pump wire as far as you can reach to do it. Trick is to hold your thumb and two closes fingers together, with the wire in the "hole" between them. Run your fingers up and down the wire so that your thumb tries gently to bend the wire as it goes. You're feeling for a point where the wire bends sharply (if there is one) where the metal wire is broken and only the insulation holds it together.

Take care.

Ken

Reply to
Ken Weitzel

No offense, but if he was stumped by that, he is not the person to do the troubleshooting (item (3) of my previous post).

With the pump plugged in, you need to use the meter to find out where the voltage is lost in the upstream power feed, i.e., there is an upstream point where you have +12V and below (i.e, as you move towards the pump) which there is no +12V - that's where the break is. It could be a relay, or a relay control signal, or a broken wire - but at some point there is an interruption in the supply of voltage.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Reply to
Bill Putney

Why did you install the new pump? Did the old pump simply stop working, or did it continue to work, but not so well? Or did it not work at all but was making some sort of noise?

The reason I ask is to help determine if you had a fuel pump failure or a problem with whatever provided power to the fuel pump. If the pump was sort of working or making some sort of sound, then you had power to the old pump. Under these conditions, if the new pump doesn't work, it is likely that you have a connector problem or a bad pump.

If the old pump simply "stopped working" and the new pump is acting just like the old, failed pump; this suggests that the old pump may be OK and that the problem is elsewhere.

Ken

Reply to
KWS

The fuel pump just stopped and I am sure it was bad because we hooked it up straight to the battery and nothing. I am now thinking that when it went bad........it caused other problems in the electrical line (blown fuseable link, relay, whatnot). I did check all the fuses in the box and everything was ok but I know there are other fuses. Thanks for all the help on this and if anyone else has any cents to throw in........please do.

Reply to
gloeliger

Our crystal balls are in the shop for repair. For the third time, someone competent needs to troubleshoot it with schematics and a meter. You posted your problem, several of us have given essentially the same answer, yet you want more.

No offense, but you're like the person who runs out of gas, and three people stop to help and advise you to put some gas in it, but you keep asking people to stop and help you figure out why it won't start.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Reply to
Bill Putney

Reply to
gloeliger

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