95 Jimmy SLE died while driving and now won't start

[DelCoch]

Here is what my book says. Disconnect chassis harness fuel pump connector. Probe cavity terminal "B" of harness for ignition voltage with a test light to ground apply fused 12v to fuel pump test terminal.
---------------------------------------
Test light on - connect test light ground to Circuit 450 (blk/wht wire) - test light still on replace fuel pump - test light off repair open circuit in Circut 450 (blk/wht wire).
--------------------------------------
Test light off - repair open circuit in Circuit 120 (gray wire).

[DelCoch]

Terminal "B" will be the Gray wire.

I have no idea what he pink wire is.

[95GMCJimmySLE]

well, there are three wires at the fuel pump connector. The gray and black wire are on the end and the pink or purple (whatever) wire is in the middle.

Where is Curcuit 450 located?

I reconnected the jumper wire to the prime connector and nothing happened. I checked the prime wire for volts and it tested good. So I would assume everything is good there.

I just don't know what this pink or purple or whatever wire is that is the only wire getting power at the fuel pump.

Sorry for all the questions. I just want to be sure I'm replacing the right part.

Thanks

[DelCoch]

Circuit 450 (blk/wht wire) is just a ground wire. It will never have current.

I imagine the Pink wire goes from the sending unit to the fuel gauge, as no other wires come out of the sending unit and the fuel gauge has to get it's info from the sending unit somehow.

Under normal conditions with the key off there should not be any current/volts on the red fuel pump jumper wire. If there is, this usually indicates the oil sending unit is bad. (I don't know about when the key is on)

Put your live 12v jumper wire back onto the red test wire and leave it there when checking for current on the Grey wire. You can check for current with a test light or volt meter, but in any case make sure you get a good ground when testing with your meter or test light. (Since you say the pink wire has current, you can use this same source for a ground when testing the Grey wire and you will know you have a good ground)

If you have NO current on the Grey wire, then the relay or PCM is probably bad.
If you have current on the Grey wire then use the black wire for a ground from your meter or test light. If you have a light/volts between the blk and Grey wire the fuel pump is bad.

If you only have current on the Grey wire when using a ground other than the black wire, then the black wire (Circuit 450) is not making a good ground.
---------------------------------
By the way, the cover on the relay box in the glove compartment unhooks from the bottom. Don't know if you ever got that cover off or not. There is a tab on each side that you press up on and the bottom of the cover will come loose. You have to have everything out of the glove compartment to get the cover off. There are two relays in there, both are the same kind/type, the one on the left is for the transmission and the one on the right is for the fuel pump. You can swap them to see if it makes any difference on the test wires.

Good Luck,

DelC

[95GMCJimmySLE]

ok, I think I get what your saying. I'm leaving to go back over there in just a few minutes so I will try those tests when I get there.

When I was testing for current, I used both the black wire and a ground to the frame and they were always the same. So the black wire should be fine.

You talked about if the red prime wire has power with the key off that it usually indicates a bad oil sending unit, would a bad oil sending unit cause these same problems I'm having?

Thanks

[95GMCJimmySLE]

ok, I jumpered the prime connector under the hood and then checked for power between the gray and black wires at the pump and it does have power.

I then removed the jumper and turned the key to the ON position and checked for power again to the fuel pump, but this time there was no power to the gray wire.

So I'm confident in the fact that the pump is bad since we jumpered the prime wire and got power to the pump but it didn't prime. But I'm wondering why when we remove the jumper and turn the key to the on position that we don't have power to the gray wire. Is there a switch or something I should be checking for this problem. Almost seems like I have two problems, one being the fuel pump and another not letting power to the pump with the key turned.

Any thoughts?

Thanks

[DelCoch]

Originally Posted by 95GMCJimmySLE

. . . I'm wondering why when we remove the jumper and turn the key to the on position that we don't have power to the gray wire. Is there a switch or something I should be checking for this problem. Almost seems like I have two problems, one being the fuel pump and another not letting power to the pump with the key turned.

You talked about if the red prime wire has power with the key off that it usually indicates a bad oil sending unit, would a bad oil sending unit cause these same problems I'm having? Any thoughts? Thanks

Have you checked the relay as indicated in the diagram I posted above?? What are the results on that? Check the fuse in the main fuse panel, its fuse #10 in my panel but the book says it's #9. Both of those will cause no power on the grey wire when the key is turned on, but remember when you turn the key on, the power is only there for 2 seconds. And, then the key has to be off for 10 seconds before it will reset and give another 2 seconds.

Do you still hear a click when you turn the key on??

If you have 12v on the Red Test Wire with key off it would cause a good fuel pump to run continuously!! How much current do have there, is it 12V or something like 3v??

The most common thing to cause the Red Test Wire to have current with the key off is a faulty oil pressure switch. (Sending unit) However, there is an outside chance that there could be some quirk in the electrical system that may cause it too, but its not likely. And yes, a faulty oil pressure switch could cause it not to start, but it can't prevent the grey wire from getting current when you put current to the red test wire.

If you can see inside the connector for the grey and black wire at the gas tank when its disconnected, what does the inside of the connector look like? If that connection is not making good contact with the wires coming from the tank then the fuel pump would not get current.

If you’re sure the fuel pump is getting current and it’s not running I would go ahead and replace the pump and then do more trouble shooting if it still won’t start after replacing it. Actually you can’t go wrong on replacing the fuel pump. If it’s not bad now it will be very shortly considering it’s a ‘95 and never been replaced.

Let me know how it’s going.


DelC

[95GMCJimmySLE]

ok, sorry for no update or responce. I got home a little bit ago after working on the car since 8am to 10a. making sure it was the pump. Made a run to the store to get flare nut wrenches and a syphen pump. Got to work about 11-11:30am and finished about 6:30pm with a break for lunch somehwere in there. Not bad to me.

Originally Posted by DelCoch

...but remember when you turn the key on, the power is only there for 2 seconds. And, then the key has to be off for 10 seconds before it will reset and give another 2 seconds...

yeah, we didn't know that then but figured it out about 1hr after I posted my question. It may be common knowledge to some but we didn't know that. oh well, it was figured out and all is good now.

Also, I did check the relays but there were only three places with only one blank and the relays were switched and flipped around. But were able to figure out anyway with a light.

I didn't have any trouble, luckly, with getting those fuel lines disconnected. I had more trouble getting the flare nut wrenches on the fittings from all the rust on them. But once on there they came free nicely. The straps loosened fairly good as well. Had some fun getting the filler tubes disconnected from the gas tank though. Once they were removed I could syphen the tank.

Once I had the tank off the pump only took about 10-15 minutes to replace. Replaced it with a Bosch pump which came with two new pump gaskets (one of which did fit) and a rubber hose to replace the pulsator with. Replacing the pump went just fine.

I tried to replace the fuel filter before putting the tank back up but there is such little room to get to the front fitting I decided I wouldn't mess it up and just go onto finishing installing the tank. I feel I can get the rear fitting just fine because there is more room but I could seem to get to the front. If anyone has any tips I'm all ears.

The install of the tank was a bit of a pain though. Getting the front hose connected to the vent things was a real pain. The rest just took time slowly lifting it and moving it around and into place.

One thing I did find that makes things a bit easier atleast to me was to remove the spare tire (obviously on four door models). Removing it and lifting the car as high as the jack stands would allow, allowed me to sit under the car where the spare tire goes. That made it easier for me to do all the work at the back of the tank where the pump and lines are all at. Without doing that I think it would have made things a bit more difficult. I was able to get a good look at things, work on the lines and test the wires all from a comfortable position.

The Bosch pump is so quite I didn't even hear it when I first turned the key to make prime the pump. My heart sank on that first turn. Then I really listened and I though I heard a very very slight hum. So I turned it over and fired right up. My girl was very happy. Checked for leaks and let it run for 15-20 minutes at idle while I cleaned up.

I found the strap around the muffler was rusted to pieces so I figured we would take it to get that fixed then just have them replace the fuel filter at the same time unless I can find a good way of replacing it without messing up the fittings.

I would to thank EVERYONE who helped me on this. We are very greatful for all your help. I kinda figured it was the pump but it was nice to know for sure plus all the tips on how to do it really helped as well.

THANKS AGAIN!!!

[viccilaine]

I have the same Jimmy and the first of two after market fuel pumps went out 2 weeks after the mechanic installed it and one week after the second has been installed it is humming very loudly.......I am thinking I should call the mechanic again....

[maxwedge]

Way too old, this thread please start a new one, thanks.