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'96 rodeo/passport fuel pump not getting volts
04-30-2013, 11:51 AM
Post: #1
'96 rodeo/passport fuel pump not getting volts
I was driving my car and it stalled without any warning. It started long enough to drive 20 yards and it would not start after work, It did turn over. I have functionality of the heater, lights, power locks, and windows. When I turn the ignition to the on position I don't hear the fuel pump turn on. I don't have juice (volts) at the plug bringing power to the pump, I ran power to the fuel pump, w/out dropping the tank, and the pump ran until I unhooked power. A year ago my car stalled while driving without warning, it would turn over but didn't start and fuel pump turned on. I replaced the starter and that seemed to fix the problem. Over the past few months my car would not start 3x but would turn over, after removing the battery and charging it for 8 hrs, even though prior to charging volts measured 12-13, it started up right away. Two years ago I replaced the fuel pump, 1.5 years ago I replaced the timing belt, and last summer I replaced the starter. What should I check next? How do I test a relay? I have a shop manual for both electrical and motor, body, and chassis, but I am lost trying to read the electrical diagrams.
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04-30-2013, 09:32 PM
Post: #2
RE: '96 rodeo/passport fuel pump not getting volts
You can usually find another relay near by for the Wipers, A/C or something. Most of the time they are all the same. Look at the part number and the prongs on the back. Swap the wipers & the fuel pump relays. Now if the pump runs and the wipers don’t, go get a relay. (Make sure it’s not raining because your wipers aren’t working. Smile

If changing the relay doesn’t fix it check all the fuses. If they are OK you might want to follow the wires from where you know that there is no power, forward, until you find power. Since you don’t have power at the relay you might as well just go from there. Pull the relay out and check for at least one hot terminal in the socket. By your drawing I’m guessing that there may need to be 2 hot terminals. Many things could cause them to loose power. Anti-theft system, bad ignition switch, damaged wires, damaged wire connectors, problem with the PCM... Sometimes scanning with a full function scanner can save time. If you take that route, record all code numbers, clear the computer & please post all of the code numbers here for review.

Please let us know what you find.

Thanks for using the forum,
Garner

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04-30-2013, 09:56 PM (This post was last modified: 04-30-2013 10:11 PM by Rupe.)
Post: #3
RE: '96 rodeo/passport fuel pump not getting volts
Knowing a little about Bosch electrical systems from years ago I can tell you the following about that relay.

30 = power (12 volts, and probably hot all the time)
85 & 86 = the relay coil (one side is power with the key and the other side is grounded by the ECM)
87 = normally closed (not used in your case)
87a = normally open (closes when the coil is energized then powers the pump from #30)

This should be enough to get you started on the diagnosis. Use a test light and draw a diagram of what is what as you work.

Also keep in mind that the pump should only run for 2 seconds when you first turn the key on and again for 2 seconds when you crank the engine. IOW, turning the key on to crawl under will show nothing because you can't get there fast enough. You will need to rig something so you can see what's happening from the driver's seat. Also try pulling the small wire from the starter so you can go to the crank position without actually cranking the engine. It really helps if you can hear things.

I'll be away for a few days but will check in again tonight to see if there are other questions before I leave.
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05-03-2013, 08:18 AM
Post: #4
RE: '96 rodeo/passport fuel pump not getting volts
I did find that (30) has 12-13volts, non of the others did. I attached a jumper wire from 30 to 87 and my fuel pump powered on car started. Does this mean the relay coil is not being energized therefore the power from (30) is not delivered to (87)? I also tried using a few different relays without success.

I really appreciate all the advice!
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05-03-2013, 09:33 AM (This post was last modified: 05-03-2013 09:40 AM by Garner.)
Post: #5
RE: '96 rodeo/passport fuel pump not getting volts
I am a little confused by reading what Rupe said “Should” be happening at the relay & what you said “Did” happen. You said that you jumped power to #87 and the pump ran. Rupe said that #87 wasn’t used on your car? May-be you jumped the power to #87a? Either way, I think that we can work through this.

For now I can only think of two things that would be causing your problem. Since you said that you tried other relays I would figure that the relay isn’t the problem. That pretty much boils it down to Key On Power or the ECM Ground signal. Rupe noted that terminals #85 & #86 is where you would need to look for this. Keep in mind that this may also only happen in that 2 second window that Rupe told you about. Since we don’t know which one is power & which is ground here’s what I would do.

Ground a test light & try to set it in terminal #85 in a position that you can see it while turning the key on. If it lights, that is the Key On power terminal. If not, try the same thing with terminal #86. After noting what happens that way, try the same procedure again except this time hook the test light wire to power. If the light lights you found the ECM ground. If the light doesn’t light at all through all 4 tests we will have to start going back toward the ignition switch & ECM looking for broken, burnt or damaged wires. Damaged, loose or corroded connectors. Faulty ignition switch or faulty ECM.

Let us know what you find so we know which way to go from here.

Thanks for using the forum,
Garner

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05-03-2013, 11:41 AM
Post: #6
RE: '96 rodeo/passport fuel pump not getting volts
I set my multimeter at 20v tested both 85 and 86 seperately, ground to the battery, turning key to on and start, nothing happened. The cavity for the middle prong (87a) has no connector to plug into unlike the other 4 prongs. Whats next? Please!
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05-03-2013, 05:21 PM
Post: #7
RE: '96 rodeo/passport fuel pump not getting volts
OK, I’m going to assume that Rupe labeled the 87 & 87a terminals backwards. That tells me that 87 goes to the pump.

Since you did things differently than I suggested I’m not much better off than last time for suggestions. I think that by grounding a multi-meter and testing the terminals you proved that there isn’t a power terminal. Now I need to know if there is a ground signal from the ECM. To use your multi-meter, put the red lead on the positive post of the battery, set to 20vdc and test 85 & 86 separately with the black lead while turning the key on.

If nothing happens on that test you are going to need to start tracing wires. If you can see the color of the wires going to 85 & 86 it will make life much better. If not you may need to unbolt the box that the relay is mounted in so you can see the back side. Once you know the wire colors you can start following the wiring harness. I would guess that at least one of those wires will run to the PCM. If you know how to do a continuity test you can check for a bad wire that way. Set your multi-meter to continuity, place one lead at the PCM and the other at the relay. If you don’t have continuity you will have to find where the wire broke or may-be a plug came apart.

Please get back to us on what you find.

Thanks for using the forum,
Garner

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05-05-2013, 09:50 PM
Post: #8
RE: '96 rodeo/passport fuel pump not getting volts
I tested both 86 and 85 as you suggested, here is what I found: 1) 85 measured .07 prior to and changed to -0.00 when key is turned to the on position. 2) 86 measured 12.25v prior to and after I turned the key to the on position. The color of the wire that connects to 86 is pink w/ white stripe, according to the wiring diagrams in the service manual this wire connects to the PCM.
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05-05-2013, 10:48 PM
Post: #9
RE: '96 rodeo/passport fuel pump not getting volts
Well, I wish that Rupe wasn’t on vacation. I’m having a hard time putting all this together in my head. I have been drawing little diagrams & the one that you posted really helps but Rupe’s experience with this vehicle would REALLY help.

I am thinking that terminal 85 should be powered with the key on and it’s not. Blown fuse? Broken wire? Faulty ignition switch?

It seems that terminal 86 should be ECM signal ground with the key on. Problem is, it seems to be shorted to ground if it is showing 12.25v with the key off. That can be a wire shorted to ground or a faulty ECM shorted to ground.

You never mentioned if you know how to do continuity tests. If you do you could make sure the fuel pump relay is removed, remove the connector from the ECM & test the Pink/white stripe wire to see if it is shorted to ground. If the wire isn’t shorted to ground I would suspect the ECM.

May-be you can check that for us, post your results & hope that Rupe gets back from vacation to tell us what he thinks. Until then I’ll re-read what we have so far, look at the wiring diagram again & see if anything else comes to mind.

Keep at it! You’re going to beat this thing.

Thanks for using the forum,
Garner

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05-06-2013, 02:08 PM
Post: #10
RE: '96 rodeo/passport fuel pump not getting volts
I tested for continuity of the pink/white wire (86) from relay to PCM plug and my meter read 16.43 and was decreasing very slowly, the reading never dropped below 12.3. I then tested the black wire (85) from the relay to where it attaches to the body inside the engine compartment and the meter read 0.00. The negative lead wasn't attached to the battery for the ohm's readings above, would this change anything?

I am wondering if it would be dangerous to connect a jumper wire to power the fuel pump to drive it home (3 miles). It broke down in the parking lot at work and it would be easier to work on if it was in my garage and it would be nice to save the towing fee.
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