1996 Explorer Fuel/Electrical issues

[Satirkyll]

Vehicle: 1996 Ford Explorer 6cyl 4dr auto

Problem: wont run

Diagnosis: whew where to begin;

so about a week ago i crank it up and drive to the store. get back in, it turns over but it wont run. i give it a second, then it starts up. i get home, go back out the next day. it wont start (same thing it turns over but wont run). i try this 3 or 4 times, this time noticing if the fuel pump is cycleing, and it is not. I go buy a fuel pump relay, it runs fine. the next day same thing. i get out wiggle the relays, get back in and the fuel pump cycles, it cranks up. an hour later same problem.

I read Chiltons, i read forums. i check the relays for continuity and phisical "clicking sound". relays are fine. i check the inertia shut off button, it is not tripped. i do a voltage check at the inertia switch getting recommended voltage. I do a voltage test on the pins where the fuel relay connects: pin 30 has constant 12v, no other pins are showing voltage whether the key is on or off. I hotwire pin 30 to pin 87, the fuel pump comes alive. i tried starting it with the hotwire, no luck. now with everything back in place and turn the key, no fuel pump initial 2 second whine, nor can i hear the relays click. would you think this is a PCM malfunction, or a wireing issue, or something i have overlooked? PLEASE HELP *pulls hair*

 

[Satirkyll]

Update

I made a Jumper Wire ( 3 inches long 14 gage wire) going from the PCM relay socket to the fuel pump relay socket (socket 85 on both relays). I plugged the relays back in and it starts right up. now, does this mean that the wire in socket 85 on the fuel relay is bad, or the PCM is not sending a signal through that socket, and if so how would i know without replacing the Powertrain Control Module (PCM)? so i now know that there is no signal going to that socket when the key is turned, should i leave it be or delve further? i don't know much about wireing, i have a harbor freight meter and do know the basics like following the instructions on testing the relays and enertia switch, and your forums have been very helpful on getting me this far. THANKS EXPLORER FORUMS but there i haven't found any documentation on the step by step how to phisicaly check that specific wire so if any of you have any suggestions please help. i look in my chiltons at the wireing diagram and it looks like a chinese abacus. i mean, i understand it a little but not enough to know how to phisicaly test it. is there a way to test that wire at the pcm without unplugging anything? if so what do i do? and if no current is comming out what does that mean? i need a new PCM?

 

[J_C]

I'm doubting it's the PCM, unless it's the electrical connection to it. In other words I'm thinking it is a fouled electrical contact somewhere, but I suppose a frayed wire is also possible.

It wouldn't surprise me if an underhanded garage said it was the PCM, to get you to pay for a high priced part then they secretly fix the wire or connector problem... happened to my father once with a window electrical problem but luckily I found where they fixed the wire and wrote a nice letter to management.

 

[budwich]

quote "....i don't know much about wireing,..." BUT it appears that you like to "blindly" jumpering things... your "testing" is admirable for not "knowing things"...

Anyways, it is unlikely to be a PCM problem since once you get gas to your engine it runs fine. So as you have found, you have an electrical fueling issue... at least. It would appear that you could "run forever" with your "last jumper" in place.... maybe that's the solution...

Ok... my guess is that you have an issue with the output of the PCM relay... either the relay itself or the subtending connector / wiring. Your "jumper trick" basically "jumps" by the problem.

Anyways, as part of your troubleshooting ... without any jumpers installed, can you tell us what the status of your Check Engine light is when your key is just turned to "ON" (not start) and left there "forever". I think that's your "clue".

 

[Satirkyll]

Well first off, thank you Bud I have always liked to tinker with stuff every since I can remember... take things apart, KINDA put it back together. Anyways, the "dead" wire isn't comming from the pcm relay, but rather the fuel relay. I jumped the power FROM the pcm relay TO the fuel relay. when i did the ignition key on/off test i was getting power readings useing my trusty harbor freight continuity meter. i tested pin 85 of the pcm relay with key off it was infinite, with key on it was 12.26 volts. I tested pin 85 on the fuel relay with key off it was infanite, with key on it was infinite (0.00)

now, in reference to your check engine light theory,before i did the "relay jumper fix" <----gold plated award winning title , the check engine light did as follows:
turned key to the "on position" check engine light came on. turned the key to the "crank" position while cranking the engine, the check engine light stayed on for a second or 2 then went off. repeated process, same results.

i was thinking that since the wire supplying power where i made the jump onto the fuel relay is dead, there are 2 things that it could be, the wire is cut or disconnected somewhere, or the pcm is bad on that pin... (looking in Haynes manual)...getting the aspirin...i think from reading the diagram that it is pin 22 or pin 80. i don't know because i don't know which diagram is for my explorer. i looked inside the driver door and it says it was made in 1995 but it says 1996 on the registration. so i dont know which diagram to go by. if it's 1995, it's pin 22, if it's 1996 it's pin 80.

seeing as how it slowly went bad over time, i can't tell which is the problem and when i did "jiggle" the box, when it started it ran fine. it would only give problems after the vehicle was shut off. now that the jumper is in place it runs fine but i'm concerend that if the pcm is faulty, it wont recieve the proper signals and over long term could damage other components.

now, i get all this information just by simply following instructions, collecting information, processing the information, building a theory, testing the theory, and trying something new. more incentive for you kids reading this to stay in school. THANKS 7TH GRADE SCIENCE! i have no knowledge of how the pcm works. i took it to autozone and they hooked up thier meter to the computer and all it came back with was an o2 sensor bank 1 sensor 1 but it has been that way since the day i bought it 5 years ago and now that i'm thinking about it, i read here on the forums that this problem can be a simple fuse i need to check first before i replace that.

anyway not to get off subject, the check engine light does come on when the key is in the on position, and eventualy turns off while cranking the motor. I'm kinda hoping it's the pcm and not the wire :notworthy. have you seen the wireing harness going from the relay box to the pcm? and how do i test this? if it is the wire how should i go about replacing it the right way?

 

[dustinjorge]

I had a sticky PCM relay cause a very similar problem. Though iirc I had no cel in on when the no start symptoms occurred. In my 95 swapping the pcm/ac relays fixed my random issues so I eventually replaced the pcm relay with a new one. I had previously replaced the fuel pump relay as well. I was all over the place with ideas and spent a long time being frustrated trying to solve this random issue. Turned out to be quite simple. Just saying, next time you have a no start make sure/ double check that you have cel and fp prime noise.

 

[budwich]

ahh.... but as I said, the "test" of the key "ON" will be the hint that will likely tell where your problem lies. It is good that your CEL light goes on (please remember I said nothing about doing a "start"... that isn't really important at this point... what you want to see is that the CEL light stays on for as long as the key stays ... that's all. that tells you that the PCM relay is operating as it should).

BUT is isn't quite that simple, as your testing has found. I am confused though by your first "test" when you jumped the fuel relay (30 to 87) and caused the pump to run but the vehicle didn't start... huh? Can you do that test again and watch the CEL light during the start attempt. I would have expected to start IF the CEL light acted "correctly".

 

[Satirkyll]

oh i see where your comming from Bud. the problem is when i did that "jump" test before i did the jump between the relays, the relays were not installed so it couldnt actualy start but i didn't figure that out til you brought it up . it wouldn't "start because i just stuck a wire between the two pins and heard the pump run.

Ok so i did the test you asked, removing my "fix" jump and just placing the wire between 30 and 87. the pump runs constantly, turned the key to "on" and the CEL stays on constant. tried to start it and fail. i think all four connections need to be"working" in order for the computer to give the go ahead to fire the engine.

and thanks JC, your confedence in your reply reassures me even more that it's just the blue and orange wire going from the relay to the pcm. so again how do i test this and if it is the wire whats the right way to go about replacing it?

 

[dustinjorge]

i get out wiggle the relays, get back in and the fuel pump cycles, it cranks up. an hour later same problem.

Suspect Relay

I do a voltage test on the pins where the fuel relay connects: pin 30 has constant 12v, no other pins are showing voltage whether the key is on or off.

a) Was the pcm relay unplugged during this check?
b) If so, that's why.
c) If not, still suspect relay.

I hotwire pin 30 to pin 87, the fuel pump comes alive.

Expected

i tried starting it with the hotwire, no luck. now with everything back in place and turn the key, no fuel pump initial 2 second whine, nor can i hear the relays click.

NO Relay click, suspect PCM relay.

I made a Jumper Wire ( 3 inches long 14 gage wire) going from the PCM relay socket to the fuel pump relay socket (socket 85 on both relays). I plugged the relays back in and it starts right up.

This is interesting, but I still suspect the PCM relay. Here's why: The power to the Fuel Pump relay is fed via the PCM relay, that is, if the PCM relay is not activated the power to the Fuel Pump relay switch is non-existent. I think you're following this fine. However, when you jumpered the two together, you essentially backfed power to the PCM circuit effectively bypassing the PCM relay and powering up the PCM directly from the ignition circuit. Please don't do this anymore, it worked because the PCM switches ground for both these relays, but the ignition circuit is not meant to be doing this. I'm surprised you didn't pop a fuse here, or worse, start a fire.

comming from the pcm relay, but rather the fuel relay. I jumped the power FROM the pcm relay TO the fuel relay. when i did the ignition key on/off test i was getting power readings useing my trusty harbor freight continuity meter. i tested pin 85 of the pcm relay with key off it was infinite, with key on it was 12.26 volts. I tested pin 85 on the fuel relay with key off it was infanite, with key on it was infinite (0.00)

See above, you jumpered the circuit. Also, with these voltage tests, did you remove each relay individually or did you have them both out. If you had them both out, the above is exactly what should have happened.

now, in reference to your check engine light theory,before i did the "relay jumper fix" <----gold plated award winning title , the check engine light did as follows:
turned key to the "on position" check engine light came on. turned the key to the "crank" position while cranking the engine, the check engine light stayed on for a second or 2 then went off. repeated process, same results.

Did you hear the fuel pump prime at this point?

Ok so i did the test you asked, removing my "fix" jump and just placing the wire between 30 and 87. the pump runs constantly, turned the key to "on" and the CEL stays on constant. tried to start it and fail.

Are you sure you didn't inadvertently swap relays at some point?

i think all four connections need to be"working" in order for the computer to give the go ahead to fire the engine.

The fuel pump relay gets it's power (85) from the PCM relay after it's switched. The PCM itself switches the fuel pump relay by way of a ground circuit (it gets 86 from fpr) Also, tranny control module gets power after this switch. There's a lot going on here, it's not as simple as a basic toggle. I suspect that you're 100% right on about all these connections needing to be made (85/86) on fpr for the PCM to allow start.

That said, these tests haven't done much in the way of solving the problem, please stop jumpering stuff, it's a good way to cost yourself a ton of money.

I still suspect a faulty relay. Could you grab the new Fuel pump relay (make sure it's the new one), and the a/c relay and plug them into the FPR and PCM relay slots (With no jumpers), then watch CEL and listen for fuel pump sounds and relay clicks while testing?

 

[dustinjorge]

Hey also, while you're testing take a flashlight and shine it down into the PCM/Fuel Pump relay slots and make sure the connectors are all sitting at the same level. If one of the little plastic holder tabs broke the connector may be sliding down into the distribution box causing an intermittent connection.

 

[Satirkyll]

This is interesting, but I still suspect the PCM relay. Here's why: The power to the Fuel Pump relay is fed via the PCM relay, that is, if the PCM relay is not activated the power to the Fuel Pump relay switch is non-existent. I think you're following this fine. However, when you jumpered the two together, you essentially backfed power to the PCM circuit effectively bypassing the PCM relay and powering up the PCM directly from the ignition circuit.

hmmm interesting... i didn't think putting two ends of a wire in two holes could be put so eloquently :notworthy i think you might be on to something but not the relay.

i check the relays for continuity and phisical "clicking sound". relays are fine.

when i did the voltage checks, it was with one relay removed at a time.

you are right when you say fuel relay wont work unless the pcm relay is engaged. i read that in haynes.

I do a voltage test on the pins where the fuel relay connects: pin 30 has constant 12v, no other pins are showing voltage whether the key is on or off.

again when i did these tests only one relay was removed at a time the only time i removed two relays is when i get the brilliant idea to check the voltage on the same pin of the pcm as the fuel relay. same relays different readings like i said when i did the voltage tests on the fuel relay only one pin was showing hot and the rest were dead no matter if the key was turned on or off. when i checked the voltage on the same pin of the pcm relay as the fuel relay, i got 12v with the key on and 0.00 when the key was off. thats when the lightbulb went off to jump the ignotion hot on the pcm to the same pin on the fuel relay. so its not back feeding the pcm relay, it's forward feeding the fuel relay. i know you want to believe it's the relay, or one of them, and i have persevered all this way painstakingly doing everything one step at a time, but i have tested each and every (all 3) relays and they all work. the thing that my brain is tingling about is the dead readings i get from the fuel relay with all the other relays installed and without the miracle fix jumper wire.

Did you hear the fuel pump prime at this point?

nope. and also switched relays as you suggested. same results.

...it worked because the PCM switches ground for both these relays, but the ignition circuit is not meant to be doing this. I'm surprised you didn't pop a fuse here, or worse, start a fire...that said, these tests haven't done much in the way of solving the problem, please stop jumpering stuff, it's a good way to cost yourself a ton of money.

i'll keep this in mind as i walk out to the explorer and start it up and drive to work lol joking joking but seriously i know this is a redneck fix the minute the idea went into my head. it's just temperary to keep me in the drivers seat. i mean i could solder the wire on there if it will keep you from calling the fire dept!

now that the jumper is in place it runs fine but i'm concerend that if the pcm is faulty, it wont recieve the proper signals and over long term could damage other components.

. and also the pcm relay DOES supply power to the fuel relay from the pcm relay only if the ignition is hot, but it's NOT directly. it doesn't just go streight to the fuel relay and say here i am! lol from what i have gathered, it travels en-route through 5 to 7 other circuits, then goes back to the pcm, then from the pcm on either pin 22 or 80 (no one has answerd that part yet and i still don't know) back to the fuel relay. at this point that wire is not showing any power whatsoever. well if this hasn't baked your noodle yet, your all alone

 

[dustinjorge]

Hey didn't mean to come off as criticizing. My apologies.

 

[budwich]

oh i see where your comming from Bud. the problem is when i did that "jump" test before i did the jump between the relays, the relays were not installed so it couldnt actualy start but i didn't figure that out til you brought it up . it wouldn't "start because i just stuck a wire between the two pins and heard the pump run.

Ok so i did the test you asked, removing my "fix" jump and just placing the wire between 30 and 87. the pump runs constantly, turned the key to "on" and the CEL stays on constant. tried to start it and fail. i think all four connections need to be"working" in order for the computer to give the go ahead to fire the engine.

and thanks JC, your confedence in your reply reassures me even more that it's just the blue and orange wire going from the relay to the pcm. so again how do i test this and if it is the wire whats the right way to go about replacing it?

OK... thanks for the clarification on that test.... BUT, I have more questions on these observations.... you say the cel stays on.... BUT during the start the cel must eventually go out otherwise, it is a "no go".... that was the rest of the cel light observation we need to know about.

further, as previously suggested by others, stop the jumpering, get out the meter... as we kniow you can jumper it to make it work... that's kind of how people "hot wire" things. It not so much a problem of destroying things... you seem to "know a few things"... we / you need to go thru the circuit as it is and find the actually condition that is broken and fix that problem.

 

[Satirkyll]

oh hey dustin its ok bud. your not criticizing at all thats just your way of obtaining the info you need to find a solution i know your racking your brain on this one i'm just trying to giving you some of my hard time. ok now let me study this diagram for a minute... ok now on the pcm follow pin 80 up. thats the wire i expect to get a hot signal for the fuel relay... the one that should have power but doesnt ...thats all i can say at the moment my head is pounding and i need to walk away from this for a few. clear me head.. now if i put one wire from this corona to the ibuprophen bottle...i'll bbl

edit~ also tell me what to read and when i go make the reading i'm going to check the pcm maxi fuse too.

 

[budwich]

you are allowed to give me a hard time... I was giving you a hard time...

Anyways, I am downing a cool one right now... its warm here in hawaii...

Your test on the output of the PCM relay is a good indication... yes houston you have a problem. As you have figured, when the pcm operates it provides 12v towards the operating coil of the fuel relay which when the pcm sends a grd to the other side, cause the relay to operate and send a nice voltage to your pump.... that grd is only momentarily based on "thinking" inside the PCM... BUT the operation of the pcm relay is "forever" with your key in run. Your CEL light on "forever" indicates that the PCM is getting power and hence that PCM relay is operating... maybe... you need to some how measure as close to pin 80 as possible. Further, with your key just in "ON", pull the pcm relay, check the CEL. Then reinstall, check the CEL. Now back to more important things,,, another cool one...

 

[Satirkyll]

Florida Caverns, wet, and raining cats, dogs..and squirrels! forecast puts our tests off for a day or 2 hopeful to have some answers by Wednesday. i am all gung-ho to do this and i get rain. i don't plan to drive in this crap and i really don't plan to drive at all until this is fixed. i never meant for this jumper to be a permanent fix, just demonstrating that it works for reference and for temporary use.

i know what Dustin is saying. yay though i had no signal to the fuel relay for the initial start, i am jumpinging to the ignition circuit of death. i could overload a plethora (yeah i know what a plethora is, i saw 3 amigo's olay!) of fuses, relays, fusible links etc.

~ loudspeaker feedback~ ... ~tap~ ~tap~ Dustin apology line 3, apology, line 3 ~click~


now, back to more important things three relays walk into a bar...no wait, a gas station... and the third relay says, "snarky? i thought you meant sparky!"

 

[dustinjorge]

Hey first, no worries man. I tend to come off the wrong way on forums.

With regard to my wanting to believe it's a relay, you're right That's a simple, easy fix. I learned a lesson about relays from a random no start issue that drove me damn near insane. It would happen once a month, or twice. At times the only CEL would light, at times only the fuel pump would prime, and most of the time both worked fine. The lesson was that faulty relays can fail 'sometimes', and work perfectly fine other times. In my case I was chasing two failing relays. I lost hair on that one.

That said, it seems that you've ruled out the relays, and the test budwich suggested would give you status of the PCM relay. They still could be intermittently failing, but let's assume they're not.

So back to the issue that the PCM relay power is not reaching the fuel pump relay coil:

Verify this by unplugging the FP relay (With PCM relay installed), test the voltage on pin 85 of the FP relay socket with the key in the on position. Also, just for gits and shiggles, test the voltage at 86 (Just to make sure we aren't thinking backwards).

If you've already done this, and are positive of the result:

If you have no voltage at the FP relay, then I'd venture that the problem is somewhere along that red wire.

I have no idea how they made those connections in the box, but where I would start is to pop open the distribution box, see if there is a red jumper from PCMR 87 to FPR 85/86 under there, and ensure it's intact. In the absence of a direct jumper, there will still be red wires, but a short would cause the CEL to not illuminate so I doubt that's the case.

You didn't mention if you have a code reader and if you tried a KOEO test.

 

[Satirkyll]

i have no knowledge of how the pcm works. i took it to autozone and they hooked up thier meter to the computer and all it came back with was an o2 sensor bank 1 sensor 1 but it has been that way since the day i bought it 5 years ago and now that i'm thinking about it, i read here on the forums that this problem can be a simple fuse i need to check first before i replace that.

and thinking again on this, when they did the OBD test, they did it when it was working fine. i should go back up there when the rain lets up and disconect my jumper then have them hookit up and see if i get a code. but i think before i do that weather permitting, i want to check the PCM maxi fuse,, then do the remove pcm relay cel test, then check voltage on the fuel relay as described with key off and key on again, then do the same thing to the pcm relay, then check continuity at pin 80 (with only a 2-3 second window) i will have to have my son turn the key on while i take the reading because again the pcm only sends a signal between 2 and 3 seconds.
agenda:
(1) check pcm maxi fuse
(2) remove PCM relay / CEL test
(3) retest FPR relay sockets
(4) retest PCM relay sockets
(5) check under PDP for a red wire jumper, and check for any loose disconnected or frayed wireing.
(6) check continuity of pin 80 at or from the PCM.
(7) go back to automoan i mean zone and do an OBD test without jumper.
-in that order
...KOEO test ... not sure if that is the same as them hooking up the OBD meter, or a function it has i should mention thereof.

well thank you for the many roads to walk down. now that i have some direction, you get to sit back and wallow in suspense
:scratch:

 

[Satirkyll]

1996 Explorer Fuel/Electrical issues ***SOLVED***

you ever get the feeling you work so hard on something, it's something simple thats the fix? poke poke dustin poke poke:

well, the sun was shining today although it said rain, so i went out to preform the diagnosis and here is what i came up with:

(1) checked PCM maxi fuse - ***FUSE FAULTY***, kicked tire, cursed my maker, banged head on fender 4 times...in that order. walked up to AdvancedAutoParts bought the fuse ($3.78) and walked back, pulled the old fuse out, replaced the new fuse, and she started up perfect. kicked the tire, cursed my maker, and laughed out loud...in that order.

(2) PCM diode - MELTED - the result of the jumper wire going from the ignition pin of the PCM relay to the fuel relay. the truck runs fine, but i don't want a melted diode in my fuse panel.

so when this all started, i heard no fuel pump prime, that was my focus, and ultimately my downfall. i went down the path that made sense to me not the path that the electricity follows. I checked the fuel relay maxi fuse, but never checked the pcm maxi fuse.

The PCM diode is not stocked at any local parts store, i had to go up to the ford dealership and order it. comes in a pack of 2 for $5.51 and fortunatly, thats all my little ingenious idea cost me, now i get to check why the OBD is giving and o2 sensor bank one sensor one code. gonna check the fuse first, then multi-meter the wires, then kick the tires and curse my maker...in that order.