1991 Ex cranks but doesnt start...HELP 911

[arco777]

The PCM is easy to access. It is behind the passenger side kick panel. Remove the passenger side sill plate on 2dr models or partially remove it on 4dr models. Remove the trim screw from midway up the kick panel in the door gap area. Then reach behind the kick panel on the firewall end and pull it out. The round Christmas tree style trim fastener and panel will come out. Now you'll see the PCM. It is held to the body by a white plastic strap. Remove a screw or two allowing you to pull the strap off the PCM and slide the PCM out, with wire loom attached. You can now read the catch code on the PCM (example UMP1) to determine which model PCM calibration you have. Loosening the bolt on the wire harness connector will allow it to be disconnected from the PCM.

 

[arco777]

Once you have the PCM out, you can remove the 4 screws holding the cover on it to look inside. Check for evidence of water damage, swelled or leaking capacitors, burnt transistors or other shorted/burnt components, and check for damage to the harness input pins. Also check that the pins on the harness connector are in good shape and no wires have come loose from their pins.

 

[bruce119]

I'm still watching this thread with interest....


How many $$$ did you put up so far...


Maybe the dealer would have been better in the long run...


Take it to a dealer spend the $150 for a diagnosis...


Wishing you luck

 

[FR-425]

Here's a good write-up for testing the EEC relay.

http://easyautodiagnostics.com/ford/relays/eec_relay/eec_power_relay_1.php

It is the brown one. If it has been replaced the plug will still be brown.

Just to be clear; the relays on 91's are under the power distribution block:

Sorry I'm just not convinced you have fully investigated this.

 

[L.A.X]

A little history to the recent replies. Truck was running perfectly. It was my daily driver. I recently went to smog the truck and it failed due to high NOX. I decided to change the cats and O2 sensors but before I did that, I decided to Seafoam. I wanted to run Seafoam before I changed my cats because I heard stories of SF ruining cats and sensors. Bought the SF spray and introduced it thru the throttle body the way the bottle and the SF video state. I did everything by the book. When I tried to turn on the truck the following day, it cranked and cranked and didn't fire up. I noticed that when CEL came on at the dash, truck would fire up. Sometimes it does, sometimes it doesn't. If and when truck does fire up, it runs great maybe for 15 or 20 minutes and completely shuts off. No sputter or anything. Its like someone just flipping the off switch. Change all relays, sensors, fuses, clean maf, tb etc to no avail. Truck gives intermittent power to PCM I believe.

 

[L.A.X]

What are all the parts of the ignition system? I've ruled out the starting system. What are the chain of events that happen when key is turned? I need an idiots guide to how a Ford Explorer runs. When you turn the key, is the next step the ICM or PCM?

 

[L.A.X]

Don't know if this would be related or not. In the past while working on my truck while running, I've closed the hood hard and the trucks idle has surged

 

[colintrax]

It's the seafoam, seafoam would cause low compression or damage the spark plugs. Feel free to pull the plugs but it's not going to cause the fuel injectors and spark plugs to not receive power. Have you checked to see if the PCM is receiving power? Do that first. Your PCM controls the check engine light, there's def a problem there. Just need to pin point it. As for replacing it, I got mine for $75 from a junk yard in tn. Only 2 in the country showed having the same one as my ranger. It's not hard to pull it apart but it can fool you. Mine looked like there was some damage (well there is) but it ended up not being the problem. So I have $75 sitting in the garage doing me no good

 

[L.A.X]

All new plugs, truck has compression. Been reading thru all the old threads. What's the EDIS Module? Where's it located and what's its purpose? Anyone have a pic?

 

[colintrax]

I don't think you have one. If you do advanced auto tests them for free.
It controls the ignition but it doesn't control fuel injectors nor the CEL. Check power to the PCM. This is a computer problem, quit trying to find other problems. You're wasting your time

 

[Turdle]

I don't think you have one. If you do advanced auto tests them for free.
It controls the ignition but it doesn't control fuel injectors nor the CEL. Check power to the PCM. This is a computer problem, quit trying to find other problems. You're wasting your time

agreed. Try to catch yourself a little break, and go back in with this in mind. Intermittent power to the PCM is your issue. Ignore everything else.

Stay on track and you will get this fixed.

 

[L.A.X]

Will do, I'll give you guys an update later

 

[larrydd999]

All the above is good advice. From my electronics and industrial electrician background it often turns out to be the simplest things such as: bad (dirty, broken) connection at a connector, loose grounding wire, dirty connection at the plug-un fuse. Intermittent problems are the worst to fix. Today's electronic modules are amazingly reliable so I go there after checking the 'dumb' stuff.

 

[FR-425]

Here goes,

The PCM has three power feeds:

1: yellow/black -from distribution box 30amp to EEC relay then directly to pin 1 on PCM (always hot) for active memory.

2 & 3 Red -from EEC to PCM pins 37 and 57 hot when ignition on. (relay closed)

So at the relay you have 2 yellow/black on same post. always hot

2 red on the same post. hot on ignition "on"

Brown/pink from ignition switch

and black/LT green = ground.

One of the red wires energizes the fuel pump relay (clue here) if the fuel pump is energizing every time with or without CEL then the EEC relay is closing and not the prob.

The other goes directly to the PCM. (pins 37 & 57)

So if your fuel pump is energizing every time the problem is between the relay and the PCM (open circuit) I don't think it is shorted or you would be pop'n the fuse.

Or the PCM itself is toast. (not likely though) since it does power up and run intermittently.

With alllllllll that said the likely suspect would be the connector at the PCM.

Or you've got mice chewing on your wires.

How to test.

Run a jumper from battery + direct to both red wires (pin 37 & 57) on the PCM.
(Use a 5amp inline fuse of course.) The CEL will confirm power up.

Or simply test at the relay RED wires ignition on = 12v.
Then go to the PCM and test pins 37 & 57 = 12v.

No 12v at these pins; then you have narrowed it down to the wire itself (open)



I need a nap now...LOL

 

[colintrax]

^very good info. Just to add onto that incase the OP doesn't have much experience with electrical stuff. The "jumper" is like 5' of 18 gauge wire. Attach it to the battery and run it across the fender and through the open door to the PCM.
A year ago I woulda never been able to visualize that lol so just making sure others understand it

 

[L.A.X]

I'm glad I'm bald, otherwise i would've lost all my hair. I'm fixing this problem today. No Superbowl for me. This truck will start

 

[cgbier]

Better take your mind of that truck for a couple of hours. Enjoy your Super Bowl and a couple of cold ones, then approach it again tomorrow with a fresh mind.

 

[arco777]

All new plugs, truck has compression. Been reading thru all the old threads. What's the EDIS Module? Where's it located and what's its purpose? Anyone have a pic?

EDIS=Electronic Distributorless Ignition System. If I recall correctly the control module on a 94 is to one side of the radiator and says EDIS for EDIS-6 somewhere on it. It is uncommon for them to fail but they do. However, the EDIS won't do a thing if the PCM doesn't wake up to command it to come alive.

 

[colintrax]

EDIS=Electronic Distributorless Ignition System. If I recall correctly the control module on a 94 is to one side of the radiator and says EDIS for EDIS-6 somewhere on it. It is uncommon for them to fail but they do. However, the EDIS won't do a thing if the PCM doesn't wake up to command it to come alive.

So the 4.0 has one? I don't think my 97 does. I know my ranger does. Had to replace it common problem for the 2.3 lima

 

[arco777]

So the 4.0 has one? I don't think my 97 does. I know my ranger does. Had to replace it common problem for the 2.3 lima

While not the best source for this info, Wikipedia suggests that EDIS was used through 1997 on a variety of Ford vehicles including the Ranger/Explorer.