E2A vs. P2A ECM

[RiverRoadInfidel]

Should the two ECMs below be interchangeable? Mine, the lower one (E6TF12A650E2A), has three leaking capacitors and a fourth that resides atop its own little patch of blueish-white corrosion. It being 37 years old, I felt it might be handy to have a replacement in the event it should fail.
I ordered one to have on hand and was told it would be a direct replacement. I had assumed direct replacement would mean the same Ford part number, which they obviously don't share (E6TF12A650P2A). I plugged the new one in to verify it would work. When I went to start the truck with it, the fuel pump relay didn't initiate and that's as far as I went. If it's a "direct replacement," shouldn't it work right out of the box? Any help would be greatly appreciated! Thanks!

Image below, I think!

 

[rusty ol ranger]

Should the two ECMs below be interchangeable? Mine, the lower one (E6TF12A650E2A), has three leaking capacitors and a fourth that resides atop its own little patch of blueish-white corrosion. It being 37 years old, I felt it might be handy to have a replacement in the event it should fail.
I ordered one to have on hand and was told it would be a direct replacement. I had assumed direct replacement would mean the same Ford part number, which they obviously don't share (E6TF12A650P2A). I plugged the new one in to verify it would work. When I went to start the truck with it, the fuel pump relay didn't initiate and that's as far as I went. If it's a "direct replacement," shouldn't it work right out of the box? Any help would be greatly appreciated! Thanks!

Image below, I think!

I think the only differences is between auto trans and manual trans assuming they are all federal emissions.

The pump shoulda primed regardless though.

I put an auto ecm in my manual 87 and it didnt seem to be right. It idled different or something.

Replaced it with a manual 88 ecm

 

[RonD]

Welcome to TRS

Suffix E2A and P2A in 1986 are for 2.9l with automatic and Federal emissions

As said above the Fuel pump system is the same in any 1986 computer for any engine size, transmission type or emissions, so suffix wouldn't matter
(1986 to 1994 computer's used same fuel system activation)

So there is an issue inside the "new" computer or in the wiring of the vehicle

Find the OBD1 connector in the engine bay on the main wiring harness, should be on passenger side inner fender, may have a CAP on it that has "EEC", remove the cap

Looks like this: https://www.supermotors.net/getfile/480935/fullsize/obd1-connector.jpg

Slots labelled here: https://www.therangerstation.com/tech_library/images/eec-iv_testing2.gif

Fuel pump Slot can be used to activate the fuel pump RELAY, which should then activate the fuel pumps, you have 2 in a 1986
Turn on the key
Use a jumper wire in the Fuel Pump Slot and then GROUND the other end of jumper wire to battery Negative or any bare metal ground
You should hear the Fuel Pump Relay "click" closed and fuel pumps should run and stay running as long as Slot is grounded and key is on

If Fuel pump relay and fuel pumps work using the jumper wire then that part of the system is OK, and you can try starting the engine with jumper in place, doesn't hurt anything

To test the Computer side of this, hook up a 12v test light or a Volt meter to the Fuel Pump Slot
Then to the Positive battery terminal
Fuel pump slot should be grounded by the computer(pin 22) to activate the fuel pump relay, but just for 2 SECONDS

OBD1 Fuel pump slot--------Test light/Volt meter--------Battery positive

So turn key off if it was on then turn key on and watch for the test light to come on or Volt meter to show voltage for 2 seconds, repeat key off and on as much as you want, to either confirm its working or its not working

 

[RiverRoadInfidel]

I think the only differences is between auto trans and manual trans assuming they are all federal emissions.

The pump shoulda primed regardless though.

I put an auto ecm in my manual 87 and it didnt seem to be right. It idled different or something.


I thought the pump should have come on, too.
Thanks!

 

[RiverRoadInfidel]

Welcome to TRS

Suffix E2A and P2A in 1986 are for 2.9l with automatic and Federal emissions

As said above the Fuel pump system is the same in any 1986 computer for any engine size, transmission type or emissions, so suffix wouldn't matter
(1986 to 1994 computer's used same fuel system activation)

So there is an issue inside the "new" computer or in the wiring of the vehicle

Find the OBD1 connector in the engine bay on the main wiring harness, should be on passenger side inner fender, may have a CAP on it that has "EEC", remove the cap

Looks like this: https://www.supermotors.net/getfile/480935/fullsize/obd1-connector.jpg

Slots labelled here: https://www.therangerstation.com/tech_library/images/eec-iv_testing2.gif

Fuel pump Slot can be used to activate the fuel pump RELAY, which should then activate the fuel pumps, you have 2 in a 1986
Turn on the key
Use a jumper wire in the Fuel Pump Slot and then GROUND the other end of jumper wire to battery Negative or any bare metal ground
You should hear the Fuel Pump Relay "click" closed and fuel pumps should run and stay running as long as Slot is grounded and key is on

If Fuel pump relay and fuel pumps work using the jumper wire then that part of the system is OK, and you can try starting the engine with jumper in place, doesn't hurt anything

To test the Computer side of this, hook up a 12v test light or a Volt meter to the Fuel Pump Slot
Then to the Positive battery terminal
Fuel pump slot should be grounded by the computer(pin 22) to activate the fuel pump relay, but just for 2 SECONDS

OBD1 Fuel pump slot--------Test light/Volt meter--------Battery positive


So turn key off if it was on then turn key on and watch for the test light to come on or Volt meter to show voltage for 2 seconds, repeat key off and on as much as you want, to either confirm its working or its not working

With the "new" ECM hooked up and jumper wire from fuel pump slot to negative battery terminal the relay closes and fuel pumps come on. With test light from fuel pump slot to positive terminal, I get nothing. No relay closing and no fuel pumps. I assume my "new" computer isn't functioning properly and should be returned? Those fuel pumps sure come in handy when driving!

With the original unit in, the truck starts as it should. It just runs bad.

 

[RonD]

Yes, it's fuel circuit is bad, not the pin 22 wire
With "new" computer in, will the engine start and run with fuel pumps manually activated(jumper)?

If not then "new" computer may not even be powering up, so "dead out of the box"

 

[franklin2]

Let me guess. You are getting these "refurbished" computers from Cardone?

 

[RiverRoadInfidel]

Let me guess. You are getting these "refurbished" computers from Cardone?

Not knowing any better, I bought one. The silver spray paint seems to be its best feature so far. I really wanted to open it up and see if it looks any better than my 37 yr old ECM but I don't want to do anything that might jeopardize my being able to get a refund!

 

[RiverRoadInfidel]

Yes, it's fuel circuit is bad, not the pin 22 wire
With "new" computer in, will the engine start and run with fuel pumps manually activated(jumper)?

If not then "new" computer may not even be powering up, so "dead out of the box"

I didn't try to start it but I will in the morning and post the results. Thanks so much for your help!

 

[RiverRoadInfidel]

I didn't try to start it but I will in the morning and post the results. Thanks so much for your help!

I tried to start truck with with the fuel pump jumpered to negative battery terminal. It has always been quick to fire up. With the fuel pumps running it never attempted to start. I got this through Advance Auto and it came with a return label so it'll go back tomorrow. Is there somewhere I can get one that at least tests them before shipping? Me and the dog are tired of walking.
Many thanks for your help!

 

[franklin2]

Sometimes people like Cardone are the only game in town. All the stores sell the same thing. On their distributors, instead of taking it back to the store I rebuilt it myself and finally had a working distributor.

On the ECMs, your best bet is to keep trying till you get one that someone turned in where there was nothing wrong with it in the first place. Have you kept your old one? If you have it, I would not turn it in, I would keep it and then tear it apart and replace the capacitors yourself.

 

[RonD]

There is no test for them, not even Ford could test them when new, or in for service
Ford shop manuals for all models with a computer was a few basic tests, like fuel pump activation and injector pulses(NOID light) then...............
"try replacing PCM", lol
Even in 2023

 

[4x4junkie]

Your old PCM is likely OK other than the capacitors...
The caps are easy to replace if you have some soldering experience. You just need to make sure that the replacement ones are the proper value.
They likely will be marked something like "2.2µF" (microfarad), "10µF" and so on, and have a voltage rating. It is important that the µF rating match exactly. The voltage rating can be same or higher (but NOT lower).

There may also be a temperature rating on them (likely 85°C or 105°C). Caps rated 105°C tend to be of better quality.