1996 SVT Cobra runs 1-2 minutes shuts off

[meanroy]

A little history:
This car was in an accident before I got it.
It was crudely hacked back together.
From the carfax info it was registered and run after the accident.
I'm trying to restore it to factory condition, it has ~80K miles.

The car starts easily, runs 1-2 minutes and dies.
It can be immediately re-started.
I replaced the ECU as the unit in the car had no identifying numbers or tags.

It throws codes P0231 and P0421.

I read the post http://www.automotiveforums.com/vbul...ighlight=P0231
Which may provide some clues but the info is incomplete, the troubleshooting tree says:
"Does the engine start?
Yes DISCONNECT PCM. GO to KC13 ."
Unfortunately KC13 is not part of the post.
I *think* that the ECU shuts down when it tries to go to closed loop operation, but I'm not sure.
====== Edit to above ====
OK I found the troubleshooting tree that post was taken from. (In my copy of the factory manual)
Unfortunately that particular section advises "KC13 ... replace ECU if you have code P0231" and I did that already!

The 96 Cobra fuel pump circuit diagram allows for at least 4 other possibilities:
1.)Bad fuel pump relay
2.)Bad fuel pump resistor
3.)Bad CCRM
4.)Broken wire in harness.

Got the relay and a multimeter, I'll let you know.


Roy

[meanroy]

Boy, this Forum is sure an active one! Ha Ha. :sarcasm1:

Now that I've solved this problem the answer is simple.

If anyone cares, post and I'll explain.

Roy

[meanroy]

Originally Posted by meanroy

Boy, this Forum is sure an active one! Ha Ha. :sarcasm1:

Now that I've solved this problem the answer is simple.

If anyone cares, post and I'll explain.

Roy

I got an e-mail from another forum member with the same problem asking for details and I thought it only fair to post the solution to the problem.

It turns out that the fuel pump circuit in the Cobras utilizes two relays in series.
There is a resistor across the second relay.
When the engine is started both relays are closed, providing full battery voltage to the pump.
After 2-3 minutes the ECU opens the second relay, placing the resistor in series with the first relay and lowering the voltage to the pump.
If the resistor is removed or fails the fuel pump will shut off and the engine will shut off.

The resistor is located under the passengers side fender.
(In my case the previous owners girlfriend had physically removed the resistor)

Good Luck!

Roy.