[rdubb17]

I recently pulled and tested my constant control relay module from my 1994 5.0 mustang GT and did some resistance & relay actuation tests on both the EEC/PCM & fuel pump relay. I found some strange results that I really was not expecting. The coil for the EEC/PCM had very high resistance, 2.285 Mega OHMs while the fuel pump relay coil had 78.2 OHMs. Based on OHMs law I thought I would not be able to get the EEC/PCM relay to click using 12v power but I was wrong - apparently the magnetic field was still strong enough to pull down the switch. I should have done a current draw test to see how much current was passing through the circuit but I didn't. Once the two coils were energized the two switch circuits showed reasonable resistance values, 0.2-0.1 OHMs. I don't suspect any issues with the fuel pump relay.

My question is:

When you had a bad PCM relay, what type of problems did you have in regards to engine functionality? Is it possible that I could have only inconsistent fueling and no other problems? What is the probably that this is what has been causing my strange I've never experienced a engine shutdown experience.

Coil Resistance Check:
EEC Power Relay: Pins 13 to 15 = 2.285 Mega OHMs
Fuel Pump Relay: Pins 18 to 12 = 78.2 OHMs

Switch circuit resistance check:
EEC Power Relay: pin 10&8 to pin 24 = 0.2 OHM
Fuel Pump Relay: Pin 5 to 11 = 0.1 OHM.

[decipha]

usually when your fuel pump relay is failing your fueling will go all over the place

I had one vehicle that had a very bad fuel pump relay, the first pull it ran 12:5 across the board, i added 6% to it and made another pull, this time it went to 17:1, i then made another removing adding 15% and it went to 10.5:1, i went back to the first tune and made a pull it went to 11.5:1

i said screw it and told the guy he had issues with his car he had to resolve first, he checked over his fuel system and couldn't find any issues, 2 weeks later he was driving and his car died, fuel pump relay went out, we replaced it and were able to dial it in no problems

thats the most substantial time I ever ran into a faulty fuel pump relay, I've had similar results many other times as well

[rdubb17]

I have always faught with inconsistent fueling - I have never been able to dial it in.

Since last tuning session I have done:

• Rebuilt engine - coolant release into lower intake manifold and damaged a rod

• New intake

Planning on doing:

• smoking intake and exhaust to confirm no leaks

• fuel pressure gauge to confirm consistant fuel pressure

• New CCRM - Wells part number 20253

We shall see if I can get more repeatable fueling results. Any other suggestions based on your experiences?

[decipha]

no thats about it, I tuned a camaro once that had a kinked fuel line, it would only run lean / loose pressure on the big end

[rdubb17]

I should be able to derive that scenario with a fuel pressure gauge. I'm hoping I can get this fueling gremlin to go away.

[decipha]

yea fuel is simple to diagnose just work your way from the pump forward