EFI Wont Start...I am soooo close

[contactwilson]

My EFI wont start. 1989 5.0 Mustang Engine/1993 Ford Mustang Factory Harness. I read through DanWheeler's (person on forum) who posted a troubleshooting link. Here is what I am looking at:

1. Engine fires when starting fluid is sprayed down throttle body

2. Fuel pump comes on when grounded to Self Test Connector

3. Fuel pump does NOT come on with key in run position (I know I should expect 2 seconds prime and stop)

4. EEC and Fuel Pump relays have been confirmed good and pinouts good (I also tried new relays with the same result)

5. I tried an A9L computer with pin 30 connected to pin 46

6. I tried a C3W computer with pin 30 connected to starting relay "S" post

7. I have a good confirmed ground that comes out by the computer

8. I have a good confirmed ground off the harness to the intake manifold

9. I have been very detailed about all grounds to bare metal including battery,frame,alternator,firewall,core support

10. The whole harness has been gone through and "cleaned up"

I HAVE 0.0 OHM RESISTANCE ON PIN 20 OF THE EEC
I HAVE 29.0 OHM RESISTANCE ON PIN 40 OF THE EEC
I HAVE 29.0 OHM RESISTANCE ON PIN 60 OF THE EEC

I understand the fuel pump is grounded by the computer to turn it on. Do I have a bad ground somewhere? All I know of is the two grounds on the harness (by the EEC and by the two ten pin connectors). Are there other harness grounds I am missing?

Any input is greatly appreciated. Thanks!!

 

[Broncobowsher]

Engine starting on juice being sprayd down the throttle shows there is spark, but does NOT show the computer is alive and controlling the spark. The TFI will throw spark without the EEC.

With the key on, check for power to the EEC, 5V reference coming out of the EEC, etc.

 

[Viperwolf1]

The 29 ohm resistance to pins 40 and 60 are strange. How did you measure this?

Inertia switch good?

 

[contactwilson]

I believe(??) the EEC is turning on. I checked the three injectors that are easy to get to. I have voltage from the red leads going to the injectors with the key on.

Good call that the TFI will fire without the computer. I didn't know this.

I measured 29 ohms at pin 40 and 60 by checking resistance from the ground at the firewall which is also tied into the ten pin connector ground. Block/alternator/frame are also grounded.

I did not put the inertia switch in yet for the purpose of simplifying my initial startup, do you think this could be the problem?

Are the only grounds on the harness at the ten pin connector and by the EEC?

 

[chadomatic]

The Inertia switch has to be there to complete the circuit to the fuel pump if you are using factory wiring unless you bypassed it.

 

[Viperwolf1]

I did not put the inertia switch in yet for the purpose of simplifying my initial startup, do you think this could be the problem

If it's a stock harness and the inertia switch is not there to complete the fuel pump circuit, then yes it could be the problem.

 

[Broncobowsher]

Grounding the self test is the same as the EEC grounding the relay. If that works, then the fuel pump setup is good. Inirtia is in the hot wire going to the fuel pump, not the logic wire from the EEC to the relay. That sounds correct and I would not mess with that right now.

12V at the injector is the same 12V going to the ignition.
It doesn't mean squat about the EEC getting power and coming alive (it should be the same but doesn't mean that it is). The EEC controls the ground to the actuators, not the power to them. Check for power at the 60 pin connector to see if the EEC is coming alive.

 

[contactwilson]

Thanks for the input guys. I will get working on it.

 

[Steve83]

3. Fuel pump does NOT come on with key in run position (I know I should expect 2 seconds prime and stop)

That's the 2nd big issue.

I understand the fuel pump is grounded by the computer to turn it on.

Actually, the EEC grounds the FP relay's trigger wire, which then sends power from the EEC PWR relay to the pump (via the inertia switch), but you've already tested that circuit by grounding it.

Are there other harness grounds I am missing?

Sounds like it - depending on what harness you're using, there could be ~8 general harness grounds, with several others for specific components.

I agree with bowsher - it seems like your EEC isn't powering up. Do you have a CEL circuit/bulb wired up? Does it light when you turn the key on? Does the EEC PWR relay click in & hold?

 

[contactwilson]

My check engine light is hooked up, but I don't get anything. The EEC power relay does click and hold. I checked pin #1, I wired it to supply constant 12V which checked out.

After everyone's input I am suspecting the EEC is not powering up and it could be caused by a ground problem.

 

[Viperwolf1]

Go back and look at pins 40 and 60. Those are the power grounds for the EEC. They should go directly to ground, zero ohms.

 

[contactwilson]

Thanks Viperwolf. The issues seem to be pointing to the grounds. Would it be a bad idea to put jumpers on the back of the 60 pin connector between pins 20,40 and 60 just to see if it runs? I don't want to cook the computer, this is why I have been reluctant to do it. I know it is not the cure, but it would help the troubleshooting process if it runs.

 

[Viperwolf1]

Thanks Viperwolf. The issues seem to be pointing to the grounds. Would it be a bad idea to put jumpers on the back of the 60 pin connector between pins 20,40 and 60 just to see if it runs? I don't want to cook the computer, this is why I have been reluctant to do it. I know it is not the cure, but it would help the troubleshooting process if it runs.

I don't see how that could hurt the computer. You could have issues with whatever is attached to the other end of the pin 40 and 60 wires though.

I think there's something wrong with the way the harness is wired. I'd spend time finding/fixing that before worrying about firing it up.

 

[Steve83]

I'd track down the wiring problems first. If you jumper those, and you have some crossed wires elsewhere, there's no telling what you'll do. Find the problem you know exists, and you might run across one you weren't aware of YET.

 

[contactwilson]

Will do. Thanks for the advice. I know I am getting overly anxious to hear it run!!

 

[contactwilson]

I got it running!!! It was the grounds pin 40 and 60. Pulled the harness and went through it. I made a stupid but honest mistake. There is a circuit breaker on the starter relay with a black/white wire. When I pulled the harness out of the wrecking yard the grounds were already cut and near this circuit breaker. I thought the wires were part of the circuit breaker and capped them in the harness.

Thanks for everyones help, I love this forum. I haven't heard it running for nine years. What a great milestone!!!

 

[crews44]

Congrats!

 

[Pedestrian]

Nine years! That's gotta be a great feeling, hearing it run.

 

[Steve83]

So, you driving it to OCBR & SuperCel? ;D