Longtime Lurker needs help! plzz

[Flyn50]

Let me start of by saying thanks to anyone who offers to help me out. After a large amount so searching the forums, (everywhere) I have come to the conclusion that I am stumped.

I will spare the details unless asked, but the short version is I just replaced the high mileage stock mill with a new crate engine. Everything went in/together flawlessly. The problem, the engine will crank, but not start. In fact, its not even trying to start...exactly like turning over the motor with the coil wire off. Sooo, I decided to go thru a mental checklist.

1. Check for spark. So, I pulled the #1 plug, and held it against the strut tower and watched for the MSD box to do its thing. Sure enough..nice fat blue spark. *Note* The MSD box fires once more after the key is off, so wait for the last spark before you move the plug off your ground spot. I am using the 1-3-7-2-6-5-4-8 firing order.

After I learned the above note the EXTREMELY hard way, and cleaned my pants after the MSD box bit me on the last spark, I was supremely confident that the engine was getting fire.

2. Check for fuel. Well, here we go. The fuel pump primes on "key-on" and maintains pressure while the engine is turning over. Fuel flows nicely from the fuel check valve. So, with my handy noid light, I unplugged one of the injectors and pligged the noid light in. Turned the moter over a couple of times and....Bingo!..Nothing. Nada thing. No light.

Soo, it looks like the injectors are not firing. I am at a loss for the solution. I checked the injector ground (coming out of the wiring harness near the back of the engine : orange wire with loop) and it looks good.

I even tried another ECU. Nothing, same thing.

If anyone has any ideas please pass them along. Normally I find the answers with a quick search, but not this time. Thanks in advance guys.

-Russ-

 

[GroverDill]

Just a guess, did you remeber to ground the fuel injector harness?

It normally mounts on the rear side of the drivers side head, I think its a small orange wire.

Edit,
I dont read well...

are you sure the Salt and pepper connectors are seated all the way?

 

[RickyB]

Soo, it looks like the injectors are not firing. I am at a loss for the solution. I checked the injector ground (coming out of the wiring harness near the back of the engine : orange wire with loop) and it looks good.

Just a guess, did you remeber to ground the fuel injector harness?

 

[GroverDill]

yeah yeah,

I caught my mistake.

 

[jerry beach]

I will start by stating the obvious. Its prolly got something to do with something that you messed with during the install. But you prolly knew that. As stated, check that the 10-pins are plugged in tightly and look along the injector harness for anything irregular. I read about a guy that torqued his lower intake down on top of the wiring harness and cut them all. Hope thats not the case.


The puter sends the signal to the injectors, so I would say check for signal output at the computer next. Maybe it decided to die, or maybe another signal is telling it to cut fuel. Try checking the TPS voltage. If its high the puter is supposed to cut fuel. The way I understand it, this is to prevent flooding. You can ohm out the wiring between the injectors and the puter, should be less than 5 ohms. I am happier when its less than 1.

Did you hook up the main ground strap for the engine? You know, firewall to engine, might need that.

If the wiring checks out and the TPS signal is under 1 volt, there is a good chance the puter is fried. I think that if the PIP signal were not present, that would cut fuel too. Hopefully someone else will chime in with better info, thats all I can think of right now off the top of my head.

 

[Flyn50]

Thanks for the reply's! As soon as I make it home I will make it a point to check to the TPS voltage and then I'll check the 10-pins and the signal wire between the ECU and the injectors. Am I correct to assume that the injectors are normally hot, and the ground is what fires them? (completing the circuit)

Oh, as for the ground strap. I double checked it, and it looks good. I guess its fine since the engine turns over...right?

Thanks again. I will report finding.

-Russ-

 

[GroverDill]

maybe, pull and injector, turn over car just to ensure its not a bad FPR?

/me shrugs

 

[SR86]

Injectors share a common power source with almost all of the sensors in the car. It would get that from the EEC Power relay, if you aren't getting power to any sensors, example TPS. The EEC power relay is hot at all times, but grounded thru the EEC.

Make sure you have all the wires hooked up to your Starter solinoid.

 

[Flyn50]

Ok, status report:

TPS Voltage was at .92. Double checked the 10-Pins - They were good. Just for giggles, I added another ground strap to the point where the injector ground is located, and checked with a meter. I haven't checked the output of the ECU, but I did check the injector harness, and all of the injectors are getting voltage to the hot side, but no ground to the ground side. So it seems the "noid" light is right.

Also borrowed a buddies speedbrain ECU, just to use the "dashboard" on the laptop, and it reports the current injector pulse-width. So at least the ECU "thinks" its firing the injectors.

Could the TFI module or the PIP cause this problem. I know that logic dictates that I missed something, but I am starting to wonder.

Thanks again for the help! I appreciate it.

-Russ-

 

[jerry beach]

I think you answered your own question. No ground to the injectors. There is a ground near the puter, is that one intact? I would be checking for ohms to ground at the ECU ground. If the puter is firing the inj., but its not properly grounded, that would explain it.

 

[BarnStang]

Jerry, I think he is suggesting that the EEC is not sending a ground to the low side of the injectors, not the harness ground which should be a shield ground to minimize electricle interference.

If the Speedbrain was in working order, and the car still would not start, or fire, then it seems that it's still a wiring harness issue. And you said you tried another EEC.

There are several ground straps and all of them should be attached.

What year is this car? I couldn't find it, or may have missed it.

If you're getting spark out of each plug wire then it reasons that the TFI is working as well as the PIP. I can take a look in the EFI book tonight, but someone will have it handy before I get home and post I'm sure.

I'm not sure if you will be able to "see" the low side switching to ground with a meter. Check for continuity between the EEC connector and the inj harness low side inj connectors. Yea, it will not be fun nor easy. You will need some help. THe other thought is to make sure the EEC connector is completly seated into the EEC. It may not be in all the way, but you have had it in and out a couple times already so you probably already know.

 

[BarnStang]

The cool tmoss diagram if it helps...

hmmm, saw this happened to some other people trying to post. Says the attachment is valid, but it won;t show. Can anyone else try to post the eec pinout diagram?

 

[jerry beach]

I have been having probs attaching file too. I will try it. Barnstang has some good advice, but check for ohms of resistance between the puter plug and the injectors. Hopefully this diagram comes up, or you have one that shows the wire colors. Resistance should be less than 5 ohms. I will try and look this up in the Probst book, I highly recommend it to anyone trying to service their own EFI stang.

 

[Flyn50]

Thanks for the replys guys!

Jerry Beach: I will make it a point to check the resistance if I run across a pinout.

BarnStang: The car is is '90 GT. I guess I will have to check for cont on the injector low side. You are right about the meter not being fast enough to see the low side change on the harness, but a light should have worked right?

Anyway thanks for trying to post the EEC pinout guys. I will look around and see if I can try to find one.

-Russ-

 

[sleeper89]

Thanks for the replys guys!
You are right about the meter not being fast enough to see the low side change on the harness, but a light should have worked right?

Anyway thanks for trying to post the EEC pinout guys. I will look around and see if I can try to find one.

-Russ-

i don't think the light will work either. the injectors fire quite rapidly and may not have enough juice to actually heat the element in the bulb.

-steve

 

[Flyn50]

Its an LED. It should light that up right?



-Russ-

 

[jerry beach]

Yes it should flash the LED, thats what the noid light is designed to check. the pin outs are listed and color coded in Haynes manuals. they are small and hard to read, I have a magnifying glass for that and have great vision too. I dont understand why I cant post attachments anymore, have to get to the bottom of this. I never could post one on the corral, thats why I am here all the time. Go to www.veryuseful.com that is the page where tmoss puts up his diagrams. It is there if you look around.

 

[BarnStang]

I would think the LED should work, the meter probably will not. Been too many years since I have done electronics theory. THere is someone on the board who knows this stuff cold. The EEC is signaling with TTL (Transistor To Transitor ) logic levels. There is no way to see the chip transition to ground. You need to use a pull-up resistor so you can see a voltage drop accross the resistor. Then when the chip switches to ground, the voltage drop will go to zero volts. A lot of painful messing around with an EEC. I'm sure someone else can make this clearer. FOund it! Man, that took awhile...THis is an excerpt from an instruction document on how to set up pin 41 on a 94-95 EEC to trigger a fan. The theory is the same for the TTL logic level. Basically, you would tie a pull-up resistor to the pin in question, then tie the other end of the resistor to the + on the battery. THen probe the pin with the - meter lead, and probe the + battery terminal with the + meter lead. It sounded strange the way he wrote it. THere is a diagram, but of course, I can't get it to post either. See below:

Testing Pin 41
In order to test whether or not pin 41 goes to ground (once the required temperature has been reached), we need to use a 2k-ohm ½ Watt resistor and a voltmeter. NOTE: Using a voltmeter by itself will indicate that Pin 41 is grounded 100% of the time.

1.The + of the voltmeter goes to the + battery.
2.The – or COM of the voltmeter goes to the 2k ohm resistor on one side along with pin 41. (Note: you could wrap one leg of the resistor around the meter lead)
3.The other side of the resistor goes to the + battery.

This will load the circuit in order to keep from getting a false signal to ground.

 

[BarnStang]

Attempt to load the diagram...

I can email the diagram if you really want it, but it's a very primative drawing. Not much to it. It was done in MS Word.

 

[Flyn50]

Didn't find the diagram in time to get to it last night, but I did get one this morning. Hopefully I will find some answers this afternoon. Thanks again for the assist.

-Russ-