Gunpilot

Trying to get my Monster started for the first time and I think the computer may be bad. Anyone have an A9L laying around to ship to Houston, TX 77089?

tbone heller

87 89 90 91 92 93 MUSTANG 5.0 ECU PCM COMPUTER A9L ECM
I am going to replace mine with one from a 1994-1995 model as advised by the guy that tuned mine.

MRM331

I have one but its intended for my next car so I need it back. If you can cover a flat rate box both ways you can borrow it.

Have you run a KOEO test to make sure all the sensors are in range?

Have you verified that you have the correct firing order?

Have you used a noid light to check that your injectors are firing?

Are the plugs firing?

Verify that the fuel feed and return are not reversed.

Pop off the passenger side valve cover and verify that you're at tdc.

I know this is all pretty obvious stuff but sometimes it helps to go over things one at a time. Everything I've listed above has happened in the past, some of them to me personally.

If it turns out the problem is the a9l you can trade it in at Autozone and get a reman one with a warrantee for about $110. If you want to buy another one you can get them on eBay around $125 - $150 or so.

-Jason

Gunpilot

Verified twice that I'm at TDC on compression stroke. Firing order is good. Plugs and coil are good. Get small ignition with starter fluid then nothing. Fuel rail is connected correctly. I am leaning towards injectors not firing due to computer. Need to get a light for injectors as you discussed. A friend locally said he recommends a computer from a 1993 DPS car (D3D). Gonna try that before I dig deeper.

MRM331

Just to update for anyone following:

It sounds like everything is working but the ECU will not fire the injectors. Since the ECU grounds the injectors to fire them he's going to check to see if the red 12 volt keyed wires running to them are getting any power with the ignition on. If they are not then we'll see if there is break-down somewhere in the 12 volt keyed (red) wire circuits. If they are getting 12 volts we have to keep looking to see why the injectors will not fire.

Firing order and timing must be fine because he's not flooding it.

He's also going to try to run a KOEO test.

For anyone who needs it, here's a link to how to do a KOEO, KOER and cylinder balance test:

http://www.corral.net/tech/maintenan...koer.html#koeo

One possibility is a bad EEC relay which he's going to swap out today and try to eliminate.

Another rare and hopefully unlikely possibility is that the donor harness has some small flaw, like a broken wire within its insulation, that I wasn't able to visually detect when building the harness. I've always figured this is a risk, but in 30-something harness builds it’s never happened. Rawn and I spoke and if we can't quickly figure this out I'm planning on exchanging his harness for another which I'll quickly build up. It stinks but is unfortunately part of using used donor parts that I can't test on a running car before sending out. If that's how we go I'm planning on tearing the offending harness apart to find what happened after I get it back.

If anyone else has some thoughts please feel free to post your ideas. Rawn is concerned with possible differences between 1988-91 and 1992-93 harnesses. Honestly I've used every year from 1986 (SD) up to 93 in the past and the pin outs are the same. I use pin outs (SD's do have some small differences) to make the mods I make so I can't see how the year could be the issue.

I do want to publicly apologize to Rawn for him having to even pick up a multimeter. He's been awesome with this and hopefully we'll quickly work it out.

We'll keep everyone posted.

-Jason

MRM331

OK, I just had a few minutes and did a quick search of things that would cause the EEC to not fire the injectors. Two big things popped up: Throttle Position sensor out of range and wrong EEC itself.

I checked 1993 wire diagrams against earlier ones and the injector wires are the same as is the 12 volt keyed feed to them. This is not the issue.

I'm putting my money on an out of range or bad TPS, a wrong or bad EEC, or a break in the red 12 volt keyed wire somewhere between the distribution block and the injector block (maybe even a loose connection in the 10-pin connectors) in that order.

A KOEO test will rule out the TPS. A check for 12 volts at the 10-pin connector and then again at some other red wire point and at an injector will rule out the last possibility.

Rawn, what is the exact designation of the EEC that you are using? I'm seeing some threads about incompatible EEC's and would like to rule that out.

Also, I remember you contacting me about the neutral safety switch loop that I add to the harness. What did you do with it? Did you leave it jumped or did you run it to the trans?

Marching on...

MRM331

Rawn just texted me to tell me the car is running. He pulled his 24 pound injectors out, replaced them with 19's and now it runs. I can't explain this. Can anyone else?

-Jason

Vic Harder

Loose wire or connection that swapping the injectors "fixed" would be my guess.

Gunpilot

Running a D3D EEC now.

At first the injectors were not getting a good 12V signal at power on (confirmed with multimeter and noid light). I found a loose wire at the EEC relay and that solved the problem.

Car still did not start. I had air, fuel, and spark so I decided to swap everything back to stock. Removed 70mm throttle body, calibrated MAF, and 24# injectors. Car fired right up.

To trouble shoot, I disconnected MAF and TPS and car still started. I then installed a second set of 24# injectors I had and the car WOULD NOT start again. Swapped back to stock injectors and car starts.

So the question is why won't the car start with 24# injectors installed?

MRM331

Where did you get the injectors? Could it be possible they are the wrong impedance?

They should have a part number cast in them near the top. Look it up on google and see what it comes up as.

-Jason

Gunpilot

I have 2 sets of blue top Ford 24# injectors. 1 set bought brand new from a Ford dealer and the other was included with a manifold I bought. Both do not work. What impedance should I be looking for, and are there different impedance 24# injectors?

MRM331

The stock ones should be "High". I'm not sure if any Ford came with low ones. Since the design of injectors in not particular to a certain make I'm sure there were low 24 pound, or at least low blue top injectors somewhere that could be mistaken for the ones you have.

Unless there is something particular to that certain designation of ECU I can't think of any reason why this would happen. Even with the wrong injectors the engine would still run, just not well.

There has got to be something you changed when you swapped out injectors. This is quite strange.

I'm glad it's running for you though!

-Jason

MRM331

Posts about the D3D ECC:

EECTuning.org • View topic - D3D v. A9L



Valid Mass-air Fox body Mustang 5.0 ECU's according to:

Fuel Injection Technical Library » Search Results » d3d

X3Z 5.0 1993 Cobra MAF / Manual
A9L 5.0 1989-93 Mustang MAF / Manual
A3M 5.0 1989-93 Mustang MAF / Manual
A3M1 5.0 1989-93 Mustang MAF / Manual
S0Z 5.0 1989-93 Mustang MAF / Manual
D3D 5.0 1989-93 Mustang MAF / Manual
D3D1 5.0 1989-93 Mustang MAF / Manual
A9S 5.0 1989-93 Mustang MAF / Manual
8LD 5.0 1989-93 Mustang MAF / Manual
A9M 5.0 1989-93 Mustang MAF / Auto
A9P 5.0 1989-93 Mustang MAF / Auto
C3W 5.0 1989-93 Mustang MAF / Auto
C3W1 5.0 1989-93 Mustang MAF / Auto
A9T 5.0 1989-93 Mustang MAF / Auto
8LF 5.0 1989-93 Mustang MAF / Auto
8LG 5.0 1989-93 Mustang MAF / Auto

-Jason