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Old 05-24-2009, 05:27 PM   #1 (permalink)
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Default 5.0L--Injectors Won't Fire

Well, I thought I was on the downhill stretch with the '65 5.0L conversion, but I've been troubleshooting the same issue for the past week.

I have yet to make the car fire the injectors. The fuel pump "pulses" when the key is turned, and the VPWR wire to the injectors is hot with the key on.

However, when you actually begin to crank the motor over, the injectors lose all power. I've verified this with both a test light and my Fluke multi-meter. Cranking the key over kills the 12 volts going to the VPWR circuit and onto the injector.

Additonally, each injector pin on the computer is showing a tiny bit of voltage, which also drops completely the minute the engine is cranked over. Release the key (back from the Start position to the On position), and power is restored.

I did try plugging a noid light into each fuel injector harness. When you crank the car over with the noid light installed, the light blinks very rapidly, which is confusing--on most vehicles, the injectors fire much more slowly. I know where the problem is, I just have no idea what could be causing it or how to correct it.

I've taken the entire harness back out of the car and verified that there are no pinched or cut wires. I've tested and verified every hot and ground point with the Fluke multimeter.

Well, I'm officially out of ideas. Somebody help before I push this thing out into traffic!
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Old 05-24-2009, 09:32 PM   #2 (permalink)
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Default Re: 5.0L--Injectors Won't Fire

I don't have any help at this time...but I do want to say that ya'll are sure making me nervous as I am putting my fresh 5.0 HO/AOD into the 66 tomorrow and will start hooking this efi mess up. Hope you find what it is that's preventing the firing...
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Old 05-24-2009, 09:40 PM   #3 (permalink)
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Thanks! Hey, if you run into any problems, PM me. Chances are I've run into similar issues with my install.

Trust me, hooking everything up isn't that tough.
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Old 05-25-2009, 01:25 AM   #4 (permalink)
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Default 5.0L--Injectors Won't Fire

Tell me more about how you have the wiring hooked up. Sounds like you have the injectors powered in the run position, but not the start position. Does the EEC have power? Theoretically, the injectors and EEC power (pins 37 and 57) are on the same line... if one loses power, so should the other. Same with the MAF sensor and the idle control motor. This all assumes that your wiring is anything like the stock wiring on a 5.0.

What harness are you using? Stock or aftermarket?

Off the cuff, sounds like you might have a bad ignition switch... but that should affect other things. Another option is a bad/incorrectly wired NDS. I dont know if that would prevent the injectors from getting 12V or not. Depending on the wiring harness, you might just have the ignition run circuit wired wrong.

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Old 05-25-2009, 08:28 AM   #5 (permalink)
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Default 5.0L--Injectors Won't Fire

CantedValve, I got a kick out of your avatar, and especially the "Biodome!" reference above it. Haven't seen that movie in years, but it's a great one.

I'm using a stock 1991 Mustang mass air harness. The EEC does show power with the switch turned on; the fuel pump primes correctly, and according to a multimeter, all of the various pins on the back of the computer are powering up.

My relays are set up identically to the FordFuelInjection site. I have five: EEC, Mass Air/02, Fuel Pump, and Ignition. I wired them according to the FFI diagram.

Other than the relays, I tried to keep the wiring as stock as possible, even to the point that I'm still able to scan the car with the Self-Test plugs. Yesterday, I pulled the codes out of the ECM memory, but the codes present only pertained to the EGR and TAD/TAB/CANP solenoids that I removed.

What are your thoughts on the NDS issue? I remember wiring that, and I wasn't sure if I had it wired correctly.

Like you mentioned, it sounds to me like the ignition circuit is wired incorrectly, that the injectors are hot in the "run" position, but not the "crank" position, but I can't seem to find anything that's wired incorrectly.

Sounds like the only thing you have left from my list is the NDS... and I am not even sure that it will shut off injectors. What computer are you running? Manual cars ground pin 30, allowing the car to start. Automatic cars get 12V to pin 30, allowing the car to start. I have a A9P... automatic (which my car is also), so I will need the NDS switch that goes in the AOD (I have one, it is broken though). When the car is in Park or Neutral, the switch is closed, sending 12V to pin 30. When it is open, it doesnt sent the 12V. This is useful to a) allow the car to start, and b) set idle points depending if the car is in gear or not. I dont know HOW the switch acts. One way to eliminate it is to jumper that circuit closed and see if you retain 12V to the injectors. BUT BE SURE WHAT COMPUTER YOU HAVE. You will fry a manual computer if you put 12V to the pin thinking it is an automatic computer. A9L is the most popular manual computer... A9P the most popular automatic. Seeing as you are coming from a 1991 Mustang, it is very likely it is one or the other.

You are wiring your harness exactly as I am wiring mine. I am being a little more liberal with the modifications (putting in a switch to test codes, eliminating the smog equipment connections, eliminating VSS, etc.), but I did wire my relays in the same fashion as on FFI.com.
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Old 05-25-2009, 08:55 AM   #6 (permalink)
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Something else that seems strange: On my '91 harness, a small connector feeds off around the master cylinder. It has the VSS positive and negative, the wires for the temperature and oil pressure gauges, and a few other wires.

One thing I noticed, however: One of the wires is feeds back to either Pin 19 (Fuel Pump Monitor) or Pin 22 (Fuel Pump) on the computer. I can't remember which pin it was, but I think it was the fuel pump monitor pin. This seemed really strange--why would there be a FPM wire there, of all places, and what could it have plugged into/operated?
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Old 05-25-2009, 11:48 AM   #7 (permalink)
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After checking out the car a few minutes ago, I'm almost 100% certain I have the NDS wired correctly. If I'm reading the diagrams correctly, the car won't even crank over if the NDS is wired incorrectly.
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Old 05-25-2009, 12:38 PM   #8 (permalink)
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Default 5.0L--Injectors Won't Fire

depends on how you have it wired. Like me, I have the stock one that controls the starter. It won't crank unless I am in P or R. The EEC one is separate from that. I can crank all day without the EEC one. You may have one switch doing both. I don't know. How about that fuel pump monitor wire? That basically needs 12v when the fuel pump is on. Is it connected to anything?

Read someplace where a guy had his TPS wired wrong and the EEC thought it was at 100% throttle, so it defaulted to "flooded" mode. Made the injectors not fire during cranking

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Old 05-25-2009, 03:22 PM   #9 (permalink)
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Default 5.0L--Injectors Won't Fire

I didn't realize there were two safety interlock systems in place. The one I have hooked up/bypassed originally went to the clutch safety switch on the Fox body Mustang.

Which wires are the EEC ones? Sounds like that may be what I'm overlooking.

The Fuel Pump monitor wire (Pin 19) is hooked inline with the fuel pump power wire. I followed the diagram on the Ford Fuel Injection site.
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Old 05-26-2009, 07:32 AM   #10 (permalink)
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what computer version are you?
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Old 05-26-2009, 05:58 PM   #11 (permalink)
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1991 A9L.

Also, I made a little headway today. I discovered that the new fuel pump I bought was dead. The pump wouldn't pump any fuel, even though plenty was getting to it. I took the lines loose at the tank and had no fuel pressure.

We'll see what tomorrow holds..new fuel pump should be in first thing. Please, oh please let this thing run!!
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Old 05-26-2009, 06:57 PM   #12 (permalink)
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Don't the injectors also need the distributor rotating to fire? Also something to check out.
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Old 05-26-2009, 07:13 PM   #13 (permalink)
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No... and yes. The PIP signal is necessary to keep the injectors in time. When I was invstigating EDIS, the one thing that was lacking was a PIP signal (crank fire didnt provide for PIP). People were running EDIS and EEC-IV without the PIP signal, but it wasnt running very well (the answer with EDIS is to get a cam syncrhonizer from a 1996 Explorer 5.0 to do PIP for you).

Good find on the fuel pump!
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Old 05-27-2009, 06:44 AM   #14 (permalink)
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Just wanted to thank everyone once again for all of the advice. I'm heading to the parts store to pick up my new fuel pump.

I've gotta say, the 5.0L firing system is strange. Looking at my Motor manuals, several other 1991 Ford products used a camshaft sensor to tell the computer which cylinder to fire on...why couldn't the Mustang be the same?

Guess Ford knew back then that one day I'd try to make this swap, and they didn't want to make things too easy on me.
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Old 05-27-2009, 09:58 AM   #15 (permalink)
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Default 5.0L--Injectors Won't Fire

Those vehicles use an EDIS ignition system. Basically 4 coils (2 pairs) in a wasted-spark configuration. The cam syncrho is there to provide the PIP signal to time the injectors.

That kind of system WILL work with the A9L. You need to source the parts, but it isnt hard nor expensive. I was going to do it with my car (and still mihgt), but I want to get the EFI running first (wiring is 99% done). You will need a tuning module that allows you to activate the feature within the EEC, but it is in there, it is just turned off.
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