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Discussion Starter #1
Finally got to a point where I could turn the key on my 5.0 conversion in my 66 Mustang. I had to cut it short as the day ran out, but unfortunately couldn’t get it to fire. Scratching my head a little, but wondering if anyone can suggest anything to try. I haven’t done a lot of troubleshooting yet but this is what I can confirm -
  • Turn to on and EEC relay clicks and primes the fuel pump.
  • Fuel arrives at the fuel rail (the one with the injectors attached which I believe is the supply during prime and crank
  • Starter engages during crank and turns engine
  • Pulling the main HT at the distributor I have spark firing
  • Can hear injectors ticking
I have checked and believe to have the correct 5.0 HO firing order. The injectors are connected in the right order.

Any ideas from anyone who has done this conversion? I feel like I have spark and fuel... so yeah, wrapped up today scratching my head a bit.

-Rob
 

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Verify your fuel at the rail, put a pressure gauge on it at the schrader valve. Any chance you have the return and supply lines backwards? The regulator on those is on the return line so if you have your supply line going to the regulator it will stop there.
 

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I had similar issues getting mine started. I had good fuel pressure and spark. It’d run just a bit on some starter fluid and I had tested the injectors before installing them. After wasting a few hours messing with the the distributor I finally pulled the injectors and tested again and found that some of them got plugged up. I replaced the bad ones and it fired up immediately. I had all new fuel lines. I must’ve had some junk in the fuels rails.
 

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First I used a test light and remote starter switch to confirm that the injectors were getting voltage and were grounding as they should. They were.
Then I pulled them out and tested them individually outside the car. I rigged up the cup from the vacuum bleeder kit, filled it with alcohol and used my compressor to pressurize it . But I saw a youtuber do the same with injector cleaner straight from the can.
 

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Does the engine have all stock components or are there aftermarket goodies (i.e. bigger injectors, MAF, etc.)? I tried for days with no luck to get my engine to start after I completed the conversion. I checked the firing order multiple times, tried flipping the distributor 180 in the event I had it 180 out, and checked spark with a spark tester. Everything appeared to be fine - would even get a pop every now and then and I could smell fuel in the exhaust pipe so I know the engine was getting fuel. Al 3 of the magic pieces were there - fuel, air, and spark - but still no fire. I suspected that the engine was getting too much fuel so I pulled the upper intake and watched the injectors spray fuel as I cranked the engine - looked like a showerhead dumping massive quantities of fuel. I knew I would need to do some EFI tuning, but I figured the engine should at least start. Once I put the tuner on it and had a proper tune for my 30 lb. injectors, the engine fired right up and ran with no problems.

In your case, my initial thoughts were that the EEC might not be getting power during cranking since (depending on what EFI wiring harness you use), you have to do some tricks to make sure the EEC stays powered up while cranking the engine. Since your injectors are firing, I would not suspect that to be the case since the EEC must be commanding the injectors to fire (assuming the ticking you are hearing is the injectors). The vintage Mustang ignition switch cuts power to everything except the starter solenoid while cranking, so you have to feed power to the EEC during crank (carbureted engine ignition system would get power from the "I" terminal on the solenoid).

Any signs of life at all such as popping in the exhaust from an occasional successful combustion? Can you smell raw fuel in the tailpipes?
 

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Discussion Starter #7
Hmmm, you’ve raised a good point. I’m just pulling my power to the EEC via a relay which I am triggering from the ignition switch itself. It’s all standard hardware, no modifications at all. I am pretty sure the ignition switch is energized in both RUN and START on the wire I’ve run from the back of the barrel. Definitely something for me to look at though....
 

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Hmmm, you’ve raised a good point. I’m just pulling my power to the EEC via a relay which I am triggering from the ignition switch itself. It’s all standard hardware, no modifications at all. I am pretty sure the ignition switch is energized in both RUN and START on the wire I’ve run from the back of the barrel. Definitely something for me to look at though....
On a '66 ignition switch, the items connected to the barrel (center threaded stud) go dead when the switch is in START. One way you can get a 12V source while cranking is to use the "I" terminal on the solenoid. This is the terminal that Ford originally used to supply full power to the ignition system while cranking.

Easy way to check it and see if the engine will run:
For an automatic transmission, make sure it is in PARK. For a manual, put it in neutral and set the parking brake.
Turn the key to RUN.
At the solenoid, momentarily jump from the battery post to the "S" terminal to engage the starter - remove the jumper when (if) the engine starts.

By doing this, you essentially bypass the START circuit so that the EEC stays powered up while cranking the engine by jumping the solenoid.

If you don't want to do that, here is another method to see if the EEC is getting power while cranking:
Remove the small wire from the "S" terminal on the solenoid so that the starter will not spin when you turn the key to START.
Connect a multimeter or test light to the power input of the EEC (or the output of the EEC power relay that feeds the EEC).
Turn the key to RUN - the test light should come on or the multimeter should read ~12 VDC.
Turn the key to START - the test light should stay on or the multimeter should stay at ~12 VDC.
If the light goes out or the meter goes to 0 VDC, you aren't getting power to the EEC while starting.
 

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Discussion Starter #9
So an update. Managed to get the entire thing to fire tonight. Not quite running on its own but being 9PM with open headers in my garage in suburban Los Angeles I wasn’t gonna force it for any more than a few seconds. I think there was a couple issues... firstly I got it to run by jump starting it off my Mercedes SUV. I think the battery I had wasn’t up to scratch and just not cranking enough. Also, I think I may have an intermittent issue with my ignition switch. Might not, but every now and then I turn it and stuff doesn’t fire, so not sure what other implications that might have on the “ON” circuit while I am cranking.

Once I get a chance to run it during the day I’ll post updates if I discover anything that might help anyone in the future reading this.

-RD
 

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Glad you're on the right path. I use the Mass Flo unit which is based on the EEC-IV. I'm very happy now but it took time and lots of money on the dyno to get the right tune with the SC.
 

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Does the Mass Flo unit use a MAF? I've never actually seen that system before!

Update - I actually did some digging and discovered their on throttle body MAF. What a cool setup.
Yes, the TB version is handy. I used the Pro M-80 MAF because of the supercharger. So the MAF is outside in the fenderwell with the conical filter for cool air.
 

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Lots of good info from Greg'66-5.0

I used the easier but costly Ford Racing EFI conversion harness that is more less plug and play so I don't have wiring harness advice for you, however I will share my experience firing the 5.0 EEC IV conversion in my 65
Before attempting to fire the engine some of the efi components had been sitting for a while, I replaced some of the sensors but the injectors were the original oem 19lbs type, figured It would be worth while to have them checked.

dropped the injectors off at a injector/turbo shop, sure enough I got a call and was told half the injectors were not working or not flowing correctly, being as I was planning on installing new larger injectors in the future I picked up another used set factory 19 lbs injectors and dropped them off at the injector shop, some of those were also not a100%... they put together the best 8 equally flowing injectors.

I set aside a day to fire up the efi conversion logically thinking there may be some issues that would send me chasing my tail when the engine didn't fire, cycled the key several times to prime the fuel system, cranked the engine and it started immediately, startled me with the open headers, eventually the idle speed started hunting and it stalled, had to set up the throttle body and tps to get the engine to idle.

If I hadn't had the injectors checked maybe the stuck or gummed up ones would have cleared out and worked or maybe not, hard to say.
 

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should have referred to that procedure as
" base idle reset " I don't know if that term is an actual Ford term however it's commonly used in the 5.0 Foxbody community.
A web search should bring up plenty of helpfull content / videos regarding base idle reset.

Assuming you have the typical 5.0 intake components, the throttle body will have a throttle stop screw, the purpose of this screw is to prevent the throttle plate from closing to far and getting jammed and technically is not intended to set idle speed.

The idle speed should be maintained by the IAC ( idle control valve ) to around 650 rpm with a stock EEC computer.

If the engine has been modified, ill tuned or has vacuum leaks etc.it may not stay idling at 650 rpm, the throttle stop screw can be used to cheat the idle to a higher speed, say 750-900 rpm this will allow the engine to stay running while you get the timing set etc.

Anytime the throttle stop screw has been adjusted a " base idle reset" should be performed, it requires disconnecting the battery for a while and checking the tps ( throttle position sensor) voltage output with a volt meter
 

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Could be on to something with the battery.
My buddy did an ls swap on his truck. Would get it to spin but not fire. Battery was dropping below 12 v.

Charged the battery and left the charger on it with nothing else changed.
Fired right up.
GC
 
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