EFI Gurus.... got a good question for you........problem solved!

[JDJ]

My coil is not getting any power, BUT...... when I connect a computer scan tool, the coil gets power and the bronco will run. Disconnect the scan tool, no power to coil. Reconnect scan tool, power back to the coil.

Any body have any ideas? I also asked the same thing under my build thread.

Thanks for your time and help in advance.

JDJ

 

[Viperwolf1]

What harness and computer?

 

[Broncobowsher]

Above plus...
Does the EEC relay turn on?
Too many other things are typically tied into the ignition power as well, like injector power and IAC power. You should be able to get power to the coil even if you unplug the computer. I am really thinking harness issue.

 

[JDJ]

RJM wiring harness with an A9P computer

 

[JDJ]

I'm not sure if the EEC relay turns on or not. The RJM harness has 4 relays and 4 fuses that mount under the the hood. The installation instructions does not tell you what each relay/fuse is for. I did check the four fuses and they were good. When I pulled the bottom fuse (with battery hooked up and ignition switch in on position) the relay closest to the fuse block started making a humming type sound and had a slight vibration to it.

I will try to post a pic if the fuse block and bank of relays mounted.

 

[JDJ]

This is the first time that I have had the Bronco running since I started my rewire project and EFI conversion..... 2 years ago. I am using an E-Z wiring harness for the body harness.

 

[JDJ]

This is the short story version. Longer version is located in my build thread in Bronco chat forum.

 

[blazinchuck]

those 4 relays/fuses should be for fuel pump,02,ing,eec

http://oldfuelinjection.com/?p=6

 

[KyleQ]

Hmm, didn't have this probem on any of my 'hack' redneck 25+ year old harness installs...

Sounds like possibly a bad relay - give them direct 12v on the other side of the relay (bypass it) and see if it acts differently.

 

[jw0747]

good spare relay handy? pull each relay separately and replace with spare to see if any are bad.

 

[Viperwolf1]

I am really thinking harness issue.

I'm leaning toward a computer problem. I can't see how the lack of a code reader could prevent the ignition circuit from operating.

I would disconnect the computer then use a timing light to see if the ignition works without the reader.

 

[JDJ]

Viper, Using the timing light is one way I checked to see if I was getting any fire to the #1 plug. With the computer hooked up, NO SCAN tool attached, there was only .72V to the coil, resulting in a no spark condition and no flashing of the timing light.

With computer hooked up, scan tool hooked up, there is 12V to the coil and spark at the plug. With the tool hooked up, the engine runs like a top ... or seems to, and flashing of the timing light.

Another question, what starter solenoid is everybody using when convering to EFI? The reason I ask is I just replaced my solenoid with a stock bronco solenoid. There was a piece of paper in the box that had the following warning:

"Do not use this solenoid for vehicles fitted with an on-board computer. Use of this solenoid for such vehicles will result in permanent damage to the EEC processor. The damaged processor can cause a rough running engine or a no start condition. Vehicles with a computer require a solenoid with suppression diodes."

Have any of you noticed this (or similar) statement about the solenoid? Does it really matter? I don't remember seeing any warnings in any of the wiring installation instructions about changing the solenoid.

 

[JDJ]

Viper, I will try disconnecting the computer to see if the ignition works without the reader.

JW.....I might have a spare relay laying around. I will check that also.

Any more trouble shooting ideas or suggestions will be greatly appreciated. Is there a way to test a computer to see if it is bad or not?

 

[Broncobowsher]

Looking at the diagram the powering of the ignition is soley by a relay. the relay is powered by the ignition switch. There is no computer tie in. But there are a few tie ins for the EEC reader. I don't know all the pins in the diagnostic port, that isn't clearly listed. But it is concivable that the tester is the jumper needed to complete some circuit. The internal wiring of the tester is another unknown. But it all points to a relay/harness issue. Nothing with a computer has anything to do with the activation of the ignition circuit power.

 

[DirtDonk]

All of the ones I've worked on we replaced the stock starter relay with a later model one. Usually out of an early-nineties Mustang or late-nineties Explorer. I've got one from an Explorer.
I can't tell you what the issue would be if you used the old one, and I know lots of people get away with, at least temporarily, using their original starter relay, but I figure Ford did it for a reason, so why tempt fate? Right?

Paul

 

[JDJ]

That's true Paul. I will consider changing it.

Hopefully I can get out to the shop tonight and trouble shoot the no power condition at the coil.

 

[JDJ]

Ok, yesterday afternoon I get home and start working on the Bronco. I had talked with a friend of mine yesterday at lunch. We talked about my problem. He said it could be a ground. First thing I check was the ground that is on the last lower intake bolt on passenger side. I try to wiggle the wire, and it moved slightly. Grabbed a ratchet and a socket and tightened it.

With scan tool hooked up but not plugged into cigarette lighter, hit the key, engine fired up and run. I switched it off and then unplugged scan tool at test port (scan tool completely disconnected). Hit the key a second time. Engine fired up and ran like a top.

It is amazing how one loose bolt that is holding a ground can cause so many problems.

Thanks guys for helping me solve my problem/issue!