Ford LRG 425 No Spark

[marcus thies]

I've got a Ford LRG 425 EFI with no spark. Power and ground to the epm no ground to the coil pack when cranking. Anyone have any ideas?

 

[Birken Vogt]

Does the coil pack have a red/green for power and a couple of yellow/? for timing?

If so, the yellows switch ground when cranking to make the spark. A test light on one of the yellows should flash off and on when cranking and be accompanied by spark. The red/green should have ignition +12v.

 

[marcus thies]

Yes that's what the problem is they aren't getting ground.

 

[Birken Vogt]

If you probe one of the yellows, if it is not grounded, you will see +12v on it, flowing in from the red, through the coil and out the yellow looking for a ground.

The controller provides that ground, so the yellow will be at 0v, and then when it wants the coil to fire, opens the circuit, which causes a spark and the yellow rises back to +12v for the dwell time, and then it grounds again.

So you are saying the yellow is staying at +12v even while cranking?

It could be a sensor problem, not seeing engine rotation, or it could be a controller just not doing its job.

 

[marcus thies]

Ok I get no voltage or ground at the yellow wires. Not trouble codes only 123

 

[Birken Vogt]

Does the red/green have +12v when cranking?

 

[marcus thies]

No

 

[Al E]

Did you get it figured out? I'm working on a JLG 600A lift with the same problem. I get a code also, similar to 123 like you're getting but the first short flash is not counted as a 1, it just means you are at the beginning of reading codes. The actual code is 23, "over maximum drive by wire" according to the Ford manual. I can only assume it's a TPS or governor problem but I'm not sure.

 

[Birken Vogt]

I believe "over maximum DBW" would equate to throttle position greater than 100%.

 

[Al E]

That's interesting, I assume the TPS operates using a 5v reference? Over maximum would suggest a voltage greater than 5V or whatever the base voltage is. Perhaps a wire rubbed through and is touching another wire? Or someone previously swapped a wire. I noticed my machine has a new cam sensor as well as a new crank sensor so they were troubleshooting it before I was lucky enough to acquire it.

 

[Al E]

Well, from what I've been reading in other LRG425 posts it would appear the 123 code is normal and does not indicate a problem.

 

[Birken Vogt]

I work on generators which run a fixed 1800 RPM and sometimes you will see throttle commanded to 102% so it may be normal in some cases. But I do not know about variable speed engines.