Explosion, now no start.

[cre]

No, you don't need to make any changes to the ignition system because you're running a colder or hotter plug. The thermal transfer characteristics of a plug have little effect on the spark. Why are you running a colder plug? Preignition problems, damaged spark plugs or high EGT?

[vikenabm]

Yeah, I thought about that after I posted: plug gap should be the overriding determinant of spark. I'm running colder based on various postings on plug choices. I haven't run the engine enough to know where my EGT's will be in various conditions, but that's an obvious and interesting way to select plugs. I'm surprised I haven't noticed that approach posted.

So it's down to the ignitor or coils. And ignitor makes more sense to me. Clearly my spark is inconsistent, and it sure seems like the ignitor fires inconsistently in the TSRM transistor test, no matter how carefully I clean the probe and terminals> I have a replacement from a running motor to test when the weather allows. Thanks.

[cre]

I don't see that you've mentioned running an extreme amount of boost. It doesn't matter much. It won't hurt anything, they'll just foul frequently if they're too cool.

There's a thread in the FAQ, I believe, about a known grounding problem with the igniters (it's an internal issue). See if you can find it and see if the fix listed works for you.

[vikenabm]

Originally Posted by cre

I don't see that you've mentioned running an extreme amount of boost. It doesn't matter much. It won't hurt anything, they'll just foul frequently if they're too cool.

There's a thread in the FAQ, I believe, about a known grounding problem with the igniters (it's an internal issue). See if you can find it and see if the fix listed works for you.

Thanks. I already had the ground mod in place. I replaced the ignitor and it is not much different. WIth all the injectors unplugged it behaves EXACTLY THE SAME as with them plugged in. I believe it is sputtering a bit and firing into the intake runner due to fuel from the cold start injector. It sputters a bit more consistently maybe with the new ignitor, but no real change. Also no different with plug to injector resistor connected or not.

So without the injectors making a difference, and good fuel pressure, is it fair to conclude that I'm down to injectors not opening as my problem? If so, i've already tested the injector resistor with an ohmmeter, simple device. So now am I to check wiring continuity to the ECU, repeat the voltmeter tests at the ECU from the TSRM, and then swap ecu if those check out normal?
I am out of other ideas at this point.

[cre]

Are the injector's grounded at the correct location and is the ground clean and sound?

I've had issues like this on a couple MKIIIs and it's always something different. Wiring harness, CPS drive gear installed 180? out after a rebuild or on a new (reman) unit, igniter and coil pack grounds were the issue in all of those cases.

You can measure the timing of the injectors against the crank pulley with a timing light. If you don't have an adjustable it's just a light show and you have to guess what the timing is but nonetheless if the injectors aren't getting power or don't have a good ground you shouldn't see anything. You just connect the pickup to the injector's wiring clip, shine the light on the markings on the balancer and while someone cranks you watch for a consistent pattern. I think you'll be looking around the 50? range but I'm not positive, I haven't done this on a 7M. The timing isn't important though, this SHOULD show if the injectors have a solid signal.

[vikenabm]

Originally Posted by cre

You can measure the timing of the injectors against the crank pulley with a timing light.

This is a great tip! Thanks, I will try it.

[cre]

Thanks for the generous donation! Made my day. I think some people think this is my site and the advertising dollars come to me... it's not and sadly, they don't. I'm just a volunteer. Thanks again.

One more thing you might want to check is that the ECU is getting a signal of >11v+ at the STA input when the starter is cranking.