Leeroy_25

So I have been having some timing issues with my 20B as most of you will know. Today when I gave it a quick run up I thought I would check and see what the Trailing side showed for timing to see if it was Consistent with the error on the leading side. I found the T1 had no signal when I connected the lead from the timing light. I tried both ends of the lead and turned the sensor clip bit from the light over too. Still no light. Thought I best try T2 and 3 too. Nothing on 3 but 2 fired the light fine. Is this common to not get a light firing on some leads or does it mean I could have no spark on two of the trailing plugs? I cannot imagine it would run very Well if that was the case?! Thoughts please, and what is the best way to check for a spark and where the error is. I guess pull a lead and crank it with a spare plug in there and the pump disconnected. I am running standard 20b coils by the way and ltx-12 ecu.

Thanks
Lee

hsmidy

Engine will still run without trailing's firing. as long as you are providing an earth for the HV you will be fine, a dummy plug for even a screw driver close to the block will do. check spark on the suspect leads.

Leeroy_25

This last little bit is getting a bit frustrating. Seems like one step forward, two steps back at the moment! So if it proves to be no spark on a couple of plugs. Would that be a lead failure or can individual cells of the stock 20b coils go dead?

Thanks
Lee

hsmidy

individual coils can fail, also worth confirming that the earth side of the primary windings is switching correctly etc.

Leeroy_25

Thanks for the reply. Just to clarify, I have the standard 20B coils.. so 1 large coil with 3 plugs for Leading and the same for trailing. Are you saying individual sections of these can fail?
Can you also explain in more detail about checking the switching of the earth on the primary windings? I am pretty much completely lost on what you are referring to there!

Thanks
Lee

Leeroy_25

Should you be able to test continuity on an HT lead with a multimeter or 12v battery and a light? I cannot get a signal across any of the leads I pulled off and one was a lead I know has a spark!?

hsmidy

Yes as they will house 3 individual coils in the one unit, you will have 3 HT outputs from the secondary windings and most likely 1 common (parallel) power feed, with 3 individual earth pins for the primary windings.

You need to be checking the resistance values of your HT leads with them completely disconnected, make sure you wiggle them while testing. The value that you will be looking for will depend on the length of the lead.

You can check that the ecu is switching the earth of the primary with a scope or even an LED test light.

Leeroy_25

Thanks for the reply and confirming about the what leads. Any idea what rough value I am looking for please? Why the wiggling out of interest?
The rest I am lost on how to do.. Checking the switching of the earth? Are you talking inside the coil? It is a sealed unit as far as I can tell. You say test with an LED test light too. Will a normal 12v light be no good? If you mean just checking for a completed signal from the ecu on each of the ecu outputs I think I see what you mean. As di recall looking at the wiring last night when I checked continuity from the ecu to coil plug which was okay. There is a common switched live going into one side of the coils. Then the negative side goes to the ecu and then an earth comes out of the ECU for each coil to ground. So I assume the ECU completes each earth to fire the coil? So to test that do I just need to pull the plug off the coil and put a loop of wire with a bulb between the live and each earth in turn while cranking the engine and watch for the bulb to light? I guess a regular bulb might not react quick enough?
Please explain if there is anything I can or should test directly on the coils. I guess if all my leading ones are firing which I need to check I could plug the trailing coil onto the leading circuit and test the coil that way? I hope it's not the ecu?! Got a bad feeling.

Thank you
Lee

hsmidy

Do not use a normal 12v volt bulb, the current draw on one can be too high and you may destroy some of your electronics...hence use an LED test light if you must. a scope would be best.
It will be dependant on the type of HT leads your running and their length but 11Kohms for 300mm as a guide without knowing more.
The wiggle is to check that there isn't a break in the conductor part way through the lead.
Correct the ECU will be used to open and close the primary side of the coils.

Leeroy_25

Thanks again.. I am getting it now.. Okay.. I will check if my tester is an LED one or not. I am not 100% and hence a bit reluctant to use it either way if you say there is a risk of damaging the circuit. What kind of scope do I need. I presume it is something that will show a graph displaying the pulses of the closed circuit but don't know what this is called to see if I can borrow one or my multimeter has the function?
Maybe the safest bet is check the resistance of the leas. they are all around 300-500mm long from memory. If they check out then disconnect the HT leads off the coils and get a spare plug and one of the leads that i know is good and also any I think are suspect and crank the engine on L1 to check for spark. I can then check all the coils in turn with a good lead and see if they all produce a spark. if not I can swap the input plugs on the coils over which I think might reverse the order the coils work? T1 become L3. Maybe not. but anyway. i can see if the same coils still don't fire. If the non firing coils are the same then I have dud coil packs. If the order swaps then this must be an ECU switching issue which I assume means the ECU is screwed? I fear for the latter!
Does that sound sensible to you?

Thanks
Lee

FührerTüner

iTrader: (5)

Dont use a timing light to check for spark.

hsmidy

If you are checking spark while cranking just make sure the high voltage has some where to go...earth.
otherwise again you risk damaging ignitors etc.

Leeroy_25

Thanks again. I will have to give this a crack at the weekend now. That is a new one on me.. I thought if the plugs were not earthed you just didn't get a spark? Didn't realise that could damage anything. I was planning on clipping the plug in a jump lead and attaching that to the chassis somewhere for ground.

I was not using a timing light to check for spark. Just wasn't getting a signal off some leads and wondered why. So now I am checking for spark!

Leeroy_25

Also do you know if the order of the coils swaps if you plug the leading to the trailing input and visa versa?
Thanks Lee

Leeroy_25

Did some testing today and got to the bottom of this.. It turns out to be a couple of dead plugs? I have never come across this before. They look fine but they don't spark! Seeing as I have to replace them I am wondering what heat rating to run. It has 9 trailing and 7 leading at the moment.. Will run around 1 bar max boost. Any thoughts. I will do a search or post a new thread I think. I know there are a few other plug types you can run I have read before. But some people claim horror stories of plug tips falling off an destroying engines!?

Thanks for all the advice.

Lee