7mgte intermittantly not getting spark

**ra65** · 03-10-2007, 02:35 AM

About a week ago my soarer failed to start. Was not getting any spark. This was right after getting a degrease done so after checking that there was no water in any of the plugs got racq out. Getting a trigger to the actual coil but none of them were sparking.

Racq guy was pretty good and ended up getting car started. Did something by grounding one of the wires and decharging the coil...?

Now all well and good but over the past week the car will randomly choose not to start. Can every now and then hear a very weak kick like it starts to spark and then just cranks until engine gets flooded.

If car is left for a while (overnight) has been starting. After leaving it for a full 24hrs since it last happened will not start.

I will check the tolerances out tomorrow with a multimeter as per workshop manual. Just wondering if anyone has heard of something similar and any pointers to look at. Being over a week since it has been degreased I would expect that any water that may have found its way somewhere to have evaporated.

**doobs** · 03-10-2007, 07:15 AM

Have you checked to see if there are any error codes stored in the ecu? Might help isolate the problem.

**ra65** · 03-10-2007, 12:51 PM

Yeah doesn't seem to be any codes. Tested the coilpack today. Getting 0.9ohms when it should be 0.3-0.5. Voltage is getting to the plugs going into coilpack, did not test while cranking though as only me home.

Does this seem good grounds to replace them. The thing is they are all on 0.9. As in all of them are dead. Is this normal? Shouldn't one or two die...not all three?

**doobs** · 04-10-2007, 09:52 AM

I don't think the coils would be a problem if they all measure .9ohm, I know mine were all about that, maybe have a look at the cam position sensor, just take the back off it and check to see if its clean and in spec, but I can't think of much more at the moment.

Are you sure its not sparking, or is it just not starting?

**ra65** · 05-10-2007, 11:53 PM

Below is an extract from http://forums.mk3supra.co.nz/viewtop...e7c377cef1c41b

Sounds to be what is happening with me and perhaps negative boost in his thread - http://www.toymods.net/forums/showthread.php?t=28599

I am going to ground the igniter, replace coil packs that I got today (0.8ohm across terminals) dunno whether the coils are bad or the manual is wrong. Seems to be dead on the money with the same issue, but as to getting it fixed...

Originally Posted by blackmk3

Hey guys im having a very intermittent issue with my supras ignition..

The car is a 1988 facelift Auto 7MGTE, and is totally and utterly bone stock, ive just done a head gasket job and a trasmission swap and now im having some issues with the starting

The car starts fine and runs fine all six cylinders Etc for a week or so and then it will (this happens when the engine is hot or cold) when you turn the key it will crank the engine coughs and then will continue to crank until the battery goes flat with no attempt to start, the spark is being disabled
if i stop cranking and crank again it will do the same thing again "crank cough crank with no start"
resetting the ECU does not change things it just continues to do this issue,

The car has no alarm system..

But if i pull out the spark plug lead on cyl 1 and short it to the engine, the car will crank for about a second then all of a sudden start throwing a spark the engine will start running on 5cyl and number one is shorting strong to the engine. If i then turn it off and plug number one back into its spark plug the engine cranks and starts immediatly with no problems...its only a intermittent fault and only does this every week or so

I have no CEL comming up and i have checked the codes with nothing stored

After a bit of a search around i found a thread on the ignition system of the 7mgte http://www.supramania.com/forums/showthread.php?t=39298

Reading through i found this line "The coil packs are all powered from one 12 volt wire through the ignition switch while the igniter supplies a ground through the big transistors"

I am thinking maybe i have faulty igniter thats not providing a ground when this starting issue happens?

Or this line "One last detail: Wire # 4. The fourth wire between the igniter and ECU is called IGf (IGnition fail). Unlike the other signals, which are sent from the ECU to the igniter, IGf is sent from the igniter back to the ECU. When a coil pack is fired the igniter senses the firing and generates an IGf. It's a confirmation spark occurred. The ECU needs to know a coil pack fired when it was told to because it if didn't bad things could happen. No spark means unburned fuel would be sent to the catalytic converter for example. So the ECU expects to see an IGf for every IGt it sends. If IGt and IGf don't "add up" for more than a few seconds fuel injection is halted and code 14 is stored in diagnostic memory. You read that right...the engine will stop"

Could there in some way be a dodgy connector or faulty igniter that is not sending this IGf signal back to the ECU? therefore halting the spark?
Expept im just not getting the code 14

Maybe when im shorting the number 1 plug lead to the engine the igniter is waking up and starts sending a IGf signal back to the ECU?

Has this happened to anyone else out there?
Sorry for the really long post

What do you guys think that this problem could be caused by?

Thanks heaps
Nick

**ra65** · 06-10-2007, 09:20 AM

Got a reply via PM if anyones interested.

I took the cps out of the head and totally rewired the wires in it, there is a couple of weird angles inside the cps and over time with vibraition and heat in had broken one of these wires

So i mearly cut all the old wiring out and replaced it with new stuff right into the heart of the cps

Fixed the problem instantly and has never had the same problem again

Also check where the wiring runs over the top of the engine, ive seen wires break in that area also, just give them a gentle pull and feel if you can feel the wire seprate

Check you codes to, even if you dont have a code light on the dash check them, the ecu will tell you whats up

Let us know hoe you go Cool

7Ms can be frustrating!

Cheers
Nick

**Blackmk3** · 06-10-2007, 11:10 AM

so how did you go with it? i wrote that info

**ra65** · 06-10-2007, 06:30 PM

Yeah been working so haven't had time to do it yet. Thanks heaps for the reply. Will let you know when I get it going.

**ra65** · 28-10-2007, 10:29 AM

Well after a week it hasn't happened again. So fingers crossed the problem is fixed. I grounded the igniter and put in new coil packs and plugs to coil packs. Car seems to fire much easier than before. Might be the ground, might be the coils. I expect mine were on the way out and getting sprayed with water didn't do them much good. I traced all the wires that were significant to ignition and none seemed to be cracked.