Coil on plug firing when ignition turned on?

[Nathanj1142]

Hello guys,

having a nightmare with the na-t build. i got the car close to starting, but had to stop as there is an issue that could cause some serious damage, fingers crossed it hasn't yet. Non-vvti GE with gte crank pos sensor and 7m-gte cps. Link G4x ecu. Whifbitz r35 cop.

If i've been cranking the car over to try get it started (timing is out hence why it wont start), then go to put the ignition on to try again, all the spark plugs will fire. This is before the car is cranking so purely ignition on. This results in a huge backfire, which comes out the intake and obviously will be happening in the cylinders which are on their compression, exhaust and firing stroke, hence why I am concerned.

The link forums reckon it's an earthing issue, and the earth variances between the ecu and the coil's earth is causing the coils to discharge without a signal. Apparently some of the first Link G4X ECUs had this issue but is now rectified with a hardware update (which mine apparently has).

I have checked the resistance on the coils, the resistance on the ecu earths, and they are all very low.

I also measured the voltage on the signal wire of coil number one. there is like 8-12v of power going to it as the ignition is turned on, I'm assuming this is to charge the coils? Could this delay in voltage be causing the coils to fire as I have the live for the coils wired to the orange/blue wire that runs to the noise filter and ignitor (b+ i think) which is a 12v switch live.

Edited April 30, 2021 by Nathanj1142 (see edit history)

[Mike2JZ]

I get this every now and again with the new G4X whilst doing first start ups. If you aren't sucessfully able to start car then cylinder is probably full of fuel, making this ignition release problem worse. Get the car started and you probably won't notice it again.

[Nathanj1142]

Oh that’s weird! That’s surely a problem that needs to be rectified by link? I’ll try get my timing dialled in tonight but yeah you’re correct it’s unburnt fuel. Could it cause damage?

[Mike2JZ]

It shouldn't cause any damage, never had any issues becaues of it. 

Once you have the engine running like it should you probably won't have any issues with it again, so I wouldnt worry too much about it, just focus on getting the engine running and not flooding itself.

 

[Nathanj1142]

Cheers Mike,

been trying to get it started today. Noticed my fuel pressure was dropping when cranking so wired 12v constant to the fuel pump to see if I can get it running. Almost got it there, so left it for 30 mins to let the fuel evaporate and went to turn the key and had a huge bang.

I’m really not confident at the minute, I’d rather sort this issue so I’m not worrying about it every time. Just to highlight how big the bang is, I’m in a large unit and it made everyone jump, sounded like a 2 step bang.

if I contact link regarding this issue are you happy for me to screenshot this thread and show its still an issue as I ideally want this rectified before I continue as this is my first build?
 

cheers

[Mike2JZ]

I saw your thread on the link forum and the video of the car trying to start.

Sounds to me like your wiring for cam signal is wrong, even though ECU is syncing sounds like its trying to fire 180 out and you are getting excess fuel from inproper combustion.  There are two cam signals G1 & G2 on distributor setup, try wiring the other signal in and see what difference that makes. 

If you are flooding your engine everytime you are trying to start it, then I'd advise you to switch Crank Enrich map to 3D and set Y axis to TPS. Set 100% tps to 0 crank enrich, that way you have a flood clear. So you can floor it whilst cranking and the ECU wont inject fuel and can clear out what is in cylinder. 

[Nathanj1142]

1 minute ago, Mike2JZ said:

I saw your thread on the link forum and the video of the car trying to start.

Sounds to me like your wiring for cam signal is wrong, even though ECU is syncing sounds like its trying to fire 180 out and you are getting excess fuel from inproper combustion.  There are two cam signals G1 & G2 on distributor setup, try wiring the other signal in and see what difference that makes. 

If you are flooding your engine everytime you are trying to start it, then I'd advise you to switch Crank Enrich map to 3D and set Y axis to TPS. Set 100% tps to 0 crank enrich, that way you have a flood clear. So you can floor it whilst cranking and the ECU wont inject fuel and can clear out what is in cylinder. 

I have both g1 and g2 wired in. Is it possible these are the wrong way round? Should I only have the g1 pos sensor in?

if I’m looking at the cam sensor installed, g1 is the top one correct?

[Mike2JZ]

The link only requires the use of one cam input, so won't make a difference if you have both wires in, but it is possible you have them round the wrong way. 

Are you using a plug and play unit or a wire in?

Assuming you are using SupraLink P&P then make sure your wiring matches the above assignments. If in doubt about cam signal, try one and a time in B25. 

[Nathanj1142]

35 minutes ago, Mike2JZ said:

The link only requires the use of one cam input, so won't make a difference if you have both wires in, but it is possible you have them round the wrong way. 

Are you using a plug and play unit or a wire in?

Assuming you are using SupraLink P&P then make sure your wiring matches the above assignments. If in doubt about cam signal, try one and a time in B25. 

Will give it a go mate. Appreciate it. It is a p and p ecu

Edited May 1, 2021 by Nathanj1142 (see edit history)

[Nathanj1142]

May have found why it won’t start. I did a log when I tried to start and noticed it tries to go then the rpm meter drops to 0 and goes back up then drops. 
 

i checked the trigger scope and the crank signal is around 0.15v. I have the trigger voltage set to .2 for 500rpm.

the battery I have is quite weak, so I’m assuming that it’s not quite outputting the required voltage/amperage. Going to get another battery and try again tomoz.

Does this sound about right? I have the timing dialled in with a light and checked the cam signal and it’s correct

 

[Mike2JZ]

Send me a copy of your log, map and trigger scope. something dosent sound right still

[Nathanj1142]

TriggerScopeLog.llgxsupra log test.llgxHi mike, really appreciate you taking the time.

i'm not sure that trigger scope is the right one as i dont want to turn the ecu back on and cause another bang lol. 

supra map use.pclx

[Mike2JZ]

Ok you have a few weird things going on:

a)

You aren't creating enough voltage on the trigger scope to get a really clean signal due to only being able to crank engine. That said, your CAM signal looks reversed compared to what is should be like:

Notice how your cam signal drops down before rising back through the 0v line. 

The cam trigger on 7MGTE CPS should look like:

Notice how the signal goes up before falling through the 0v line. 

This is normally due to incorrect wiring, need to swap trigger 2 signal and signal ground, in order to reverse the polarity on this signal. 

If you aren't sure what to do, please write with as much info as you can how you have wired your 7MGTE CPS, what pins on the CPS to what pins on the ECU. And what pins you wired your crank sensor to. I'll see if I can guide you from there. 

Once you have swapped polarity you will need to redo your trigger offset settings, although the Link base map settings should be close if all is in order. 

Your trigger arming voltages look fine. Maybe change 1000rpm cell to 0.5v if you have a bad battery, but typically not needed. 

b)

Towards the end of your log, the MAP sensor shoots to 2 bar and triggers the ECU to hit a map limit and cut all fuel. I don't have an reasonable explanation for this, unless you have some weird wiring for your MAP sensor. 

According to your ECU statistics, you have hit the map limit 150 times. Which is odd considering the engines never started haha. So maybe need to look into what could be causing map sensor to glitch out. 

 

Otherwise things on the map look about right to get a 2J started, normally they start even with awful non optimized settings in it. Troubles with starting are 9/10 a trigger issue. 

I don't know what injectors you are running, but if they are big then maybe consider pulling out 20-40% fuel out of crank enrichment and warm up enrichment. If they are smaller than 700cc then you can leave current settings. Also reduce your startup offset table to something more sensible like 20. If the engine fires with 100 offset, then it will rev its tits off. 

 

[Nathanj1142]

Nice mate thanks for clarifying. I think I know why the signal was backwards as the yellow wire in the cps has aged to look white so I may have got them mixed up, switched them around.

I just repinned the GE map sensor to the link 3 bar map sensor. Is it possible it’s not a 5v supply for the stock ge sensor? I’m going to check the ground now and signal to make sure In right place.

 

cheers

[Nathanj1142]

Nice mate thanks for clarifying. I think I know why the signal was backwards as the yellow wire in the cps has aged to look white so I may have got them mixed up, switched them around.

I just repinned the GE map sensor to the link 3 bar map sensor. Is it possible it’s not a 5v supply for the stock ge sensor? I’m going to check the ground now and signal to make sure In right place.

Update:

checked the resistance to each pin and found the 5v had quite a high resistance. Will be checking the connection is ok at each side and if not will run a new wire rather than tracing to issue. Does this sound like it could be my issue

cheers

[Mike2JZ]

3 minutes ago, Nathanj1142 said:

Nice mate thanks for clarifying. I think I know why the signal was backwards as the yellow wire in the cps has aged to look white so I may have got them mixed up, switched them around.

I just repinned the GE map sensor to the link 3 bar map sensor. Is it possible it’s not a 5v supply for the stock ge sensor? I’m going to check the ground now and signal to make sure In right place.

Update:

checked the resistance to each pin and found the 5v had quite a high resistance. Will be checking the connection is ok at each side and if not will run a new wire rather than tracing to issue. Does this sound like it could be my issue

cheers

I normally do the same and repin the factory map sensor to a Link one, never had an issue. Even from factory it uses 5v supply. 

I'm not sure to be honest, not sure I've had to check resistance on map sensor circuit before. 

[Nathanj1142]

2 minutes ago, Mike2JZ said:

I normally do the same and repin the factory map sensor to a Link one, never had an issue. Even from factory it uses 5v supply. 

I'm not sure to be honest, not sure I've had to check resistance on map sensor circuit before. 

Huh, strange. Glad to know I’m on the right lines, I’m guessing any interference across the 5v could cause it to freak out I’m not sure? I’ll see if it solves the issue thanks again