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S15 Link g4+ nil start


Thesmokeisout

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Gday team, I posted this up on one of the fb groups and was recommended that I post it on here.

I am trying to start my mates S15, she cranks but won’t fire. Doesn’t even cough or try to start.

- SR20DET
- Link g4+
- Taarks kit R35 coil packs, I have used the ignition test to make sure wiring is good, it sparks but to me the spark looks weak, I have adjust the dwell table to the PRP specs they provide. I am getting 11.55V at the power wire on the coils.
- Bosch 1650 injectors, I have used the injector test to make sure wiring is good, I have also pulled the plugs and they are wet with fuel, I have changed the deadtime table to match the specs for the injectors (as best I can)
- Taarks Trigger kit, I have set it all up according to their instructions and I am getting “YES” on both Trigger 1 and 2 in the Runtime page.

I have done a scope and came up with the pic attached. I’m not really sure what it should look like, but definitely seems off from other scopes I have seen? Is this just due to the nature of the Taarks kit?

Using a timing light; it seems to jump around quite a lot, seems to be most consistent to TDC @ -15 offset, but a few people have said it is more common to see -260 odd with these kits? I tried to flip it 360 but still didn’t want to fire (I only tried this for a few cranks tho).

Any hints from you legends would be much appreciated

0C908163-9D45-4DAC-B8F6-7DFAF314E5F5.jpeg

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I would have liked to see a log of it craking also but nothing looks too out of place in the tune or triggerscope.   You have fuel injection turned off but I assume this was just while checking timing?

Do you have realistic RPM showing in PC Link when cranking?  Say 150-250RPM.

 

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Sorry, I thought you meant trigger slope log when you asked for a log, I will see if I can get my mate to save a log of it and I will send that through.

yeh the injectors were just turned off as to not flood it, we have been turning hem back on to try and start.
 

The rpm is low, but it is reading around 160-170RPM.
 

This may be a dumb question; but how can we tell if the timing is 360 degrees out? I tried changing the timing but still nothing?

The only think I can think of is the Taarks coilpack kit doesn’t get the coil packs to sit the best and may be causing it to not sit on the plugs 100%.

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12 hours ago, Thesmokeisout said:

This may be a dumb question; but how can we tell if the timing is 360 degrees out? I tried changing the timing but still nothing?

You cant, you can only try it on both options.  With cars with visable cam pulleys you can paint a TDC mark on the cam sproket but that is not an easy option for a SR.

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Alright here comes a long winded tail of how we went backwards yesterday.

I went back to my mates to try grab a log for you as I talked him through saving the tune and getting a trigger scope over the phone but he couldn’t get a log to work……aaaand we now have more issues.

Plugged the laptop in and straight away we got a low voltage warning (reading 7.6V).

Tested the battery (it’s in the boot) and we had 12.6ish.

We tested the positive terminal in then engine bay and it read the same.

We tried cranking it anyway and the ECU would immediately drop out (assuming due to the low voltage?).

Then we noticed the fuel pump randomly priming.

My mate went to check the front positive terminal again and it was loose. He wiggled it and the starter motor wire arced out against the body (f**k).

Checked all the fuses and the IGN fuse was blown.

Now the fuel pumps won’t prime and ecu won’t connect.

The ECM relay is also buzzing rather then clicking now.

Swapped out the relay with the headlight one and it does the same.

Tested wiring either side of the excitation wires and had perfect continuity. But across the pins there is only 7V.

Tested on the battery side; it has 12.7, but there is 5V coming out of Pin 4 of the ECU, is the is normal?

I guess my question is now; did the short blow the ecu potentially or…..?

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Pin 4 should be near 0V when ign is on.  Pin 4 is controlled by pin 36.  So first check there is 12V on pin 36 with ign on, if not you need to trace where that has gone. 

If you have 12V on pin 36 but pin 4 is not at ground then that would suggest something maybe damaged.

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Thanks for the fast reply Adam, really appreciate you putting up with our muppetry!

I checked pin 36 and it has 12V.

We hung the factory ECU board and it switched the ECM relay on nicely (it only had 8v across the ECM relay pins tho which was interesting) but the output on pin 4 was not a solid 5V like the Link board was.

If I pull the Link out, would I be able to see if something is fried?

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From what I can see, there is no obvious damage to the track or the transistor. It looks like the lacquer has run a little in that area, but other then that, looks fine, but as you said, not the easiest to see.

could this also be why we had the “low” voltage reading on the link software?

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23 minutes ago, Thesmokeisout said:

could this also be why we had the “low” voltage reading on the link software?

No.  The FET circuit that controls the ECCS relay is completely independant of the ecu and only switches the relay on/off.

The Main ECU power comes in on either pin 38 or 47 - this is where the batt voltage reported in the software comes from.  

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