'87 GTA turbo ignition wiring diagram

Hi Folks,

Just wondering if anyone has an ignition wiring diagram for an '87 GTA turbo. I have no spark at the coil. To narrow this down, I have replaced the crank angle sensor, I have checked the ignition relay, ecu has been checked and given a clean bill of health, earth checked for continuity from the coil to the top of the strut tower. I have 12 volts at the coil when the ignition switch is on but I only have .15-.18 volts at the 2 pin trigger on the coil, I read somewhere on the forums that this should be about 5 volts. I changed the ignition module/ coil and it started up albeit as rough as guts. It ran for about 4 mins then abruptly died, it has not started since. I have come the conclusion that my second module has blown in the same way as the original one, leading me to believe that there is a short somewhere. An ignition wiring diagram would make light work of the investigation process. Any help would be appreciated.

Thanks folks

Howard

Hi Howard. PM sent .

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Howard,

The test is pretty easy, the ecu driver to the coil is open collector i.e. it pulls the trigger input of the coil pack to 0V to trigger a spark event. So you can do this manually with just a wire and touch it down to ground (trigger pin on the coil pack, ecu trigger connector disconnected of course), with a sparkplug in the king lead you should see a spark each time you do that, ignition on... Done this loads of times, also found intermittent coil drivers this way.... If that works each time you ground the line, your problem is between the ecu and the coil pack. The nominal o/p is closer to 12V than 5V on all the ones I have checked.

Enjoy,
Martin

Check your messages Howard.

Thanks Guys,

Martin re the test, have done as you say and have no spark. As mentioned before, this was a brand new coil/module, it ran rather roughly for about 4 mins and then died. Now if I replace it with a third one I run the risk of it damaging it too, so I need to find the cause which I suspect is a crossed wire somewhere.

I will study the wiring diagram Lee forwarded and get back to you if I have any ideas.

Thanks again

Howard

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Hi Howard,

Send them to me and I'll test them on the bench. These are pretty robust units from my experience... are you sure you had 12V, and a true ground connection when you were testing? It is one of the worst 12V feed lines in the loom, as it loops both sides of the front cabin to the door pillars (immobiliser options), and goes through multiple connectors before it gets to the coil pack....

As I say happy to test however many you have on the bench & see if and how they have failed, may give you some clues, but very odd...

Regards,
Martin

Hi Martin,

Apologies for radio silence I have been preoccupied and not had time to investigate since last corro. I have 3 coils/ modules, all display the same voltage output at the 2 pin trigger connector on the coil (disconnected). The one closest to the centre of the coil reads 0.06v, the outer one reads 0.15v. I have a clean 12 volts at the 3 pin connector with the ignition on. I will attempt again tomorrow on the bench with direct 12 v battery connection and get back to you.

Cheers

Howard

I don't know if this pic below gives you any more info than you already have, but you can follow the wiring more easily via the colour coding.
Basically with everything connected you should have 12v across pins A & B on the 3 pin connector. ( do not rely on a chassis earth when checking this ....... it must be across the pins )
On the two pin connector, which only has one wire attached ( according to the cct diag, it should be an orange wire) if you have an analogue meter set at approx 10 volts, you should get the meter needle kicking when you crank the engine. The control voltage according to the manual is 5v but it is very unlikely the meter will show 5v as the duration of the pulse is unlikely to be long enough for the meter movement to fully get to 5v, but the needle should kick on each compression. You will not be able to do this pulse test with a DVM.
I hope this helps.

GTA Turbo Ign.jpg

Oh bigger, I just wrote a bloddy essay on my findings and when I went to submit it locked me out and I lost the lot!! Arghhh!!

Tomorrow now

Thanks John,

That diagram came in handy. OK so just to let all know that there has been some progress, car now starts and runs. For the benefit of other members and readers I will explain the process I went through.

John, regarding what you said, yes I have 12v across pins A&B on the 3 pin coil connector, so no problem there. Unfortunately I don't have an analogue voltmeter to check for trigger (good suggestion though so I have bought a basic one on ebay for $5 so in the post). The best I could do was to check continuity from the trigger pin no. 27 on the ecu to pin B on the 2 pin trigger connector at the coil, all good there. I then checked the main earth between the gearbox and the body underneath the car, cleaned it up and checked continuity, no problems. I also checked continuity of all earth straps that I could see, including O/S rocker cover to strut, again all OK. I then checked continuity of the crank position sensor (CPS), white wire on the harness to pin 11 on the ecu and the red wire to pin 28, both were reading 0.00 to 0.04 ohms or thereabouts, so all good there.

At this point still no starting so I decided to check the engine harness. I grabbed it from the front of the engine and gave it a little tug, cranked the ignition and it immediately started. Whist the engine was running I gave it another tug and the engine stopped. A third tug and the engine started. Thinking that there may be a frozen wire inside, I picked the harness apart so I could see each wire individually, they all looked clean and intact. Next was to wiggle each one separately with the engine running, I started with the prime suspect - CPS. Sure enough when moving this one the engine would cut out. I checked continuity of both red and white wires of the CPS to the engine side of the main harness plug (disconnected) at the rear o/s engine bay area, no problems. I then checked continuity on the ECU side with the harness plug connected, again no problem, but when I wiggled it the engine still cut out?? I pulled the main harness plug apart, cleaned the terminals with some emery, compressed air and lots of co contact cleaner. Still had the same problem. In the end I bridged both the white and the red CPS wires to their respective from the engine side of the plug to the ecu side of the plug, thereby bypassing the plug altogether. It was the red wire causing the problem, no amount of scratching or cleaning of the plug terminals worked, it had to be bypassed. Car now starts every time.

This brings me to the second part of the problem. So car now starts every time and idles smoothly but once warmed up it runs rough and stalls on light acceleration and blows black smoke. Either way there is very low power when driving and if I stop it after about 20/30 mins of driving it needs to cool down before it will start again. Despite recently changing it, I started with the Coolant Temp Sensor (CTS). checked for voltage at the connector, I have between 4.95 to 5.05 volts, so all good there. Resistance when cool is around 29 ohms and about 300 ohms when warm, I'm thinking that is probably within the right parameters. The next thing was the Manifold Absolute Pressure (MAP) sensor, this is located just behind the coil on the o/s rear engine bay. Vacuum is sufficient at the intake manifold when running, no carbon blockage. I then replaced the vacuum hose from the MAP sensor restrictor to the intake manifold. It seemed a little old and I thought it may be collapsing under vacuum thus giving a false vac signal to the sensor, unfortunately no result here. Next was to check voltages by back probing at the 3 pin MAP sensor connector whilst connected. I have 5V at pin 1, 2.31v at pin 2 and obviously no problems with earthing at pin 3. The 2.31v at pin 2 is at 0hg of vac (nil vacuum). Unfortunately I do not have a vacuum gage so the good ol' suck the hose had to do. Under 'mouth' vacuum, I managed to bring the voltage down to 1v so this would have to suggest that the map sensor is working somewhat.

Now from my understanding, at 0hg most other cars have a voltage reading at pin 2 not too dissimilar to that of pin 1, so around 5v. Might anyone know what the specifications should be for the GTA MAP sensor?

I have also cleaned out the idle speed control valve with throttle body cleaner.

Still have poor hot running so any other advice would greatly be appreciated.

Thanks again to all those who have responded your world of knowledge is greatly appreciated.

Cheers

Howard

Good progress..I sympathize..

I had a CPS sensor connector issue..took me ages to sort out....replacing connectors pins and the sensor. Needed a wiggle to start.

There was also a concurrent issue with intermittent connectivity within larger white plug to the ignition module.

Occasionally it would die and after cooling would start again. It happened a couple of times on major motorways...pretty scary.

The heat must have been a factor.. guessing thermal expansion somewhere was just enough to break contact.
(In fairness the plug housing clip was a bit dodgy..so probably did not help...so replacing that and cleaning barbs/pins resolved)

Evidently a GTA is blessed with many wonderful failure modes
....but thought I'd share one of my personal favourites as you mentioned ignition modules earlier + hot stalling.

Your symptoms sound a little different...but some similarities to warrant a mention.

Thanks John,

Coolant Temp Sensor (CTS). checked for voltage at the connector, I have between 4.95 to 5.05 volts, so all good there. Resistance when cool is around 29 ohms and about 300 ohms when warm

Howard

Howard, that's out of spec if it really is 29 ohms... that will definitely make it run rich.... Spec is 280 cold to 420 ohm hot, just wire in a 390 ohm fixed resistor temporarily on some leads instead of the sensor, to test prove, and see what you get..

Puncture / perished old fuel pressure regulator diaphragm is another culprit..

Regards,
Matin

Martin,

Thanks again and please forgive me for the confusion. Sorry my CTS specs were in fact 294-305 ohms when cold and 340 ohms warming, to 374 ohms when fully warm (must have been the vane rouge I was slurping on during the last post). Re the pressure regulator, yes I actually changed this as it started to fail a while ago. I plumbed in an after market adjustable unit which I have operating between 2.8-3.0 bar on the fuel pressure gauge.

I checked the manifold absolute temp sensor (MAT) at 0 deg, it had around 258 ohms. When the engine was warming is it was about 330 ohms, I didn't check at full operating temp.

I then back probed the throttle position sensor (TPS) connector. Disconnected I had 5v at pin A, 0.02v at pin B - the earth, and 5v at pin C. I checked the earth to battery voltage and all OK there. Now with the TPS connected I back probed pin A with the meter. With closed throttle I had 0v. Now as I started to open the throttle I heard the micro switch inside the TPS click. The voltage immediately jumped to 4.97v. with nothing in between. I tried this several times all with the same result.

From my understanding TPS sensors are in effect potentiometers, wouldn't we see a gradual increase in voltage as the throttle moves its way way to wide open throttle, or is this just normal for GTA's?

Thoughts?

Howard

Hi Howard.

No the TPS is just a set of two microswitches. So it only knows three positions - idle and WOT or anything between the two. (So effectively 3 voltage options via the two wires that feed back to the ECU)

It's not a potentiometer so the voltage isn't linear. It's just one of the three positions with any throttle opening at all (other than WOT) being a single value that the ECU interprets. (Later Renaults used a more sophisticated set-up)

All the actual load input is just derived from the MAP sensor so the TPS isn't used much at all.

Only 3 positions see.