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87 Chevy Sprint Turbo; what a blast
Topic Started: Aug 31 2011, 09:22 PM (20,438 Views)
Memphis metro


Keep your eyes open for a resistor on the positive side. Probe both sides of it and check for voltage. Mwebb might think resistance is futile but the people who make repair manuals and testing instructions as well as electricians must believe in it. ;)
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t3ragtop
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Turbo3 and Twincam Tweaker

i don't believe that the coil uses a ballast resistor. the coil is powered from the key switch in the run position. the coil's negative post is switched by the ignitor module to ground. the ignitor module is triggered by the ecu and returns a "proof" signal back to the ecu to show that the igntion event was triggered.

if the ecu doesn't see the ignition proof signal, it shuts down the fuel pump and injector operation.

it's very common for the ignitor module on the mk1 to go belly up and cause the no start/ no run condition. the module also shares and controls the anti-knock function.

the mk2 system integrated the anti-knock and ignitor drive circuits into the ecu but still uses an outboard ignitor (large current transistor that pulls the coil's primary to ground allowing it to fire the secondary of the coil.)

as usual for these old cars, the ignitor module is no longer available as a replacement part. you'll have to find a used part. happy hunting.
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Memphis metro


87 was among a couple of years of change there when it come to ecm controlled engines, they were just getting started ^o) . It might have a resistor or it may not.
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Jittney
Anchorage 92 XFi

Hans is taking his turn outside.
With key off, voltage reading on the ignition coil is 0
With key on, voltage reading is 11.7
I had him try to start it, so I could read the voltage during starting...and it was down in the single digits.
However, I saw sparks coming out of the top...where the distributor wire goes.
Plugged it in, and it almost fired up....heard it spark once or twice.
Unplugged it again, to check spark, and noticed that this time it only sparked once....when he was 'giving up' trying.
Plugged it back in and nothing.

Diagram from Turbo Supplement shows ignition has to be closed for juice to go to ignition coil
At least that's what I'm reading of the circuit. (see Page 19 of t3ragtop's link in post #30)
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Memphis metro


Check air gap between pickup coil and reluctor using feeler guage. Should be between .008-.016"
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Jittney
Anchorage 92 XFi

blue rhino
Jan 22 2012, 05:31 PM
Check air gap between pickup coil and reluctor using feeler guage. Should be between .008-.016"
I don't understand
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Memphis metro


Can you get a picture of your distributor with the cap removed?

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idmetro
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Very much like setting ignition points (if you've had that experience) also much easier to do with non-magnetic feeler gauges (they make brass ones for this purpose) but regular ones can do the job.
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Jittney
Anchorage 92 XFi

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Bottom view of the key cylinder.
The 'inside' part of the gray cylinder, which the key goes into, is a bit loose.
Bear in mind, the key no longer just goes in (yellow arrow) and one can turn it.
Rather, we have to pull the key out an eighth of and inch and press it towards the driver.
Then it can turn away...to the ON position and ultimately to START.
The 'door open' buzzer was intermittent and the key didn't turn, which I thought was significant.
When I would wiggle the blue and brown wire sets, the 'door open' buzzer would stay on.
But, it didn't make any difference to get the coil to spark.
However wiggling the wires on the back side (red arrow) did make some difference in getting it to spark more.
Still, not enough to be consistent...so as to start.
Here is the backside view.
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Jittney
Anchorage 92 XFi

blue rhino
Jan 22 2012, 05:42 PM
Can you get a picture of your distributor with the cap removed?
Have to take the intercooler off....it's right in the way.
I can barely squeeze my hand under it to reach the distributor.

Edit: Hans is working on removing the cooler, while I try to grab some lunch :)
Edited by Jittney, Jan 22 2012, 06:00 PM.
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Memphis metro


;)
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Jittney
Anchorage 92 XFi

Distributor cap off
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Next layer off
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idmetro
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If you can't reasonably get to the distributor you could at least use a mirror to look in there and verify no major damage has occured or that the gap is grotesquely large/small. Next step I would say would be to go the the connector coming from the distributor and measure the resistance across the two wires. FSM for my 92 vert gives a value of 140-180 ohms. Last resort might be to mark the location of the distributor, then remove it from the car, check the gap, adjust if needed then reinstall. Not the most pleasant job when it's cold (let hope it doesn't come to that). I am far more suspicious of the ignition/key switch issues you describe. Good Luck!
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Memphis metro


From the looks of that rotor, you might just start with replacing that! Put a new distributor cap and rotor on and it will probably run.

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clarkdw


The fact that wiggling the wires affects the outcome of checks is a pretty good indicator of something amiss in the switch. If it was me, I would run a fused jumper from battery + to the positive of the ign coil and try to start it. If you don't have a fused jumper then run an unfused wire to the B/W wire on the back of the switch. Assuming your schematic from post 38 is correct you will now have everything powered up. If it is a switch problem you have now bypassed it and it should start.

I used to live in northern Alberta and the North West Territories and I know that when it is very cold the fastest diagnoses is the best.


EDIT: your distributor pic just appeared. Replace the cap and rotor first.
Edited by clarkdw, Jan 22 2012, 06:22 PM.
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