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Electronics, no start 86 spider

4785 Views 117 Replies 10 Participants Last post by  andylarry
Thank you to all of the members that have offered suggestions about how to get this car started..
Since this thread has been going on for the better part of a month it has gotten pretty confusing as to just what has been done and the result.I wanted to start with a fresh and follow up on the problem of no spark.

A recap

1986 spider quad, red.
Sitting in the garage for 18 yrs w/head off as a result of a blown head gasket. Recently removed and rebuilt engine. starter and alternator rebuilt, gas tank and all the fuel lines replaced. Fuel pumps both replaced. Engine installed, starter reconnected correctly, engine turned over , oil pressure up to over 50 lbs, did not start. Tested fuel rail flow good, tested cold start injector, good. Testing showed two bell housing sensors to be bad, replaced. Testing also showed the coil to be bad, replaced. Testing showed the CTS, and the TTS to be good. Grounds have been checked and rechecked and are clean
Now looking for a reason for no spark. Battery is brand new and shows voltage at 11.50 during cranking.
There is no voltage to speak of at coil during cranking

Looking over past posts about spark problems, 187949/#post-1069191, I followed a series of tests as follows;

When you turn the key on do you get 12 volts;

fused side of fuse 7 for voltage, yes
+ side of coil with body as ground, yes
fused side of fuse #8, yes
ignition ECU connector terminal 10 good, green black wire to from drive relay terminal 15 via connector G121, yes
ignition ECU connector terminal 4, violet wire from ignition switch terminal 50 via connector G121, no
Two black ground wires tested for continuity at ECU plug, terminal 1 showed 28 ohms resist, and terminal 19 showed .6 resistance. That is continuity but terminal 1 is high. Contacts at engine just above 4th injector have been cleaned several times, the connector has not been replaced.
When cranking the engine the positive post on coil shows .28 volts when cranking using the second post as circuit.

I have also tried jumping hot side of fuse 5 to hot side of fuse 6, cranked the engine, still no start.
Basic problem is no spark , the culprit being the ecu, the ignition switch, possible bad connection in the G121 connector,a mystery gremlin or as someone suggested missing Yugo powder.

The main ground connecting body to transmission is good and clean

Need help.

PS Thanks for the tutorial on glove box removal, I have remove it to get at the G121 connector if necessary for testing.
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Are you sure you got the coil connections correct?

Did you check the flywheel sensors? If faulty there will be no spark.

What is the voltage while cranking? Measure it at the battery or the +ve post in the engine bay.

I don't know if you're aware, but the ECU for ignition system is a seperate unit from the fuel ECU. It sits on under the side carpet/panel behind the passenger. It says "motronic" on it.
The fuel ECU uses the spark pulses to generate the injection pulses - so no spark, no fuel.

Coil connections are exactly as they were originally when the car ran. Both flywheel sensors are brand new and tested good. Voltage when cranking was 11.50. I’ve been testing the ignition ecu connector for continuity, and voltage. Can’t seem to get a spark.
you tested for spark at the plugs, correct?
what about at the coil? (idea being if you do have spark at coil, then the problem lies in the distributor, and you do not need to look further)

But let's presume you have no spark out of coil.
you have confirmed battery voltage at coil +ve.

Put a 12v test light (one of those cheapo tools that looks like a screwdriver with a lead/croc clip out one end) between coil (edit) - ve and ground. Now crank the starter......does test light flash?
No? then you have no pulse (no pulse, no spark)

  • coil wiring incorrect (but you say it is correct: so, the green/blacks are all on the positive side and all other wires are on the negative side, correct?)
  • sensors (I know you replaced them with new, but did you plug them back in to the correct connector plugs?...check again, don't assume, otherwise we will be running 'round in circles;))
And check those two connectors are good, that the pins are making contact between male and female ends, and not shoved back)
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- bad ecu (and this is the one thing you cannot test to be sent out, or swopped for a known good one to test...or yours put into a running spider to test that way)

one final thing to test that is not such a common fail point:
on the coil neg there are 2 whites and a white/black (likely also a yellow and a solid black)...remove the "thinner" of the whites, that is the tach signal try to start.
Any luck?
If it does now start, you have a short on this wire to tach.
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Thank you for the response, This is getting very confusing . Back to it on Thursday, will go thru your check list then. Just want to hear the new motor run.
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So I went thru all of the tests you recommended, no luck
Battery voltage 12.54 at coil +ve and grounded with key on
With key on and test lite connected to +ve coil and grounded , light on , no pulse during engine crank
Green black wires on +ve side of coil(2) and all other wires on -ve side.
Sensors are in correct position, and test at 954, and 964 resistance. Pins look good
Removed the small white wire from -ve side of coil, cranked, no start.

what now?

I am racking my brain over this, the car ran great before this, I have tested and replaced the coil and the two sensors that went bad just sitting, the car has never had rust or corrosion problems, I had one squirrel bite on a wire coming from the power junction terminal on the drivers side firewall but the culprit didn’t get into the wire, just the plastic. Taped and protected now. I did notice one mangled pin receptor on the ignition ecu plug , #8 which is a rpm transmitter. It looks like someone pushed a probe in too far. My first time looking at it so don’t know. If that is a problem can you access the contacts from behind? Just wondering

I did notice one mangled pin receptor on the ignition ecu plug , #8 which is a rpm transmitter. It looks like someone pushed a probe in too far. My first time looking at it so don’t know. If that is a problem can you access the contacts from behind?
Displaced contacts in the plastic connectors is not uncommon. There is a small tab that is supposed to keep the metal connector in place but they can easily get bent allowing the contacts to move out of position. See: Bosch (sensor) connector
if you think the #8 pin to ref transmitter is pushed in so far as to not be making contact with the ecu, then that certainly needs fixing.

you could try pull the pin back out again a bit more, perhaps using pointed tweezers (I doubt needle nose pliers will fit)
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Is there a safe way to test the continuity of the #8 pin connection when the plug is connected to the ignition ecu?
Is there a safe way to test the continuity of the #8 pin connection when the plug is connected to the ignition ecu?
I would not test continuity into the ECU. I have repinned those connectors before due to corroded pins. If it is pushed in to far, you might be able to take the connector apart and fix the pin so that it stays in place
Do not ever test anything into the ecu ever.
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Just now getting back to this project. When I last spoke I was looking at a mangled connection in the motronic plug. As it turns out disassembling the plug was simpler than I thought. I have included pics. RE-formed contact #8 in the head and reassembled the plug. Also replaced the ignition switch just in case, still nothing, no start. No pulse at the coil, there is power at coil with key on but no pulse. I realize the ecu takes over to create the pulse once the engine is rotating. Are there any other tests to try before I go in and recheck the flywheel position. Both the sensors are in correct position and are new. They test good as well. Would there be any other ways to test the tachymetric signal , if there is one etc?
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Another thought, testing the sensors from the motronic plug end , contac number 8&27 for the rpm and 25 & 27 for the ref.
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the best way to test the sensors is test for a signal.

set your meter to Volts AC and clip it to the same 2 pins you used for the ohms test (connectors in engine bay near water bottle)
now have someone crank the should see a few volts AC (4 perhaps) from one of the sensors (the one that reads the nubbins) and perhaps a very low reading from the other sensor, because that reads off the flywheel teeth and there is no "gap" to make a signal.
Normally this test would be done with an oscilliscope, but volts AC test gives an indication.
the nubbins here:
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a final thought.
You say "Sitting in the garage for 18 yrs w/head off as a result of a blown head gasket. Recently removed and rebuilt engine" and "before I go in and recheck the flywheel position."

does that mean you removed the flywheel? are aware the S3 flywheel needs to be timed.
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Good evening,
The test , looking for voltage from the flywheel sensors showed 1.4 with the meter at 200 volts ac and the other sensor showed .1 volt at a regular interval with the meter at 200 volts ac. Is this voltage too low?

the answer to your other question, yes I removed the flywheel and reinstalled. Honestly I can’t remember what I did. My machinist made marks on the flywheel to help with the installation but after that I don’t know . I do know that I was so concerned about the tdc and rotor position on the distributor to avoid valve damage that that took precedent. Is there a way to check the flywheel position without removing the transmission?
1.4 V AC is likely OK....some people got 4 some got 2 but you never know the accuracy of their meters (it is not written in a manual what the voltage should be, because as I said this test would normally be done with an oscilliscope and you are looking for a square wave of some sort)
So....I think as long as there is a reading, then it is sending a signal (My S4 crank sensor, ok not a flywheel sensor, is also about 1,4V AC)

there is, I believe, a way on checking flywheel timing w/o removing the whole shabang.
looking at the flywheel from one of the threads below, the nubbins seems to be about 2 o clock, when the flywheel mark is at 12 o clock
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Knowing that, with the engine correctly at TDC #1 on compression (front cam lobes facing out, pulley on mark etc) and the flywheel correctly assembled, then the little 'nubbins' one would guess must be close to where the sensor if you remove the sensor and look through the small hole in the bellhousing the nubbins should be close, if not exactly right at the
Maybe there is another way, I am just thinking out aloud:)

see here:
flywheel sensor pin position relative to sensor on...
and here
Flywheel positioning

if flywheel was assembled correct, and with the 2 new sensors (AND these plugged into the correct plugs), and voltage at coil....yet still no is sounding like the ignition ecu.
Can you borrow one to check?
Maybe say where you are, an alfisti might be in your area who can test your ecu in his car.
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What a brain tease. To confirm, yes on the two new sensors plugged into the correct locations, I thought about switching them just to check on a dislexia option??? And yes there is current to coil with key on but no pulse out as tested with a noid lite. Both relays under bench near ecu’s click with ignition switch activation. New ignition switch “jumped “ showed no change. I will climb under neath and take a look at the nob, I had taken off the stamped metal cover already but you can’t see a thing. Also I called centerline the other day about testing ecu’s, they referred me to an outfit in Florida that tests and possibly repairs ecu’s , the name is Programma. Anybody heard or used this company? The motronic part number I gave them crossreferenced to many other cars including BMW and Mercedes. I am located in the Seattle area, anyone have an extra ecu or would be willing to try mine for a test.

Well a great silence was heard when asked to barrow or lend out a ecu for testing. That’s ok, there wont be anyone around when I break down along the hiway in Montana or Wyoming. Got to figure this out in steps.
the jury is coming back on the no start issue, looks more a do more like the flywheel is on wrong. I hooked a start switch up and rotated the engine from below looking for the nub to line up in the sensor hole. Prior, I had set the #1 piston to tdc and lined the rotor to the notch with no site of the nub in the sensor hole. I now have the valve cover off to set cam lobes pointing out, the piston #1 tdc and the rotor on notch. I think the way the timing is set up now it is severely advanced or retarded. I’ll be back. Thanks for staying with me on this one.
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Are you in Montana? I’m just over the border from eureka, bit north of kalispell... No S3 stuff so wouldn’t have a car to try your ecu’s on anyway.
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