simxxi

My 87 924S, After sitting several months while I was out of town I have no Spark. Jumpered out DME relay no start. I have 12 volts at ignition coil but none out, replaced cap, rotor, rotor secure on shaft. Swapped out ignition coil still no spark. Checked coil to distibutor lead, Replaced DME relay with a new one, had ECU tested by ECU doctors, Clean bill of health. Checked both reference sensors. Replaced a little over a year ago. Ohm chk good as well as AC voltage check. Cleaned and checked all grounds. Continuity checked all ECU cable harness pins to all sensors, replaced ignition switch, oh and checked the timing. Fuel pump good. Checked starter/ transmission interlock relay, Fuses all check good, No imbolizer as far as I know. Continuity checks good from all ground points back to battery. New battery. I have run out of ideas. Looking for some input and or someone in Tampa Bay area or west central Florida area... Oh yeah the tach does bounce while cranking. I have read plenty of threads regarding this similiar issue but unfortunately not many post the final solution.

doc_

Sounds like a problem I had, turned out to be a bad ground from the wiring harness coming from the reference sensor to pin 26? 27? of the DME. Testing the DME with a grounded testlight to one of those pins while cranking fired her up. Good luck, it took me 3 months to track down that one bad wire

John_AZ

simxxi,

You have been thorough.

You have an '87 924S automatic.

You have replaced the HG. Did the car run OK after the replacement?

Check the AFM connection. Clean and tight is required.

Recheck the interlock and pins under the gear selector. Trace the wires and clean connections.

J_AZ

simxxi

Thanks for the suggestions. Yes I replaced the HG and had finished reassembled everything before I left town for a few months. I had not yet fired it up.

John_AZ

Recheck the wires from the reference sensors to the connection. You may have reversed the sensor wires.

Read the sensor install paragraph:
http://www.clarks-garage.com/shop-manual/ign-02.htm

GL
J_AZ

StoogeMoe

I didn't see you mention about an alarm. Does your car have one? Is so, you might want to bypass it.

Did you measure the reference sensors at the DME plug? Maybe the signal isn't making its way. Also, if they're not gapped correctly, they won't work.

Does the fuel pump run while cranking? That's an indication that the DME is awake and sensing crankshaft rotation.

Are you getting a pulse on the green wire at the coil?

Jfrahm

How did you determine that you have no spark? Did you check the fuel pressure? Do the plugs get wet?

simxxi

Plugs have fuel smell, not soaking wet, Fuel pump does run while cranking. Reference sensors checked at DME plug ohm check good and ac voltage good while cranking. No Alarm. Have not measured pulse on green wire at coil. But I do have 12 volts on both sides of the coil with key in run position. Have not yet checked fuel pressure need to scrounge up some adapters for my gauge to check. Should I remove the sealing ball in the fuel rail when I check the fuel pressure? Verified DG and BG connections. I actually still have wire markers on them from the harness side. I did have greater than 2.5 volts ac while cranking. I have not yet put a scope on them I will do that this weekend. Even though I replaced both of them about a year and half ago. Thanks everyone again for their input.

Jfrahm

How did you determine you do not have spark? Spark checker?

doc_

A DIY way I was checking for spark was taking the cable that goes to the dizzy and hooking up a spark plug to the cable, grounded the spark plug and cranked. You should see the spark plug sparking if you have spark.


Tried to find a diagram online of what I'm trying to say, but clarks garage already said it for me in the ignition coil test

http://www.clarks-garage.com/shop-manual/ign-04.htm

And for the record, my harness and all the grounds gave me correct readings also from my DME plug...I know exactly how you feel

Jfrahm

It's important to see the spark jump a 10mm gap through the air, which is close to firing under compression. If you can spark across a 0.5mm gap outside the head that does not mean it'll fire at 175 psi. This might not help the OP but when the going gets tough it's time to re-check everything and really challenge your assumptions (one of which is probably wrong.)

simxxi

I used a spark tester from the distributor to the plug. No go. Then from ignition coil to distibutor cap, still no spark.

StoogeMoe

Did you try the coil test as described in Clark's garage?

I ask this because I measured 12V at the black wire but it didn't pass the coil test. It turned out that the wire had a break in it and was barely making contact. It didn't have enough amps to fire the coil. I jumped directly from the positive battery to the black wire and it started right up.

It's unlikely that is your problem also, but you are doing a fantastic job at troubleshooting. You'll find it soon!

simxxi

Okay, last evening I checked the coil as suggested. COntinuity checks from Clarks Garage revealed good. But hooking a spark plug to the coil wire and grounding only produced one faint spark while cranking. Not even enough to drive my spark tester. I then tried the 10mm gap spark test. Nothing until I touched the spark lead to ground with a jumper wire. It appears as though my coil is collapsing and my "Spare Coil" I swapped in are no good. Ordered a new coil last night but makes me wonder My next step will be to see if the 12 volt supply for the coil is shorting out during the cranking sequence. Thanks guys let ya know what happens.

Hollisterkiid92

I'm in the same boat!