it started with it running on 3 cylinders, so i got new plugs/wires and sent my injectors to witchhunter and that didn't fix the running problem. so i get a dme harness and replaced that thanking that the injector wiring may be broken. it ran but still on 3 cylinders. but i had a moment of stupidity and unplugged the reference sensor (i think i thought it was plugged into the wrong connection) while it was still running. it shut off and didn't turn back on. i thought i blew my computer so i sent it out to get tested and it was fine (they put it in a running 944 and it ran just as it should). i tried by-passing the alarm and didn't get anything. tried 3 different dme relays and nothing. tested for spark and injector pulse and neither were getting anything until i stopped cranking, then it would spark/light twice. so i figured i messed up the reference sensor. i installed a new reference sensor but didn't change the gaping mainly because it shouldn't change (or maybe it has in the 20 plus years the car has been around) but also because i don't have a .8mm washer and i don't know where to get one. then i changed the dme harness back to my original one and tested the reference sensor plug for a connection before i put it on and all 3 wires had a good connection. none of this has worked. i installed a new speed sensor tonight, it ran for about 2-3 seconds then turned itself off. i tested for spark and injector pulse and get the same thing, wouldn't light during cranking but afterward it lights twice. i then replaced the ignition switch. it ran for 2-3 seconds again then turned itself off, just like before. it seems like the only thing i haven't changed is the coil, think it can be that?

thank you
nick

 

anyone?

 

No Start Check List, I hope this will help.

This has been extracted from a past post, authors Billysdad and John_AZ on a Start Problem.

Posts: 364
Re: 1987 starting problem
« Reply #1 on: Jul 25th, 2009, 10:28pm » Quote Modify

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Hmmmm.... that could be alto! you really have to go step by step and check the ecu harness and voltages to each area as you go. Here is a list of some test you should do one by one and eliminate problems.
Air/fuel/spark/compression
start by making sure we have a battery that is in spec.
all fluids topped off
no obvious broken wires and all vacuum hoses intact on visual inspection.
OK we have 12v at the battery with adequate cranking voltage we get in and turn the key.
12v from battery to ignition switch
12v from pin 50 on switch to pin 4 on DME plug (start signal)
12v on pins 1 (ignition pulse to ign. coil) and 18 (to G5 dme relay power supply)
12v pin 30 at DME Relay (fuel pump power supply)
12v to pin 86 at DME Relay in the run position (primary coil voltage)
12v to coil + black wire to ground 12v to - (green wire) to ground
12v to one side of the injectors
All ground contacts are clean
Fuel pump will run if DME Relay is jumpered 30/87/87b
Fuel pressure at the rail is psi +/- 3 (jumpered 36 psig)
20 minute leak down not under 14.5 psig
Fuel flow rate is 28oz after 30 seconds
Ignition coil primary resistance across + and - is between .4 and .6 ohms
Secondary resistance is between 5000 and 7200 ohms
Ignition wires are good no cracks or splits including coil wire and seated
Plugs are properly gapped
Ignition rotor is seated correctly with the set screw
Timing belt is installed correctly
Firing order is correct - 1 - 3 -4 - 2
Reference sensors are gapped correctly with .8mm clearance off the flywheel
Reference and speed sensors resistance checks in spec pins 8 and 27 speed 600-1600 ohms and pins 8 and 23 >1m ohm
Reference and speed sensors voltage checks 2.5 and 2v on oscilloscope (good luck)
Reference and speed sensor wiring is not broken at connector to sensor or to dme
OK, I'm tired anyone else want to add or be more specific?

John_AZ
Do a compression test.
Reference Sensor Tach bounce when attempting to start the engine. The Tach bounce is very slight-1/16 of an inch. Clean connections as mentioned above.
Injector "noid" light. Very basic tool but will tell you if the DME is sending a signal to the injector. An oscilloscope is the best.
Clean connections at major parts like AFM, ISV, throttle body.

Cheers,
Larry

 

Check your grounds on the engine block and next to the battery. Sounds like the starter is pulling down the battery voltage while cranking. Also, check the battery cable to the starter. Have you cleaned and tested you injectors?

 

i did have the injectors cleaned by wichhunter. i'll check the grounds and battery lead when i get home tonight. where are the grounds on the block? are they the ones right next to the speed/reference sensors? also what are the symptoms of a bad coil?

 

Yes, the engine grounds are near the sensors. There is another battery ground connection next to the battery. A bad coil could cause a no start or a miss, get a spark checker and see how hot the spark is.