964 ignition problems stumped

[rkeele]

Hi Steve My friend and I both seem to have the same problem, the primary plug that comes from the DME computer{ECU} will run my 91-964 on the primary side igniter-coil or the secondary side without issue even when other side is disconnected nothing wrong there, however the secondary plug does not work right, motor will start and backfire when used as only plug. The wires seem to Ohm out Igniters checked coils checked WOT switch checked, idle micro checked, harness checked out, this is a new 5hr. motor with 993SS cams headers Steve Wong chipped for race gas, only making 240 at the wheels. Posted on Pelican Parts tech. one response was hall sensor bad , however I can't find that part anywhere Was wondering what do you think?? thank you Bob

[Steve]

Hi,

First, a bad Hall sensor will not prevent the ignition system from working, only the knock sensors are affected and total timing. Hall Sensors are inside the distributor.

Do you have spark in the upper & lower plugs while cranking?

Does the engine start and run smoothly on the upper plugs?

Does the engine start and run smoothly on the lower plugs?

Did you check the distributor belt and rotor phasing?

Lets start the process with these questions.

[rkeele]

Yes spark on upper and lower plugs
Yes engine runs smooth on upper plugs
No engine starts and backfires stalls on lower plugs only [ note will run when primary plug is hooked to secondary side igniter}
motor is transplant so no OBD1 to check
distributor belt and phasing look OK, both rotors look to be correct

[Steve]

Since this is not a 964, is this a recent transplant?

Has the engine ever run correctly?

It sounds like a coil and/or ignitor problem.

[rkeele]

no I think it has always been down on power, led me to rebuild it, 2 diff. camshaft profiles 2 new chips 1 for 100 race gas and dyno shows no change while checking wiring where I put primary side igniter plug is what works , what we have found is secondary plug will not work however it will start and idle, backfires when throttle opens We have changed igniter no diff. we did static test for ohm"s on coils however not under load so maybe , using a meter we found secondary igniter plug was getting 12v. and ground was good, the white pulse wire also was working. I have another harness I was going to use thought it might fix it, but have not found a bad wire.

[Steve]

JMHO, but you should have addressed the primary problem before making any performance upgrades.

Wiring and connectors are at the top of ANY electrical issue that should be thoroughly investigated before doing anything else and especially with an engine transplant.

Get out the shop manuals for the 964 engine wiring and your car to make sure everything is connected correctly!

[rkeele]

Thanks Steve this stuff isn't easy Anyway I have found green with red coil wire is causing all the trouble it's on the secondary igniter plug side take it out and bingo motor runs on either coil pack, Next check will be the ground wire is right next to the green -red stripe one in the igniter plug problem might be there in plug.

Bob

[Steve]

[rkeele]

Well problem found in igniter plug bad connection green and red from coil not connecting right at plug wow right in my face!! Thanks so much for all your help in this, will think of you when the dizzy needs rebuilding thanks again Bob

[Steve]