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'85 SPG - hard starting except right after shutdown
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Posted by Jeff Cullen (more from Jeff Cullen) on Thu, 11 Mar 2010 00:13:11 Share Post by Email
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Hi folks,

I've got an interesting hard starting problem with my '85 SPG (T16) which seems to be getting worse...

The only time the engine starts properly is if I shut the engine off and restart it fairly quickly. For an indicator of how bad it is, after 10 minutes of being off after a 20 minute highway drive, it was difficult to start. It's the same dead cold. Really, the only time it's okay is right after shutdown.

Difficult to start in this case means 15-20 cranks, then what sounds like it isn't running on all four for a while, until it eventually runs fine after 30 seconds or so.

It blows black soot out of the exhaust during this misfiring period, and fluid which smells/tastes like water fairly often (cooling system is filled with 50% water/coolant, so I'd expect it to smell/taste like coolant if it were coolant...) There's black soot all over the wall in my parking space where the tail pipe backs up to the wall from these shenanigans.

My fuel consumption had been abysmal, so I replaced my *original* O2 sensor and swapped in an AMM from a car with no problems, and dialed the AMM in using an analog multimeter on the test plug, ending up with ~235 ohms between pins 3 and 6 being what seemed like the spot where the needle would spend a roughly equal amount of time between 12v and 0v.

Checked timing and it is set to 16BTDC with the vacuum advance disconnected and hose plugged.

When dead cold, I pulled the spark plugs and turned the engine over, wondering if coolant or fluid would fly out. Nothing. Didn't visually inspect piston tops. 3 spark plugs looked good, however #2 looked like this:

http://img15.imageshack.us/img15/8559/img02811.jpg

I threw in four new BCP7ES plugs before firing up. Usual antics with long cranking and misfiring.

Later that day, I replaced the #2 fuel injector with a known good unit, suspecting perhaps that one was leaking. No change.

My idle is often uneven despite having tried three different AICs and checking extensively for vacuum leaks. In fairness, I haven't tried cleaning the throttle plate.

My battery seems very strong (it can take all this cranking even after having left the parking lights on for hours once!) however I have noticed my charging light fails to go out until the engine has revved above 1250rpm or so, which often doesn't happen when it painfully sputters into life in its usual manner. Interestingly, all lights are dim and the interior lights noticeably pulse at idle.

What else can I report... compression is between 155 and 165 on all four, original fuel filter was replaced ~10,000km ago, oil looks good, coolant reservoir looks good and no bubbles/weird stuff, etc etc.

It seems to me to be an ignition problem, and all the fuel that is injected during extended cranking isn't burned until it starts firing properly, hence black soot all over the wall... I have relatively new Bougicords, but who knows how old the ignition coil or ICM are. Cap and rotor were replaced about 25,000km ago.

Perhaps this is a strange symptom of the infamous '85 vegetable-based wiring harness starting to degrade somewhere?

Thoughts?

Thanks!

--jeff

posted by 70.79.19...

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