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Intermittent Ignition Problem - Help!

1115 Views 6 Replies 6 Participants Last post by  Stan Murray
Hi Guys, 86 Alfa Graduate Spider, 30k miles.

Just yesterday I turned the key, starts cranking, nothing.
Check some wires, turn the key nothing, keeps cranking.
Wait a few minutes, turn the key, fires right up.

Drive 20 mins.
Let it sit 2 hours, won't fire. Plenty of cranking, but nothing. Check everything, nothing. I leave it for another hour, fires right up.

Here's what's been replaced in the last year:

Plugs (checked the gap to try to diagnose this)
Distributor Cap/Rotor (yesterday)
Ignition Coil

Here's what I checked:
-Pulled a plug out, no spark
-Pulled a different plug out, no spark
-Tried to get the coil hot wire to spark by laying it near the top of the motor, no luck

Well, it's running now, but I know the next time it fails will be the time that i'm far from home. Also, it never dies while running. It only happens on startup.

My questions are:
What could this be?
Some other ignition component?
Next time it happens, what can I check?
If i put a multimeter on the two sideposts of the coil, what should it show while cranking?

Thanks in advance for all your help. This board has been very helpful to me so far!
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I'd suggest putting a voltmeter on the battery and see what it reads while cranking the engine. It is possible for the battery to have enough oomph to crank the engine with seemingly good power but, if the available voltage drops below the computers 'wake up' threshold (~ 10.3V), they'll be no signals for spark & fuel.

If you are certain the battery is good, I suggest cleaning/tightening the battery cables, the ground connection at the floor of the trunk and the grounds on the engine itself (plus the ground strap and its connection to the body near the bell housing).

While you have the battery dis-connected to clean its terminals, reach in under the intake and clean/tighten the connections at the starter motor, too.
Also check the source for the coil. I think it goes to the starter. These leads sometimes fail due to vibration. You may find a lead barely connected and not flowing enough under starting load but OK once running.
Could be anything, I had a similar problem, replaced many things and eventually found the problem by tapping things with a screwdriver while the car was running, it was the little aluminum relay near the computers under the rear luggage area.

I forget where it is check in this forum, there is a detailed troubleshooting site for your car.

'85 Graduate
Watch your gages and dash to see if they are getting power when you get the no start symptoms. Turn key on and see if things power up prior to turning it to the start position. If they do not, then it could be the ignition switch.
Thanks for the great suggestions. I'll run through all of this today.

It is MUCH appreciated.
one thing to check is the main fuel pump. I found With cars with similar problems, sometimes the pump would run and other times not. So when you are in a non start saga listen to your pump when you switch the key on...pre-start.
If you don't hear the little zzzzt then your pump is not getting signal.
My fix was replace the big black relay under that rear shelf. I also noticed that I could trick it by attempting to start then quickly release, quick twist back, and then try to restart while the starter was still whinning a little. I could never figure out why this worked. If you have a friend with another Ljet then swap the black relay and see what happens.
All the ground cleaning and battery cleaning ideas are excellent. A funny chemical forms between metal connections that you can't see and disrupts connections. Even if they look clean, clean them again...sir.. yes sir..make them shine. Then use a little lectric grease to keep the moisture out.
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