Ignition problem, symptoms, ideas

If you can't reduce the richness and maintain good driveability, you might try a set of the NGK Iridium plugs to see if the fouling interval can be extended out to something not so annoying . Anti-fouling (or, maybe, better resistance to fouling) is a true benefit of these small diameter center electrode plugs made from the exotic higher melting temperature materials IME.

 

This sounds very similiar to a problem I had. The culprit was a bad/weak condensor. Compare the coil performance on front vs rear bank by holding each coilwire 1/4 inch from engine while cranking. Bright snappy blue or dull weak yellow? Just my .02
Bill

 

Just my experience, but my carburrated car also tends to like it a bit rich (actually all Ferraris do giving them their historic reputation for fouling plugs around town). There are two things I would suggest you look at doing that worked for me.

I have had a very good experience in keeping plugs clean in a relatively rich environment with the MSD 6 multi spark box and an MSD hot "Blaster 2" coil combined with a relatively hotter plug for street driving. Your car would require two MSD 6 boxes and MSD Blaster 2 coils, one for each coil. This combination gives multiple very hot sparks at lower rpm ranges where fouling is common, and in combination with a hotter plug rating my little car has never fouled and been bulletproof reliable so far for 4 years, even with around town driving.

Another somewhat more involved thing you may want to look at are your carb jettings and settings. Most of day to day around town driving and cruising is actually done on the idle/transition circuit (unless you are really ripping everywhere). One change to consider is going down one size on your idle jets if they are larger than 50s. for example, if you are running 55 idles, you may consider downsizing to 52s, or even 50s. If a flat spot in transition ensues with the smaller idle jet, you can bring in the main circuit earlier with one size`larger main jet for a smooth transition. This has been a successful strategy for me.

I would look at providing a hotter spark first as Steve has suggested, and follow up with the carb changes if fuel fouling persists. Good luck, this will be a good thing.
best
rt

 

I'm running BP5ES plugs in my 77 and they stay pretty clean. I ran the 1st set for 5 years and just recently did a "birdman" carb tune up and replaced the plugs. I am running a Pertronix breakerless ign. and set the timing at 7*btdc. Car runs good.

 

My first thought was to go to the BP5ES plugs as well. It sounds like everything else in the system is in good condition. Try the hotter plug and see if that helps keep them cleaner. Otherwise, the carbs my need to be adjusted or rejetted to lean them out a bit.

 

I agree Seamus, man those are DARK plugs! LOL!

Go to the BP5ES that's what I run and truthfully even your gap at .025 is the upper part of the specified range, .015 - .025...I gap mine just a smudge tighter, bang them on the driveway 'till they read .022....

And quit loafing arounf town, get out there and hit the HIGHWAY!!!!!!

I guess I'll have to spring for some Iridium, if Steve M. likes them !!
I have one cylinder wanting to misfire it won't be long......crap for gas these days...

 

I have gone to MSD coils only, like Russ decribes, in an otherwise stock ignition, they have an epoxy potted one that is made for our laydown installation, couldn't hurt......

 

IMHO, since it worked OK for 3000 miles the changes you made aren't the problem. I'd use an Occum's Razor approach and check for a bad or badly connected coil high tension wire, bad plug wires, etc.

 

Hey Seamus,
I had a similar problem on my 75 gt4 many years ago. The culprit was a weak alternator and battery. The farther I drove the worse it got.
The fact that you lost a whole bank of cylinders in a snap sounds electrical to me. What were your gauges doing while it was running bad? Mine were jumping all over.
I am not a mechanic but I did stay at a Holiday Inn.....
Good Luck,
Dave

 

I have to agree with Dave. While change to a different plug may help for certain conditions, you have a whole bank failing at once. That's got nothing to do with plugs that are too hot or too cold, the culprit is a fault. Go over your ignition system with a tester, shouldn't be too hard to trace.

Good luck!

 

Sorry, I should have elaborated: The simplest solution is probably the correct one.
Go over the ignition system for that bank

Check the distributor cap for cracks
Check the resistance from the pins inside the distributor to the end of the lead, especially the one that goes to the coil with a VOM
Check the low tension lead between the coil and the distributor - clean up the contacts and wiggle the wire looking for an intermittent short
Check the points (burned/pitted?) and check the timing, especially the advance (rev motor and make sure the distributor advances.
Swap the coils and see if the problem changes banks
etc...

 

I've got a similar situation with my '85 euro. Engine starts, runs fine for a short period (few minutes to 1/2 hour), pops, and then the rear bank drops out.
We've tried swapping the modules, swapping the coils, replaced the distributor caps, replaced and swapped TDC sensors, checked alternator output, checked plug wires, suppressors, coil lead.... Frustrating!!!!

 

Hi Phil,
Does this happen once in awhile or every time you drive it ?
Does the engine cooling off seem to help for awhile ? another cycle of good to bad.
Maybe someone else has experienced this phantom problem.
Dave

 

Dave,
It has been in the garage for a few months now, and a little time is spent on it each week. Basically every time, it starts cold, and then runs for a while, anywhere from a few minutes to a half hour before the bank cuts out. When restarted warm or hot it will usually run a shorter length of time before it cuts out again.
It acts like a heat related problem but don't know where else to look.

 

Phil,

If I recall correctly, your car has three sensors; one for the tach, one for the front bank and one for the rear bank. Is the shop aware of this set-up? Two of these sensors are semi-visible, the third one is not.

If I were working on this car, I'd have a scope connected to the "suspect" bank, starting at the correct crank sensor to see if your losing the signal to the electonic ignition unit. If so, great; there's the problem. If not, just keep moving upstream to see where the ignition signal is lost. Swaping parts is great, but if you have an intermittant connection/connector, they'll never find it this way.

Although I can feel your frustration, this should be a fairly straightforward problem to find.

Regards,
David