I once had the same problem . Diagnosis was that one of the carbs was uber rich and fouling a particular plug on start up / heavy choke. Removed of the plug,wire brushed,applied heat gun, replaced plug and fired up fine.As you say if it starts it'll clear in a few mins.Balance the carbs/ weaken mixtureand see if this works, also check choke isn't stuck on.
Rolling road sessions on cars with high comp / tuned engines sometimes result in start up problems like this from cold, depending on where you take it.
Here's a problem for your collective minds. I have a 997 with 295 head, bit higher comp ratio, warmer cam and H4s. The problem is that the engine has a hunger for spark plugs. The senario is : engine runs sweetly for a few hundred miles and then when laid up for few days or possiblya week, runs on three cylinderson start up.If left runnning for a minute or two the final cylinder kicks in and all's ok. After a couple of times of this, only a change of the offending plug will remedy the situation. I generally use NGK plugs, but changed to Champion briefly and the problem remained. This all started with BP6ES andduring a rolling road session they were changed to BP7ES and still remains. The only clues I have is that if anything the engine is running slightly rich, but not so bad as to be really obvious, and the usual offender is Nr2, but not always.
Thanks for that, I had wondered about the possibility of overfueling being a factor. I will look at this when its not too cold and see if I can alleviate the problem.
imported post
I once had the same problem . Diagnosis was that one of the carbs was uber rich and fouling a particular plug on start up / heavy choke. Removed of the plug,wire brushed,applied heat gun, replaced plug and fired up fine.As you say if it starts it'll clear in a few mins.Balance the carbs/ weaken mixtureand see if this works, also check choke isn't stuck on.
Rolling road sessions on cars with high comp / tuned engines sometimes result in start up problems like this from cold, depending on where you take it.
Hope this helps.
Hi everyone
Here's a problem for your collective minds. I have a 997 with 295 head, bit higher comp ratio, warmer cam and H4s. The problem is that the engine has a hunger for spark plugs. The senario is : engine runs sweetly for a few hundred miles and then when laid up for few days or possiblya week, runs on three cylinderson start up.If left runnning for a minute or two the final cylinder kicks in and all's ok. After a couple of times of this, only a change of the offending plug will remedy the situation. I generally use NGK plugs, but changed to Champion briefly and the problem remained. This all started with BP6ES andduring a rolling road session they were changed to BP7ES and still remains. The only clues I have is that if anything the engine is running slightly rich, but not so bad as to be really obvious, and the usual offender is Nr2, but not always.
I look forward to some ideas!
imported post
Thanks for that, I had wondered about the possibility of overfueling being a factor. I will look at this when its not too cold and see if I can alleviate the problem.
AMS