How common is this phenomenon of leaking injectors on 355 models?
If its driven not very common. If they are older then 5 years yeah. Use a fuel pressure gauge and see if the pressure drops. Of coarse black the fuel pump end More more very common is the O ring that seals them is leaking. They last a few years only. The best replacements are custom made slighty larger ones. RC engnieering has them Do nto get that ebay crap
What is the problem are you trying to fix (suspecting that injectors are leaking)? It is probably common enough if you consider "leaking" to be either a bad o-ring (ambient to inlet) or the injector itself not closing fully (fuel leaking). I got mine tested/rebuilt at RC Engineering and they give a nifty before and after test result sheet. I apparently had three dripping. Also of interest, was the flow balance at 80% duty cycle were improved from 9.5% to 0.7% I had them rebuilt because I though that this was why mine would take two tries to start when cold (mine is a '95...) Bad news was that with fresh clean injectors, it didn't fix my cold start problem. Good news was that my seat of the pants dyno says that the car pulls a bit harder at full throttle.
It is probably because of fuel pressure loss (run back into the tank) over time. This can be through not perfect sealing in the fuel pressure regulator and/or the fuel pump check valve. You can add a manual switch for the fuel pump to prime the system before starting or leave it as it is because, as somebody said in another post, two cranks is good - the first primes the oil pump and pre-lubes the engine.
I have a 96 355 that runs hot on bank 1, verified with a laser thermometer. It does not feel like it is misfiring but that is subjective. It also idles at 1200 rpm leading me to think that there is extra fuel in the cat. Hence, leaky injectors
Well, it's OBD II so you should be able to check the LT fuel trim. If injectors are leaking causing a rich situation you should see negative LT trim. But engine running hot is more a symptom of a lean condition. In that case you should see positive LT trim. You don't say where you measured temperature so it's hard to know what you mean by running hot. Increased idle could also be due to lean conditions as from a vacuum leak.
The car was not driven for a long time and I took it out last week when it developed this little problem. I parked it and moved on to the next car. I have not had a chance to do more than pointing the laser thermometer at the very end of the header where it mates up to the cat converter. It is hot. I am going to park this thing and do a few other things to it before I can drive it again so no big hurry to solve it. It needs the dash recovered in Alcantara anyway. My immediate project is the 95 misfiring. This was right after the 996 engine swap, the 997 turbo engine out, the 997 GT3 clutch job, in the middle of resurrecting two 1970 Fiat 500 and .... you get the drift. I have not had the time to deal with the misfire.
Well, I can report that the two Fiat POS are now running again. Point and condensors, yuck. and why is the quote function not work on this site?
Alright update: Injectors back from Mr. Injectors and they are not leaking. A little low on flow but not leaking. Next idea for excessive fuel in the bank is ... regulator. How do they fail? Just the vacuum diagram breakage?
Did you ever scan it or just assuming excess fuel? If it's idling high due to a vacuum leak ecu could be pulling out all the timing in an attempt to reduce rpm which would cause high egt. I would start with what JohnK said but yes, -usually- regulator failure is diaphragm break.
I took a guess in the dark with the injectors. They actually never got cleaned so that is needed anyway.
A quick scan will tell you a lot. You may be going down the wrong path in trying to fix this. My first thought would be cam timing but don't know the history of the vehicle.
If your bypass valve has the slightest leak at idle if can turn one or both side full rich. I block them off when setting up for tuning with a piece of sheet metal. Just an observation Also the TB are leaking pigs. I smoked 6 so far and 4 were wide open leaking the other 2 minor I'm still chasing one side is leaner then it should be, hope to get back to that Anyway heres them leaking
