Alfa Romeo Forum banner

61 - 69 of 69 Posts

·
Registered
Joined
·
2,778 Posts
Fuel pressure can be viewed in diagnostic data. It doesn't change that much but I think from memory it should be over 1000psi (calculated from what it displays).

Checking spark with a plug out is one thing but how it behaves in a pressurised combustion chamber where the molecules of air are squeezed together is something else as the spark has to be as many times stronger as the actual compression inside the combustion chamber. Then factor in the heat which impedes the spark...

The static spark test is useful for checking if something works or not but is less useful in helping to determine the cause of poor running or an intermittent fault. A spark tester between the stick coil and the spark plug would be more helpful and they cost less than £10 for a set of 4. That said, I still think it will be of limited use as the coil works but it seems to malfunction in certain conditions which suggests low voltage and current reaching the coil which causes a weak spark- possibly too weak to jump the spark plug electrode gap.

Just to be absolutely sure, number 3 plug is the 3rd plug from the timing belt end and not from the flywheel side as French cars used to or still do. I know that probably sounds patronising but I'm trying not to leave any stone unturned, so to speak.
 

·
Registered
Joined
·
33 Posts
Discussion Starter #64
Yes 3rd from timing belt, second from air intake hose. I'll take a look on the pressures.
 

·
Registered
Joined
·
2,778 Posts
As mentioned, I cannot accurately remember fuel pressure right now and do not have access to car right now due to virus measures.

Perhaps my JTS was 50 bar at idle reaching around 75 bar. Anyway, fuel pressure seems good then so discount that idea.
 

·
Registered
Joined
·
2,778 Posts
Sounds quite possible- even likely.

Checking O2 sensor voltages when running poorly and comparing readings when running smoothly may help. I'd use readings of slightly over 1500rpm. Hopefully there is a marked difference.
 

·
Registered
Joined
·
33 Posts
Discussion Starter #69
I've come to a realize that the engine doesn't behave according to the O2 sensor readings when cold. So that's probably not my problem. So you're probably right that my problem could be the injectors, fuel system or bad compression. I probably won't have time to dig any further in the next 2 weeks but I'll tell you when I come up with something.
 
61 - 69 of 69 Posts
Top