Mondial - 7 out of 8 pistons !

Hi all I have a Mondial QV and you may recall I had a query (ECU) some weeks ago. Thanks to this FANTASTIC forum I located an ECU from one the FC members. This forum is invaluable ! Well the ECU is fitted but the wire loom going in to the ECU is pretty shredded. It seemed that the plug was wrongly wired and has been reversed by my mechanic BUT only 7 out of the 8 pistons are running. Changed dist cap and leads, but still no luck. Looking for an auto electrician but any ideas in the meantime. Need this car back on the road for the summer. Thanks for reading !!

 

Unless you have a plug not firing, you have another than an electrical problem.

 

Does it have any compression? It may seem a dumb question, but its really the starting point. When asked about compression in a recent poll, 7 out ot 8 pistons said they like to have some

 

Thanks F308Jack but can you add to your comment or is it just speculative ?

 

Compression is one of the three things you should check. If you definately have fuel then it would only leave spark. Pull the plug from the dead cylinder and with the plug lead reatached rest it so that it's earthing on the engine somewhere. Get someone to crank the engine while you look for a spark.

 

Before pulling the plug to check for spark, purchase an inductive spark tester. It's a little pencil shaped tool that you hold against your spark plug wires. If there is power going through the wire, the tool's light will flash. You can also use a timing light to do the same thing, but you have to have a power source for the timing light. The spark tester costs less than $10.

 

Not speculative.

You need to first determine if the plug on the dead cylinder actually fires, suggestions on how to do that above.

If it doesn't fire, swap the plug. (You said caps and wires are new, but are they good? New parts can fail too.)

If it does fire, you have to dig deeper. Do a compression test and see what you find.

If you have good compression and spark, you have a fuel delivery problem to that cylinder, which could basically only be the injector.

If you have low or no compression, you have bigger trouble.

Hope this helps you on your way!

 

Anytime I have a question and have a plug out, I often take the compression just for peace of mind, kinda like taking BP. And you dont even have to pull out the rest of the plugs, just disable the ignition and crank it 5 pumps, if it makes anything over 100 it will run. That is NOT to say 100 is okay, its just that without pulling all the plugs you cant really expect to get a high reading. If its near zero you can stop looking for other possibilities, its a mechanical problem, and you should go ahead and do a leakdown to confirm it. Saves a lot of screwing around looking for a needle in a haystack that may not exist.

 

Thanks for responses so far - I will try these but just wanted to be prepared for the worst - what does it mean if there is no pressure in the piston ?

 

At least a valve job involving removing the head. At worst a rebuild.

 

Thanks for all your responses - problem was one of the Flywheel contact pegs had sheared off !! Back on the road now.