Technical Engine firing on 4 Cylinders

[ericmcl]

My friends 2Ltr Fiat Marea Saloon is running on 4 Cyiinders. All 5 coils seem to be working "OK" as on changing over connector plugs spark can is obtained from the plug at faulty cylinder (No 5).

Seems as if timing signal to the coil is not being received though on a quick volt meter check readings seem to match other coil leads

Any info on how ignition timing and spark (ignition system) operates would be appreciated to try and track down the fault.

Suggestions on components wiring to chack would be appreciated ......

Due to the type of ECU using Fiatscan S/Ware I cannot read fault codes as I do not have registerd copy ... so in dark needing inspiration !!

Many thanks in advance

 

[Notorious131]

Are you sure that it's not the fuel injector. If you are getting a spark at faulty cylinder, then it would imply that the plug and coils are ok.

 

[ericmcl]

sorry to clarify ... To test the coil the lead from the adjacent coil / cylinder was used to get a spark confirming that the coil and assosiated plug are working "OK" ....

With the Cylinder's own plug connected to coil no spark is generated when turning the engine over giving impression that the Engine Management ECU is not supplying the "timing pulse" for coil primary winding to give HT spark at the plug ...

 

[Notorious131]

Still unsure, so have you tried the coil from faulty cylinder on another, to make sure the coil is working and have you checked the spark plug from said cylinder is working. Remember these engines have one coil per cylinder.
Basically check all coils and then check all the plugs if all these are fine then I would suspect an injector. If the wireing is the problem then i thought you would have got in ECU light on the dash.

 

[ericmcl]

thanks for your reply ...... yes coil and plug both work when tested when plugged into supply lead of adjacent cylinder.

No engine Management light On ..... Would have thought that the injector would impact on fuel delivery ..... With own supply lead connected the coil and plug do not spark giving impression issue with the electrical supply (pulse) to the coil ?? :bang:

 

[Renegade_8]

thanks for your reply ...... yes coil and plug both work when tested when plugged into supply lead of adjacent cylinder.

No engine Management light On ..... Would have thought that the injector would impact on fuel delivery ..... With own supply lead connected the coil and plug do not spark giving impression issue with the electrical supply (pulse) to the coil ?? :bang:

This looks like a wiring issue on that cylinder. If you swap the timing signal I would expect the fault to follow the wire. If it does then its a case of getting the multimeter out and checking continuity, With a modern car loom it may be easiest to run a new wire. Yuo could do this for quck check and tidy it up if it works.

 

[Notorious131]

ok, i understand now, it does appear as Renegade said you have an electrical issue. Have checked to see if you are getting voltage to charge the coil, may be something as simple as a broken wire or loose connection in the actual connector??
Bring back carbs and points atleast then you could see if everything was working.
I'm old and now need to sit down and rest

 

[ericmcl]

Many thanks to all that gave suggestions, problem traced to a wiring fault at the ECU plug ....

Now running smoothly again !!!! :worship: