I have a problem with my 1998 Punto 75SX where the Injector warning lamp comes on and the engine appears to be just firing on two cylinders. I've checked out the ignition coils, leads and connectors and the spark plugs seem to be sparking OK. Unplugging the connectors from the ECU and spraying them with contact cleaner sometimes makes the fault go away for a few days and then it comes back again. The Haynes manual doesn't show the injector wiring for the multipoint system so I don't know where they are connected to on the ECU to check out the individual connectors. Any helpful advise with this problem would be much appreciated.
s
|
Engine code and make/type of ECU?
|
The engine code is 176A8.000 and the ECU info plate says: Magneti Marelli, IAW 49F.D1
|
|
|
|
|
If "spraying them with contact cleaner sometimes makes the fault go away for a few days and then it comes back again" provides a temporary cure, doesn't this indicate the area of the fault? Perhaps the contacts in the connector are a little loose?
|
If it was my car i would be either swapping the 4 injectors round to see if the problem moved and also putting some injector cleaner in the tank when the fuel level was quite low seing as the pump is in the tank and difficult to get the car to run on the cleaner neat
only what i would do mind
|
|
|
|
Dave
That's info's perfect to ID the right diagram. On that engine and system, the injectors are commonly fed and commonly switched on a single wire to ECU pin 18. It's thus impossible for an ECU fault to affect only two injectors.
You could have two injectors failing [injector failure is very common - check each injector's resistance is 16 ohms] but it's more likely to be a coil-driver fault shutting down one coil and two cylinders. [Coil switching is on pins 1 and 19.]
|
Screwloose,
I also thought it was a coil related problem as the problem only occurred on the cylinders controlled by the White/Black wire from Pin 1 of the ECU. I tried soldering a length of wire from the ECU pin to the coil and monitored the voltage at the coil. The problem was still there, yet when I took the HT lead off the spark plug and connected to a loose spark plug held against the engine, a spark was present. I concluded, perhaps wrongly, that the fault was therefore not associated with the ignition circuit. Any thoughts?
|
>>and monitored the voltage at the coil.
The coil switching wire should carry a conventional primary waveform. How did you assess the signal, against the other coil's one with a 2-channel 'scope?
However; if there was still a good spark; then check the individual injector resistances next.
|
Checked all four injectors and all have the same resistance reading of 14.5 ohms. Swapped middle pair of injectors for outer pair and the fault still remained. Injector warning lamp ON and no firing on cylinders 1 and 4. Rechecked spark at the plug leads and a good spark present. Removed ECU and took back cover off to check for a dry joint. Metered through all the connector pins to the circuit board and no dry joints were found. Refitted ECU and started the engine. Injector warning lamp was on and stayed on when I turned on the ignition. Started the engine and after about 1 second the fault disappeared. No injector warning lamp and engine running OK. Unfortunately I can't take it for a test drive as the MOT has expired.
Bit of a loss now as to what to do next. Anyway I've left the battery disconnected and will try again over the weekend as it's now started raining.
|
Dave
You're going to have to get the fault-codes read to make any sense of this. I'm still thinking coil more than injector circuitry - but Fiats love weird faults.
|
|
|
|
|
Plug leads? My wife's 85SX misfired badly but still exhibited a good spark when the lead was connected to a loose plug. The fault (failure) in the lead was scarcely visible and only had an effect when the lead was connected to a plug screwed into the head. The sparking current was shorting through the fault in the lead to the metal of the cylinder head.
|
|
|
