Hopefully somebody can help me. I've got a uno, L reg with a 999 Fire engine.
It has single point bosch fuel injection. (mono jetronic, i think). It was working fine then suddenly stopped and it won't start.

There is a spark and all the electrics appear ok. When I try and start it the injector doesn't appear to spray any petrol. So thinking it may be a fault with one of the sensors and the injector I changed them all including the potentiometer. With no luck. All the connections are clean, and have sprayed them with WD40.

I can get it to run for a few seconds by putting a small amount of fuel directly into the throttle body, but this still doesn't make the injector spray its own fuel. I have checked the fuel pump and there is good pressure going to the throttle body. The throttle body has been cleaned out and I have tried a different one on it, but still it doesn't work.

I have no more ideas!! Could it be the ECU?? Is there a way of checking it, rather than taking it to a garage?? Is there something simple I am overlooking?? Please help

Hello! You can try to check the signal that arrives from ECU to the injector. You could use a normal tester in order to check this signal. It arrives to one of the three the plugs which are connected to the throttle body. It is not difficult to identify the right plug. Looking from the front of the car, on the left of the throttle body there is the potentiometer plug. On the right there is the plug for the idle motor (it is connected very near the accelerator cable). The correct plug is on the rear of the throttle body (seeing it from the front). You have to disconnect it: you'll can see clearly 4 connections. The first two from the left are for air temperature sensor; the other two (which are on the right) bring the injection current from ECU to the injector. You have to connect a tester (in AC position) to this two connections (AVOIDING to short circuit them because this cuold burn the ECU output stage) and try to run ignition key (starting electrical engine). If you will not see any signal, probably is the ECU which does not send signals to the injector. Note that if you see a signal, this does NOT mean that ECU is completely OK because the signal could be not correct. This is a simple test: if you don't see a signal, the ECU is not working (caused by an internal fault, or by a connection fault along the cable from ECU to the injector...).
Did you tried to change your injector? It is a solenoidal valve (or something similar), and it could be interrupted in its coil. You can also check this coil by measuring the injector resistance: you need a tester in OHM position, and you have to test the two correspondent injector connections in the same jack that I described before, but from the throttle body side. The first two connections are temperature sensor (approx 500 - 2000 ohms) and the other two are the injector connections: if it is OK you have to misure a very small resistance (not more than 3 or 4 OHMS).

Sorry for my bad English but I'm Italian!!
Hope to help you,
Andrea.

Dear Fishbones,

Last time I had similar problem with my Uno Selecta, as Andrea said it could be interupted in its coil. But mine was Digiplex 2 fault, quite expensive :-(.

Now I need Potentiometer, but could not find. Could you tell me the price in your country ?

Hope you could solve the problem

Best regards,

Hendro. N

ndroz2003,

I happen to have a potentiometer in my garage, which is used but in working order. Still attached to part of an old throttle body. Could you confirm for me your type and model of vehicle, as it may fit. I would be willing to sell it for 20 GBP.

Hope this is of help.

Andre, thanks for the advice, I have spent the last 4 hours in the rain checking these and they all are within limits. I have now given up and the car is going into the garage to see if they can find the problem. However if it costs too much money the car will be up for breaking. Watch this space.!!

Hi there Fishbones



Bosch Mono-Jetronic Injector on 999 Fire.

You said you checked and changed all the ECU sensors.

Did you try replacing the throttle position switch?

According to the Haynes manual, this only faulty ECU sensor to make the injector inoperable (no start) when malfunctioning (P 13· 74 – picture 9D.8 and part 10). - Only a vague description of its location. Please let us know how you go on as heaven forbid, it might happen to me. It seems like the Porter manual wants you to go to a FIAT garage for a diagnostic (and probably a large bill).

Louie Bee,

Thanks for the advice.

Yes I have changed the throttle position switch, and unfortunatly that didn't work either. I've gone through the haynes manual aswell, with a lot of head scratching at the wiring diagrams.
I have found a specialist fiat garage that will have a look for half the price of the main dealer. It is going there today, will keep you updated.

Dear Fishbones,

My Car is 1372 CC Uno Selecta, year 1992. Let me know whether The Potentiometer would fit to my car. Please contact me privately for discussion about payment and delivery.

By the way, have you checked the wiring harness from ECU to sensors, apart from bad Digiplex 2, I had it problem with wiring harness too, specially in junction (cause old enough maybe ?).

let me know if it fixed.

Hendro. N

Dear Fishbones,

My Car is 1372 CC Uno Selecta, year 1992. Let me know whether The Potentiometer would fit to my car. Please contact me privately for discussion about payment and delivery.

By the way, have you checked the wiring harness from ECU to sensors, apart from bad Digiplex 2, I had it problem with wiring harness too, specially in junction (cause old enough maybe ?).

let us know if it's fixed.

Hendro. N

OK: I think that a garage is the thing to do... you checked almost all what you could check!!
However let us know what men's garage sayd to you. I' m curious for the problem of your car! I hope it's not an expensive problem!
Best regards,
Andrea.

Andrea

Please see my new thread for results to car.

andre79ge said:

OK: I think that a garage is the thing to do... you checked almost all what you could check!!
However let us know what men's garage sayd to you. I' m curious for the problem of your car! I hope it's not an expensive problem!
Best regards,
Andrea.

Click to expand...

Hello,

I have Fiat Uno 1,4 S and it won't start. My electrician said that spark is not enough strong to start the engine. He said that spark must be at least 1 cm long. He also sad that problem is in my digiplex 2 MED 433 m.

Anyone who have similar problem, please refer to this post. Help me please!