General Uno newbie - pressure regulator!

[x_kng]

Hi every one
I am a newbie in fiat Uno , I just bought the black (1991 1.4 ie) Uno 6 weeks ago.
Unfortunately, I am having a problem with my uno from the beginning.
It was having a problem when I first bought it, the car starts normally, but when its warm it acts like there is no fuel and finally its go down.
The technician from the repair shop said that it’s the fuel pump fault (low pressure), it had a 1.5 kilo ( I don’t know kilo what !!) fuel pump. He said that it must be at least 3 kilo because the pressure regulator in the carburetor will not open in the 1.5 kilo and the fuel will not return to the tank by the return pipe. And if that is the case the trapped fuel in the carburetor will be heated and will evaporate and form a gas bubble!!
Therefore, he changed the fuel pump with a 4 kilo and the problem was solved.

My problem now is the bad economy, really bad economy ( average 5.5 km/l), I changed the sparkplug but it still comes back black.:bang:
I did some research on the internet ( and that how I found this great forum) and I found that the fuel pump for the Uno is 1.1 bar.
So I am confused now, is the high pressure that is causing the bad economy? or not ?
Or its may be not the fuel pump fault from the beginning and it’s the pressure regulator ?!
Any help will be very appreciated.
Thank you
………….
…………
Sorry for my bad English.​

 

[Uno driver]

Maybe technician disconnected temperature sensor at inlet manifold and forgot to reconnect it.

Other possible causes for bad economy:
- leaking fuel tank
- bad temperature sensor
- bad fuel pressure regulator
- wrong type of pump
- lambda (~+2L/100km)
- vacuum advance regulator (~+1L/100km)

The last two wont make so bad economy

 

[alexGS]

I think your technician was wrong. Assuming that the 'kilo' is referring to 'kilopascals', the fuel pressure (400 kilopascals = 4 bar) is probably now too high for the single-point injection (not carburettor) - the technician was most likely thinking of a multi-point injection system. As a result I guess that it is now over-fuelling - the ECU operates the injector as best as it can, but the injector sprays in too much fuel due to the higher pressure.

The fuel pump could have been faulty (from your description) but it should have been replaced by a genuine part (in my opinion) and not some other pump. So that's what I'd suggest - get a pump from another Uno 70SXi.e. and fit that.

-Alex

 

[x_kng]

Maybe technician disconnected temperature sensor at inlet manifold and forgot to reconnect it.

Other possible causes for bad economy:
- leaking fuel tank
- bad temperature sensor
- bad fuel pressure regulator
- wrong type of pump
- lambda (~+2L/100km)
- vacuum advance regulator (~+1L/100km)

The last two wont make so bad economy

Thank you,

I checked for the fuel leak but its not leaking from any ware. The heat sensor is connected. For the lambda sensor, I think its not working properly, because there is soot (or carbon, I don’t know the suitable word) in the exhaust output, so I think that the lambda sensor is covered by that too. Any way I checked the lambda sensor by the AVO meter ( I know its not accurate ) but its generate max 0.4 volt .​

 

[x_kng]

I think your technician was wrong. Assuming that the 'kilo' is referring to 'kilopascals', the fuel pressure (400 kilopascals = 4 bar) is probably now too high for the single-point injection (not carburettor) - the technician was most likely thinking of a multi-point injection system. As a result I guess that it is now over-fuelling - the ECU operates the injector as best as it can, but the injector sprays in too much fuel due to the higher pressure.

The fuel pump could have been faulty (from your description) but it should have been replaced by a genuine part (in my opinion) and not some other pump. So that's what I'd suggest - get a pump from another Uno 70SXi.e. and fit that.

-Alex

Thanks Alex,

I think that too ! he is wrong !​

However, there is no genuine part fro fiat Uno here, because they are very few. Al the parts are from disassembled old cars.​

And yes, its "BOSCH MONO-JETRONIC FUEL INJECTION SYSTEM"​

Now how I can check the pressure regulator?​

 

[Uno driver]

If you measure output of hot lambda sensor when it is still connected to ECU, the voltage should change fast from 0 to 1V, so digits on your AVO meter are constantly changing. But if you have so high consumption, I think you won't get it right as there must be something else wrong. For a while I was driving without lambda and consumption was 8-9L/100km instead of ~6

Check resistance of hot temperature sensor, it should be ~230 ohm if I remember correctly. Check if he didn't mess up inlet and outlet fuel hose at throttle body or at fuel tank (but I'm not sure if car would work in this case)