Technical MK1 strange problem

[Ovidiu176]

Hey! I have a strange and interesting problem with my Punto mk1 '95 (1.1 petrol, 176.B2.000). This weekend I made a 200km journey (100km there - 100km back). On the way there very often happend the next thing: driving normally... then a slight hitch or two, and then I was pressing the gas pedal for nothing, the revs where coming down. Having no choise I was stopping and the engine didn't stay idle. The rev counter was on that little suport needle, and the engine struggled to stay on. I turned off the engine, waited 2 minutes, and then it worked fine another 2-3 km, and then the story repeted it self endlessly until I reached my destination, for 100 km. At the destination I stayed for about 15 minutes, then headed back home. On the way home all was perfect, nothing went wrong ... a little odd I would say.
I mention that the same simptoms I have when the petrol level reaches below a quarter of a tank, but then I just fuel up and it's all good. When I left this weekend I had a nearly full tank.
If anyone has a clue about what might be wrong I would really appreciate it!

 

[MadMan0]

The fuel filter could be clogged. It's a service item every 2 years i think.

 

[Ovidiu176]

I changed the fuel filter in November... :shakehead:

 

[Dcthebear]

Was it raining?

 

[Ovidiu176]

No, it wasn't.

 

[Austin Mini]

Hi, you have an electrical fault. You need to check low tension circuit electrics from the key start to the distributor.

 

[Ovidiu176]

The fault just pops in when I have below quarter of a tank of gas, or randomly (this weekend's case) ? If there is an electrical fault shouldn't it always manifest?

 

[Dcthebear]

Rules out water then. Yep, go with electrical twinge in there somewhere and could be a bitch to find if its intermittent.

 

[Ovidiu176]

Darn it :bang:. I appreciate it guys! Still hope someone has another idea before I start to look for the needle in the haystack.

 

[Dcthebear]

No. Electrical faults can be complete arses to find. A dry solder joint can work for years, then fail, then work again for years. Thankfully with cars due to constant vibration and big changes in temperature they do reveal themselves in the end in most cases. Worst thing is it'll be something tiny 99% of the time. Try starting with some continuity checks with a multimeter. Bad connections will show a higher resistance and draw more current causing components to fail until they cool down. Pull the battery negative off though with continuity checks.

 

[Ovidiu176]

I have to find and make time for this. I'll have my hands full

P.S.: Could it also be one of the induction (ignition) coils?

 

[fingers99]

I'd check for water in fuel -- run the car as dry as you can, drain tank. Refill.

I'd then buy one of those little glass fibre pens like this and some silicone grease like this (although petroleum jelly is almost as good) and spend a day cleaning up all the connectors to do with the fuelling and ignition systems and greasing them as well as the main earth connectors.

You might also try -- although it's just a guess -- replacing the TDC sensor.

A coil going down is more likely to result in a very distinct misfire, but they're very cheap.

 

[PuntoHowTo]

I agree with everything fingers99 says

and would like to add the possibility of air getting into the fuel pipes when the fuel level drops. maybe a hole or some damage to the in tank fuel pump

 

[kyller]

your fuel pump try to tell u that she are too old
replace fuel pump insert before u stuck "in the middle of nowhere"

 

[Ovidiu176]

and would like to add the possibility of air getting into the fuel pipes when the fuel level drops. maybe a hole or some damage to the in tank fuel pump

I have tought of a bad o-ring at the in tank fuel pump when I noticed the simptom each time the fuel level dropped. But happening with a almost full tank confused me
@kyller: So, yes I might have a tired fuel pump. You're saying to try to replace the whole fuel pump that is underneath the back seat? You sad the fuel pump insert, I can't figure out what you ment by "insert"

 

[fingers99]

The "insert" is just the actual pump which sits inside the pump body.

I'd not rule it out completely, but pump failures/wear outs are pretty uncommon, even on Puntos as old as yours.

The insert from an SPI Cinq (or Sei) should be the same as yours (MPI one will be different).