Starting problems...

[Njkip]

Any ideas guys.....I'm having problems with starting my bis, it is mainly when it is cold or being stood, even for a day. I have replaced the tank as it was rusting inside due to it being stood for a good while before I bought it....I have put an inline filter on the intake side of the pump, after it was stood for a while the fuel filter would empty as if the fuel had drained back into the tank....so took a while to get it started until fuel got to the pump/carb.

Problem now is.....fuel filter remaining full but will it hell start unless I take off the return pipe and sort of vent the pump, it's as if it's air locking. Once fuel spurts out of return on pump it starts to fire, I then stick the pipe on and she's away. Tried today and despite the fuel coming out of pump return it will not fire up...I haven't checked to see if the pipe from the pump to the carb is airlocked.... it's started to pee it down...😳 thing is before I changed the tank it fired up every time, despite the then inline filter being contaminated with rust sediment hence the tank change!! Can't understand why it's now playing up.....I also can't understand why the pump seems to be airlocking.....I have a new pump.....would it be worth trying that ....thanks....😉

[Abarth982]

Just a couple of thoughts ...
Take the inline filter off just to make sure it's not faulty.
Try starting it with the fuel cap off. I wonder if the tank with the fuel cap on is creating a vacuum and pulling the fuel back?

[Njkip]

Thanks Abarth.....I'll give that a try.....see how it goes.....👍

[andyzeetec]

Like Abarth sais about the vacuum, it could be the tank vent valve,
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[Njkip]

Thanks for the advice.....im now leaning towards the ignition side of things....🙄 It's becoming problematic to start even when it's run.....it's had an electronic ignition fitted using the standard coil....but it seems that the spark is very weak, I mean my lawnmower generates a better spark than the fiat....so I'm wondering if the coil is failing....I went out in it yesterday and it's runs pretty well, a bit of a misfire and hesitant at times, tappers need setting! But is very reluctant to start....even when hot....so I'm wondering as it's been stood for a while if things are just starting to give up three ghost....😳

[andyzeetec]

Thanks for the advice.....im now leaning towards the ignition side of things....🙄 It's becoming problematic to start even when it's run.....it's had an electronic ignition fitted using the standard coil....but it seems that the spark is very weak, I mean my lawnmower generates a better spark than the fiat....so I'm wondering if the coil is failing....I went out in it yesterday and it's runs pretty well, a bit of a misfire and hesitant at times, tappers need setting! But is very reluctant to start....even when hot....so I'm wondering as it's been stood for a while if things are just starting to give up three ghost....😳

Misfire, could be lots of causes, too lean or too rich air-fuel mixture, bad ignition spark/wrong timing of the ignition spark, low compression/air-fuel mixture is leaking out, the timing of the inlet/outlet of the air-fuel mixture is wrong.

[Abarth982]

As Andyz said, could be any number of things ...
In the old days, which I remember well alas, the first thing we'd often do is go for a run, drive home and immediately switch the engine off.
Then whip the plugs out to see what they're like, black and sooty too rich, black and oily, maybe rings, white, too lean and/or ignition timing out, etc etc
A bit old school but might point you in the right direction.  Funnily enough the old Haynes manuals used to have pictures of spark plug conditions and possible causes, not sure if they do anymore though ...

[Njkip]

Well I remember the old days too.....and the Haynes manuals.....😳😳 the plugs are a light brown colour which suggests a healthy mixture etc.....when I first got it it started up in a nano second....ticked over great, apart from one tappet needing setting.....but due it to being stood the tank was full of rust sediment.....so I changed the tank.....it's only got just over 10k miles on it so it hasn't done very much....but as I've sort of been starting it and running it, things have started to present themselves which is understandable I guess....I have another bis and have compared the spark with that and it's definitely not as strong....so my plan is to try the coil from the other one, put some new plugs in and new leads as one of them has a few cracks in outer cover......I'm gonna test the battery as I feel it could be turning over a bit better than it is......I've already done the timing with a strobe so that's ok......tbh I can't see it being much....I'll keep you guys posted and thankyou for your help, it's very much appreciated.......👍👍👍