Title: Idle speed erratic and dies away Post by: andyps on 04 January, 2021, 02:31:42 PM Looking for some advice. I've had my Fulvia S2 started and running a few times recently after it had stood for a long time. I rebuilt the carbs (standard Solex) to get all the jets cleaned up but haven't done anything about the float levels. I bought the guide to set up from Omicron which I have followed and am reasonably happy that they are balanced - not perfect but it runs OK and revs smoothly. However, the idle speed is a little erratic and if I leave it it seems to idle for a while and then gradually slows down and stops if I don't do anything. Also, it isn't easy to start - when cold it takes a while and when it has got warm it sometimes needs a little choke to start it, immediately then running without choke.
Once the car is on the road I'm happy to take it to someone to get it set up properly (I'm in Yorkshire) but would like to get it a little better than it is if possible before that stage so any advice welcome. Almost ready for a first drive, I was aiming for 2020 but the roads at home were covered in ice for the last few days so I didn't bother rushing to get it out of the garage! Title: Re: Idle speed erratic and dies away Post by: andyps on 04 January, 2021, 02:32:17 PM And just realised I forgot to say Happy New Year everyone!
Title: Re: Idle speed erratic and dies away Post by: peteracs on 04 January, 2021, 08:20:03 PM Hi
First question is how old is the petrol you are using? If stood for a while will not help the situation. Peter Title: Re: Idle speed erratic and dies away Post by: lancialulu on 04 January, 2021, 10:21:17 PM Very hard to diagnose from a distance. Statement of the obvious is to go through everything , valve tappet clearance, compression when hot, ignition timing 8 deg static, float levels (easier than you think), fuel pump pressure when idling, clogged fuel supply line etc etc.
Title: Re: Idle speed erratic and dies away Post by: davidwheeler on 04 January, 2021, 10:56:38 PM I had endless trouble with mine until I cleaned the earth on the (electronic) ignition. It is always worth checking earths!
Title: Re: Idle speed erratic and dies away Post by: jus on 04 January, 2021, 11:45:44 PM Could be an air leak. Try spraying some carb cleaner carefully at different areas of the carbs (spindles and mounting rubber for example) and see if the idle changes. If you have a brake servo or ignition advance hose - check for vacuum leaks there as well.
Do you have a mechanical or electronic fuel pump? Do you hear an equalising pressure change when you open the fuel cap? Do you have an inline fuel filter that could be a bit clogged up? Title: Re: Idle speed erratic and dies away Post by: andyps on 06 January, 2021, 11:42:36 AM Thanks for the replies, been a busy few days back at work so I hadn't had chance to look at them until now.
Petrol is fresh so shouldn't be an issue hopefully it's a couple of months old at the most but probably less than that. I've done all of the valve clearances, haven't checked compressions, sorted the timing as far as I can tell, fuel pump (both electric and mechanical) are new and I've cleaned through the lines. Sounds like I should check compression which I'll try next time it is hot. All earths have been cleaned with additional earthing added as I couldn't get it to run at all at one point. I'll try the carb cleaner for air leaks, it doesn't sound to have any but may be a small leak somewhere. The brake servo hose is something I have intended to replace as it is the only old hose left. Some ideas for this weekend, I'll let you know how I get on. Title: Re: Idle speed erratic and dies away Post by: lancialulu on 06 January, 2021, 05:01:21 PM Normally an air leak (manifold or servo pipe) leads to a rising (>2000rpm generally) tick over.... I can vouch for this as it was a problem I had when recently installing a pair of solexes on a 1600.
Sound more like the mix is too rich and when it warms up the air/fuel is too low for the engine to tick over comfortably. When it starts to drop tweak the no1 mix screw in and see if the revs slightly rise. If so do this to all until it is stable..... Title: Re: Idle speed erratic and dies away Post by: andyps on 06 January, 2021, 05:52:03 PM Thanks Tim, I've been trying adjusting the carb screws but this is my first car with Solex carbs so I am learning about them! If it had SUs I'd understand what I'm doing a lot better. It is running a lot more smoothly than it was, just not as well as it should be, if it would sit at idle without assistance I'd be happy enough for the moment.
Title: Re: Idle speed erratic and dies away Post by: nistri on 07 January, 2021, 08:34:16 AM worth checking the needle valves: their opening and closing can become erratic. Assuming that their needle washers are correct for size and thickness, the valves often respond positively to soaking in carb cleaner for a few hours. Andrea
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