RUMCars Forum
General Category => Unusual Microcar Discussion => Topic started by: Bob Purton on June 21, 2015, 07:58:27 PM
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This evening I got the car reassembled and decided it was time for the first test drive up my road.The engine pulls quite well but the problem is that once i switch off I cannot start it again. I turn it over and over on the dynastart until it backfires.
Now here is the odd thing. If I take the plug out and put it straight back in the engine restarts and runs fine. I have not encountered this before but as the spark seems to be ever present I'm guessing its a carb issue? Fuel air lock?
Any ideas you villiers guys?
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not sure Bob but I feel sure I have seen the querie raised somewhere else fairly recently hmmmm
best of luck with it
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? air lock in the petroil pipe from the tank to carb ? , time taken to remove the plug refill's the carb ???
loose crankcase drain plug ?
petroil in tank low - turn on reserve tap ?
wandering a bit here but what most dont realise is , if 9/11E was ex IC transplant , then its spent all its life running in reverse when fitted to the cripple car .
(and finaly the egigable age for a bus pass is 60 ;) )
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Hmmm, I have an electric fuel valve and not a very good drop on the fuel line from tank to carb. Maybe tomorrow I will rig up a shortened fuel line bypassing the tap and see if it cures it.
Thanks for the suggestions but keep them coming please.
It has a full tank of fuel, engine is rebuilt with new crank seals.
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I think that's an AWFUL way to describe an invalid car Plas Man ! badly chosen words I think
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True but please dont change the subject, you can come back to that issue later!
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My money's on the fuel valve , how bigs the fuel chamber on these carbs ?
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Fairly big.
Another thing it could be has just been pointed out to me on the other forum by a Bond owner. The car backfires when trying to restart it and does so just as I let go of the ignition switch. It could indicate that the dynastart is using all the current and not enough to produce a good enough spark so when the starter is switched of the plug kicks in and causes the backfire. Could explain it but doesnt offer the cure. The plug, coil and condenser are all new.
Any more ideas?
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Backfire is timing, or unburned fuel in the exhaust being ignited by a hot discharge. That would suggest its not a fuel prob, unless its to much fuel.
That places the fault as electric once checked. A dodgy dynostart will take all the power and reduce the HT output. sO A STARTING TEST WITHOUT THE DYNOSTART MIGHT BE IN ORDER. dEPENDS IF YOU CAN DO THAT IN CONTROLED CIRCUMSTANCES. wINDY GUN ON THE ENGINE. STATIC BUMP START.
My continuing problem here is you can no longer buy quality HT lead ends to make up good HT leads. I have several where I have reused parts to get back to copper cored HT leads that are playing up. The best items screwed in, or were pinned across, rather than relying on a crimp I have not the tool to recreate.
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Or maybe a test involving use of a separate battery feeding the ignition system?
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Yes.
But once running you need to find out where the dynostarter system is not working. A give away is not turning over backwards, as its a weaker unit in that direction. If it worked first off, and then is troublesome, that suggests, if dyno fault, a poor joint or contact. They get hot and thus the electrical resistance increases sapping spare energy. This can end in a burned out area. So I would be a bit concerned to be running the engine for very long until I have more data to suggest where the fault is overall.
Sadly its one of those rather tedious jobs of illiminating each item in a logical sequence. I have several cars to do and am finding motivation hard to muster with so much else on. Invariably it is down to a simple error, a useless new replacement part or assuming the previous owner would know the simplest of the simple.
Earthing is always a good start. I always have earth to engine and chassis from the battery on a dynostarter car due to the large voltages. The black box is also earthed to the engine and chassis.
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Thanks Al. I just checked and I have earth to chassis but no earth to engine, only engine to black box and the black box is bolted to the chassis. I will run a seperate earth from battery to engine and see if it makes a difference. Also will check the box back plate is making good contact with chassis metal.
Better leave it till later in the day as now the car is in the front garden, what with my home made silencer, I will not be popular! ;D
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A nice megaphone exhaust Nice!
Both Schmitt and Treinkel follow this practice. The Treinkel having a specific double ended earth strap. But of course the Treinkel has no Black Box.
Next fav is Coil. If it gets hot connected in 5 to 10 minutes, its suspect. Again the resistance increases as it heats from a short. The spark dies. Condensers are just weird. Ideally both should be away from heat sources, a design principle not well followed by some manufacturers! Fiat 126 is very bad here, and that is a million made car!
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Thanks Al. I may take the coil off Thumper as I know its a good un and try it with that after the earthing exercise.
On the sister forum Nick suggested just closing the plug gap but I really cant see that making enough difference to be it. Still, I will try all the suggestions. Isnt it great to have such a microcar community thats willing to to help!
Ps. The dynastart appears to funcion correctly , works in both direction and is lively. The dyo lights all go on and off as they should.
Well I say that, but as its been a long time now since I had the schmitt, when reverse rotation is selected, should both igintion lights come on or just the one?
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when running either forward or reverse all lights should go out , if reverse light is on then suspect a short on the bottom bush's/holders .(Siba Dynastarters).
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The ignition light will come on for either direction, if the shunt has connected. The reverse light is to tell you your in reverse mode. Both should be out while the engine is running. I was going to ask if it was charging. Sounds like it is.
Spark plug gap - I think, crumbs memory, that a spark has to work harder to jump in the presence of fuel/air mix. its not a charged material, or in a state of excitement, nor is it conductive. So, theory, the density means it cannot leap as far. That is why a wet plug fails to work, as well as offering a shorter route to earth if there is a lot of carbon about. You can get a missfire with the charge nipping across the inner gap of the plug, not out where it can ignite the charge. I believe this is why platenium plugs were offered for in town driving, where deposits could build up and you did not get the chance to blatt that crap out. Living out in a rural area I found these plugs did not work for me but Neville Stevens and other city dwellers used them to better effect, I believe. I have rarely suffered a whiskered plug.
Always worth swapping a plug. They are not really quality items nowadays and I find you have to shuffle to find a good one. Indeed my box of cleaned second hand plugs often supplies a better plug than new! Bless the Trabbi and the recycled Jupiter plug.
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Yes, the light goes out when running for either direction [ I'm not that green! :)] . Just couldn't remember if the red light comes on as well as the green when flicked into reverse. You confirmed it should so all is well there. I tried several plugs yesterday with identical results so am pretty sure that's not it.
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just a though , during the re-build a timing cam from a Twin has not taken residence ???
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Narrrr. This is an old Scootacar engine that Andy Hammond thrashed until it the clutch went. Its been undisturbed until I bought it and did the rebuild. Anyway, surely a wrong cam would effect its running all the time not just sometimes.
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Fuel tank breather.
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Happy to report the problem solved! I made up a new earth cable and connected it from battery to engine casing and immediate the engine sounded like it was running better. After a few blasts up and down my road to get it nice and hot I switched off, restarted in reverse and forward several times and all was well. I did close the plug gap a little too as advised but it wasnt a big gap anyway so I'm positive it was the bad earth that was causing the problem.
Yet again Big Al is the hero of the piece! Thanks Al and remember you are welcome to sign onto the sister forum any time.
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I wish I could fix my own cars! Contrariwise and know-how, as the phrase has it.
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;D Well if you ever need a mercury barometer or a Wimshurst machine sorting out, I'm your man.
Thanks again.
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dont know what on EARTH all the fuss was about 8)