Joined: Aug 2017 Posts: 3,329 Threads: 372
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Sidedraft 26VA running from gravity tank. Plenty of fuel visible coming through the modern inline filter at all times.
Running was fine on accuspark distributor [but I've changed over to a self-rebuilt DK4, co-incidentally].
Car idles very low and sits running in drive for 3/4 hour fine. When I start road testing, when it has got warm I get kangarooing and it grinds to halt. Then restarts and gets going again with lots of pedal.
I've been through all jets, the hidden jet, and cleaned the emusion block (but am waiting to fit new gasket there)
Does it sound like something to do with float height (which I am yet to understand)?
I have changed over a float bowl (I've checked they are the right type for the main body as per Ruairidh's comment on thread elsewhere) and the problem got worse, so that obviously disturbed something or contributed to the problem.
Could it be fuel vapourisation when the sidedraft carb is so high above the exhaust, or can I discount that? It was warm that day but not that warm.
I can't see to duplicate the problem when operating throttle in drive (and haven't wanted to run it hard under no load)
Joined: Aug 2017 Posts: 612 Threads: 19
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Location: Hampshire UK
Hi JonE
It may indeed be a fuel problem, but misfire and poor running under load are also symptoms of a weak spark. If ignition voltage is marginal it may be just OK at the low cylinder pressures at idle, but fails to spark when cylinder pressure rises under load. Typically caused by a faulty condenser or coil, both of which can be worsened as temperatures rise.
Joined: Mar 2018 Posts: 694 Threads: 33
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Location: Lot region FRANCE
Back to the distributer. Check the top bearing play on the rotor shaft, points cam and check max and min points gap. Even check that the plate the points are fixed on isn't loose and the screws done up well as they conduct the electricity to earth.
Had a similar problem on my RN when I was convinced it was fuel
Joined: Aug 2017 Posts: 254 Threads: 3
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Location: Shropshire, UK
Jon, you say "plenty of fuel visible coming through the modern inline filter at all times" what you are seeing is fuel filling the filter housing, you can from that, have no idea of the rate of flow. I have had personal experience of inadequate fuel flow from a bulkhead tank to a side draught carb. Liquid flow, gravity fed, through any orifice is entirely regulated by "head" which is precious little in your situation.
Remove the fuel pipe at the carb and direct it into a pint clean bottle, turn on the fuel tap and time exactly how long it takes for the bottle to fill. Any longer than 5 minutes and you have inadequate flow for bottom gear full throttle up a steep hill situations.
Many of the fuel taps have very fine mesh filters incorporated in the construction. Even when clean these severely reduce the rate of flow.
Joined: Aug 2017 Posts: 3,329 Threads: 372
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ok, thankyou all. lots of things for me to check next visit down - I have made a list! Fuel is quite fresh so can be discounted I think. I did change the condenser over for a new one and seem to remember that it was left on. Can one "test" a condenser?
So, check all four cam lobes points opening.
If 6V coil is showing resistance across the poles of 1.8/1.9, can that signify all being well, or is there another test I need to perform?
Joined: Aug 2017 Posts: 782 Threads: 26
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Location: On a hill in Wiltshire
Re: condenser
I use a digital meter on the highest, in my case, 20 megohm resistance setting.
Make sure the condenser is not in circuit with anything else.
Apply the test leads to the condenser, usually to the case and the one lead or terminal that it has.
Don't have a finger on each of the leads or you will introduce your own resistance into the circuit.
You should get either no reading, or, more usually a "kick" of a reading - say 5 megohm - which steadily decreases to zero.
Reverse the connections. You should get a bigger "kick" which again reduces to zero.
Any reading above zero means the condenser is scrap.
I don't think this guarantees the condenser is good, but it does tell you if it is definitely bad.
No kick either way probably means it is open circuit, and , again, scrap.
Simon
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Will test...!
I'll also check earth for coil against bulkhead, although still unsure whether that is important for running or just for safety.
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A simple condensor check is to leave everyting in the distributor as per normal, and simply connect another condensor (vitually any type, say a Lucas type 1950s to 1980s) direct to the coil. The condensor can be earthed between the coil and its strap.
If this fixes the problem, then either the original condensor is a dud, or it has an earthing problem.
Leaving the original condensor in circuit doesn't seem to matter.
Make sure that the moving plate in the distributor is properly earthed.
Joined: Aug 2017 Posts: 3,329 Threads: 372
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Dave - which coil terminal should one connect it to please - or does it not matter?
