Cold start Yes - Hot start No! Asdvice sought please.

[Doris53]

Hi all
I have been restoring my 1953 SII for the past year or so. It has the original 803cc engine and is still +ve earth with dynamo.

I have not actuallly got her out on to open road yet but am getting close to doing so. However, I have an engine problem that I hope a more experienced owner could help me with. The engine will start first time, every time, when cold. However, when I have her running and warming up, if I try to get her running of the choke too early she will cut out. The problem then is that she will not start again! I will have to leave her at least 2 hours before she will fire up again. I have only had her running nicely off choke once but was not in a position to take her for a longer drive that day.

So if anyone has had this problem themselves, or knows how to resolve it, I would be very grateful for the advice.

Regards
Steve

[svenedin]

It sounds like a fuel vaporisation issue but I’d suggest a systematic approach to the problem including checking ignition as well as fuel delivery. I have seen cars with the fuel line from fuel pump to carburettor misrouted above the exhaust manifold which causes fuel vaporisation and is dangerous. Check fuel pump, carb, float chamber, float level (fuel level in float chamber is important), and ignition. Check points are clean and gapped correctly and fit a quality condenser if not already done. Basically you need to eliminate problems one by one.

Stephen

[geoberni]

It seems a bit odd that it runs OK and doesn't cut out on you, but if you stop it, accidentally or intentionally, it won't restart.

Stephen's comments are all valid, but before going down a fuel problem route, I would add a quick check to see if you actually have spark, because you haven't said if it just cranks over with no attempt to fire up.
It might be that something other than the engine is warming up and a gap opening up in a wire somewhere. Such as in the Coil.
When I got my car, having trailered it some 75 miles home, it cut out on me on the first trips I did over 5 miles.
But car would start fine after RAC had took me home
Found it was the Coil, with a broken solder joint inside.

[Doris53]

Thanks to Stephen and 'geoberni' for your replies.
The complete ignition system is new with parts supplied by The Distributor Doctor. I am confident the fuel pump and carb are working correctly having stripped them several times!
Fuel vapourization could be possible I suppose, but all fuel pipes are routed correctly. Also, it's not as if I am running in hot weather - I live in the UK! The fuel pipe from the tank to pump is new. The tank is clean.
Regards
Steve

[svenedin]

OK that sounds a good start but clearly something goes wrong when you try to re-start a hot engine. I think Bernie's suggestion of a possible bad electrical connection is a good one. When you are having the trouble, I would take a spark plug lead off and hold it with insulated pliers against the block whilst trying to start the engine to check for a good spark. I would also confirm that fuel really is flowing well from the fuel pump by taking the hose off from the carb and directing it into a container then switching on the ignition (but do not try to start obviously). You do not want any sparks when there is fuel around. Finally I would take the lid off the float chamber and check the fuel level. I have had a float needle valve that sticks shut, the float chamber runs dry and the car will not start.

Stephen

[Bill_qaz]

When you try to restart are you trying with and without choke. I know you say it's warm but if it restarts with choke then it point to a carb issue.

[Doris53]

Stephen
I have checked the spark, float chamber, and fuel supply many times - always good. Thank you for suggestions though.

Bill
I have also tried many times, with and without choke. Still no joy. I need to leave car for a couple of hours, a bit of choke, and she fires up again. Thanks,

Steve

[svenedin]

Certainly a puzzle! What about checking the jet centring and whether piston falls with the all important metallic clunk?

[paul 300358]

Check the compression when cold then check again when hot.

[Doris53]

OK folks - having tried again, yetserday and today, I know that this is NOT a hot start problem!

The problem is real, but not related to a hot engine. Today I started her up first time, as usual for first start of the day (same yesterday). Then I stopped the engine after a minute. So, engine not hot. Immediately tried to restart - nothing! So, it will ALWAYS start first time if it is the first attempt that day, but then when I stop and restart (regardless of how long it has ben running) it will not start again - until the next day.

So any ideas? It must be something that occurs when engine is started/running that needs to 'reset' before another successful start. It is so frustrating - I just cannot figure it out!

[simmitc]

That makes fault finding easier

Very basic, as soon as it will not start, remove the HT lead from the centre of the dizzy cap and wedge it with the end about a quarter of an inch from a good earth (such as the block). Turn the engine on the key. Is there a good spark at the HT lead? If NO then we can start looking at the ignition system. If YES, then replace the HT lead on the dizzy cap, remove No.1 spark plug (nearest to radiator), reconnect its HT lead and wedge the plug so that it has a good earth. Yurn the engine. Is there a good spark at the No 1 plug?

Report back for the next steps.

[Doris53]

Hi simmitc
I have a good spark at all plugs. I have tested this several times using an Accuspark Flash Tester to confirm spark visually.
Regards
Steve

[simmitc]

OK, sparks good, and following Phil's advice, at correct time. Check the fuel and also remove the air filter and feel inside the carb to confirm that the piston moves up and down freely. With the damper present, you should feel resistance on the way up and have a smooth fall; with damper removed, easy up and a rapid drop with a clunk. Check that the air filter is clean.

[Doris53]

Hi
All checked - again many times. Whilst I can see these are valid things to check with a non-starter, it does not really explain my problem. Surely if any of the things you have mentioned were a problem, then the engine would not start first time, every time, after being left overnight.
Steve

[simmitc]

The point is to check them when the engine will not start. If it won't start, then there must be a reason; and the only way to find it is to check everything. If I understand correctly, on any given day, you can start the car at the first turn of the key, switch it off, and immediately it will not start again until 24 hours later. If you leave it running, then it's quite happy to continue to run.

There is no timer circuit in the car, so it has to be something like a loose connection, faulty component, fuel / mixture. What about some lazy valves that are OK when running, but stick open when the engine stops, and then slowly close? Frankly it sounds far-fetched, bit no more so than having to wait 24 hours. Water getting into the cylinders and then evaporating?
How long is it really? Start and stop the car at 08:00, it won't start at 08:05, but when will it? 12:00, 14:00? 20:00?

[Doris53]

Thanks 'simmitc'
I do appreciate your thoughts on this. It just seems that I have checked the usual stuff so many times. I guess it must be something strange and more far-fetched.

All the electrics are new, and the ignition system components are new (except the distributer but all electrical components changed).
The head had some work done professionally, and was reassembled professionally.

I have just remembered something that may be relevant. Yesterday, after the same problem for the umpteenth time, I pulled the spark plugs. The 2 furthest from radiator (3+4) were a bit wet. 1 and 2 were dry but a bit sooty.

I will have another go at it tomorrow and let you know if I discover anything!

Thanks again.
Steve

[simmitc]

Ah... Now that is interesting. Were they wet with water or wet with petrol - sniff them when checking. When the car is running, are there any bubbles in the radiator? Is the radiator level changing? Have you got a compression tester? It would be useful to know the readings across all four cylinders.

Another thought: Is it a standard 1098cc single manifold?

[Bill_qaz]

When it will not restart have you tried removing the fuel filler cap, just incase the tank is vacuuming and the pump cannot suck fuel and after standing long enough it can.
You seemed to have checked many other things multiple times

[oliver90owner]

If you are confident it runs and pulls well enough, I would think it has an inlet manifold leak and is, otherwise, running too rich.

At this point, I would be running the engine and spraying oil around the inlet manifold joint to check if the engine changes note.

An alternative would be to give it a good run with a hot engine, then remove and inspect spark plugs to see how each cylinder is running.

I suspect it is flooding, so won’t start until those two cylinders dry out, but just guessing. Have the valve clearances been adjusted properly?

A compression test will rule out real compression issues (so might steady hand cranking), to roughly compare compression of all four cylinders.

[mowogg]

As above I would suspect a inlet manifold leak.

You could try tightening the manifold bolts bit if this fails replace thr gasket.