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winners

Lack of Power On Acceleration - S1

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I'm putting this in fuel systems but it could well be ignition!

I have an intermittent fault, the car runs fine but when it gets warm it won't respond when the throttle is opened more than just over tick over. Flooring the throttle almost kills the engine. Sometimes it comes back after driving gently, but it always returns to normal after switching off and leaving for a while. I've got an electric ignition conversion so assumed that it would either completely fail rather than demonstrate this sort of symptoms.

Not experienced with carbs but could it be something sticking or some sort of fuel blockage.

Ta

Mark

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Sometimes it comes back after driving gently, but it always returns to normal after switching off and leaving for a while.

Could be the coil overheating, work's fine again after it's cooled down again so next time it happens if it's too hot to keep your hand on it then it's f£%&ed :o

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I agree with John.

 

definitely a coil that is going out. The problem is that it is tricky ,almost impossible to measure.

The good thing, a new one does not cost a fortune.

 

I have a pertronix instead of points and I changed the coil (the old one also overheated) to a  flamethrower epoxy coil 3 ohm 40611.

The old one started giving trouble, when I was at SPA francorchamps queueing for almost 45 min. Because of the long idling. The coil cant loose its energy and starts overheating. Ones it is gone to far , it will give trouble.

When cool, it seems OK.

 

To be honest, when you have this kind of problem, I would renew ignition coil,spark plugs, ignition cables and may be also rotor and cap.

This often make miracles happen to a cars response.

 

Geert

Edited by gvy

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Check the fuel flow. Take the pipe to the carbs off and stick it into a jar and turn on the ignition...see how much fuel gets pumped through. If it's a dribble, you've found the problem. Check the points too - if your car still has them - they close up in use as the heel wears on the cam. Check that the accelerator pumps are working properly...they should squirt like miniature fire hoses.

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Mark - while you are looking at the carbs you might also check float heights.  If you are getting plenty of fuel to the carbs and you can see that the accelerator pumps are OK next thing to look at is the mixture - are you using high octane fuel?  Check the plugs and tail pipe if black and sooty could be that you are too rich.  Good luck.  John.

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Hi,

 

Do not forget the trouble starts when the engine is warm .

I understand that when it is cool, the engine runs fine. When you let it cool down for a short while (engine still warm, but electric is cooled down) it runs fine too? right?

It is really important to check, when exactly the problem starts....

 

So I don't think it is a fuel problem.That would expose itself with engine cool and hot.

Now wrong float hights will create stumbling, but they will do it cold and hot.

Same for accelerator pumps

 

So again.

There are different kind of coils.

If you have a 3 ohm 12V coil, you do not need the resistor, or a resistor wire to feed the coil.

If you use a 1.5 ohm 6V type coil, you need the 4 ohm resistor  in series or the resistor wire.

What are you using instead of points as electronic ignition?

f.e.  an ignitor II will use a 0.6 ohm 12V coil

 

I mean, there can be various reasons why a coil is not functioning well or degrading fast if it is not the correct match.

 

Look at new ignition wires , a new rotor and cap. Those are all parts of the ignition that can start malfunctioning when the engine gets hot or better, when the electrics are getting hot.

I have seen this happen on my Esprit, but also on my classic 1970 opel GT ( with electronic ignition) I had a distribution cap and rotor malfunctioning. There was no trace and nothing to measure but they were bad. The car started and drove but after a while started hesitating and stopped. After a short cool down (not the engine, just the electric) it started again.

 

Geert

Edited by gvy

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Hi Geert

 

I now suspect ignition too. When it was running poorly there was back firing, which would indicate, un burnt fuel not lack of fuel.

 

i'm running a Lucas DLB 105 sports coil with an accuspark electronic ignition.  The symptoms were there with the previous coil though so bought the new up rated sports coil. I have checked the wiring of the ignition and cleaned contacts, there was also a small split in the  insulation+ wire from the coil so I replaced that. Don't know if that would cause the problem. I haven't had chance to test drive it since. 

 

there is something I am missing either in the wiring or set up of the ignition.  As you say it runs well until hot, which would suggest it's not a faulty unit and is correctly set up but I am at a loss to what may cause this other wise and electrics are not my strong point. So at the moment I have just checked the obvious such as poor connections and possible shorts. Will look at a new cap and rotor if the symptoms are still there tomorrow.

Edited by winners

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So, if the wire you replaced was the resistor & you replaced it with a standard piece of wire then you're now running a 6 Volt coil on 12 Volts which is causing it to overheat. :o

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The Lucas DLB105 is a 3 ohm 12V coil. I think that is OK. It does not need a resistor wire or an additional 4 ohm resistor in the circuit.

Now , if an accuspark electronic ignition is installed and used with your 3 ohm lucas DLB105, it is important that you do not use a ballast resistor or do not have a resistor wire in the circuit.

You need a straight 12 V on the + of your coil. Measure that. If you have something like 8 V there , a resistor or resistor wire is in the circuit.

 

You should have fig 1A situation : http://www.accuspark.co.uk/fitting_guide.html

 

Geert

Edited by gvy

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Road test the car. Carry a spare plug. When the problem occurs, leap out and pull a plug lead and stick your spare plug in it...earth the plug thread on the engine and operate the starter ( an assistant helps!) Inspect the spark...if any. No point in changing things until you know the problem;  diagnosis is the key...and only change one thing at a time!!

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Geert, thanks for asking. It turned out to be spark plug leads. Annoyingly simple!!! The new coil and electronic ignition was producing too much energy for the old leads to handle, hence why the issue coincided and made the issue worse.

Mark

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