Annoying misfire

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Steve68
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Annoying misfire

Post by Steve68 » Mon Aug 05, 2019 9:28 pm

My SE5A runs very well, starts first time and idles well warm or cold. But as soon as I push my throttle further than around an inch and a half it spits and farts like a llama.
The car has new or very recent...
Plugs
Leads
Cap
Rotor arm
Points
Condenser
Coil
Air filter
Fuel pump
Fuel filter

It's so annoying as it's when the car is under load. If I'm stationary it revs up beautifully at any throttle opening.

Any help MUCH appreciated.
Cheers,
Steve. :D



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Annoying misfire

Post by Old and Slow » Mon Aug 05, 2019 9:40 pm

My first thoughts on this...
Is the fuel delivery OK, or just managing to supply enough for tickover/no load?
Could be when moving from the Idle Jet to the Main Jet the fuel flow isn't working, so possibly there's a blockage in there somewhere.
Can you see whether the accelerator pump in the carb is delivering a squirt of fuel when you put the pedal to the metal?
Timing might be too retarded, but not likely, given that it revs up OK.


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Annoying misfire

Post by scimjim » Mon Aug 05, 2019 9:50 pm

Definitely sounds carb related - what’s the history, did it suddenly start or is this a resto that’s been sat in a garden for years?


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Annoying misfire

Post by philhoward » Mon Aug 05, 2019 9:55 pm

I’ve had similar symptoms from both a failed condenser and blocked main jet(s). Does it do it at all revs, or just with more than, say, 2000rpm on the dial?


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Steve68
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Annoying misfire

Post by Steve68 » Mon Aug 05, 2019 10:05 pm

Thanks all.
It's only just started doing it and it doesn't matter what the revs are or what gear I'm in, (manual O/D box) as soon as I ask for some power it holds back badly. I'm not great with carbs so I don't really know what to look for, all I know it's a twin choke and I believe it's a 38 DGAS???



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Annoying misfire

Post by philhoward » Mon Aug 05, 2019 10:12 pm

If it’s got a fuel filter, I’d be surprised if it’s got any muck in the carb (unless it’s a failing hose dumping little bits of itself into the carb) - but could be a failure of the condenser as that doesn’t care what revs you are - they tend to be load dependant when I’ve had them fail.


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Steve68
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Annoying misfire

Post by Steve68 » Mon Aug 05, 2019 10:17 pm

I think I'll buy a new condenser and coil when I get home from work tomorrow. It's such a bad misfire that It's undriveable on anything other than a very small throttle opening.



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Annoying misfire

Post by AJL Electronics » Mon Aug 05, 2019 10:18 pm

Mechanical advance jammed?


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Steve68
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Annoying misfire

Post by Steve68 » Mon Aug 05, 2019 10:26 pm

AJL Electronics wrote:
Mon Aug 05, 2019 10:18 pm
Mechanical advance jammed?
How do I check that?



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Annoying misfire

Post by AJL Electronics » Mon Aug 05, 2019 10:42 pm

Steve68 wrote:
Mon Aug 05, 2019 10:26 pm
AJL Electronics wrote:
Mon Aug 05, 2019 10:18 pm
Mechanical advance jammed?
How do I check that?
First try moving the rotor arm to ensure it isn't seized and will rotate slightly by hand. Then run the engine as slowly as you can with timing light attached and with vacuum hose from the carb to distributor disconnected. Rev it and ensure that the timing changes in response. Suck on the carb end of the vacuum hose with the engine idling. Again you should see the timing change in response.


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Steve68
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Annoying misfire

Post by Steve68 » Tue Aug 06, 2019 9:34 pm

Thank you. The rotor does rotate slightly but I didn't get chance to test the timing. I was going to move the car away from the house wall so I could have more work room.....and the clutch cylinder went. Master or slave I don't know but the fluid has gone. :cry: So, I better fix that now..... :evil:



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