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Backfiring and Popping

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andywen8156
Posts: 34
Joined: Fri May 05, 2017 8:21 pm
Location: Tiverton England

Backfiring and Popping

Post by andywen8156 »

Hi, I have a Lanchester 14 recently had head skimmed with new copper head gasket also cleaned carb jets with air along with new gasket's. The problem I have is it will not stay running however it backfires and popping when trying to start. The only way I can keep it going is by pumping the gas pedal, I have just done a compression test with readings of around 110 psi. Checked plugs and leads the resistance is normal in all the dizzy cap seems to be okay and points adjusted but timing not sure about if its right? any help please :D :D :D

JT7196
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Re: Backfiring and Popping

Post by JT7196 »

Hi Andy, sounds as if you have a bad Air leak in the Inlet Manifold, I would suggest that you remove it and check for cracks .

Best wishes Alan

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andywen8156
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Joined: Fri May 05, 2017 8:21 pm
Location: Tiverton England

Re: Backfiring and Popping

Post by andywen8156 »

Thank you Alan will have the inlet manifold off and give it a good look over :D :D :D

qantasqf1
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Joined: Mon Mar 07, 2016 10:13 pm

Re: Backfiring and Popping

Post by qantasqf1 »

Check the HT leads are connected to the right plugs.

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andywen8156
Posts: 34
Joined: Fri May 05, 2017 8:21 pm
Location: Tiverton England

Popping

Post by andywen8156 »

Thanks have done so but as Alan said about the inlet I found there are two bolts holding the inlet manifold to the exhaust mainifold these were loose so have tighten them. Still got popping going on have pull number 3 spark plug wire while engine running.

Seems to become a lot worse when number 3 is connected also a knocking sound seems its not looking so good although the compression test on number 3 was good maybe my thoughts are lower engine.......? when I bought the car 3rd spark plug was very loose ;) ;) ;)

Sydsmith
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Re: Backfiring and Popping

Post by Sydsmith »

The more I read the more I think this is an ignition problem, either as has been suggested the plug leads have been refitted in the wrong order, the distributor has been refitted wrongly or the timing is a mile out. I am thinking if it were air in the manifold or weak mixture you would be able to compensate by adding more choke.

The knocking symptom suggests that a plug or plugs are being fired at the wrong time either because the wrong plug is fired or the ignition is very much too far advanced causing the fuel to be fired as the piston is rising and has not reached TDC. Syd

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andywen8156
Posts: 34
Joined: Fri May 05, 2017 8:21 pm
Location: Tiverton England

Re: Backfiring and Popping

Post by andywen8156 »

Thanks everyone Syd you was right for some odd reason the firing was all wrong the wires fitted such as the back cylinder was number one, so have taken the wires out of the cap and put in the correct places. Pleased to say she fired up straight aways! although its hard to keep it running guess adjustment needed, so hard without timing marks apart from the one on the flywheel which seems unreadable on my one. Will tinker with the dist.... amazing the advanced peg was pushed in thus not working on the auto advance slider in the base. cheers! :D :D :D

Sydsmith
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Re: Backfiring and Popping

Post by Sydsmith »

Glad to be of help Andy.

In my youth good tools were out of reach and a timing strobe was a luxury pipe dream, we always warmed up the engine and set the engine speed to a comfortable tick over, slacked off the distributor and gently turned the body back and forward very slowly to achieve maximum even speed. It is surprising how accurate you can set the timing using this method, certainly well enough to then set up the carburettor. Syd

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andywen8156
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Joined: Fri May 05, 2017 8:21 pm
Location: Tiverton England

Re: Backfiring and Popping

Post by andywen8156 »

Thanks Syd will have a go tomorrow your advice is very useful because trying to determine where tdc is by checking the number one valves seems a big error hope she will be ticking over good tomorrow will update cheers! :D :D :D

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