back fire on accelration

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Vintage man
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back fire on accelration

Post by Vintage man » Tue May 29, 2018 7:25 am

Hi all
Where to start ,1600 TP motor in a late bay.
When accelerating jerks and power low then it back fires.It started doing this and then cleared but this weekend no luck.Checked the timing and dwell angle and that is spot on.



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John Alves
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Re: back fire on accelration

Post by John Alves » Tue May 29, 2018 7:57 am

when does this happen? engine cold? engine hot? all the time? does it happen on deceleration as well?
touch the exhausts see which one is cooler than the rest, possible bad plug??
No sense being pessimistic. It wouldn't work anyway.

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Re: back fire on accelration

Post by Vintage man » Tue May 29, 2018 8:08 am

All the time ,seems only on acceleration .will check plugs and leads as soon as I get a chance.Will check the exhausts as well.Thanks

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Re: back fire on accelration

Post by Eugene » Tue May 29, 2018 9:22 am

No...let John come feel the damn exhausts :twisted:
You can never have enough Garages :-(

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Tony Z
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Re: back fire on accelration

Post by Tony Z » Tue May 29, 2018 10:33 am

sounds like the pump jet isnt working as it should

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Re: back fire on accelration

Post by Vintage man » Tue May 29, 2018 11:38 am

Hi Tony ,I will check the pump jet system but it also does it a constant acceleration.Nothing on de-acceleration.

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Re: back fire on accelration

Post by 73type2 » Tue May 29, 2018 12:38 pm

I had a similar issue on my '71 Beetle. I found a leak on the intake manifold.

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Tony Z
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Re: back fire on accelration

Post by Tony Z » Tue May 29, 2018 5:40 pm

Vintage man wrote:
Tue May 29, 2018 11:38 am
Hi Tony ,I will check the pump jet system but it also does it a constant acceleration.Nothing on de-acceleration.
Then likely a vacuum leak

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Tony Z
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Re: back fire on accelration

Post by Tony Z » Tue May 29, 2018 5:41 pm


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John Alves
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Re: back fire on accelration

Post by John Alves » Wed May 30, 2018 7:58 am

Eugene wrote:
Tue May 29, 2018 9:22 am
No...let John come feel the damn exhausts :twisted:
I now have a laser temp gauge so no more finger burns :)
No sense being pessimistic. It wouldn't work anyway.

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Re: back fire on accelration

Post by Vintage man » Wed May 30, 2018 8:28 am

ok so what temp should it read

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John Alves
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Re: back fire on accelration

Post by John Alves » Wed May 30, 2018 10:29 am

the colder one would be the one with the misfire (if the problem is plug related)
No sense being pessimistic. It wouldn't work anyway.

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Re: back fire on accelration

Post by Terry Phillips » Wed May 30, 2018 2:27 pm

Sucking air use the old hair spray trick, my 2c.
I think I was barking up the wrong tree.I was thinking of de acceleration. :oops:
Last edited by Terry Phillips on Sun Jun 10, 2018 11:03 pm, edited 1 time in total.

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Re: back fire on accelration

Post by Vintage man » Sun Jun 10, 2018 3:34 pm

Reset the volume and bypass on the carb as per Google and runs smooths. Out on the highway and a bit of town driving, I'm chuffed, Thanks all that gave advice as I did do as adviced as well so another learning my bus.

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