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back fire on accelration

Posted: Tue May 29, 2018 7:25 am
by Vintage man
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.

Re: back fire on accelration

Posted: Tue May 29, 2018 7:57 am
by John Alves
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??

Re: back fire on accelration

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

Re: back fire on accelration

Posted: Tue May 29, 2018 9:22 am
by Eugene
No...let John come feel the damn exhausts :twisted:

Re: back fire on accelration

Posted: Tue May 29, 2018 10:33 am
by Tony Z
sounds like the pump jet isnt working as it should

Re: back fire on accelration

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

Re: back fire on accelration

Posted: Tue May 29, 2018 12:38 pm
by 73type2
I had a similar issue on my '71 Beetle. I found a leak on the intake manifold.

Re: back fire on accelration

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

Re: back fire on accelration

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

Re: back fire on accelration

Posted: Wed May 30, 2018 7:58 am
by John Alves
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 :)

Re: back fire on accelration

Posted: Wed May 30, 2018 8:28 am
by Vintage man
ok so what temp should it read

Re: back fire on accelration

Posted: Wed May 30, 2018 10:29 am
by John Alves
the colder one would be the one with the misfire (if the problem is plug related)

Re: back fire on accelration

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

Re: back fire on accelration

Posted: Sun Jun 10, 2018 3:34 pm
by Vintage man
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.