1500 MOTOR BACKFIRE

[Jack Nel]

My mechanic has been fighting with the 1500cc motor on the Karmann Ghia for a while now, and he's about to give up.....

Please help with any advice.

Motor starts easily and idles nicely, rev's smoothly up to about 1500rpm and then starts backfiring.
He's checked tappets, timing, played with different jets, checked spark plugs and leads, condensor and coil, fuel line etc etc
Also swapped over everything from my Beetle onto KG and still the same..

[Cyndi Kritzinger]

AS FAR AS I'M AWARE, A BACKFIRE IS NORMALLY CAUSED BY A TIMING ISSUE BUT I'M NO MECHANIC.
I'LL SPEAK WITH A GOOD MATE OF MINE WHO IS AN OLD SCHOOL VW GUY (AND SERVICE CENTRE OWNER) AND SEE IF HE'S ANY THE WISER.
NO DOUBT THE BOFF'S ON THIS FORUM WILL SORT YOU OUT WITH THEIR PEARLS OF WISDOM.

YOU MAY JUST HAVE TO WAIT FOR THEM TO GET HOME FROM WORK.

MARK

[Tony Z]

check for vacuum leaks
where is he setting the timing?

[retrovan]

Vacuum pipe is off the dizzy, or sucking air,

manifolds loose and sucking air,

firing order incorrect , make sure you count it clockwise 1-4-3-2

leaking tappets

Crack in head

Good Luck

Herman

[73type2]

Perhaps advance the distributor a couple of degrees and see if the situation improves?

[Jack Nel]

Thanks for the responses, we will check everything by process of elimination and give feedback.

[Dawie]

Is it backfiring out of the exhaust, sounding like gunshots? Or more like a coughing through carb?

[fig]

I agree with retrovan and TonyZ, this sounds like a vacuum leak at the manifold. And don't assume it's not the condensor just because you already replaced one. Try another, known good one.

[Haans]

What Dawie is asking......is it farting or coughing!!

Big!!!! Difference ?

Haans

[sean]

Don't believe its only something external. You could have internal issues. Leaking valves or cracks as Herman mentioned.

I had a motor in a bus that I purchased last year, that continuously just kept popping out the carb when the revs picked up. What had me stumped is that its compression was 100%, so the valves wren leaking. I eventually discovered the camshaft was completely worn away on 2 lobes and virtually couldn't open the valves...

[Jack Nel]

Don't believe its only something external. You could have internal issues. Leaking valves or cracks as Herman mentioned.

I had a motor in a bus that I purchased last year, that continuously just kept popping out the carb when the revs picked up. What had me stumped is that its compression was 100%, so the valves wren leaking. I eventually discovered the camshaft was completely worn away on 2 lobes and virtually couldn't open the valves...

My mechanic believes you might be on to something here, thanks Sean.

[sean]

Don't believe its only something external. You could have internal issues. Leaking valves or cracks as Herman mentioned.

I had a motor in a bus that I purchased last year, that continuously just kept popping out the carb when the revs picked up. What had me stumped is that its compression was 100%, so the valves wren leaking. I eventually discovered the camshaft was completely worn away on 2 lobes and virtually couldn't open the valves...

My mechanic believes you might be on to something here, thanks Sean.

Remove the tappet covers and start the motor. Check the rockers if they all have full lift.