| [ Total Views: 785 | Total Replies: 18 | Thread Id: 95506 ] |
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 jimmybay
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 posted on February 23rd, 2012 at 05:34 PM |
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Backfire mystery
Howdy vdubers I have a 75 1800 kombi.
In the last week or so the bus has been backfiring and running rough randomly then it comes good and runs well again.
I took it in for a service but as the backfiring in sporadic it's hard to diagnose what's going on. At first I thought carby problem I had a quick
look this arvo when she was playing up nothing visual that I can find. I'm now leaning towards ignition it has a crow cam fireball xr700 electric
ignition I have been told it's an unusual choice for a bus as it may not handle heat well( could be failing ) .
Can someone please help as we are traveling oz I found work but I need the bus to run smooth to get there.
Any help would be great thanks.
Didyoubringdemgumnutsin?
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AA003
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| posted on February 23rd, 2012 at 05:41 PM |
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When is it backfiring?
On overun, accelerating, driving, hot, cold?
I read it on samba, so it must be correct.
Sometimes Volkswagen dealers sell spare parts. Amazing isn't it!
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 vw54
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| posted on February 23rd, 2012 at 05:58 PM |
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it may be sucking air some where on the inlet side
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shokwave2
A.k.a.: Matt Hamilton
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| posted on February 23rd, 2012 at 06:00 PM |
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Check your coil or borrow one and see if that's the problem. I had similar symptoms, thinking it was the carbies or an exhaust leak, when it turned
out that the coil was on the way out.
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jimmybay
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| posted on February 23rd, 2012 at 06:49 PM |
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Thanks guys I dont think it would be a vacume leak as it's not idling high and a leak would prob make her cough all day long. When it's playing up
it idles rough and backfires under load like a leak but then clears up but it is getting worse( longer episodes of bi- polar) Total of three times
first was 5 mins today was 30 mins
I'm thinking you might be onto something shokwave2 do you know if i can I check the coil with a multimeter ?
Didyoubringdemgumnutsin?
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shokwave2
A.k.a.: Matt Hamilton
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| posted on February 23rd, 2012 at 06:53 PM |
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Not sure. Maybe a veteran of this site can answer that. I just borrowed a coil, thru it in, and it ran perfectly. Before that i took my carbs off
twice and my exhaust system off about three times chasing a non-existent leak 
Where you at? Maybe a fellow dubber can lend you a coil to test.
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AA003
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| posted on February 23rd, 2012 at 07:02 PM |
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Tracking in the distributor cap?
I read it on samba, so it must be correct.
Sometimes Volkswagen dealers sell spare parts. Amazing isn't it!
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jimmybay
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| posted on February 23rd, 2012 at 07:17 PM |
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AA how would I check the distributor ? Ill have to look tomorrow loose button ? Burn marks ect I'm a bit new to workin on my bus I'm trying to get a
bit of experience :-)
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vw54
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| posted on February 23rd, 2012 at 07:32 PM |
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grab hold on the carbies up high n give them a shake that will tell if tehre loose
Also check the vacuum balance line
then go for the dissy and leads n coil
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greedy53
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| posted on February 23rd, 2012 at 07:46 PM |
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wait till night than start her up get some one to start and you watch the engine see if there is any stray sparks failing that get a squirter ottle
and half fill with washing up soap and water crank her up to around 2 rpm and spray aroundthe manafods if there is a leak it will sucked in the soap
bubbles make it easy to see it
good luck
steve
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AA003
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| posted on February 23rd, 2012 at 09:20 PM |
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| Quote: | Originally
posted by jimmybay
AA how would I check the distributor ? Ill have to look tomorrow loose button ? Burn marks ect I'm a bit new to workin on my bus I'm trying to get a
bit of experience :-)
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Have a look inside the cap. If it looks scratched or just old and shitty, replace it.
I read it on samba, so it must be correct.
Sometimes Volkswagen dealers sell spare parts. Amazing isn't it!
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bajachris88
A.k.a.: Chris Leete
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| posted on February 23rd, 2012 at 09:50 PM |
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| Quote: | Originally
posted by greedy53
spray aroundthe manafods if there is a leak it will sucked in the soap bubbles make it easy to see it
good luck
steve
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or wd40 or some aerosol, and if you hear the revs pick up as a result of spraying the stuff around manifold joins and boots, then you know there is a
vacuum leak/breech.
mind you if you had a substantial vacuum leak, you should have a weaker idle, or worse no ability to idle without pumping the throttle.
I was getting alot of backfire with a crook distributor at one stage, and was worse underload, caused hard starting and missing during load and was
on/off. swapped it straight over and allowed me to get home. Points looked ok, as to whether it was condensor or advance issue is yet to be
determined. See if you can borrow a whole other dissy, set the timing and see if your prob disappears.
(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears. 
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta! |
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jimmybay
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| posted on February 24th, 2012 at 10:50 AM |
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Have checked for leaks, checked leads, check fuel flow rate carb not loose, checked distributor button for resistance I'm loosing my mind!! Going
down to buy a new coil and maybe a resistor if that dosnt fix her I think it must be the crowcam ignition system.
Didyoubringdemgumnutsin?
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jimmybay
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| posted on February 24th, 2012 at 04:09 PM |
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Ok so I havnt found the problem it's still a bit under powered and is missing slightly but the bus is running alot better.it's running a gt40r coil
with a ballast resister into the elec ignition.
The dizzy is measuring 1.9 ohms disconnected and so is the resister any idea if this sounds right??????
Next step will Be removing the whole set up and going back to standard dizzy and points to eliminate another area but that won't happen till next
Friday.
At the moment I am driving an hour to work so we are packing up and moving closer so I can catch the train to work. Incase the bus stops altogether.
Another kombi adventure haha
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jimmybay
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| posted on February 25th, 2012 at 08:30 AM |
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Changed the coil out this morning with no effect :-(
Down to the dizzy and elec ignition
Didyoubringdemgumnutsin?
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shokwave2
A.k.a.: Matt Hamilton
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| posted on February 25th, 2012 at 08:39 AM |
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Have you checked all electrials in the engine bay. Could be a bare wire touching tinware or another wire. Or loose connection on coil/distributor.
It's a pain chasing these problems.
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bajachris88
A.k.a.: Chris Leete
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| posted on February 25th, 2012 at 10:11 AM |
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hmm putting my bets on electric ignition 
Just swapped my mates electric ignition dissy over to points and condenser, and now purring like a kitten. Mind you, it was missing and kangaroo
hopping as opposed to backfire. But when i had my dissy failure it was backfiring.
The base of electronic points dissies (if bought as a whole dissy) is simply a 009 shell (if no vac advance), and a set of points and condensor just
bolts in. My mate and i got this advice from Roger at south side vw, points are not as high maintenance as people say. Takes a minute to check the gap
every so often, and if its drasticallly out another couple min to reset ignition timing after setting gap.
Condensor and points (in bosch german quality form) ended up only $24 ish... cheap check.
(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears.
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta! |
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jimmybay
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| posted on February 25th, 2012 at 03:52 PM |
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This is the set up is that vacume advance on the dizzy?
Didyoubringdemgumnutsin?
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bajachris88
A.k.a.: Chris Leete
23 Windows of Awesome
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| posted on February 25th, 2012 at 04:46 PM |
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certainly is! if the advance mechanism gets jammed or the vacuum line connected/blocked, it can cause big woes too another thing to check.
(ô_!_/ô) (ô_!_/ô)
69' baja: kombi box, thing spindles, irs, disc front, type 3 rear drums, 2 inch lift kit, 31x10 rears.
New engine in process: 94mm p&bs, 74mm C/w chomol Crank, 35.5x39 SP heads, turbo. Wierd combo, hopeful torque monsta! |
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