Backfiring

[Pogel]

My bus had an enormous backfire then stopped. If I restart when cold it starts up and turns over ok. Then in starts to stall, has a large backfire then stops. The spark plugs were black and I have cleaned them. I also changed the inline fuel filter, but it does the dame thing. The distibutor is new. It has dual solex brosol carbs which I think are 34s. The engine is 1641 on a 1500.

[65Busstop]

Check timing?

[Da TOW'D]

Backfiring out muffler or carb ?
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[caseyjones]

Maybe old gas being burned?

[Pogel]

The muffler is smoking and then the flame can be seen coming out it when it backfires. Gas is not old. I always use Shell 93 octane. I've got to wait till a friend comes over Saturday to check the timing, compression etc. A couple of people have thought maybe the float in the carb is sticking.

[ekimikem]

Was it running fine before the first backfire incident?

[Utiledulci]

Busstop hit it on the head...timing is the first thing to check. A timing lite is cheap enough to buy at Autozone, anyone with a vintage car should have one of these along with a good fire extiguisher. Next thing I would check are the carbs to make sure they are configured/jetted/tuned the same way. This will cause it to run rough too.
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'nuff said

[65Busstop]

I don't think the compression on a VW engine is high enough to run that high of octane. You might research that as I am not positive on it. If you have Muirs idiot guide it tells you how to make a static timing light for near nothing.

[60freak]

Is the distributor "loose", sometimes the clamp/bracket can be loose that holds the distributor in place and the distributor will pop up and loose it's physical connection with the driveshaft and cause problems similar to this. If the distributor has been changed recently and now you are having troubles, that would be one of the first things I'd check out, 2nd being the carbs to inspect for plugged jets, incorrect/stuck float level, etc. Good Luck.

[SurfCityRacing]

As these guys said, double check the timing. Sometimes if the advance mechanism is fouled up, the timing will look good, but it won't be. Dynamic timing with a light is the only way to eyeball the advance.
Hope that helps.
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[Alaskan Adventurer]

does it have points or electronic ing? Mine was doing the same thing at BB last nov. I discovered the electrionic modular was loose under the dist. cap.. Also has it been sitting long? The carbs could be gummed up/ Pluged jets... Kevin
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63 DC
60 SC daily driver

[Pogel]

I checked the distributor and it was not loose.

It has points.

I recently had to change a brake drum. When I jacked it up it tilted over at quite an angle (bus is drastically lowered). A friend said the oil could have sloshed over and into the heads. He thinks I should run the engine to burn off the oil.

[Alaskan Adventurer]

Ok, Maybe cracked dist cap or rotor? Jacking up the bus did not do it,
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63 DC
60 SC daily driver

[BarryL]

Black plugs = way too rich. See if the choke is opening and make sure the float and all that fuel pump pressure stuff has been checked.

[bill may]

[60freak]

When the distributor was replaced, did you hook up the wire from the distributor to the negative/correct side of the coil? I remember years ago a friend who hooked up the distributor and ignition "hot" backwards on the coil and the vw ran for a short while before backfiring and running like crap and then eventually catching his wiring on fire in the engine compartment, it was a mess. Good Luck, hope you get it figured out. I'd look into the last things you messed with for the problem, distributor first and then onto the carbs.

[Pogel]

Ok I've checked a few things. It is a pointless dizzie. I hve it running and not backfiring when the timing is 10BTDC. If I back it to TDC or ATDC it backfires. It is 1641cc on an H block with no vacuum advance and the dual carbs, blue coil. Is BTDC correct? I have yet to road test it.

[BarryL]

Post up the distributor number and Glenn might pipe up; he's the distributor guru. My guesses have been off lately but I'm thinking 7.5 to 10 degrees static before.

[slow36hp]

all timing i know of is supposed to be some amount before tdc or btdc also you most likely depending upon compression are making your motor run hot with 93 octane
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[Culito]

If it's a 009, you want to time at full advance. 30degrees, I think.
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