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jim73vw
20-05-2008, 11:01 AM
Hi all,

Ahead of the roof panic (see Your cars) we had a problem with Nena in traffic.

We had to queue for @45 mins in static traffic with occasional 1st gear movement. We were on a hill (upwards) so turning engine off wasn't an option.

Temp guage never rose, but when we started to move off into the showground she was very lumpy underfoot. After a bit of stuttering I had no power, even with foot down she faultered, it felt like when you overchoke a car.

We pulled up, tried to restart a couple of times, and after @5 mins rest she started up. Some revving and she seemed to run free again, and we made our way into the show.

On the journey back she ran well except when coasting. She now appears to be ticking over too slow/lean and stall on coasting.

I suspect the long queuing stuffed up an idle jet?? Perhaps the carb (original 34pict VW) needs a service.

I am aiming to go back to the Weber 32/36 carb in the next few weeks when time allows, so don't want to spend ages on the old VW unit.

Anyone any ideas why this happened??

Spacenut
20-05-2008, 11:27 AM
Could be a blocked jet, the symptoms seem to match. There again, there are several other possible faults that could cause the same symptoms. The lumpy idle, not starting etc. could be down to fuel vapourisation while stood in traffic, but something seems to have changed permanently, and the vapourisation would only have been temporary. If you strip the 34PICT don't forget to check the float chamber for crud, check the needle is seating properly and is not ridged, and check the float level is within spec. I'm sure you are running an in-line fuel filter between the pump and the carb(s), but occasionally some muck can get through and clog the jet(s). Also don't overlook the possibility that something in the air intake may have entered the carb. That was my problem - I ran the Green Machine up with no air cleaner and that's how the shard of fibreglass got in :D

Might be worth checking that there is no sediment in the bottom of the tank blocking the outlet; you might be getting a restricted fuel flow to the carb.

Good luck with the diagnosis!

Lauren

letterman7
20-05-2008, 01:23 PM
I agree with Lauren. The mention of fuel vaporization was my first thought, and won't necessarily go away immediately, especially if your lines are close to the heads. We call it 'vapor lock' here in the states, and I've experienced it even with the engine off in hot summer months. But, a suspect idle jet and sticking float are better bets here.

jim73vw
20-05-2008, 09:21 PM
Well I think the cause is becoming clear,

Decided to investigate this evening, and couldn't help notice the garage smelt a little more car like than usual - definate petrol note !

The carb is visibly wet around the base, and it appears one of the section joints has leaked. There is fuel seeping out, which can never be good news.

I guess the prolonged tickover and heat in the engine bay finished of Wolfsburgs finest !? The stalling when coasting was probably down to the air/fuel mixture being out due to the leak. A close call I guess.

I don't intend to refurbish or replce a stock carb so am going back to the new Weber 32/36 kit I have on the bench.

Tonight I removed the fan shroud and alternator and fitted the Weber manifod.

More soon,

MicksRedNova
20-05-2008, 09:47 PM
Jim

If you fix or replace your carb and the issue still exists then try taking a look at the capacitor / condensor (assuming your still running points) as it may have cooked and the insulation broken down in the heat of stationary traffic, specially if it was an old one. That would also cause lumpy running, stalling and bad starting.

Mick

jim73vw
20-05-2008, 10:32 PM
Cheers for that Mick, all electricals were new with the new engine, so hopefully still ok, though will chck if problems persist.

Once I am happy with the carb set up I aim to go for a Pertronix electronic ignition system as well.

Here is the offending carb

http://farm3.static.flickr.com/2266/2508970943_408a4eaaa8.jpg

Note the leakage at the front, which I beleive is from the upper joint. In the background on the right you can also see the air cleaner base which also contained some fuel like deposits??

Never seen that before on this or previous engines - do we think it is all linked to the general failure of the carb??

All out now anyhow, engine bay looks like this !

http://farm4.static.flickr.com/3196/2508971361_265f451d49.jpg

More soon,

Spacenut
21-05-2008, 08:10 AM
The upper joint is at the top of the float chamber bowl, so it would appear to be overflowing. The normal fuel level is usually 3-5 mm below the top of the carb (that's general, I don't know about the PICT specifically). So it may well have been due to the needle valve sticking open. Just make sure your lines are clear before hooking up to the DCD, and use an inline filter to catch the crud before it gets to the carb.

Well done, Mr Progress!

Lauren

jim73vw
28-05-2008, 11:15 AM
Well Saturday was D day !

New carb was finally fitted, and fine tuning of throttle and pedal linkage.

Had a good test run in the afternoon after adjusting the carb and all running smoothly :clapping:

Now can get on with bedding in the new engine,