ok, heres the low down... I have a 54 beetle with a 40HP engine bog stock.

I drove to work one cold morning - manual chock was working fine, I didn't feel any problems at all... the trip took about 15 mins. after my 7 hour shift, I started her up, all fine, but when I started to move off (ie: pressing the accelerator as you do) she starts to hesitate - it's like a flat spot were the revs nearly drop to stalling point (this is with the clutch disengaged). A few light taps of the roller pedal and the engine starts to pick up a bit but doesn't spin freely to the high revs. (even with the choke off as i know that will inhibit the breathing). Trying to get uphill was even more of a task as it felt like i was going to stall at any point coz the engine wasn't using the fuel or someting...

I have checked the timing, the plugs are new, the mixture is correct, the butterfly isnt loose to a point where it will let in too much air fro outside the carby...

At home with the car stationary and engine cold, i tried accelerating the engine again with the oil bath air cleaner off, i tried accelerating again and again it sounds like a MASSIVE flat spot and the occasional back fire from the exhaust and sometimes vapour from out of the carby too! When the engine warms up more, the symptoms subside a bit. and when the revs rise, there is no coughing or spluttering either...

I'm lost...

bad jets?
sticky valve/s?
broken valve spring/s?


PLEASE HELP!


:cry

Vacuum advance tube come off??

Vacuum leak on carb or manifold base??

Butterfly plate stuck open??

Points rat sh!t??

Tried timing it with at timing light. Dizzy could be stuffed and not advancing??

All the vacuum gear seems to be in place - tube looks good and sealed, i moved the parts connected to the vacuum advance componant and it sonds like it would work - theres an audible rubber suction/diaphram noise and it rotates freely.

have cold static timed it to 7.5 degrees BTDC using the grrove on the dizzy body (cylinder one)

a modern strobe light tells me the i have timed it something stoopid like 30 degrees BTDC!

Points are fine, gapped properly (last time i checked anyways) and not pitted
The manifold base looks to be sealed and gasketed fine...

anymore ideas?


:cry:cry

With the engine OFF and looking down the throat of the carb is the spray bar thing in the carb?

Is fuel coming out evenly with the accelerator pump action?

Idle jet blocked???

I haven't realy seen a properly functioning carby, but i don know that the fuel is supposed to spray out of the spray bar thing pretty smoothly yeh? It seems that it is bubbling a bit out of mine... I've got a 28 PIC carb so the spray bar is vertical coz on later models it's horizontal innit?

I'd be checking for manifold freezing, probably from a slighlty blocked heat riser and the lower temps we are getting down here at the moment.

Have a look at the manifold straight below the carbie, with the motor running. If there is a lot of frost on the pipe, then freezing is causing the flat spot. This is usually warmed by exhaust gas passing thru the small pipe attached to the bottom of the manifold. If this is blocked the warm exhaust cannot get thru to warm the manifold. Probably be ok whenthis cold snap passes.
Or you can get an electric manifold heater from Aussie Vee Dub Performance center in Croydon. It just wire that wraps around the manifold. Connected to the coil wire for power. You can get them in 6 or 12 v
I have one on my Oval, works a treat.

hey grey..

possibly...

but it tried it just before...as in 10 mins ago and there ain't no frost around!

:o

:thumb

Run it at a fast idle for a while and see what happens. Icing will be on the bend below where the carbie attaches. Will only ice when the air velocity increases as you open the throttle. (give it the gas)
If you are unsure touch the tube and i its really , really cold then this could be the problem.

Only other prob that causes this is a stuffed or blocked accelorator pump valve. A carbie overhaul kit will fix this. You will have to strip down and clean out the carbie to fit the new valve.
Pretty simple stuff. Most kits have a full exploded diagram included. So it shows what goes were.

Tofu

when you look down the carb and actuate the throttle cable there should be a nice stream of fuel coming out with that action.

If not that is your problem. Could be
fuel pump
blocked accelerator jet
blocked needle and seat
fuel filter.


You could take off the carb top and see if the bowl is full

Warming up now...


When giving it some gas, the fuel should
be delivered in a fine spray shouldn't it?

just stalled it....

When i took off the choke and gave it some gas (stationary), it started to flat spot and then die and then it died...

The manifold just below the carb was still cold though i doubt 10 mins of idling would warm it up sufficiently...

Cant get it started again either... prolly flooded it... weeeeeeeee

Check mech advance by twiddling the rotor back & forth & you should see & hear the centrifugal weights moving around. Check the vac advance by starting up, disconnect the vac line at the dist and ( you may need a bit of flex pipe for this) try revving the motor & sucking with your mouth on the the pipe you removed from the dist. If it improves, bingo! If not look for something else.
Or if you can get hold of a strobe timing light , you can followwhat's happening to your timimg directly.

The 28 PCI carb accel pump has no nozzle. The fuel sort of gurgles up from memory over to one side just above the venturi- ie it happens before the throat gets narrow. If you work the accel pump by pulling the the pump lever directly forward with your finger, you should be able to get a good squirt of fuel.

It would be a good idea to remove thge main jet (14mm brass nut) & clean it also.

might have to strip the carby and fuel pump this weekend by the sounds of it....


:vader

Is this anything to do with it?

http://www.lowbugget.com/adjust_accelerator_pump.html 

You don't need frosty air to get manifold icing - it still happens in 40-degree summer! The pressure in the intake manifolds is very low (which is what sucks the air and fuel through the carb), and consequently condensation/icing will happen even at hot outside air temperatures. A proper heat riser is essential to prevent it. Many non-stock exhausts (extractors) don't have a connection to the heat riser or have a poorly designed connection, resulting in icing. At least that's what Bob Hoover says!

It is true

Just have a look at the take off points on a stock exhaust
One is near where #2 exhaust leaves the head - high pressure
The other on #4 side is extended and goes inside the muffler itself near the "collector" - low pressure

This gives and exhaust flow from right to left.

Almost ALL ( never seen otherwise but i know aircooled.net will modify one) headers just have 2 ports at the high point AND they are usually blocked.

AT BEST the gas will pulse back and forth.
VW actually thought about things when they designed this bit

I touched it the other day when i was trying to warm it up.. it was idling for only about 10-15 mins and the manifold heater tube feeding from #2 was warm enough to touch but the manifold was stone cold... i doubt idling it for only 10 mins would warm it up sufficiently, but next time i get the bugger (no pun intended) running, i'll check it out.. the whole manifold is new looking with all its paint on it... its not rusty or &^%$# up like some others i have seen....

Well... i'll see if i got time this weekend to take apart the carb and check the jetting, the mixture screw and fuel float chamber... i hope its the carby and not a sticking/ cylinder valve or broken valve spring..... eeeech!


wish me luck!

And keep those suggestions coming... coz no one has suggested anything valves... does that mean i'm totally off the mark?


:cry

Greetings fellow insomniacs!

Tofu my old son, it pains me to see you in difficulties but it's agonising to see you rip into something without confirming the problem!
If you think it's valves etc can you do a compression test? If you have no guage, do a "poor man's comp test"-rip the plugs out & crank the motor & listen. It will spin fast (no compression because ther's a hole where the plug should be). Put back No. one plug & crank. Listen to the noise. Remove No. 1 plug & put in No.2 & crank & listen to the noise. It should slow down & you will hear the cyl compressing each time you replace a plug. If you put a plug in & crank it sounds like "no plugs" then you have a crook pot & you need to investigate. This procedure is pretty rough but it will tell you if you have a major problem eg broken rings/piston or leaky valves. You can do a similar test by getting it running & disconnect or short out each plug in turn. If you disconnect a good cyl, the eng will run rougher & slow down. If you disconnect a bad one, ther will be no change to the eng speed.

You want to test the heat riser? Fine! Borrow a hair dryer & play it on the manifold at full bore till the manifold is really warm. Or you could set up one of those dinky fan heaters on it & walk away for a while. I think it was Ettore Bugatti who when a Swiss gent complained bitterly his cars were a bitch to start in cold climes: "Monsieur should extend his central heating to his garage, n'est pas???". Now try the eng. If the prob is still there, look for something else.

Accel pump adjustment? The 28 PCI has none- it's fixed unless you want to play "cut & shut" with an oxy welder & lengthen the linkage. But you can improvise a test here too. Can you get some fuel in a squirty bottle like a small oil can? Then try to run the motor with no air cleaner & see if squirting in a small amt (5ml- 1 teaspoon) of fuel helps. If it doesn't, leave the pump alone & look for something else.
I'll pass on a saying an old German VW mech told when I was just a lad. "If it misfires sitting still it's probably a fuel problem. If it misfires under load (eg straining up a long hill) it's ALWAYS an electrical problem".

It's great that you guys all offered genuine remedies, but sorry you're all wrong you need to try the naturapathic remedy.

Farting and Coughing- try charcoal tablets and fishermans friend lozenges.....




sorry:alien

Thanks everyone for thier advice.... I'l let you know what's wrong with it soon.... i hope! Wish me luck!

Still can't start the engine....
I've tested the spark from the coil by hooking one of the leads onto a spark plug and grounding the cathode on the engine tinware... but i dont know how big the spark is supposed to be... it seems to be sparking ok though with a yellowish spark. I changed the dizzy cap and the rotor button; the plugs are gapped to .026" and the points are good and gapped to .016"... I'm getting fuel into the craby fine too...


Anyone know anything?:cry