Stumbling type 1 , 1641

[bac2ba6]

After various things ive sorted and renewed on the bus im still getting more of an annoying problem than a serious problem .

When accelerating either pulling away or lower down the rev range im getting a bit of a lag on the power almost like the dredded 009 flat spot untill you reach the higher rev range 2300rpm ish onwards its fine . also does seem to struggle a bit to get above 50mph unless its slightly down hill ?

new things fitted

Fully refurbished solex 34pict3 carb " professionally done " and to be fair it did look gleaming out of the box like a completely new carb .

new leads
new plugs nkg gapped correctly
new svda accuspark elecy dizzy
new accuspark coil
new fuel pump and push rod
new accelerator cable

i have recently had the engine out to check all the head bolts which were fine and the manifold to head gaskets were renewed and tightend up correctly , manifold boots are new ish ( silicone ) with proper clamps also lightly sealed with blue holimer , plus have tested for any leaks and everything seems fine .

did check the valves gaps for a second time a couple of weeks ago but going to check again tomorrow evening . carb as far as i can tell is set more or less correctly have adjusted the accelerator pump a bit which seemed to slightly improve things . ( was set in the middle when i received the carb ) would setting it less make any difference ?? as have read you only really need to adjust to the + side if you running a 009 ? .
( was doing this problem on the old carb aswell )

timing is pretty much spot on using a strobe , been makeing tiny adjustments to both carb and timing to try and sort it out .

it ticks over lovely , doesn't stall and will rev nicely all be it a very very tiny hesitation on low throttle .

but once under load that hesitation is more apparent 4th gear is a wast of time unless you scream it in 3rd before hand and then does struggle to get above 50mph although it does given enough rd but definatly not above 60 ? accelerator cable is opening the throttle pretty much all the way all be it about 5mm of travel

if your still awake after reading that lot then fair play :lol:

any other suggestions i haven't checked or may have missed if you please

 

[lard]

Hi,

Just to mention re your problem - you say it was doing this on the old carb, was it running fine at one point then?

The one that caught me out (replacing bits e.t.c.) was an air leak on the servo side...the pipe wasn't sealing correctly and when I braked, the action would just dislodge the pipe to let air in and would stall when I came to a stop (idled fine!) - so I'm keen to share my pain with anyone having issues on a 71 servo fitted bus, and to say check the servo/pipe doesn't have a leak - just by blocking off the servo connection on the manifold and see if the problem goes away (or it idles differently when the servo pipe is disconnected and plugged)

 

[bac2ba6]

Hi,

Just to mention re your problem - you say it was doing this on the old carb, was it running fine at one point then?

The one that caught me out (replacing bits e.t.c.) was an air leak on the servo side...the pipe wasn't sealing correctly and when I braked, the action would just dislodge the pipe to let air in and would stall when I came to a stop (idled fine!) - so I'm keen to share my pain with anyone having issues on a 71 servo fitted bus, and to say check the servo/pipe doesn't have a leak - just by blocking off the servo connection on the manifold and see if the problem goes away (or it idles differently when the servo pipe is disconnected and plugged)

Sorry meant to say non servo bus . TBH its been a bit of an on going problem although it is drivable its driving me mad as you have to plan everytime you go to pull away from a junction as theres a big dead area on the lower rev range

 

[K@rlos]

Is the acclerator pump set right? Might not be giving a strong enough shot of fuel.

 

[bac2ba6]

Have played around with the pump, adjusting it towards the + side , its now on max but no different

 

[jonboylaw]

Is this a TP engine? Sounds like it is.

It can only be two things, sparks or fuel.

For sparks, have you always run the same dizzy ? If so, can you borrow a known good dizzy. This will eliminate a knackered/sticking base plate, or springs.
Coil sounds fine, as do leads etc.

Fuel,
Have you got an alternator fitted? Is the acc pump lever rubbing / catching in the alternator body? Check for rubbing.

Can you take the carb off and check the acc pump is actually delivering the extra fuel ? Fill the bowl and then pull the throttle arm to simulate acceleration, have a small beaker ready under the carb to catch the fuel. If it is not pumping the right volume then could be a split or badly fitted diaphragm.

You can set the acc pump as per the Bentley manual.

Could you possibly borrow a good carb to test out ?

If the carb is ok then check for air leaks, especially on the manifold to head. If the engine is out you could try swapping the gaskets, but this time, if using the metal ones, try running a thin bead of silicon around the sealing joint and leaving to dry before fitting (do both side of the gasket).





Sent from my GX64 SatCom phone using Tapatalk

 

[Trikky2]

A couple of things.

Just because the carb is gleaming on the outside doesent mean it has no dirt or swarf inside.

Remove and check the idle jet. Its accesible from the outside of the carb on the right hand side - no need to remove or dismantle the carb.

The drilling is very small and is fed from low down in the carb so it will pick up stuff from the bottom of the float chamber. Check its clear using a strong light shining through the microscopic drilling, just looking at the outside wont do.

If the idle jet was ok then the next thing to do is is to set the tickover mixture. If not set correctly it will cause these symptoms.

First check that, with the choke off, the throttle stop screw touches the lowest segment of the stepped cam. It should rest on it without holding the throttle butterfly open. It is literally a throttle stop screw and should never be used to adjust tickover.

The two screws on the left of the carb - the big one does air and the small one below it does fuel. Anti clockwise is more, clockwise is less.

With the engine warmed up adjust the small (fuel) screw either way to get the fastest smooth tickover you can.

If the engine idle speed is now too high then slow it down by screwing the big (air) screw inwards (clockwise).

If you needed to slow the engine down with the big screw then just re check the small screw for max idle speed again.

If your idle speed did significantly go up when you adjusted the small fuel screw then you may find your flat spot has gone.

 

[matt-me]

We had this on a 78 type 1 ex fuel injected beetle. I don't know how accuspark dizzy's are selected, but we found someone had put in the totally wrong code vw/bosch points dizzy, for a type 4 engine, not a type 1. When we changed for the correct model dizzy and timed it up correctly there was an instant 80% improvement.

Then we basically carried out all the cleaning and set up ot the carb as tricky has set out above. It is explained in a little more detail here http://www.vw-resource.com/34pict3.html" onclick="window.open(this.href);return false; This got about 15% improvement. We didn't look at the accellorator pump but my mate has just done this, he thinks this is now 3% better. So nearly there, always room for improvement.

As i say i don't know if there are different accuspark dizzys for different engines, there loads of different VW/bosch ones. This made the biggest difference.

Good luck Al

 

[bac2ba6]

Thanks guys a few more things to have a look at