just can't cure it

[dandaz]

fuel pumps do not make your bus hesistate,the pump fills a chamber and that chamber slowly releases to drive your bus ,if the fuel pump was faulty the bus would break down at 50-60...

it`s more likely to be carbe icing [although the warmess of your engine bay would say no]or your ignition timming is not right , are you running a 009 dizzy?

 

[froggy]

Have you had the carb apart recently, remember (vaguely) that you can get issues with the float sticking (or not reset correctly after a re-build) and the hesitation can be caused by not enough fuel being pumped to the carb (either the pump or the carb float)
Worth stripping the carb down and getting a re-furb kit and for the sake of a tenner i would try a new pump (i might even have 1 knocking around you could try) before paying your hard earned out to some mechanic that you dont really know

Hiya Froggy, thanks for the offer and didn't realize your so close to me.

Moved down here Mid july to be closer to the wifes family in West horsley.
Hope you bottom out the problem, it would be nice to hear whats causing / caused it in the 1st place

 

[streetboy]

fuel pumps do not make your bus hesistate,the pump fills a chamber and that chamber slowly releases to drive your bus ,if the fuel pump was faulty the bus would break down at 50-60...

it`s more likely to be carbe icing [although the warmess of your engine bay would say no]or your ignition timming is not right , are you running a 009 dizzy?

Youre right I'm afraid changed pump, fuel lines etc and still no dice :?
As I said I have lost my way somewhat and need a fresh head and eyes on it.
Di have 009 but now has an SVDA. Maybe it is not working as it should, I don't know.

 

[streetboy]

You know someone else might take a look and twig it straight away, I've spent too much time and my brains cooked :lol:
But rest assured there is a reason for it and eventually It will surface.

 

[streetboy]

Update. Took it to the vw guy and even he is scratching his head :lol:

But to be fair he needs a day of tinkering in between other jobs to see if he can nail it.Gonna leave it with him Monday.

 

[cyberdyne systems]

I had an identical problem, it turned out to be a vacuum leak. Let me explain some more, I have a servo connected to my manifold as its a US '71, there was a slight split in the tube. The only symtoms were setting the mixture (and the slight hesitation mainly when under load/going up hill), it was only smooth when i took it out quite a bit more than the 2.5 turns recommended.

So have you had to take your settings out of the normal range to set the carb up? Regardless it may be worth changing the gaskets on the manifold, even if it doesn't appear to be leaking.

The best way to check the vacuum on the distributor other than sucking on it to see if it moves, is to use a good timing light, you should be able to see when the throttle is blipped the advance climb and then fall in a different way to when you have it plugged and just observe the centrifugal advance alone. Above 3000 revs it should pull more than the 30 degrees when the vacuum is connected.

I have also had minor blocking of the idle (pilot) jet, causing a poor transition between idle and full revs, might be worth blowing this through (if there has been dirt in the fuel it may have affected both carbs you tried).

If it were fuel starvation I wouldn't expect to be able to rev through the hesitation.

 

[Slammed]

But if it was happening with the 009 it can't be vacuum leak as they have a mechanical advance - unless one of the vacuum outlets wasn't blocked.

 

[cyberdyne systems]

But if it was happening with the 009 it can't be vacuum leak as they have a mechanical advance - unless one of the vacuum outlets wasn't blocked.

No i meant the manifold had a vacuum leak not the distributor, i was just saying how to check the vacuum distributor to make sure its working correctly - not that it was the cause of the problem

 

[streetboy]

I have also had minor blocking of the idle (pilot) jet, causing a poor transition between idle and full revs, might be worth blowing this through (if there has been dirt in the fuel it may have affected both carbs you tried).

If it were fuel starvation I wouldn't expect to be able to rev through the hesitation.

Hi Cyber. Ok I don't want to get carried away but I may be on the road to sorting this. I was trolling through the bay window forums on the Samba in the early hours of this morning, under 'hesitation'
I read a post with regards to a chap who had problems with his idle jet, not blocked but done up too tight believe it or not :shock: I don't recall everything about the post but do remember he recommended undoing the idle screw when running and finding a sweet spot. Yeah it sounded odd to me too :? then once found drop some lock tite on to set it.

I forgot this until leaving work this morning and though Id give it a go, jesus I've tried everything else :roll: So once warmed up I cracked the idle jet and wound it out about three turns. Started it up and it immediatley died. I wound it in a little and started again, this time in kept running, albiet a little rough, until I very lightly knipped it (barely)to the body of the carb. It idled fine again. I set off thinking it was not going to make a blind bit of difference, but the Rythmic hesitation was gone! :shock: I say gone, and I may be looking for things that are not there, but hardly noticable if at all.
He also said that the carb would need setting again so maybe (and Cyber it did run better richened up) need to weaken it off again.
As I said I am not calling it cured at the mo and will see what happens when I readjust the carb. There is no way I would ever had twigged that the idle jet could be done up too tight.

What I want to know is if this does infact cure the problem then what is going on in the idle circuit? The idle jet is that which came with the new carb, and is no longer/shrter than a genuine solex jet.

So fingers crossed I might have some good news later

 

[cyberdyne systems]

I have read about this myself, never made a difference on mine but then they recon its cause the jet was over tightened into the body. Not totally sure I agree with the idea, in my mind by opening it you are letting fuel bypass the jet slightly - whether thats possible or not i don't know. Anyhow its worth a go just to eliminate it

 

[streetboy]

Agree with it or not it would seem to have done the trick. I readjusted the carb gave it a spin, a bit of tinkering on route and got it running 99.9% right I'd say the 0.1% is most like in my head. :lol: The jet is literally just squeezed onto the body as opposed to me having given it a firm twist. I've loctited it now and can but see what happens over the next few days.

 

[streetboy]

Agree with it or not it would seem to have done the trick.

Cyber, just read this back and its not what it might seem. I too am not sure it is the right way to do it, but it appears to have worked.

 

[cyberdyne systems]

Well if it works that great news, enjoy hesitation free motoring!

 

[streetboy]

well lets see after a week

oooh, and I can perhaps get some twin carbs now

 

[streetboy]

I let the engine cool right down and while doing that I cleaned up my new vaccum oil bath filter. Fitted it , just advanced the timing a nats to the full 32, and took it out for another longish run. All seems well so far and it is running the best it has since I put the engine in back in April

 

[streetboy]

Just back from a trip to the new forest and the bus went well. Still now and again felt a little fluttery under load but much more bearable As far as cruising was concerned she sat at 65-70mph no trouble
Hopefully twin carbs beckon, and hopefully that will put an end to it once and for all.

 

[BJ1]

Just out of curiosity - would your carb be a Bocar by chance?
This all sounds very familiar - Bocar carbs have an inbuilt idle jet problem exactly as you describe.

 

[streetboy]

Hi BJ1, its not a Boscar but not a solex either. Brought off the net new.

 

[BJ1]

Hi BJ1, its not a Boscar but not a solex either. Brought off the net new.

Hmmm - that sounds a bit dubious :lol: Does it have a makers name or just the magic word "Taiwan" on the side?
Seriously - there are no repro "Solex" carbs worth buying, except the excellent Brosol H30/31, but they only fit sp manifolds.
Try getting a decent OG Solex - you will get rid of hesitation and idle problems and have more torque available. I conducted a little experiment a few years ago. 71 Westy plus Bocar - 30mph max up the hill out of the village. Same van plus OG good Solex - 41mph up the same hill. Nuff said?