I got tired of poor cold running over winter and the old 34PICT-3 on Olive had miles of throttle-shaft play and she idled erratically. Also the needle and seat had given up and she sometimes flooded.

So I decided to give Olive a treat and bought one of those chinese knock-off carbies on ebay for less than $150 delivered to my door.

The carby fitted okay. There was an extra vacuum port, which I capped off, otherwise everything looked good.

Olive now starts every time, idles nicely, never cuts out. So far so good except...

I have a massive hesitation when I floor the throttle. If I rev it a couple of times and keep my foot down then run through the gears accelerating hard, she is brisk, perhaps the best she has ever run. But if I'm cruising along for a few seconds and then put my foot down in any gear, then this hesitation occurs. Same if I slow for a roundabout or a corner.

When the hesitation occurs I also hear a backfire "pop". Not sure if it's through the exhaust or carb. No signs of black smoke behind me. This happens if I try half-throttle or full throttle.

I have not changed any other parts or adjustments at all, not timing, valve adjustments etc. I checked and reset all that two months ago.

My thoughts are:

- Accelerator pump not working properly in new carb.

- Old carb was flooding, perhaps fuel pump supplying too much pressure (stock pump). I did replace the gaskets on the pump a few months ago. But, if the pressure was too much, wouldn't it run rich at idle and smoke black fumes?

- Differing jets between old and new carbs?

Any advice appreciated.

Thanks,

First thought - accelerator pump not deliving enough of a shot of fuel... most likely just needs adjusting.

Second thought - what dizzy are you running... the stock one with vacuum advance or something else ??? Could be a case of the now infamous "009 flatspot"....

Since you say it runs nicely everywhere else I don't think it'll be jetting or flooding.

Hi,

The dizzy is a 1yo SVDA with electronic ignition, not a 009. I'm hoping it's as simple as adjusting the accelerator pump.

Cheers,

I adjusted the accelerator pump today (so it pumped earlier) and the problem got worse.

I did find that fuel was literally dripping off the rear carby stud at idle. So it does seem likely it's too much fuel pressure. There also seems to be fuel oozing out ofg the fuel pump top cover.

Maybe fuel is pooling on the throttle disc and dumping in when the throttle is floored, making it flood.

Cheers,

Today I removed the fuel pump and put another gasket on it to reduce the pressure. This made no difference to the new carb's performance. In sheer desperation I refitted the old carb and it's now running fine.

So now I suppose I'm going through the whole return or replace circus. I've already sent the seller a message via eBay.

Cheers,

maybe blow the air through the fuel inlet on the carby
could just be a grain of dirt making needle not seated properly

Check for an air leak at either the manifolds to heads or the rubber bellows , as if leaking at any point between the carby and the head you will have this problem .

There are no air leaks, I've checked the bellows and all vacuum lines and sparyed WD40 around the carb base.

I've bought a new carburettor to bolt on and go, not mess around with fault finding and rebuilding it. As soon as I remove the top cover the warranty would be void anyway. Besides, if I'm going to go to that hassle I might as well rebush and rebuild my old Solex. Apart from idle and cold starting it runs better with that fitted than this new POS.

I'm returning the carb to the seller for a refund. I'll either rebuild my Solex or source a similar carburettor locally.

Cheers,

I went through the same saga with my L, eventually rebuilt a good solex out of three old ones using the least worn body and it's not perfect but heaps better than the new clone which now sits shiny and forlornly in it's box. Have found Rob and Daves tech site a great help in tuning the sucker

Just compare the main jet size on the new carb to the old one and even try swapping the main jets.

I fitted one of those brosal/bocar repoop carbs to a mates S bug a few years back and the new one had a killer flat spot hoofing it about 1500-2000rpm,
I had to open up the main jet abit, new one was a bit lean out of the box but this engine did have extractors though.
Good as gold after that.

Joel, your description does sound similar to what I experienced with this carb. But everything on my engine is stock as far as I know, except the dizzy.

The seller is yet to give me an address to return the carb, so I might end up neg-repping him and keeping it.

give stan a call , i think he knows a few tricks about those carbys
http://www.stanpobjoy.com.au/#!contact 

OK, so the seller isn't a bad egg after all. Refunded me the cost of the carb, so I'm only down for the shipping cost and I have a shiny new paperweight.

I'll try swapping the main jet across fromthe old carb to the new and see if that works.

I'd feel guilty ringing Stan Pobjoy and asking him, since I didn't buy the carb off him.

I decided I had some spare time to have a look at this carby again today.

I pulled the old worn carb off and swapped all the jets across to the new Chinese carb. I put the new carb on the car and it started and idled without difficulty. But, if you depressed the throttle rapidly (ie: stomped on it) the engine would backfire through the carb or even stall. Same problem as before.

I took the top off the float bowl on the new carb looking for answers. It was then that I nociced that the accelerator pump discharge tube was slightly flattened or crimped on one of the bends. Working the accelerator pump I realised that the crimp was reducing the flow through the tube. This was resulting in the lean-out problem when the throttle was rapidly depressed.

I tried the obvious solution and swapped in the accelerator pump discharge tube from the old carb. It seemed to fit okay. I did notice the bends were a different shape but thought nothing of it.

I bolted it all back together and the lean-out problem seemed to be cured. You could floor it from idle and it would not backfire or stall.

So I drove her up the street. In first gear she felt good. I changed into second and she cut out! I couldn't get her restarted so I pushed her the 50m or so back home.

I pulled the air cleaner off and I could see the problem straight away. The accelerator pump discharge tube had come out and disappeared down the intake. The float bowl cover was a different shape on the new carb and it did not retain the old discharge tube in place. Viola, one ingested discharge tube.

I raced up to super-crap-auto and bought a boroscope so I could try and find the missing discharge tube. Alas, I could not see it anywhere in the intake manifold. I can only hope it has lodged behind an intake valve or something rather than gone into a bore. Now I have the fun task of removing the intake manifold and seeing what I can find.

Then once that is sorted I have to buy a new carb. I'm sure the old discharge tube is going to be damaged beyond reuse and the new discharge tube is obviously faulty. Maybe time for twin carbs???

Olive is now parked and I have taken my MR2 off the sub-bench.

ahhh the joys of Chinese carbs

Either get a 34 Pict rebuilt or go weber/dells

My bet is the discharge tube has gone through the engine like pork through a goose.
I doubt any damage has been done.

I hope so Phil.

It may be a fruitless search but I'd like to know it's either gone safely into the exhaust or extract it. But I admit the though of bunging another carb on and seeing what happens has occurred to me.

I had an air cleaner stud from the top of a DGV weber escape into a Gemini engine once. I ended up taking off the intake manfold at the side of Cowpasture Rd in Sydney. Quite a miserable experience. Fortunately it lodged behind an inlet valve and did not damage anything.

I've ordered a reconditioned GERMAN 34 PICT 3 from an American guy on The Samba.

Question: Can I remove the centre part of the intake manfold without removing the end pieces on a dual port 1600? Or is it easier to simply remove and replace the end pieces one by one? Either way I'll fit new rubbers and gaskets to anything I disturb.

Cheers,

well, hopefully, it may have caught on the rubber boot...

I presume You can take the middle bit out OK.. ????
but have never done one...

Maybe slide one way then the other???

One problem You may have...

If You find the accelerator pump nozzle sitting over a valve

You cannot get it out with a Magnet... as they are brass or copper... so they are soft when scrunched with a valve... lol

Best of luck...

LEE

Not all of these new carbies are bad. Some are better than others.
I guess the old saw "you get what you pay for" can be applied.
As for getting the manifold centre out, forget it if you have an alternator. Easier to drop the engine out.
If you have a generator, I'm not sure.

easier if you take the fan shroud off with the alternator

Still a prick of a job

Should take no more than half an hour to remove the inlet manifold with the engine still in. I had to do it about 2 weeks ago. It can be a pain to some but if you don't have engine removal tools it's the only way. I got to it by removing the decklid (for easier access and removal of parts), removing the fan shroud, and removing/loosening the manifold ends. You may even be able to have a look inside the head ports once you remove these parts, if the nozzle is not found.

My carb arrived from the US on Thursday and I fitted it this afternoon.



Mmmm, pretty.

I looked inside each of the bores with the camera and I couldn't find where the nozzle went. So I guess it's in the exhaust now.

The accelerator pump linkage must be different on US cars, or one not equipped with an alternator. The one on the reco carb fouled on the alternator casing. Swapping the linkage parts from my old carb fixed that. There was also three extra vacuum ports to block off. (only two blocked in the photo.)

She starts and idles beautifully now and seemed to have more grunt in my short test drive. We will see how she goes when used for commuting this week.

Cheers,