Small carb'? problem.

D

DazUK

Cheers Daz
Hello gents ... not posted for a while as I havn't had any running issues for a while, but now I do!

I have a very annoying 'hesitancy' from my carb' (34DATR) which some opinions would be welcome. It idles fine and pulls really well, but, inbetween idling and full gas it bogs down for a second or two untill it picks up and away. Not a problem really if you 'toy' with the gas and drag the clutch some at junctions etc, but its just started to do this..:sigh:

Lines are new rubber, all in line filters look clean and all jets were removed and blown out. Made no difference.
 
sounds like the accelerator pump on the carby has given up, its a little pump to give the engine a boost/squirt of fuel when you put your foot on the throttle.
It could just be the inlet to this pump is blocked, but in my experience you normally have to replace the rubber parts in the pump.
 
I think all the answers are correct but...

Daz, take a look at the mating surface between the top of the carb body and the float/chamber bowl. As this old metal gets tired and the heat of the X engine bay is sever, the top of the bowl cover warps. This causes 'A' a vacuum leak, 'B' the appearance that the accelerator pump is lacking the correct amount of flow. To check warm up the car and look at the seam when the engine is running and has been warmed up and stopped. You will see fuel dribbling from the seam when stopped. If this is the case a new cab top or some careful filing or machining will be required to correct the problem. A fuel proof sealer may also help, but I have found the enviroment harsh for sealers to last very long.

TonyK.

Grimsby Ontario Canada.
 
Hey Daz... long time no see...

Sorry for your trouble...

If the carb checks out OK... consider this...

Just what kind of dizzy advance do you have?

If a combo vacuum/centrifical... the problem may lie in the advance also. Technically, the dizzy effectively retards (vacuum-wise) when you mash the throttle for an instant... so the engine can catch up to the timing...
 
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Vacuum leaks may have been possible a few weeks ago, but both the inlet/bakelite and bakelite/carb gaskets were replace with original Weber 1mm card replacements. Before this there was no gasket between bakelite shield and the carb'!:hmm2:

Also all the nuts and bolts were firmly nipped up and spark plugs replaced with NGK Iridium jobbies and the washable air filter cleaned and re-oiled. The car really flew after this and was nudging 100mph (which feels VERY fast in this car lol) with no issues ie pinking and blackish smoke as before.

The pumps filters and other bits were all changed in the carb' when it was stripped cleaned and rebuilt two years ago, but did notice there is some damage (Scuffs and small burrs) to one of the jets whilst cleaning, maybe its not sitting square?
Its a centrifugal type dizzy, which looks to be working fine. Just checked the plugs and there are still slightly sooty.

Also, damn thing takes two or three attempts at starting in the morning now, starts ok, but just dies on first and second sometimes third try. Will replace plugs back to standard as a trial, but can't see it being this to be fair .. will just retrace my steps.
 
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Still sounds like the carb.

Years ago I did the very same thing. Rebuilt my 36 DCNF Weber and the car ran great. Then a few weeks later I noticed it was hard to start and had a flat spot. What had happened was that the new top gasket had now compressed and a fuel leak started at the top of the carb. Since there was a leak the fuel in the carb evaporates over night and hard starting was occuring.

Still sounds like a carb problem to me.

TonyK.

Grimsby Ontario Canada.
 
Welp... ya sure had yur hands on...

... a lot of things that could have led up to this problem!

As TK says... and without a vacuum advance... it puts the focus firmly back on the carb. Either a vacuum leak or accelerator pump. Time to pull it apart again... and see what ya can see.

OH... one last thing... make sure the centrifical springs are firmly attached so that you are not advancing too quick. One coming off could be a possibility and theoretically simulate your problem.
 
I have the 34DATR and my acc pump diaphragm was torn when I had this exact symptom (hesitates on acceleration). Check if the pump is wet on the outside.
 
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