Carburetor Vacuum Leak

theartur2000

theartur2000

Daily Driver
My car would not idle at all on the idle circuit, its RPM drops until it dies. Spraying carb cleaner at the base of the carb, near the throttle shaft, makes the RPM go up. I think there might be a leak there. I'm just not sure where exactly it might be, are there common leak spots? The carburetor is a Weber 32 DATRA. Thanks!
 
The gaskets are new, I replaced them a while ago and just checked them again yesterday, they're fine. The problem was still there even with the old gaskets.
 
Check the base of the carb with a straight edge to see if it is warped. Also check for play at the throttle shaft as it passes through body, these can wear.
 
I'd add to the statement above, and advise to check all mounting bases ie. Carb, phenolic (if using one) and, intake manifold.
 
A vacuum leak will cause a too high idle, not a dead idle. If the carb has an idle jet solenoid, make sure it's getting 12v and also remove it and make sure the idle jet is not plugged with crud.
 
Your symptom suggests what the problem is, spraying onto the throttle shaft raises the idle. The bushings on the throttle shaft could well be worn allowing unmetered air in along the shaft.

A master rebuild kit should include those bushings.

I would pursue other avenues first but the shaft bushings may well be the culprit.
 
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So, while trying to disassemble the throttle shaft, I snapped one of the bolts which gave me an idea. I had this second carb that came with the car as a spare part when I bought it, and I've been pulling parts from it onto the other. I never tried testing it but I put it on and it works like a charm! It's a DMTRA and I have no way of controlling the choke from inside the car, but still, the car runs! I probably should have done that from the beginning.

The shaft was very loose on the DATRA and I'm pretty sure that was the problem. The DMTRA's shaft was firm and works great.

But thanks for the help anyways, guys!

My next project is figuring out how to move around those coolant hoses from the water choke from the last carb.

Side note: What does the number on the stamping of the carb mean? One of them was 32 DATRA 100 and the other was 32 DMTRA 200, I am referring to the 100 and 200.
 
theartur2000 said:
Side note: What does the number on the stamping of the carb mean? One of them was 32 DATRA 100 and the other was 32 DMTRA 200, I am referring to the 100 and 200.
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The 32 is the diameter of the carb barrel in millimeters. The 100 and 200 are model numbers, with no particular significance except that a 100 will be slightly different (maybe a different configuration of vacuum ports, something like that) from a 200.

All X1/9 32 DMTR and DMTRA carbs are interchangeable, as are the 32 DAT, DATRA, and DATR carbs.
 
Ah, ok. That makes sense. Is it fine to just plug the coolant hoses that used to go the water choke with a screw? Or is there a more sophisticated way to go about it?
 
The sophisticated way is to modify the parts by removing the hose nipples and structurally plugging the holes. The easy way is a short piece of hose with a bolt shank as a plug and the fast and easy way is a length of hose that goes from one nipple to the other.

If it's a mechanical choke you can get one of those "HELP" brand universal choke cables and run it into the cabin through the pass-through all the wires go through. I made an L-bracket and mounted the knob near the handbrake.
 
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A water choke does have the same barrel diameter as the electric choke assembly so it should be an easy upgrade.
 
Alright I'll look into the electric choke upgrade as well as the universal choke cable.
What might be some advantages and disadvantages of both?
 
Electric = automatic action, no thought or effort required to operate.
Manual = you must activate and deactivate it according to the engine's needs, easier to forget and leave it on.
 
any new info? I had the usual problems with mine, stalling/bucking after warm up, idle mixture screw had no effect, rough idle, black smoke, hesitation etc but was ok in higher revs. the carb had warped between the top and bottom parts of the carb mating surface (remove the gasket and put the carburetor together and check the clearance) and wasn't sealing the gasket which caused a vaccum leak and raw fuel to be sucked in at idle when theres higher vaccum, I had to sand the bottom half flat using a glass plate however the top part of the carb is difficult as there are things in the way, you can remove the auto choke with three screws behind the fast idle cam whick makes it slightly easier. I used a long strip of glass about an inch wide with sand paper tightly wrapped around it and a lot of trial and error got it flat enough and now it runs fine. If u need info from workshop manuals email me i can send u the downloaded copy as they have the specific setup for the carbs
 
My carburetor runs fine now, because I switched over to a different one all together. My old carburetor loved to spit flames out of the exhaust so I'm trying to figure out how I can do that with this new one, even though that's the opposite of a problem.
 
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