DCD Weber problem
- Thread starter rubyalpine
- Start date
If fuel doesn't stop flowing when the float is up the needle valve is no good. You can run Col's experiment again, but this time don't use a container under the carby cover. Just hold the carby cover in your hand with the gravity fed reservoir attached and push the float with your hand up gently to see if the fuel flow stops at some point. Try it a few times.
If you don't mind, you can try another way. Take the needle seat out and with the needle in, try sucking on the fuel inlet. You should be able to create enough vacuum that your tongue will stick to it and the needle won't fall out.
If you don't mind, you can try another way. Take the needle seat out and with the needle in, try sucking on the fuel inlet. You should be able to create enough vacuum that your tongue will stick to it and the needle won't fall out.
That's the usual starting point in my experience!
I'm intrigued if you found the problem or resorted to the box of matches.
AFTER getting the insurance in order, of course.
Alex, I have ordered a "repair kit" from ebay (which includes a new needle and seat) and still waiting for it to arrive. After fitting the new kit, I will keep all informed of results. Still keeping the matches handy!
Henry
Henry
Just get the insurance right before striking the match!!! Oh, and be careful just to burn the carbie, not the car....
Repair kit eventually arrived. KIt in sealed package from Italy, with gaskets stamped "MADE IN ENGLAND" and sent to me from an ebay seller based in Chech Republic! but still half the cost of other ebay sites.
Anyway, installed new gaskets, washers and needle and seat, checked float level and finished assembling carb. While waiting for kit to arrive, I removed spark plugs, cleaned them and refitted .
Pressed starter button (in engine compartment) and engine fired up first shot. Revved it up to about 1500 rpm to warm engine and noticed fuel coming out of main jet!, Damm. It didn't take long for the plugs to foul up and after swithing off, would not restart.
Fuel should never come out of main jet at low rpm, with no load. So what now? I'm at my wits end.
Henry
Anyway, installed new gaskets, washers and needle and seat, checked float level and finished assembling carb. While waiting for kit to arrive, I removed spark plugs, cleaned them and refitted .
Pressed starter button (in engine compartment) and engine fired up first shot. Revved it up to about 1500 rpm to warm engine and noticed fuel coming out of main jet!, Damm. It didn't take long for the plugs to foul up and after swithing off, would not restart.
Fuel should never come out of main jet at low rpm, with no load. So what now? I'm at my wits end.
Henry
Ah Henry this is annoying.
You did check the float with the carb off like Col / Shultz suggested? ie. checking to see if the float moves freely on it's hinge, not getting caught anymore, or sticking in any range of it's movement?
And you are testing all this with choke / throttle disconnected, and choke and throttle blades are moving smoothly?
And you have tried with another carb haven't you?
You did check the float with the carb off like Col / Shultz suggested? ie. checking to see if the float moves freely on it's hinge, not getting caught anymore, or sticking in any range of it's movement?
And you are testing all this with choke / throttle disconnected, and choke and throttle blades are moving smoothly?
And you have tried with another carb haven't you?
Henry.
One of my old maxims when in the trade many years ago. Listen to the customer. When he has departed ignore everything he has said/tried. Then proceed in your own way !
You seem to have done everything to solve the problem. Different carbs ? Missing air bleed/emulsion tubes, the thingys with the holes.
Making no sense in regard to the above but...Your DCD model carb [I have one] doesn't have choke butterflies as we know them [Jim]
It has an enrichening device instead. Could we be looking at a problem with this ?
Anyone ?
One of my old maxims when in the trade many years ago. Listen to the customer. When he has departed ignore everything he has said/tried. Then proceed in your own way !
You seem to have done everything to solve the problem. Different carbs ? Missing air bleed/emulsion tubes, the thingys with the holes.
Making no sense in regard to the above but...Your DCD model carb [I have one] doesn't have choke butterflies as we know them [Jim]
It has an enrichening device instead. Could we be looking at a problem with this ?
Anyone ?
Bowie, yes to all of the above. I have tried 2 other carbs, all same result!
Wildebeest, I have checked the enrichment (choke) device on all 3 carbs, all working. The are not connected to main fuel system and are basically a separate carb. I have tried with and without choke. Still the same.
I have been "playing with these carbs since the late 60s and have never seen or heard of anything like this before.
Wildebeest, I have checked the enrichment (choke) device on all 3 carbs, all working. The are not connected to main fuel system and are basically a separate carb. I have tried with and without choke. Still the same.
I have been "playing with these carbs since the late 60s and have never seen or heard of anything like this before.
What about the mechanical pump spring? Sitting in the correct location, coming back once throttle is released?
Ah sorry, that no doubt is the enrichment device you referenced above.
Ah sorry, that no doubt is the enrichment device you referenced above.
Hi. How very frustrating this challenge is.
Firstly I am not familier with the engine, but do have some experience with DCOE Webers - a long time ago.
The photographs show that this is a very non complicated straight forward installation.
I agree with many of the prior suggestions by others.
Also is this only occurring on the primary barrel or on both primary and secondary barrels?
1,000 to 2,000 RPM is well above idle, and I would not rule out the main jet circuit being activated, even at no load. But the main jet circuit should not be flowing at idle. It seems from your comments that the main circuit is not flowing due to venturi action, but by a fuel chamber pressurisation effect.
Where does the fuel bowl vent to? Is this vent blocked?
Some other thoughts.
Is the ignition coil in good order?
Is the rotor button aligning with the terminals in the distributor cap when the points break (open)?
If I think of anything else I will post.
Cheers.
Firstly I am not familier with the engine, but do have some experience with DCOE Webers - a long time ago.
The photographs show that this is a very non complicated straight forward installation.
I agree with many of the prior suggestions by others.
So the key question here is: What has changed? Everything was running normally prior to the head work being performed. I know some of the following have been asked previously and some questions are a bit left field, but need to be asked anyway.
- Has there been a rag left in the ports or inlet manifold?
- Has something been reassembled in a different orientation?
- Do all the valves/rocker arms have the specificed clearances?
- Is valve timing correct?
- Is ignition timing correct?
- Has the Weber had anything changed from pre head work to post head work?
Also is this only occurring on the primary barrel or on both primary and secondary barrels?
1,000 to 2,000 RPM is well above idle, and I would not rule out the main jet circuit being activated, even at no load. But the main jet circuit should not be flowing at idle. It seems from your comments that the main circuit is not flowing due to venturi action, but by a fuel chamber pressurisation effect.
This is a key observation. Need to determine where the fuel is going to.
Where does the fuel bowl vent to? Is this vent blocked?
Some other thoughts.
Is the ignition coil in good order?
Is the rotor button aligning with the terminals in the distributor cap when the points break (open)?
If I think of anything else I will post.
Cheers.
One thing is for sure. It'll be very obvious in hindsight.....
One thing is for sure. It'll be very obvious in hindsight.....
Henry,
Looking over your original posts you've mentioned trying two or three other carbs. After changing over jets etc.
This appears to me that the other carbs have not been complete?
Have you got a complete known unit ie one that has come off a running engine. If so this may eliminate any doubt about the carburettor?
Fuel pressure =2 to 3 lbs/sq ". Float level ? OK. Been there, done that, got the T shirt !
Could there be any other items affecting the running, for instance...vacuum connections, crankcase breathing hose to the carb/air filter?
Bowie's fuel bowl vent [see above].
Whenever I've had to remove Weber idle jets for cleaning with advice on refitting the jet into its holder. Being a press fit it is advisable to not push the jet all the way in. This will allow the jet to seat itself correctly. If not the jet will allow excess fuel to enter the circuit.
Looking over your original posts you've mentioned trying two or three other carbs. After changing over jets etc.
This appears to me that the other carbs have not been complete?
Have you got a complete known unit ie one that has come off a running engine. If so this may eliminate any doubt about the carburettor?
Fuel pressure =2 to 3 lbs/sq ". Float level ? OK. Been there, done that, got the T shirt !
Could there be any other items affecting the running, for instance...vacuum connections, crankcase breathing hose to the carb/air filter?
Bowie's fuel bowl vent [see above].
Whenever I've had to remove Weber idle jets for cleaning with advice on refitting the jet into its holder. Being a press fit it is advisable to not push the jet all the way in. This will allow the jet to seat itself correctly. If not the jet will allow excess fuel to enter the circuit.
Yes, I have 3 complete carbs, but only one set of jets, choke tubes for correct tune for Renault motor. All 3 of the carbs were originally fitted to 1500cc Cortina GTs.
There is no vent to the float chamber. The top gasket seals the top of the float chamber on all 4 sides.
Henry
There is no vent to the float chamber. The top gasket seals the top of the float chamber on all 4 sides.
Henry