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 Weber 28-36DCD Help Please...
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Dirtbiker
V4 Mad

United Kingdom
606 Posts

Posted - 04 Feb 2018 :  21:09:43 Show Profile Visit Dirtbiker's Homepage Reply with Quote
Hi All,
I am not very knowledgeable when it comes to carbs so please treat me gently...
I have a Weber 28-36DCD on the correct manifold on the Green 96. It has probably covered 500 miles since being refurbished by Gower and Lee.
I don't fully understand how the starting device works (I understand how a choke works but not this). I have the Haynes Weber Carburetor Manual but can't get my head around the problem I have.
THE PROBLEM: I asked Gower and Lee to jet the Carb as per diagram supplied by Pete C but actually don't know if they have or not. When I fitted the carb I found that it started with just a small amount of pull on the choke cable (controlling the starting device) and wasn't happy with more than this. It was very lumpy when cold but quickly settled and ran beautifully when warm, although I suspect a little rich. I left it like this because I only do a few hundred miles a year and have about a million other projects that needed attention first (my fault, I know!)
Anyway, on the last couple of drives it is now almost un-driveable until warm and I fear a backfire causing an engine fire. It really smells of fuel and really misfires, a bit like trying to drive a car with stale fuel.
I know 99% of carb problems are said to be electrical problems(!) but with the smell of fuel I'm sure it's the carb. It still runs great when warm.
So, where do I start? I have the Haynes Carb manual but it seems like a too much and too little information if that makes sense. I could take it to an old school mechanic I know who lets me work on his ramp with him but I would like to see if I can solve it first (with your help!)
Thanks in advance,
Gareth

melle
V4 Guru

United Kingdom
2429 Posts

Posted - 04 Feb 2018 :  22:22:35 Show Profile Visit melle's Homepage Reply with Quote
Gareth, DCDs are great carbs because you can remove the idle and main jets without the need to completely dismantle them. This makes checking the most important jet sizes a five minute job. I will email you a couple DCD manuals that clearly point out what is where. Have you made sure the idle mixture is correctly adjusted?

www.saabv4.com
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john-saab
Administrator

United Kingdom
2665 Posts

Posted - 05 Feb 2018 :  08:24:39 Show Profile Reply with Quote
Melle..could you post the manuals. Some of the manuals say "prime jet size *** but there is no reference to where each jet sits within the carb AND use the same language as the suppliers..it's frustrating when the supplier calls the jet something else.

'73 96 (Vernon),'74 95 (Veronica)plus 4 other 95's and 2 96's
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melle
V4 Guru

United Kingdom
2429 Posts

Posted - 05 Feb 2018 :  09:13:49 Show Profile Visit melle's Homepage Reply with Quote
One manual is on my website, will upload the other as well when I get to it: http://www.saabv4.com/index.php/project/carburettors/

www.saabv4.com
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Doive
V4 Fan

United Kingdom
114 Posts

Posted - 06 Feb 2018 :  00:39:53 Show Profile Reply with Quote
This sounds a bit like a problem we had with our 95 fitted with an ICH34 - would start with barely a sniff of choke, ran like a rocket when warm, but misfired like mad when cold, and completely refused to restart when hot. The problem for us was eventually tracked down to a modern foam float that had cracked, and filled with fuel, meaning the electric fuel pump poured neat fuel straight into the inlet manifold. When cold this vastly richened the mixture, meaning the choke was not required, but when hot it flooded the engine & fouled the plugs, making hot starting a right pig. It was cured by fitting an old fashioned brass float, and has been perfect ever since.

1970 95 V4 van
1973 95 V4 estate
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melle
V4 Guru

United Kingdom
2429 Posts

Posted - 06 Feb 2018 :  09:38:06 Show Profile Visit melle's Homepage Reply with Quote
DCDs always have brass floats as far as I know. Hard to diagnose this from behind a keyboard, I would start hunting for vacuum leaks.

www.saabv4.com
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Dirtbiker
V4 Mad

United Kingdom
606 Posts

Posted - 06 Feb 2018 :  20:25:53 Show Profile Visit Dirtbiker's Homepage Reply with Quote
Hi All,
Thanks for the help and Melle, got the email.
I'm going to have a proper look at the weekend but the more I think about it I think maybe an electrical problem... The heavy smell of fuel could just be that it's not getting burnt because of a spark problem...?
I think I will try a new coil then a new condenser before anything. I think often you hear of a coil breaking down and not working when hot but worth a try this way around.
Doive - I'll check the float but starts really well hot so we'll see.
Melle - I'm not suspecting vacuum leaks as no "hunting" at idle. Maybe though, I will investigate.
Cheers and I'll keep you posted.
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melle
V4 Guru

United Kingdom
2429 Posts

Posted - 06 Feb 2018 :  20:34:56 Show Profile Visit melle's Homepage Reply with Quote
Check your coil before you replace it; I would suspect coil issues surface with a hot engine rather than with a cold one. Otherwise I would first replace the condenser (or get rid of the damn thing!) and then the coil.

www.saabv4.com
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john-saab
Administrator

United Kingdom
2665 Posts

Posted - 07 Feb 2018 :  07:38:44 Show Profile Reply with Quote
Re the coil. I am working on a car at the moment and it took several churns of the engine before it would fire..when it was running it was OK but the spark yellow rather than blue. While hunting for the problem the coils + spade terminal fell off in my hand. Corroded wires. Fixed it and the it fired 1st time with a bright blue spark.

'73 96 (Vernon),'74 95 (Veronica)plus 4 other 95's and 2 96's
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melle
V4 Guru

United Kingdom
2429 Posts

Posted - 07 Feb 2018 :  21:21:10 Show Profile Visit melle's Homepage Reply with Quote
I scanned the excellent factory DCD manual today, but for some reason I can't get it uploaded to my website at the moment. If someone needs it urgently, please let me have your email address and you'll get it in your inbox. Gareth and John, will email it to you in a minute.

I can also highly recommend the Weber Tuning Manual. It's still in print, so I can't upload it to my website. There are copies online elsewhere, but they're cheap enough to get a paper copy from Fast Road Cars: https://fastroadcars.co.uk/store/index.php?route=product/product&product_id=162

www.saabv4.com
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john-saab
Administrator

United Kingdom
2665 Posts

Posted - 08 Feb 2018 :  08:08:28 Show Profile Reply with Quote
That is superb Melle. Thank You. I will print that out later.

'73 96 (Vernon),'74 95 (Veronica)plus 4 other 95's and 2 96's
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pchristy
V4 Guru

United Kingdom
1763 Posts

Posted - 10 Feb 2018 :  14:15:28 Show Profile Reply with Quote
The DCD doesn't have a choke as such, or a "fast-idle". It only has a "mixture enrichment control". This basically just does what it says, and richens the mixture. It is very powerful, and only needs pulling out a small amount. Pulling it all the way will result in a very rich mixture and probably a strong smell of petrol! I always found that even with only a small amount of enrichment, the idle would be very lumpy. Its really only intended to get the engine started initially, and should be pushed in as soon as the engine is running. If pulled out too far, the engine will keep stalling rich. Unless its very cold, I found the car would start quite happily with just a few pumps on the throttle to prime it beforehand - no need for the "choke" unless its very cold.

Make sure it is shutting fully when you push the choke cable in. Its really important that it fully shuts! Only pull it a small amount, and push it back as soon as you possibly can! If you pull it all the way, then engine will be awash with fuel!

Cheers,


--
Pete
"Duct tape is like the Force: It has a light side and a dark side, and it binds the Universe together!"
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melle
V4 Guru

United Kingdom
2429 Posts

Posted - 12 Feb 2018 :  09:40:19 Show Profile Visit melle's Homepage Reply with Quote
Factory manual now downloadable from the carb section on my website: http://www.saabv4.com/index.php/project/carburettors/

www.saabv4.com
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Dirtbiker
V4 Mad

United Kingdom
606 Posts

Posted - 16 Feb 2018 :  22:51:14 Show Profile Visit Dirtbiker's Homepage Reply with Quote
Thanks for all your help on this everyone. I haven't even been under the bonnet yet as it's an outside job and it seems to be dark and cold whenever I get half an hour! Also lost this week's day off to a joyful time doing MOT welding on the work transit outside in the rain...
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melle
V4 Guru

United Kingdom
2429 Posts

Posted - 16 Feb 2018 :  22:56:13 Show Profile Visit melle's Homepage Reply with Quote
Did you get my WeTransfer link? Check you spam folder if not!

www.saabv4.com
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Dirtbiker
V4 Mad

United Kingdom
606 Posts

Posted - 17 Feb 2018 :  11:10:21 Show Profile Visit Dirtbiker's Homepage Reply with Quote
It's true - 99% of carb problems are electrical faults! A new condenser has transformed the car. I tried another coil first but as predicted this made no difference.
Pete - Good to know your carb only needs a tickle too. That's how mine has been since fitted and I always assumed was incorrect. Any plans to get out in the 96 to any events this Summer?
Melle - Thanks for all the info. I haven't seen the wetransfer email but I have been avoiding my work email for a few days so it will probably be waiting in my inbox on Monday! I would like to get rid of the condenser and do what you have done with the Distributor - a project for another day though!
I am going to check all the jets on the DCD out of interest but for now the car is running great!
Cheers
Gareth
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