Idle problem on Weber 30DGS - Page 2
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  1. #26
    Tadpole
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    Thanks for the tip Ken.
    I may have that pocketbook for the GS. Will check it out.
    I also saw one for the GSA on Amazon.
    C.

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  2. #27
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    Quote Originally Posted by citrocees View Post
    Shanadoo, you just added another suspect. The carb is from a GSA and mounted in a GS. As a consequences, the carb has a return pipe, I have nothing to connect that too. There is no line returning to the tank. I was going to put a nylon T in the hose before the pump and connect it to that, but this hasn't happened yet. Currently that return pipe just has a blocked of piece of hose on it.
    Could it be the pressure build up would be too much for this carb's float valve? That would mean that on a GS carb (w/o the return pipe) the float valve would have to be stronger. In any case: I checked for leakage by cranking the engine with ignition off and i did not see fuel leaking onto the butterfly valve, but I will double-check.

    Working with a vacuum gauge would be new territory for me.

    Alan, so barrel 2 may have something to do with? I need to know for certain. For now, since it has a seal on its adjustment screw I will assume it is OK and focus on barrel 1... also because all documentation that I do have indeed says not to mess with it ("factory set with micrometer precision").

    Jaahn, I do have the Haynes and a bunch of other docs including from Citroen, but nothing seems to have that functional description I'm looking for. Just exploded views and setting procedures.

    Regards,
    Cees.
    Return line fitting gives you a hint about fuel pressure. Think about when the engine is running and the float is vibrating in frequency inside the chamber. {It's quite common on dual side draft Webbers and Dellortos' and down draft 4 barrel carbs}. Impossible to tune correctly without a set of balancing gauges or gauge unless one has a good ear.
    Fitting a tee for a return line is a good idea, but you'll have to make something to connect back to the tank,
    Last edited by shanadoo; 15th March 2014 at 04:40 PM.

  3. #28
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    Default Vacumn gauges, ?

    Quote Originally Posted by shanadoo View Post
    Return line fitting gives you a hint about fuel pressure. Think about when the engine is running and the float is vibrating in frequency inside the chamber. {It's quite common on dual side draft Webbers and Dellortos' and down draft 4 barrel carbs}. Impossible to tune correctly without a set of balancing gauges.
    Fitting a tee for a return line is a good idea, but you'll have to make something to connect back to the tank,
    Hi
    Shanadoo, what is the your proposed use for the balancing gauges. Cees does not have two carbys or a dual throat in which the two open together. It is a mechanical progressive opening two throat carby ?

    Cees you can fit a T in the line from the tank to the fuel pump as you have said and return the fuel there. It can however give problems with sucking up the fuel from the tank on startup. It may take longer as the fuel tends to run back to the tank when stopped. But in MHO it should work OK without the return line connected. It was usually fitted to reduce a bit of unburnt hydrocarbon emissions after the engine stops for pollution reasons.

    jaahn

  4. #29
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    Thanks Jaahn & Shanadoo,

    The GS carbs didn't have a return pipe, only the GSA, and as far as I can find out, neither had the GS fuel pump a pressure relief mechanism. So on that basis I think there should be no reason to suspect trouble with a blocked off return pipe on a GSA carb. But I will check for leakage out of the bridge anyway.

    Jaahn, I always thought it was in there to avoid vapour lock. I remember myself as a kid with my family in our Lada + caravan stuttering and chocking on Paris' Peripherique ring-road, with a queue of angry French motorists behind us. All because (as it turned out) that return line was blocked causing the fuel to boil whenever the flow was low enough and the temperature in the engine bay (of that marvel of Soviet engineering) high enough.

  5. #30
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    Default Vapour Lock :0

    Quote Originally Posted by citrocees View Post
    Thanks Jaahn & Shanadoo,
    The GS carbs didn't have a return pipe, only the GSA, and as far as I can find out, neither had the GS fuel pump a pressure relief mechanism. So on that basis I think there should be no reason to suspect trouble with a blocked off return pipe on a GSA carb. But I will check for leakage out of the bridge anyway.

    Jaahn, I always thought it was in there to avoid vapour lock. I remember myself as a kid with my family in our Lada + caravan stuttering and chocking on Paris' Peripherique ring-road, with a queue of angry French motorists behind us. All because (as it turned out) that return line was blocked causing the fuel to boil whenever the flow was low enough and the temperature in the engine bay (of that marvel of Soviet engineering) high enough.
    Hi
    The GS has a mechanical fuel pump which is a regulated pressure by design. The diaphragm is pushed by a fixed spring pressure which is set by the manufacturer and does not vary and cannot be too high.

    The return pipe does help with vapour lock as it keeps the fuel lines cooler by circulating fuel back to the tank. This can be a problem particularly in traffic, as you have noticed My daughter made the 'mistake' to buy the Soviets finest so I had some experience of them .

    As I recall the return lines were fitted after pollution rules came in, mainly to get some reduction in unburnt hydrocarbons after the engine stops. It by allows the fuel in the pump and vapour in the lines to return to the tank instead of being released to the carby throat. This also helps with a hot restart.
    jaahn
    Last edited by jaahn; 9th March 2014 at 09:41 AM.

  6. #31
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    citrocees - Welcome to the GS community.

    While I may lack the technical prowess of many on aussiefrogs, from my limited experience, have you done a basic check on the fuel tank quality? Check out (like yours) a '73 GS Break (go to last post)

    GS Break Purchase

    Be great to see some photos of your project?
    '73 & '74 GS Break
    '00 Xantia Break
    '78 504 GL - gone to good home
    '69 ID19B - if wasn't for mortgage would still have, '74 DS23 Pallas
    '74 Renault TS , '69 Renault TS - last seen forlorn at Taminda wreckers

  7. #32
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    Hi Sparkey,

    Thanks for the welcome.
    I have no reason to suspect the tank but I'll double check.

    Wow your break does look good. Mine is not quite there yet: first things first, and for me that is a smooth running engine.
    Did breaks only come in beige down under?

    Attached photos show the car when I bought it. It was sold as someone's project on hold: swapping a 4-speed with a 5-speed, both engines delivered with the car (photo), he had already cut out the gear box brackets, "should be easy". Not. There's a bit more to it, I now know. Anyway, that job has been done.
    He also hadn't mentioned the dents, the rust and that the driver's door had been opened so far the top hinge had been torn off somewhat (photo). So that will need some specialist bodywork.

    I was about to attach some more photo's, but what is the best way if you want to show more than a few?

    Cees.
    Attached Thumbnails Attached Thumbnails Idle problem on Weber 30DGS-gs-003.jpg   Idle problem on Weber 30DGS-gs-006.jpg   Idle problem on Weber 30DGS-2009_12_arrival-027.jpg   Idle problem on Weber 30DGS-2009_12_arrival-052.jpg  
    Last edited by citrocees; 11th March 2014 at 08:41 AM.

  8. #33
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    deleted because it's too boring.
    Last edited by shanadoo; 15th March 2014 at 04:45 PM. Reason: Boring

  9. #34
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    [QUOTE=shanadoo;1237781]The pressure from mechanical fuel pumps can and does vary considerably. If the wrong arm is fitted it will over stroke, or if the fiber insulator is missing from the mounting face,[if it was required from new] or the wrong thickness gaskets are fitted [too thin], or if it's the wrong pump for that model ie; again wrong angle arm, it will overpressure. As you probably know pumps come in a variable pressure regulated format [they're different is what I mean] It doesn't always rely on the lever to camshaft relationship nor the size of the pump or stroke. Small pumps are invariably the higher pressure.
    QUOTE]

    You do realise that a GS pump is a pushrod pump not a lever arm pump. The rest of your article is spot on. Weber carbs only require a modest fuel pressure to avoid pressurising the needle and seat. Typically 2.5 -3.5 psi
    My son ahs a pressure regulator fitted to he RS 2000 to control fuel pressure to a pair of 48 IDFs. It is cheap and fully adjustable.
    Cheers Gerry

  10. #35
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    Deleted as boring uninteresting stuff to everyone .
    Last edited by shanadoo; 15th March 2014 at 05:01 PM.

  11. #36
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    Quote Originally Posted by shanadoo View Post
    Doesn't matter if pushrod or lever or direct cam. The faster it goes the higher the pressure until the diaphragm can no longer cope and begins to stretch and the valves no longer seal. Also if the pump is the rebuildable type. Frogs in a Well will say it hasn't been assembled correctly. Again, the use of a fuel pressure test gauge [cheap] will determine if it's up to scratch, i;e will it hold pressure, how much, and how much vacuum does it pull and maintain, each proving the valves not leaking. Over the years I have found many brand new, non repairable, mechanical pumps which had faulty valves or operated at around 12psi instead of say 4-6. Some operated at around 2-3 psi when they should have been 6psi. Suppliers claim the pump will settle down after it's been running for a while, CRAP. But it's something to watch for, If you haven't got a test gauge you're guessing. Fuel pumps are often ignored yet they're like trucks, without them Australia stops. That doesn't work but you get what I mean.

    Pressure regulator is a good thing especially with electric pumps. There used to be a little aluminum thumb screw adjustable, pressure regulator called the Little Gem on the market many years ago, it came with all fittings, took a couple of minutes to fit on the carb fuel inlet and worked like a beauty. No fuel vaporizing in the traffic, no hot start problems, and good fuel economy. I had one for years and used to swap it over when I changed cars. What ever happened to things like these. Worked too well, I guess.
    Hi
    Sorry but I cannot let some statements go without comment. Make of all this what you will people.

    "Doesn't matter if pushrod or lever or direct cam. The faster it goes the higher the pressure until the diaphragm can no longer cope and begins to stretch and the valves no longer seal."
    Actually the diaphragm is not forced up and down, it is actually pulled down by the cam and returns by spring pressure as the fuel is used. If the fuel flows slowly the diaphragm only strokes a small amount and the stroke matches the flow. Most of the time the stroke is small. The pressure is set by the return spring not the cam pushing it or the speed of the engine to a large degree. IMHO an old elegant system, tried and proven over time for carbys.

    " But it's something to watch for, If you haven't got a test gauge you're guessing." agreed

    Some pumps may be faulty ! agreed

    "Pressure regulator is a good thing especially with electric pumps." Agreed
    jaahn

  12. #37
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    OK.
    So I finally got time to work on the car again. I made myself a list of steps to take, based on all your valuable input. Here's a first report.

    I started by pouring another 10 liter in the tank.
    Took the fuel line off the carb and cranked the engine -without ignition- until the fuel was squirting out. Clean.
    Reconnected the fuel line.
    Now whether the extra 10 liter has anything to do with it or not, I don't know, but cranking the engine again the carb was overflowing like it hadn't done before! Very strange.
    Proceeded by connecting the until then blocked off return line to a T before the fuel pump, but this had no influence on the overflowing.
    Removed the lid from the carb. All looked fine. I took the opportunity to find out (using some fishing line) what channels lead where and this confirmed what has been written before. More on that later as it doesn't seem relevant anymore.

    Checked the float distance to the lid: just under 6.5 mm as per spec.
    Checked float for leakage: OK.
    Checked the needle by blowing into the inlet: closed fine.
    Took out both idle jets, i.e. the one with the electromagnetic valve and the one that serves barrel 2. Pulled them apart a bit and fitted them again, as suggested before. Took them out again to see how far they were pushed in: all the way. Repeated the fitting.
    Checked the idle mixture needle: no damage, seat seemed fine to. Cheked if it closed and it seemed to.
    Put the lid back on and cranked the engine: no more overflowing... Go figure. I didn't really change anything.

    Reconnected ignition and started the engine. Still running poor on idle but now I noticed some dripping out of the barrel 1 bridge onto the butterfly valve. Aha! That ain't good!

    Tried with the return line blocked off, connected to the T or even discharging freely into a container: this had no effect on the dripping.
    After stopping the engine, checked again by blowing into the inlet: completely closed.

    So. The float seems to work correct but sits too high?
    I opened the carb a few more times, each time tweaking the float distance: from initially just under 6.5 mm to just under 7 mm now. The dripping seemed to diminish but not sure; it didn't go away. I was reluctant to go further and move beyond the spec. Could there be another reason for the dripping?
    I also noticed only barrel 1 is wet. Barrel 2 is bone dry!!! But perhaps that's becasue it's completely shut and so no draft is sucking fuel out of the bridge?

    In summary, this dripping is for sure the cause of the idle problem. But where does the dripping come from?

    Meanwhile, from my prodding in the carb I can confirm the following.
    The 'secondary idle jet' is fed from the secondary emulsion tube and feeds the progression hole(s) of barrel 2 only. There are 2 holes. The lower half of the lower hole is covered by the butterfly valve. The second hole sits just a bit higher. The valve itself seems completely shut bar a less-than-hairline.

    In the same way the 'primary idle jet' - the one with the electromagnetic valve - is fed by the primary emulsion tube and via the mixture screw exits in barrel 1 just under the butterfly valve. This barrel has at least 5 more holes in its side above the valve, and one that sits just under or is covered by the valve (hard to see). One of the holes above the valve I suspect is for the ignition advance and 1 for the enricher mechanism. The others I suspect are true progression holes, all fed by the 'primary idle jet' circuit.

    There are a few more holes and channels that I don't understand. Like a third hole in the float chamber floor, right next to the two brass jets (c in the photo). And a channel right next to the secondary emulsion tube (d). Plus there seemed to be fuel not only in the emulsion tubes but also in at least two other cavities of the carb (a & b).




    Idle problem on Weber 30DGS-img_1513.jpgIdle problem on Weber 30DGS-img_1514_3.jpg
    Last edited by citrocees; 12th March 2014 at 10:34 PM.

  13. #38
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    I also found some very useful info here:
    Carburatori Weber
    including, it seems, a way to measure the float level with the lid on by removing the air correction jet and emulsion tube and using a caliper (Part Two - figure 45 near the bottom).

  14. #39
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    [QUOTE=jaahn;1238046]Hi
    Sorry but I cannot let some statements go without comment. Make of all this what you will people.

    again I deleted my stuff as boring, long winded
    Last edited by shanadoo; 15th March 2014 at 05:02 PM.

  15. #40
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    bored with all this reading. Now there's a mile of information, on the web citrocees. Google it and read. No malice intent but we all have to take a step back every now and then, restock and revalueate the situation. Otherwise we finish up going around in the same circles. Some say my eyes do that.
    Last edited by shanadoo; 16th March 2014 at 08:45 AM. Reason: without Malice

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