Volvo RWD 700 Forum

INDEX FOR 10/2025(CURRENT) INDEX FOR 9/2007 700 INDEX

[<<]  [>>]


THREADED THREADED EXPANDED FLAT PRINT ALL
MESSAGES IN THIS THREAD




  REPLY TO THIS MESSAGE    PRINT   SAVE 

1990 740 carburettor model with auto gearbox stalling 700

Hi Guys
Merry Christmas to you all.
1990, 2.4 litre 4 cyl engine auto
Drove my car in fairly cold weather today and once warmed up, it stalled as I came to a standstill at traffic lights. Never done this before and it started again immediately.
It kept running at really slow revs and trying to stall after that.
Any ideas what I should be looking for? Carb? electrics? air filter? Maybe too cold for it?
I think this model has an auto choke and I pressed the accellerator down to the floor before I started it.
Pete








  •   REPLY TO THIS MESSAGE    PRINT   SAVE 

    1990 740 carburettor model with auto gearbox stalling 700

    Pete,

    You mentioned running on (dieseling). I had an '84 740 with this problem and the cure was to replace the vacuum operated fuel cut off valve on the Pierburg carb. This valve stops the fuel flow internally when you switch off. It has a rubber diaphragm that degrades over time and can cause tickover problems.

    Happy New Year!

    Ian








    •   REPLY TO THIS MESSAGE Replies to this message will be emailed.    PRINT   SAVE 

      1990 740 carburettor model with auto gearbox stalling 700

      Hi Ian
      The running on was fixed by the previous owner. My problem is very low idling when cold.
      Been reading up and there is talk the IAC valve may be dirty or the engine breather/flame trap may be blocked?
      Will need to check all this out.
      Pete








  •   REPLY TO THIS MESSAGE    PRINT   SAVE 

    1990 740 carburettor model with auto gearbox stalling 700

    Joyeux Noël, Pierre.

    Where are you located? We never got carburetted 740s in North America, so more details of your setup (carburettor make and model, for example) would be appreciated.

    How cold is it? Your symptoms could be ice in the gas line, easily cured with a few ounces (100 to 150ml +-) of methyl alcohol in the tank and a bit of time.

    --
    67 144, 86 740T, 91 945SE, BMW R69S, R60/2








    •   REPLY TO THIS MESSAGE    PRINT   SAVE 

      1990 740 carburettor model with auto gearbox stalling 700

      Hi
      I'm in London, England. Yes, I thought you guys in North America would no have got the carb versions due to the emissions regs (I think)
      I don't know what type of carb it is.
      It was not that cold-about 3 or 4 centigrade so doubt it was iced up.
      I used it again today and it idles really slow especially when first started up-under 1000rpm-more like 700 rpm. In fact its so slow that it tries to stall at tickover and the red dashbord lights flicker as if its about to cut out.
      I thought the carb would have a mechanism to adjust the idle speed to suit the temperature? Not sure if this gives you any clues but I found a receipt from the previous owner who had the "Thermal part of the choke unit replaced to cure high idle speeds and running on" That was 6000 miles ago.

      Should I just adjust the idle screw so it idles a bit higher do you think?

      I see you have a '67 144-I had a '67 142 with twin carbs-great car-wish I'd never sold it-very rare in the UK.

      Cheers
      Pete








      •   REPLY TO THIS MESSAGE    PRINT   SAVE 

        1990 740 carburettor model with auto gearbox stalling 700

        Hello Pete
        I'm guessing you have the Pierburg 2B7 setup. When your engine is warm it should idle at 900rpm, although when you first start the car on a cold morning it should idle much faster (at least 2000rpm I think). As the car warms up the revs should go down. You probably need to adjust the choke if this isn't happening. Firstly make sure that the choke flap is fully open when the engine is warm and that the CO level and idle speed are correct.
        You said that your engine stalled once the car had warmed up. Did it stall as soon as the engine was warm? This is a very common problem on these carbs. I don't know what causes it but raising the fast idle speed helps. Even better might be a manual choke conversion. There is a screw at the back of the carb underneath the stepped cam which adjusts the fast idle speed.

        You might also want to check that the choke actually works. You need to do this when the car is cold before you drive it. Under the bonnet, there is a black plastic thing with rubber hoses attached - to the right of the engine looking into the bonnet. If you remove the single nut that secures it you can remove it and look at the choke flap. The flap should be closed initially. If you gently tap the accelerator pedal the flap should close. If it doesn't then your choke is faulty.

        I hope some of this will help you and not lead you astray.

        Cheers
        William








        •   REPLY TO THIS MESSAGE    PRINT   SAVE 

          1990 740 carburettor model with auto gearbox stalling 700

          Hi William
          Yes, its a Pierburg double barrel carb. The outside of it is so filthy dirty with oil/grease that I could not see any numbers other than on a tag that read:
          VOLVO 1357108 7 17952 51
          I removed the plastic carb cover with the single nut. The choke butterfly valve was seized solid-I could not budge it. I cleaned up the mechanism, oiled it and freed it up with some pliers!. It now spins freely. HOWEVER, the L-shaped rod that comes up from the bottom of the carb (which I think is what makes the choke butterfly valve open and close) is not connected to the butterfly valve shaft. It is connected at the bottom (where I think there is a shaft to the thermal spring mechanism?) but flaps about loose at the L-shaped top end near the choke butterfly valve shaft. Should this L-shaped rod be connected to the chole valve shaft? There IS a dark red platic piece that sits on the choke shaft at about the right place where the L-shaped connecting rod sits but I can't see how the L-shaped rod connects to it....I think a piece of this red plastic bit (perhaps with a hole for the L-shaped rod?) may have broken off......so the L-shaped rod has nothing to connect to? The L-shaped rod does raise up as the engine warms up so I think the thermal spring part of the choke mechanism is working as it should.)
          Please can somebody confirm my suspicion about the drak red plastic piece? Perhaps when the choke mechanism seized, the L-shaped rod tried to pull down and broke off the pastic connector piece? But I can't see the choke thermal spring exerting so much pressure to break a piece of plastic? I did take a picture of the top of the carb if anyone would be kind enough to take a look at it.

          Also, the top inside of the carb is filthy dirty with a think black oily junk which is what must have caused the choke butterfly valve to seize solid. And the outside of the carb is just as filthy dirty with the same black/grease/oil.
          Any tips or help from anyone with the Pierburg carb would be appreciated.
          Thanks
          Pete, London UK








          •   REPLY TO THIS MESSAGE    PRINT   SAVE 

            1990 740 carburettor model with auto gearbox stalling 700

            Hello Pete
            The choke flap shouldn't be stuck. You should always be able to move it whether in the open or closed position. It shouldn't move that freely either. There is a bi-metal spring inside the choke unit. The spring pulls on the choke link rod (the L-shaped rod you described) and controls the flap opening. The top of the choke link rod connects to that red plastic thing you described.
            Don't worry about the grease all over the carb. It's best not to try to clean the carb unless you are giving it an overhaul as dirt can get into the jets and holes. The choke link rod is a snap fit into the red plastic thing.

            The faulty choke may have caused the low idle speed but i'm not convinced that it caused the engine to stall after 20mins of running. If the flap was stuck open it would make the car hard to start from cold and would run poorly until warmed up. If the flap was stuck closed the car would start up okay but would begin to make a chugging noise after a while.

            If you think the red plastic thing is broken you should still be able to get one from Volvo. They still sell most carb parts. I have no idea how to fit the part though.

            I used to have a carb like yours but changed it for a new Weber replacement after spending too much money repairing it. I must have spent £200 overhauling it before buying the Weber for £250. It's reliable and gives me peace of mind. The Weber conversion is very popular here in the UK.

            Cheers
            William








            •   REPLY TO THIS MESSAGE    PRINT   SAVE 

              1990 740 carburettor model with auto gearbox stalling 700

              Thanks William
              The choke was stuck in the open position hence the poor running till warm. But you're right-that does not explain the stalling when warm-I'll see how I go.
              Hmmmm, the broken red plastic thing is a worry though. If its a snap fit, then it is missing a piece for sure. Not too much of a problem that the auto choke doesn't work unless we get some really cold weather which is very rare in London and the 740 is a 2nd car anyway. Still-would be nice to get it working though.

              Tell me, what is it that makes the auto choke engage? Is it pressing the accelerator before starting? Or does the thermal spring (bimetal spring) engage it when the temperature drops?
              Thanks for all your help.
              Pete








              •   REPLY TO THIS MESSAGE    PRINT   SAVE 

                1990 740 carburettor model with auto gearbox stalling 700

                Hi Pete

                As you probably know, when you press the accelerator pedal it moves the throttle spindle on the carb. At the back of the carb, there is a screw fixed to the throttle spindle. This is the fast idle screw which sets the idle speed when cold. The screw rests against a stepped cam. The cam is connected to the lower choke spindle and is sprung (not by the bi-metal though). When the bi-metal spring is cold it tries to close the flap but prevented doing so by the fast idle screw which rests against the stepped cam. When you push the accelerator pedal the fast idle screw is moved away from the stepped cam allowing the cam to rotate by action of the spring and shut the flap.
                I probably make it sound quite complicated.

                I've just had a look at my old carb and found how to remove the red plastic thing. Simply remove the two brass screws which secure the flap to the spindle, rotate the flap into the open position, slide out the flap, and slide out the choke spindle. Make sure you keep a photograph of the red plastic as you will need it for installing the new one.

                Cheers
                William








                •   REPLY TO THIS MESSAGE    PRINT   SAVE 

                  1990 740 carburettor model with auto gearbox stalling 700

                  William
                  Thanks so much for taking the trouble of looking at your old carb for me. That's very nice of you thanks. Now all I need to do is find somewhere that will sell me that red plastic part-if its still available somewhere......
                  Thanks also for explaining how the auto choke works.
                  Pete








                  •   REPLY TO THIS MESSAGE    PRINT   SAVE 

                    1990 740 carburettor model with auto gearbox stalling 700

                    I think Volvo would only sell you a complete top half of the carb. There is a mail order company I once used, called Carburettor Hospital. http://www.carburettorspecialists.com/stock.htm
                    They have lots of bits for sale but I found their online catalogue very difficult to use (many parts with the same name). They're also quite expensive. Your best bet would be to visit a breakers yard and buy a complete carburettor for about £20-£25. Don't pay any more than £25. You can then either remove the red plastic part or replace the entire carburettor. Besides, the second-hand carb possibly won't have the stalling problem.
                    My carb is a 2B5 so wouldn't fit your car without modifications. You need a Pierburg 2B7 with part number 1357108. The part number is the same number you found stamped on a metal tag.

                    Good Luck
                    William








                    •   REPLY TO THIS MESSAGE    PRINT   SAVE 

                      1990 740 carburettor model with auto gearbox stalling 700

                      Thanks again William for all your tips and advice. I'll see what I can find at the breakers or on ebay.
                      Happy New Year to you.
                      Pete








        •   REPLY TO THIS MESSAGE Replies to this message will be emailed.    PRINT   SAVE 

          1990 740 carburettor model with auto gearbox stalling 700

          Hi William
          Thanks for your message. Before I started the car today, I did as it says in the owner's manual and pressed the accellerator pedal (I think this engages the automatic choke?). It did not idle any faster and was about 800rpm. After a mile or so, I pulled over and the idle was much lower-below 500rpm which meant the engine was very nearly stalling.

          In answer to your question, the stalling happened after about 20 minutes of running so not as soon as the engine warmed up.

          I think the auto choke must not be working because it never idles higher than 900rpm when cold.
          Will take a look at the choke workings tomorrow as you suggest. But if its not working-then what? Is there any way I can free it up somehow?
          Pete








  •   REPLY TO THIS MESSAGE Replies to this message will be emailed.    PRINT   SAVE 

    1990 740 carburettor model with auto gearbox stalling 700

    Hi, and Merry Christmas to you too!
    What you describe could be a lot of things, a failing crank position sensor springs to mind. I assume your engine is a B230K, if so it should have a CPS mounted on top of the bellhousing. They tend to fail gradually, resulting in temporary loss of ignition.

    Erling.
    --
    My 240 Page







<< < > >>



©Jarrod Stenberg 1997-2022. All material except where indicated.


All participants agree to these terms.

Brickboard.com is not affiliated with nor sponsored by AB Volvo, Volvo Car Corporation, Volvo Cars of North America, Inc. or Ford Motor Company. Brickboard.com is a Volvo owner/enthusiast site, similar to a club, and does not intend to pose as an official Volvo site. The official Volvo site can be found here.