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2l air cooled twin carb running with no power

Discussion in 'Engine & Transmission' started by Tony&Trudi, Nov 19, 2007.

  1. Tony&Trudi

    Tony&Trudi New Member

    Messages:
    67
    Location:
    Adelaide
    Hi All
    I am after some advise. My motor will hardly run above 2000 rpm. It is like i hit a brick wall and all power is lost.
    It feels like a fuel problem and came on quite suddenly yesterday.
    I have checked the fuel pump which is electric..it seems to flow ok but stops completely if i put my thumb over the outlet. Have to be very careful with that one.
    I have checked the timing and points and even changed the distributor completely.
    I have pulled the carbs apart and all looks ok.
    I feel it might be the pump or some suspect fuel.
    The valves were done a month ago and should stil be fine.
    The only other clue is i have an electric choke setup and when i switch on the choke while driving things improve considerably.
    The motor idles ok but seems a bit rough.
    .... any ideas would be appreciated.
    Regards
    Tony
     
    Last edited: Nov 19, 2007
  2. cbus

    cbus Well-Known Member

    Messages:
    13,570
    Location:
    sunshine coast
    If you have suficient fuel flow it doesnt sound like blocked filter but I would change it,
    Thought of no advance but you have swapped dissy to no avail and hopefully it was ok
    If you have timing light do a check just in case.

    The choke helping suggests mixture is lean

    Either adjustment out
    or restriction of fuel

    My gueses
    Try fuel system cleaner
    New filter
    Fuel flow test

    Adjusting carbs

    Hopefully not blocked jets

    I have had similar problems with bad fuel [imediately after filling] and also crap blocking tank outlet

    If you remove the air filter box and hoses to expose the carb throats you can slowly move a hand or piece of cardboard across the top to restrict airflow.

    Listen for changes in revs or smoothness of idle as you aproach 1/2 3/4 cover
    If it becomes rougher then mixture is rich
    If smoother and revs increase then original mixture is lean.
    This is what I would expect as you have already done this with the choke.

    cheers
    col
     
    Last edited: Nov 19, 2007
  3. glow-monkey

    glow-monkey Active Member

    Messages:
    1,319
    Location:
    Kenilworth QLD
    Similar thing happened to me about a week ago, I got out had a look on the side of the road and found this hose off, as soon as i put it back on the idling sped up, got in and drove off with no problem since.

    Notice the hose end under the heater blower, it plugs on to the brass pipe just on the base of the plastic air funnel behind the blower. You can see it right below the blower just behind the metal throttle arm that connects the carbies.
    [​IMG]
     
    Last edited: Nov 19, 2007
  4. kombidaze

    kombidaze Member

    Messages:
    466
    Location:
    Uki NSW
    could be a vacume leak check all the rubber hoses that connect up between the two carbies also the vacume brake booster take off down low on the outside of each inlet manifold and also the hose that runs from the firewall to the brake booster if they are perished or cracked they must be replaced or if they are loose tighened them up with hose clamps
     
  5. Tony&Trudi

    Tony&Trudi New Member

    Messages:
    67
    Location:
    Adelaide
    Thanks

    Thanks for the advise i will let you know how i go when i next get a chance to work on Lotti.
    Cheers
    Tony
     
  6. dennisg

    dennisg New Member

    Messages:
    1
    Location:
    Hobart, Tasmania
    I also am looking for some help regarding loss of power on engine start up. Am only a new owner and have a 1977 Kombi Camper, 2l twin carbi. Will cough and splutter, stall and just appears to run on 3 cyclinders untill it gets hot. Has just latet sometimes refuse to start.

    The local mechanic has had it a few times now - replaced points, a few new fuel lines - he thinks it now may be sticking choke on LHside carb.

    Unfortunately I have no manual as yet & it's 22 years since I sold my bug ( my first car 1956, had it for 15 years!!) & I have totally lost touch. Can anyone please advise how I can really check this out or fix?

    Thanks
     
  7. Van Housing

    Van Housing Well-Known Member

    Messages:
    10,434
    Location:
    Yarraville Vic
    Hey Dennis, welcome! :)

    mmm, if it sounds like it is running on 3 cylinders then I would do a compression test to make sure all four cylinders are okay... also check out cbus' post above...

    I would also recommend you look for a mechanic with experience in VW engines (especially a VW specialist). It may cost more per service, but you will save money in the long run....

    Also look out for John Muir's "How To Keep Your Volkswagen Alive"... it is a well-written, easy to read, trouble-shooting and maintenance guide - it makes an ideal first manual.
     
  8. Blue76Bay

    Blue76Bay New Member

    Messages:
    26
    Location:
    Western Sydney NSW
    Hi Dennis,

    I had exactly this problem. I live in Sydney and it only occurred in the Winter months first thing in the morning. If I started the Bus later in the day everything was fine. I took it to a VW mechanic but by the time I drove it there, the Bus was warm, so it was hard to troubleshoot the problem. Also the Bus was the only family car so being off the road for too long was a hassle. So when the Bus feels like it is running on 3 cylinders and then comes good after it's warm these are the things I check.

    1. The distributor cap. There are 4 small copper posts inside that get a build up of carbon on them. This happens as the rotor passes and the high voltage from the coil has to jump the small gap. Condensation forms inside the distributor cap and this combines with carbon to form an insulator. Depending on the amount of carbon and condensation this may prevent the spark jumping the gap and firing the spark plug until the condensation evaporates as the engine warms. Take the distributor cap off and give the post a clean with a sharp knife to scrap the carbon off. While you're there you may as well clean the rotor too.

    2. Check each spark plug lead with an Ohm meter. If you have one of those engine analyser meters that has a Tach/Dwell/Volts setting, usually it has an Ohm setting as well. What you are checking is the resistance of the cable and spark plug connector. The spark plug connector has an inbuilt resistance of 1K Ohms. If you look at the end of the connector it usually has 1K ohms stamped on the brown insulator. These 1K ohm connectors are the things I think lead a lot of people to misdiagnose a problem as being a carburettor problem. Those times when the Bus stumbles and you think it was probably a bit of dirt passing through the carby, is probably an intermittent 1K ohm connector or something else in the ignition system. I read there was old saying that "90 percent of carburettor problems are ignition". I used to be pulling my carburettors apart all the time until I read this. The 1K ohm connector can measure "open circuit" but still fire a spark plug. I think the carbon in the 1K ohm resistor breaks down forming a small gap (open circuit) but the high voltage from the coil jumps the gap. This can lead to the Bus driving OK at times but with a weak spark in one cylinder and other times no spark occuring in one cylinder and you're left running on three cylinders with the Bus stumbling and spluttering with no power. Now back to how to measure the 1K ohms using the meter. Turn the switch on your meter to the ohms setting. There is probably a high/low ohms switch also. Set this to high. Join your the leads of the meter together. If you have a digital meter this should read 0.00. If you have a meter with a needle, the needle should move towards the right, towards zero on the resistance scale. If the needle doesn't reach zero or goes past zero there is a small dial usually called "zero adjust", turn this until the needle lines up with zero. Now remove your spark plug leads one at a time and join the leads from your meter to either end. It should read about 1k ohms or 1000 ohms. Now wiggle the spark plug lead around to make sure there are no loose joins. If the needle of the meter doesn't move at all when you connect it to the spark plug lead you have what is called an "open circuit". You can replace just the connector or bite the bullet and buy a whole new set of spark plug leads. Depending on the age and condition of your old spark plug leads this maybe a better option. You can then keep any of your good old leads as spares. I find that the long spark plug connectors on cylinders 2 & 4 usually go.

    3. Sometimes coils can be intermittent when they get hot or cold. If you have a spare, swap it over.

    4. Now what turned out to be the fix for my Winter running problem was loose exhaust manifold nuts. Climb under your Bus and remove the small piece of tin between the heater boxes and the crankcase. You should now see the exhaust manifold one for each cylinder. The nuts work loose sometimes, so check they are on tight with a socket. If they have worked loose and there is enough thread you maybe able to put a second nut on to lock it down otherwise I would use some loktite, the one that is not permanent. Sure enough, if they have worked loose once, it will happen again!

    If you don't feel confident in checking these things I would, as suggested by others, take it to a Mechanic that specialises in old VWs.

    Hope this helps!
     
  9. Tony&Trudi

    Tony&Trudi New Member

    Messages:
    67
    Location:
    Adelaide
    The Problem is fixed

    Hi All,
    Well Lotti is back on the road finally. Thanks for all the replies.
    The problem was the left carbie. After much pulling apart and cleaning I noticed that the two carbs were slightly different. The left one when you looked down the throat had a couple of jets visible were as the right one you could see one jet and a small round brass plug with a tiny hole in it. I guessed that this must have come out and been eaten by Lotti. I went to a local carb place and they had the top of an ancient solex carb with one of these plugs in it. So for $5 it was mine and i headed home to hack it apart. The brass plug is only held in by punching around the edge so I added a bit of super glue carefully so i didnt cover the small hole.
    I eagerly reassembled the carbie and a run around the block confirmed that was the problem. I was very relieved to say the least.
    I had to go back and re-tune her from scratch but now she is back to her old self.
    Thanks again for all the relpies and support.
    Regards
    Tony:)
     

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