1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

76 Kombi: Fuel starvation after driving around

Discussion in 'Fuel System & Electrics' started by johnnybegood, Mar 22, 2015.

  1. johnnybegood

    johnnybegood Member

    Messages:
    40
    Location:
    Wellington, NZ
    I've had an intermittent and temperamental fault with my 1976 Kombi fuel system for a few months. I'm hoping to drive from Wellington to Taupo for the NZ VW Nationals at Easter, but it will be an anxious trip if I can't get the fuel issue sorted.

    The engine is a 2L with the standard twin carbs and a mechanical fuel pump. When its running it goes really well.

    Three times recently however I have been driving along a highway with the bus chugging along quite happily at 90km/hr when suddenly I lose acceleration, no power when I put my foot on the gas, and it stutters to a stop while I'm frantically try to pull over safely. First time it happened I had to get towed (about 15kms) when it just refused to start. I'm no mechanic, but with some help I put in a new fuel filter. The engine started right away and I drove around locally for a week or so.

    The fuel starvation problem happened a few more times while I was driving (on test runs) for say an hour or so out on the highway. On those occasions I was able to wait for a few minutes, start up , drive off and (with bated breath) get back home. The second time I coaxed it home and had fitted a new hose from tank to filter, drained the gas tank and removed a few small flecks of perished rubber (from the old fuel filler elbow which I've had replaced). Yesterday after losing power out for the third time out on the highway I managed to start it up no problem and drive home again. It does seem like a fuel issue rather than electrical to me.

    Any suggestions why this should happen? Is there an obvious solution as to why its an intermittent fault?
    I'm thinking the next step would be to get someone to dismantle and flush out the fuel pump and or the carbs?

    Any advice would be appreciated. And may the best team win in the cricket.
     
  2. Alpal

    Alpal Moderator Staff Member

    Messages:
    8,528
    Location:
    Melbourne Bend of Islands
    Does it die going up a long hill? If so probably fuel pump. On a long hill you are using more fuel so the bowl does not fill up quickly enough. If you stop and wait for a few minutes does it fire up?
    Had the problem some time ago. Went electric.
     
  3. johnnybegood

    johnnybegood Member

    Messages:
    40
    Location:
    Wellington, NZ
    Thanks Alpal-
    That's an interesting idea- although each time it's happened on a dead flat highway (coincidentally the same stretch of road although in different directions and after different mileages). But each time it's happened I've been chugging along at a fair rate (i.e. with the engine under a bit of load). Yes, each time (except the first as I explained) I waited a few minutes, and then I could start up no problem and drive off like nothing ever happened. Maybe I need to switch on and go electric? :)
     
  4. cbus

    cbus Well-Known Member

    Messages:
    12,048
    Location:
    sunshine coast
    had very similar issue in daughters bf kombi.
    prev owner had same and actualy changed engines to no avail

    ended up being silicone rubber in fuel tank from some idiot attempting a repair on the filler neck.
    had dissolved[naturaly] and lumps in tank gave intermittent blockages.
    mechanic found it and cleaned it out .
    no issues since

    would often run hot[lean
    not run at all
    fail to start after filled
    often down on power and very intermittent issue
    or run with no issues

    may need to recheck tank for bits . Guessing you don't have the nut type fitting on tank outlet?
    If you do then check it has the fine gauze filter in place
     
  5. johnnybegood

    johnnybegood Member

    Messages:
    40
    Location:
    Wellington, NZ
    Thanks cbus
    I'm pretty sure the tank is now free of any debris. the only time I've had this problem is when I've been chugging along at 90 km/hr. I've never had a problem starting from cold or running around the local beautiful Wellington coast roads at 50 km/hr while road testing and trying to replicate the problem.
     
  6. cbus

    cbus Well-Known Member

    Messages:
    12,048
    Location:
    sunshine coast
    No prob
    I would continue with the flush thru fuel items.
    clean pump as Al suggested and easy enough to pull the carbs yourself and check or crap in bowls and needle/seat on inlet. blow the jets with air or a can of WD40 with nozzle.
    I do agree that its sounds like a fuel issue

    cheers
     
  7. oldman

    oldman Super Moderator Staff Member

    Messages:
    8,740
    Location:
    Avalon Beach NSW
    Check that the fuel cap breather is clear & allowing the tank to "breathe".
    Fuel cap should be vented to allow air in as fuel drains out, otherwise there will be a negative suction created in the tank.
    Has been known to starve fuel pump from fuel, causing the symptoms you describe.
     
  8. geoff62sw

    geoff62sw Member

    Messages:
    769
    Location:
    sydney
    Yah I conncer with......^^
    poss vent in fuel cap blocked,I have had a similar problem
    cheers
    geoff
     
  9. vwfreak03

    vwfreak03 Well-Known Member

    Messages:
    1,550
    Location:
    Hobart, Tasmania
    agree with alpal....sounds like fuel pump. only way to check is to take it to a garage and get it tested...will take about 5mins . but will tell u if its the pump or not. if its not then move on
     
  10. johnnybegood

    johnnybegood Member

    Messages:
    40
    Location:
    Wellington, NZ
    Thanks for all the advice. I've had an electric fuel pump fitted after the original mechanical pump was found to be leaking some fuel and oil. I also had the carburetors checked and balanced. I drove it for a few hours today including out on local highways and it never missed a beat- much more positive acceleration and less hesitation right through the gears... so far so good. Pretty sure it was the dodgy fuel pump. Now may the best team win at MCG tomorrow... GO THE BLACK CAPS
     
  11. cbus

    cbus Well-Known Member

    Messages:
    12,048
    Location:
    sunshine coast
    really good idea is to fit a tachometric relay and fuel shut off solenoid plus pressure regulator when fitting electric pumps.
    also don't park on steep slopes till you do have the above as its common for fuel to leak past needle /set and into sump
     
  12. Alpal

    Alpal Moderator Staff Member

    Messages:
    8,528
    Location:
    Melbourne Bend of Islands
    One of the best tuning results was obtained by purchasing and using a carbi balancing device. Nothing like a bit of balance!
     
  13. johnnybegood

    johnnybegood Member

    Messages:
    40
    Location:
    Wellington, NZ
    The first thing I did when I bought my Kombi about 18 months ago was to replace the fuel filler elbow because of the strong smell of petrol inside the Kombi.

    As it turns out, my fuel problem turned out to be exactly the same- little bits of silicone or rubber from the perished fuel filler elbow which someone had tried to repair had collected in the tank and at times were sitting right over the tank outlet. My mechanic fished them out after I had to get towed to his garage in the week before Easter.

    I took the Kombi up to Taupo for the NZ VW Nationals at Easter (Google if you want to see some pics) and the Kombi never missed a beat during a 1500km trip. Hopefully that will be the last of the fuel problems. There's nothing quite as unsettling as not knowing when the Kombi is going to stutter to a halt on a highway.
     
  14. cbus

    cbus Well-Known Member

    Messages:
    12,048
    Location:
    sunshine coast
    another example that there's no lack of unskilled kombi owners or idiots :)

    All good for someone to make a guess but an educated guess is preferable.
    Silicone rubber doesn't resist petrol. Probably even states it on the label as well:rolleyes:

    Glad you found the source of the problem.
    Nearly went to see the nats in Timaru last year.
    Seems that many motor events are pretty big in NZ , especialy considering population size.
    Nice n cold in Taupo?

    Better add,
    and before everyone gets upset, I was refering to the person who used silicone as the silly one.

    We all guess to a fair degree when putting potential answers/solutions forward but that's part of the problem solving process ;)
     
    Last edited: Apr 19, 2015
  15. johnnybegood

    johnnybegood Member

    Messages:
    40
    Location:
    Wellington, NZ
    NZ Nationals at Taupo- fantastic event (25th Anniversary), great venue and beautiful sunny weather all weekend. About 350 VWs and approx 55 Kombis turned up.
    Next year will be at Nelson, and in Wellington for 2017

    P1012374.jpg
     
  16. Bert the Kraut

    Bert the Kraut New Member

    Messages:
    1
    Location:
    Gold coast
    Had similar problems recently and changed fuel pump to a pierburg with tachometric relay. Very easy to do and you can leave the old mechanical pump in there disconnected just in case. Still did not solve fuel starvation problem. After 1 hour driving all the sudden loses power , backfires slightly and wants to stop . After 5 minutes rest as good as ever.
    Here is a little tip. I noticed the lockable after market fuel cap is very tight. When I took the rubber seal out it ran fine without a hitch which led me to believe that there is a slow vacuum building up in the tank which eventually causes fuel starvation problems.
    I put the rubber seal back on and drilled a small 2 mm hole straight through the key barrel and through the centre of the cap. Lock still works and this should prevent a vacuum building up again.
    Please let me know if anybody else solved this with modifying or changing fuel cap.
     
    David H and MAP77 like this.
  17. David H

    David H Well-Known Member

    Messages:
    5,205
    Location:
    newcastle
    Another great thread revival:D. Good on you Bert the Kraut;). How many thread revivals are we getting now! How good is the KC memory bank for help:cool:. Obviously newbies are better at the 'search function' than I am;).
    Cheers
     
    Last edited: Jul 29, 2019
  18. cbus

    cbus Well-Known Member

    Messages:
    12,048
    Location:
    sunshine coast
    Found another starvation cause today.
    Breather vent system blocked at left hand side hose joiner.
    Cotton covered hose had deteriorated inside .
    Was still without cracks externaly.but blocked internally.
    Which means I need to sus the r.h as well .

    Chased primarily due to difficulty in filling tank but thinking back , the starvation was also evident.
     

Share This Page