Possible Fuel Starvation?

Discussion in 'Mech Tech' started by Avid, Jul 26, 2022.

  1. Hi All,

    Long time lurker on the forum, but first time posting as I'm after some advice/guidance on next troubleshooting steps.

    Been away in the van for the weekend (all fine, no issues) however half way home (120ish miles still to go) and we came to an unerring halt having lost power. After some rudimentary checks, fuel lines/ filters, cranking to check fuel to carb (all passed ok) and replacing the 123 dizzy that went in last weekend with the original 009 we got underway again. 10 miles later and same symptoms such that we're now enjoying the sunshine on the side of the A5 and waiting for the yellow truck of shame.

    My question is this ... to me this feels like having filled the carb float when cranking to fix the first breakdown I've simply masked the issue and once the carbs empty we've stopped again? Next step seems to me to be, drop the engine and check the tank / lines more thoroughly but are there other things I should/could be checking first?

    Engine is 1600, single carb, dizzy has had the points checked and timing is 7.5BTDC (or near as damn it as I marked the 009 up before taking it out)

    Thanks in advance, all and any advice gratefully received
     
    Last edited: Jul 26, 2022
  2. have you looked to see if you have a blocked fuel filter?
     
    Avid likes this.
  3. Yep, checked the filter and fuel running through (which I equated to mean it isn't blocked?). Got a new one at home though so might swap over in any case, just to be sure.
     
    paulcalf likes this.
  4. MorkC68

    MorkC68 Administrator

    Is your fuel tank clean (no paper from parts stickers floating around..it’s been known)
     
    Avid likes this.
  5. Hi Mark, the short answer is, I don't know (have had the bus a couple of years but not needed to tinker with the tank previously). I'm thinking it's likely to be something exactly like that though; at least I won't be the first!
     
    MorkC68 likes this.
  6. Any other obvious gotchas to look out for?
     
  7. mikedjames

    mikedjames Supporter

    You would only go about 10 feet on a full float chamber.

    Best case its a fuel tank crap blockage or points closing up..(its a 123 so no) . In this case it would crank normally but not start.

    Maybe a fuel pump pivot falling out , gravity works to help until the tank gets emptier..

    Worst case you overheated it because of mixture issues or timing issues, it half- siezed. In that case cranking would be slooow until it cooled down . .then its OK until it gets hot...
     
    Avid likes this.
  8. Hmmm that description of half-siezing when hot sounds ominously accurate ... it had cooled down when it restarted the first time. Feels like a happy weekend working through and checking/resetting everything is on the cards (assuming I can't locate a sticker in the tank)
     
  9. mikedjames

    mikedjames Supporter

    Mine did this but it turned out to be a blocked fuel filter.. no fuel (unlike your report, so not your issue) until you blew back through the filter and waited for everything to cool down.. but nothing came out if I pulled the hose off the pump inlet. Kept doing it pedal to the metal at the top of fast hills on a really hot day last year..
    Wouldnt idle, wouldnt start but cranked normally.

    Every time I could get at least 30-100 miles further..

    Changed fuel filter a few days later. no problem this year..
     
  10. Certainly won't do any harm to swap it out, so I've added it to the list. No shortage of fuel though if I pull the hose from the pump inlet.

    The more I think about the symptoms, they match up better with your suggestion of half siezing than my original idea.
     
  11. I would very much doubt that your engine is seizing.
     
    Avid, Meltman and Lasty like this.
  12. Now now, you have to make a suggestion of your own to be in with a chance of the grand "that fixed it" prize

    *equivalent monetary value of grand prize is likely to disappoint, t's and c's apply.
     
    Lasty and Jaysparx like this.
  13. Could be your coil overheating. After cooling down all was good for a while until it overheated again. Try swapping out the coil for a known good one. Easy fix if this is the issue
     
    Avid and mikedjames like this.
  14. Faust

    Faust Supporter

    Some one if you have no locking cap ..could have stuffed so plastic or other foreign matter into your tank that floats about then get dragged to the outlet restricting the fuel supply . It has happend before .
     
    Avid and mikedjames like this.
  15. Poptop2

    Poptop2 Administrator

    Coil, pump pin ( they wear ) or carb has a blockage somewhere maybe?
     
    Avid and mikedjames like this.
  16. Thanks chaps, a good list to work through for the weekend :thumbsup:. I'll report back on success/failure and see if any more pointers needed
     
  17. Ozziedog

    Ozziedog Supporter

    May be a vent block issue. As soon as it runs crap, take your fuel cap off and listen for a gush of air or a plop type noise, describing noises is not my strong suit I must admit ;)
    My other idea was similar ^^^ with some crap intermittently blocking your fuel tank exit and I’ve seen a few beeeeauuuties of these, predominately from when these vans were worth less than a hundred quid and peeps would use a plastic bag rather than buy a new cap worth as much as half the van and some would end up in the tank.:mad:

    Ozziedog,,,,,,,,,, you seem to have fuel a plenty when stationary :)
     
  18. Mr Apollo

    Mr Apollo Supporter

    We've had the same issue, see a thread about a month ago. Clearly running dry on a long motorway hill. Disconnecting the fuel line at the filter and blowing (having first attached a longer pipe to keep it above the level of the tank) seems to fix it. However, it just occurred to me that it never happened until after I replaced the fuel filter six weeks or so before the first time it did it, which was also the first time we hit the motorway after the replacement. Just out of habit I changed the fuel filter when I changed the oil, replacing a large filter with a smaller one. The replacement was a Bosch standard one said to be appropriate. I don't know the make of the previous one, but it was about twice the size. Is there anyway this could have influence it? The old one had a small amount of magnetic crud in the bottom, not much, the filter paper looked fine, but the plastic housing could hold a lot more petrol than the new one. Could the old one have been acting as a buffer, as it were, delivering more fuel when needed even though there was a slight blockage earlier in the line to the tank? Never had the issue driving off the motorway, where I guess the restricted flow could be filling the old filter up? I still need to clear any crud out of the tank/lines, but may fit a larger filter as well.
     
  19. mikedjames

    mikedjames Supporter

    All the filter can do is act as a resistance to flow. It can not store really store fuel unless there is a way of it changing volume or you can change the pressure in it a lot so the air bubble in it gets larger or smaller.
    If a smaller filter blocked up faster than a big one then there is a good supply of fine silt in your fuel tank.


    I think mine took more like 10-20k miles to block up exactly like yours... same scenario..
    One thing you can do is get a couple of big fuel filters, go for a drive to stir up the tank.
    Come back, connect up the first filter to the tank with a bit of hose on the output and a clamp or valve. Then keep filling a 5 litre fuel can through the filter from the tank and then tipping the contents back in to stir up the silt.. repeat..
    Discard the contaminated filter. Or connect up a loop with a filter and an electric fuel pump.. but dumping 5L of fuel in at once will stir up the silt.

    You could have the tank drained, removed, cleaned and phosphate. treated in the longer term.

    Then switch to the second filter and fit to fuel pump as usual
     
  20. Zed

    Zed Gradually getting grumpier

    I once found someone had fitted a petrol filter by kind of screwing it into the pipe rather than pushing it straight on. The filter inside the pipe had twisted and almost blocked the flow causing it to apparently run out of petrol on a run.
    Or
    The fuel pump pushrod can, when the plastic pedestal get hot, get jammed. The lever in the fuel pump it pushes can also jam up. Both these things happen at the top or near the top of the stroke such that the pump might still pump a bit with very reduced stroke as the pump spring fails to push the rod back down again.
     
    mikedjames likes this.

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