Runs, stops, wait a couple of minutes then repeat...

Discussion in 'Mech Tech' started by JT1, Nov 5, 2019.

  1. JT1


    Just limped back home after breaking down 5 times on a 5 mile journey.
    Symptoms - lack of power, then engine dies. Wait a couple of minutes then it restarts, runs for a few hundred metres then repeats itself.
    Back home I've noticed the fuel pump (electric) becomes much noisier just before the power fails (it's attached by rubber bobbins so is usually fairly quiet). If you put your hand on it you feel it thumping away, the engine note changes (becomes irregular) then it'll revert to its normal state and the engine runs smoothly again.
    So I'm thinking it's definitely fuel related :thinking:
    It's an elderly (6 years) JK pump so is this behaviour a sign of it beginning to fail or are there other areas I need to investigate before replacing it? Blocked fuel filter, dirt in the carbs? Fuel pump regulator failing?
    It's a type 4, twin Brazilian Solexes, the attached image shows the set up of the pump and regulator. Sorry it's a bit rubbish but it's pitch out there and not the best camera phone.

  2. I've an electric pump in the Fiat 500, and as its just above your knees (next to the fuel tank...) you can hear it pretty well!
    It tends to be noisier when there isn't much fuel going though it, so my bet is that its fuel starvation and the pump isn't getting enough fuel to it.

    My bus is doing a similar thing, but I know for a fact it wouldn't get a few hundred metres, so you should think yourself lucky :(
    Valveandy, JT1 and Faust like this.
  3. Blocked filter
    Something in the tank blocking outlet
    Low fuel level
    Water in fuel
    Stuck floats in carbs
    Coil breaking down
    Condenser or electronic ignition breaking down
    Engine seizing
  4. JT1


    Engine seizing:eek: - cheers Matty!
    Coil breaking down - it should be hot if it's failing - no?
    Hope to God it's not the tank as that's an engine out job to check isn't it?
    Purple likes this.
  5. You are lucky. with a t4 engine if you pull the carbs and fan you can get the tank out. But try the others first - I did but then had to bow to the inevitable and get the muck out of the tank.
    JT1 likes this.
  6. Dubs

    Dubs Sponsor

    It does sound like the pump is being starved of fuel. Check for any kinks in the hose, or change it if it looks old, it could be breaking up internally.

    You could test it by removing the carb end of the hose, and pumping fuel into a can for a few minutes.
    Lasty, JT1 and mgbman like this.
  7. do you have a fuel filter between tank and pump? as said the best way forward is to remove the fuel hose from the carb and check fuel is being pumped.
    JT1 likes this.
  8. JT1


    Didn't know you can get away with wriggling the tank out without removing the engine, thanks Andyv. I'm hoping it's not that

    Good idea to check the hoses and pull the pipe and check for flow Dubs, it idles ok so there could be a restriction which only shows up when more fuel is needed and yes mgbman, there is a filter, a Ford Ka one I think, fitted by 81a shortly after I got it and that's where I'll start as it's knocking on a bit and must be due to be changed.

    Thanks again for all the help. :thumbsup:
    Dubs likes this.
  9. One other thing to check is, is the air getting into the petrol tank to replace the petrol, if not it can create a slight vacuum which could cause the issues you are seeing. Next time it happens open the fuel filler and you should notice if there is a partial vacuum. Probably not the most likely but has happened in the past and is easy to check.:)
    JT1 and mgbman like this.
  10. I replace my fuel filter once a year at least with a large Meyle clear plastic one, its not just the rusty bits from the tank, but waxy crud caused by Ethanol in the fuel, the waxy stuff can also clog up the carb. Ethanol is a pain.
    JT1 likes this.
  11. The fuel pumps do get noisy when no fuel is in them, Thats what happened to mine just before I ran out !
    JT1, mgbman and Dubs like this.
  12. JT1


    Yes I was thinking that too. However when taking the fuel cap off there was no 'whoosh' so I'd assumed it was breathing as VW intended. What's the simple check you use Surfari?

    It is, it attacks soft metals too so your SUs will not like it either. I only use Esso Supreme + which in this neck of the woods is ethanol free but the filter is overdue for replacing; good tip to use a see through one to see what crud its capturing in there.

    Me too, the fuel gauge is hopelessly optimistic and that's what I thought it was originally as the pump went mad!
    F_Pantos likes this.
  13. That should do it, and it should run better straight away:thumbsup: It sounds like the pump isn't getting fuel, its also possible there is something in the bottom of the tank, I've heard of the paper seal from some Redex getting stuck in there and even a pair of underpants:eek: (presumably it was used as a makeshift petrol cap at some point).:thinking:
  14. JT1


    Underpants! Heard of tights being used as an emergency fan belt but not that. Imagine explaining that to the mechanic who fished them out :oops:!
    Guess what I'll be doing this afternoon and it won't involve underwear.
    Surfari likes this.
  15. What, you're doing it commando style!!!
    Lasty, JT1 and scrooge95 like this.
  16. Ok here's an idea:eek:
    Attach some fuel line to the pump output and feed it back into the filler neck, energise the pump (turn the ignition one step?) and let the pump run, if its all good it should run smoothly, if its a flow issue it should quickly show up as it will be pumping at full capacity.:thinking:

    Well what does the collective think?
    JT1 likes this.
  17. I’ll reiterate the layman’s formula for is there enough pressure in my fuel system. Take precautions to make sure the motor can’t start, like rotor removal or whatever. Disconnect fuel pipe as close to both carbs as poss before it spurs off. Plonk fuel pipe into a clean second hand clear one or two litre water bottle shove it in an inch or so and have the bottle laying on its side. Energise you’re fuel pump and it should almost jet to the bottom of the bottle. If it does and continues to do so for a good thirty seconds or so then the supply issue is past this point and closer to them carbytooters. If it don’t do it or does for just a short period, then you can isolate the pump and give the pump a new supply and try again, if it works well then it’s the fuel supply line and not the pump but if the pump can’t maintain a decent head with a clear and new supply then I’d say your pump is goosed.

    Ozziedog,,,,,,,, just track it down:)
    JT1 likes this.
  18. JT1


    Update - decided to start with the fuel filter, changed it and went for a 3 mile drive (around the roads near home - just in case...) and it performed fine. Gave it some beans too but not 100% convinced the problem is solved yet as even with the old filter it would tick over fine, only when on the move did the problem manifest itself. May take a couple of brave pills and venture onto the local dual carriageway latero_O
    jivedubbin likes this.
  19. JT1


    Took a couple of brave pills, went out and dead as a dodo. Battery & ignition light glimmering very dimly. Hadn't left anything switched on but it is cold. Now on charge but suspect battery may have decided it's had enough.
    Doesn't bad luck come in threes?:(
  20. You have probably killed an old battery with many starts and not enough fast running...or your alternator is needing a check over...

Share This Page