Mysterious Fuel System Fault

[Doug]

Any clues? – When cold or warm, the engine starts without any trouble although it is ‘rough’ and has to be gently nursed to above idling. It can then be revved up to the max without any discernable problems although there is the occasional ‘miss’ every few seconds in the 1000 – 2000 range.

Driving until the engine is hot it appears to be OK and then begins to miss at all speeds and will stall if slowing down (it can recover if taken out of gear and revved up) but then starts to stall again at lower speeds. It is then almost impossible to start again (or drive) but the problem continues when it does!

Leave it until the engine is cold and the engine is back to the same condition as at the start of this tale of woe above. The Bongo is now un-driveable and SORNed for the moment.

It has had injector cleaner, new fuel filter, and the glow plugs have been checked. The problem is a complete mystery and discussions with a couple of local mechanics have not helped except to say that it may be a process of elimination with everything on the fuel system – sounds an expensive route to put it into a garage.

Any opinions will be greatly appreciated.

[francophile1947]

First check the simple and free. Fuel filter changed, but was the banjo filter cleaned? It's a small strainer under the fuel pipe union where it joins the pump. If you do a search for banjo, there's loads of info on here.
Failing that, are there any signs of a fuel leak?

[Doug]

The fuel filter was changed by my local garage and they were aware of the banjo filter - I'll check myself as soon as the snow clears a bit, thanks for the suggestion Francophile.

[BongoMTBer]

Doug, you may wish to consider my post here: http://www.igmaynard.co.uk/bongo/forum/ ... 80#p460980

Good luck.

[Doug]

Thanks for the suggestion BongoMTBer, but I did try running without the cap. Because there is a problem on start-up (it really struggles to keep going on idle when cold until I gently lift the revs), I couldn't see how it could be a vacuum problem but thought it had to be eliminated.
It's the two symptoms at cold and at hot that stumps me - why start when cold but not when hot? - and that's apart from the fact I daren't even take it out on the road until I find something wrong. I'm sure it's just one problem, so when I fix the problem at idle speed, everything will be OK.

Doug

[helen&tony]

Hi
I had a similar problem on an old Diesel Landy....The problem was a pinhole in the fuel line , so when parked up, or sometimes on a run, the fuel wanted to run back to the tank....not an uncommon problem....now on a Landy , it meant bleeding the fuel system every time until I put a new fuel line in, but as the Bongo is self-bleeding, it MIGHT be what's giving those symptoms...and the fuel line should be replaced every so often anyway...not an expensive task, and quite easy!
Cheers
Helen

[fatcatlawyer]

My bongo (2.5 Diesel) has been a sod to get going and I put it down to too much oil in the fuel. However, following it not starting on Wednesday and every day till this morning after charging the battery each day, I did some checking and realised that the fuel supply line to the pump from the filter was "loose" on the inlet pipe just above the banjo filter. A new clip tightened it up and it seems all OK now. It is a matter of physics, it is easier to suck air than fuel and any hole in the fuel line could cause problems.
ian G

[helen&tony]

Hi
Exactly, Ian...it is the same scenario,,,remember, though, the fuel lines need replacing...it's on my ROUND TUIT list...and brake lines (flexible)...and...and...
Cheers
Helen

[mister munkey]

Leaf in the tank scenario?. Swishing about when on the move but gradually being pulled toward the feedline after a while causing a blockage.

Leave it for a while & it drops away again . . . . .

[Northern Bongolow]

have a look round the vacuum pipes,in particular round the egr valve. is the cold start working/moving the throttle on start up.

[BongoMTBer]

Thanks for the suggestion BongoMTBer, but I did try running without the cap. Because there is a problem on start-up (it really struggles to keep going on idle when cold until I gently lift the revs), I couldn't see how it could be a vacuum problem but thought it had to be eliminated.
It's the two symptoms at cold and at hot that stumps me - why start when cold but not when hot? - and that's apart from the fact I daren't even take it out on the road until I find something wrong. I'm sure it's just one problem, so when I fix the problem at idle speed, everything will be OK.

Doug

Doug, I meant my post before that. My symptoms were similar (ie. running like a dog when hot). When the pump is warmed up, the nose seal leaks on the input shaft, causing air to be drawn in. A cheap fix, but certainly checking the fuel lines first is the way ahead due to the pump removal. Anyway, if you work your way to diagnosing the pump, then don't buy a new one as a lot have people have on this forum, unles you try changing the nose seal first.

[mikexgough]

Thanks for the suggestion BongoMTBer, but I did try running without the cap. Because there is a problem on start-up (it really struggles to keep going on idle when cold until I gently lift the revs), I couldn't see how it could be a vacuum problem but thought it had to be eliminated.
It's the two symptoms at cold and at hot that stumps me - why start when cold but not when hot? - and that's apart from the fact I daren't even take it out on the road until I find something wrong. I'm sure it's just one problem, so when I fix the problem at idle speed, everything will be OK.

Doug

Doug, I meant my post before that. My symptoms were similar (ie. running like a dog when hot). When the pump is warmed up, the nose seal leaks on the input shaft, causing air to be drawn in. A cheap fix, but certainly checking the fuel lines first is the way ahead due to the pump removal. Anyway, if you work your way to diagnosing the pump, then don't buy a new one as a lot have people have on this forum, unles you try changing the nose seal first.

Good tip although didn't work on mine, still needed a new pump.....you should have seen the swarf recovered from the Injectors.... .....my pump was "breaking" up inside.... Been brilliant since my replacement last December.....especially as the Diesel pump has been re-timed spot on.....with a DTI

[Diplomat]

Leaf in the tank scenario?. Swishing about when on the move but gradually being pulled toward the feedline after a while causing a blockage.

I'm wondering if leaves get into the tank when Bongonauts are taking the cap off at home to pour in some veggie oil and going back and forth to the hoard for the next can with the filler left wide open?


After all, you don't tend to find trees enhancing the forecourts of filling stations!


Frank

[The Great Pretender]

Thanks for the suggestion BongoMTBer, but I did try running without the cap. Because there is a problem on start-up (it really struggles to keep going on idle when cold until I gently lift the revs), I couldn't see how it could be a vacuum problem but thought it had to be eliminated.
It's the two symptoms at cold and at hot that stumps me - why start when cold but not when hot? - and that's apart from the fact I daren't even take it out on the road until I find something wrong. I'm sure it's just one problem, so when I fix the problem at idle speed, everything will be OK.

Doug

Doug, I meant my post before that. My symptoms were similar (ie. running like a dog when hot). When the pump is warmed up, the nose seal leaks on the input shaft, causing air to be drawn in. A cheap fix, but certainly checking the fuel lines first is the way ahead due to the pump removal. Anyway, if you work your way to diagnosing the pump, then don't buy a new one as a lot have people have on this forum, unles you try changing the nose seal first.

Also worth fitting a pump before IP to put it under positive pressure, a quick fix until the Bongo can be off the road for repair.