Last couple of times I’ve driven the bus it’s been struggling to tick over correctly and a bit smoky. Ok on a drive and still pulling fine but obviously something not working properly. On startup I can normally hear the elec fuel pump clicking for a few seconds then stopping once it’s up to pressure (huco low pressure pump). Once it’s stopped clicking I give it a few pumps then I will usually start on the first turn of the key. Coinciding with my running issue I’ve noticed the pump not stopping (ignition on, engine not started yet) which made me think needle jets either stuck open or worn, so it’s not getting to pressure- just keeps pumping more fuel through which would explain why it’s idling poorly. so, got me some nice new viton tipped needles. Just in the middle of swapping them over now. Old ones have been in for maybe three years now and they’re definitely showing signs of wear. question - new ones have a hole that I don’t have on the old ones - what’s that for and will it cause a problem?
If you look at the needle , it has three ridges. Between the ridges, the fuel can flow. All that is going on is that the extra holes can let out fuel of the sides of the valve rather than running out of the bottom of the valve. No real difference. One thing I have to add (based on recent experience) is that the viton tip compresses slightly with time so the float level may eventually need to be dropped by a couple of mm to avoid too high fuel level and dripping down the throat causing juddering at low load, or the the reappearance of the symptoms you get off a worn needle. As Larry Niven has it..there aint no such thing as a free lunch ...
Ok they are fitted and I just fired it up. Absolutely no difference Ignition on, engine not running, the pump just keeps going where previously it would have shut off when it was up to pressure. Float heights were fine, maybe one of the floats isn’t floating? Or fuel pump pressure sensing stopped working?
Possibly that. Mine does this from time to time but it's never flooded the engine. A mystery for me too as my pump is powered through relays that should ensure it only pumps with either the starter churning over or the alternator kicked in. lol As long as it's not filling the engine with fuel I'd shrug my shoulders and carry on (like I do).
The viton needle may be slightly different in length to the older brass one. Make sure you reset the float level according to the book. And check again in a few months based on it squishing down.
Plus your pump may have a bit of crap in the outlet non return valve or have some wear so it leaks back a bit now. If its one of the solenoid type ugga chugga pumps it should at least slow down.
Ignition on engine not running Clamp the fuel pipe after the pump If the pump stops running then I’d say you either have a fuel leak after that point or the float valve/valves are not shutting off properly
How does the pump know to shut off . Pump should surely only put out a constant 3/4 psi ? It should be wired that it runs off the coil when engine is running ?
I wouldn't expect the pump to keep stopping and starting. Most odd. Ideally it shouldbe powered through a relay.
it has a pressure sensor within the pump itself. its wired via the coil, on with ignition. i wired mine also via the fire extinguisher so if that's triggered it cuts power to the pump and also shuts the (separate) cut off valve i have installed. its been fine for 3 of 4 years.. http://www.gowerlee.dircon.co.uk/HU...ves upwards,pushed through the pressure valve. Planning to test the floats tonight.
I find my pump overruns and i get some flooding on left carb if im parked at a particular angle with front pointing downhill and van leaning to left (kerb side) or at least that's what i observed when messing with float heights. probably totally irrelevant to you but nevertheless its a thing!
Just to update my own thread in case this happens to someone else, I tested the pump by blocking off left then right carb. Pump stopped ok with the right carb tube stopped, so the pressure sensor still works, but just kept pumping when I had the left tube stopped, with the right carb just filled up and overflowed. Changed the float for a new one and checked the height and it seems to have solved the issue. I’m out tomorrow for Bicester Sunday scramble so that’ll be a good test.
