by Progenator » Tue Nov 27, 2018 7:33 pm
You mentioned something about air sounding like it was hissing it when you open the water-drain tap at the bottom of the fuel filter. That denotes to me a problem right there. It could be a blocked filter, but it could also be a blocked inlet into the filter/fuel line. This is a problem I see often on tractors where farmers have muck falling in when they fill up their tank with Diesel, grass, straw and pine needles, anything you can imagine gets into the fuel tank over the years. This then gets sucked up to the intake of the filter and sits there blocking fuel before it gets to the filter paper itself. Well, in fact it often eases off when the engine is shut off such that it allows fuel past to some degree (so it starts), then it blocks totally or partially when the fuel is sucked through. This means a problem that is hell to find unless you know about it and look for it. All you have to do, in theory, is remove the filter unit and visually inspect it and perhaps blow it out with a compressor (too dark and bad angle to check with torch and mirror in-situ usually - I have tried it). But that still leaves muck in the fuel line, and the only way to get it out is to suck the line somehow, or blow it through from the other end (means you have to take the line out of the fuel tank = big-ish job). But to make matters worse, sometimes - million to one chance (but it happened to me on holiday...) a conical pebble had got wedged into the fuel pipe intake *inside* the fuel tank, It couldn't fall out, but it wasn't stopping fuel totally, only partially, until driving, then it would be sucked right in and stop the engine. After stopping, it would fall halfway out (but not right out). I could even blow compressed air down the pipe and it seemed clear enough! I was tearing my hair out with this one till I removed the entire tank and started from square one to find the fault. I'd never seen a cone shaped pebble in my life before until this one ended up in my fuel line. But it does sound to me as though you may have something stuck inside the fuel line or fuel filter unit intake. Run the van from a clean bottle of diesel and see if the fuel pump sucks there and the van runs - then you can trace the problem back. The good news is that generally the muck stays by the filter inlet or at the top end of the fuel line so it can be pulled out/sucked out and is clearly visible if you make a sucking device that allows the sucked fuel to fall into a glass jar. Don't try blowing the line down into the tank to test it, or the muck just comes back later. With some vehicle's fuel tanks you can put your hand over the filler cap hole and stuff compressed air down the fuel return line - enough to flush the feed line outwards with mild pressure.
PARTIALLY BLOCKED FUEL LINE, BLOCKED FILTER INTAKE