WB fuel problems

[SLR_dave]

I was coming back from a trip the other day, and was running low on fuel. The store I thought I could get fuel from didn't have any, and I got home by vapours.

I'm thinking that there is gunk in the bottom of the tank? or would it be in the fuel line? I can't get under it, so I'm just wondering if there's anyting I can do without getting it towed to the mechanic.

Hi xale,
I think you've pretty much answered your own question here.

What happens is of course is as you have suggested. The car is more than 30 years old, it is very likely to have all sorts of sludge in the bottom of the tank. The fuel pick up from the tank on these vehicles is attached to an arm on a float that sends the signal to the fuel gauge. This means it draws from close to the top of the fuel level of the tank. When you run it close to empty, the fuel is now being picked up from the bottom of the tank. Grains of grot/dirt/sludge tend to get sucked up and into the fuel system. This material (depending what is is) can block up just about anything in the line. Quite frequently an issue will be dirt blocking a jet in the carburetor, but that wouldn't usually stop it starting - its possible of course. (Dirt in the jets will usually make it run poorly and be really difficult to drive, but -usually -it keeps going in some form).

If its not starting, and you aren't getting fuel at the "first" filter (how many filters have you got on it btw?) and you got some fuel back after blowing into it, it sounds more like the line between the tank and the filter. A block can form in this line just about anywhere I spose, but where the rubber hose goes around the corner coming out of the tank, as well as the joins and other bends are suspect areas. Its also possible a really sludgy tank could block the mesh on the fuel pick up in the tank. Its also possible that the vent pipes at the separator could get blocked and maybe slow the flow rate... but I'd leave those till last.

A useful thing to know when you get this sort of problem, is that its easy to actually create a carburetor jet block as a secondary problem when working on fuel lines. This is because whenever you separate and re install an old piece of rubber hose from the line it may have granulation's of rubber that break off on re-installation, these then flow up the line - often straight into the carby. If this happens you can introduce a new problem because they are a great size for blocking a carby jet.

So it can often save a later headache to replace hoses you take off with good new hose (not the Chinese stuff, it perishes in a few years) or at least make sure the end of the hose is cleanly cut, and not be overly casual when refitting it.

Blowing with your mouth may not be enough to clear a fuel line block. You may need to blow the line back with compressed air (take the fuel cap off first), not too high a pressure, be prepared for fuel to rush back out the line when you take the compressor off it (and all over you if you are at the join under the car) - (lol).

All that said, Vombils advice is sound. Once you think the line is clear, start with a full tank, (or at least 3/4 full if you can). With the tank that full it should flow fairly freely on its own to gravity before the fuel filter in front of the fuel pump with the car on level ground (check the hose position at the motor of course, needs to be about chassis level, and might need some suction to start it). If it doesn't, you have have a problem backward toward the tank from there. (Btw, I'd be getting it to a stage that I felt it was blown out and clear at the joins under the car before filling it - 1/2 a litre of petrol on the torso is a good thing to avoid!!)

You may need to have a good look at the hoses that come out of the tank to get the line clear first. Why is it you cant you get under the car? (I'm just thinking if there's some issue with the way its parked, you might be lucky, could be half your problem?)

Dropping the tank to do a full system flush is a pain in the butt, usually you wouldn't bother, just keep the tank above 1/4 full after fixing the prob, but in some cases you may have to have a good go over everything.

Best of luck. Btw, if you do end up with your shirt soaked in petrol don't put it in the wash! You'll end up with petrol spread though your machine and subsequent wash load(s). Just hang it on the line in the hot sun for a couple of days, till the hydrocarbon evaporates and you cant smell it anymore. Then wash it.