Hi,
I own a Liteace 1988 petrol 3y 4wd. When I switch off the engine the fuel level shown in the sight glass on the carb is at the correct level. However if I leave it overnight there is no sign of fuel in the sight glass at all which results in excessive cranking on start up to re-fill the float chamber.
Where is the fuel disapearing to?
I've checked the fuel lines and there are no leaks. I've also checked the filter and that seems to be fine. I can blow through the fuel supply line back into the tank so no blockages or restictions. No visible leaks on the carb and the float valve seems to be working fine i.e. it refills with fuel on cranking to the correct level and no more.
Any thoughts or ideas would be gratefully appreciated.
Many thanks,
Justin.
- (#15434) Justin, 17 Feb 05 03:45
Well, the fuel has to be going one of two places- back to the tank, or into the inlet manifold. Might be worth disconnecting the supply and return lines some evening to verify whether the fuel is syphoning back to the tank or not. If it is, I'd go with leaky valves in the fuel pump allowing the fuel to slowly flow backwards...
- (#15434) david miller, 17 Feb 05 03:58
A long shot here Justin as I run a diesel but, is your tank/filler cap vented? I do remember, on other petrol vehicles that a full, or partial, blockage of the fuel filler cap vent, could give the symptoms which you describe, especially if the fuel pump valves are in any way suspect and, it's worth checking the integrity of the check valves in the fuel pump. It has been known that a good petrol pump will cause the tank to "flex" if the vent is restricted and, overnight, that flexing, back to shape, can suck the fuel back.
After all, that disappearing petrol must be going somewhere and, unless there is a strong smell of petrol when you go to the vehicle on start up, my guess would be that it is syphoning back into the tank.
- (#15434) John Davis (Leics), 17 Feb 05 04:00
To add to what John's just said, you're likely to have a sealed cap, but a selection of checkvalves and possibly a charcoal cannister connected to the top of the tank...
- (#15434) david miller, 17 Feb 05 04:09
Also, re what David says about the inlet manifold, is there any possibility that there is a connection between a faulty crankcase breather, ie, leaving a depression in the crankcase which gradually pulls any surplus fuel into the bores?
Also, re the theory of a vacuum in the tank, a good test would be to remove the filler cap, momentarily, when stopping the engine last thing at night, therebye removing any vacuum, and checking the sight glass before starting next day.
- (#15434) John Davis (Leics), 17 Feb 05 06:41
Wow! Thanks for the responses guys - really appreciated.
I'll try your suggestions tonight and see what happens. I'll post my findings back here tommorow.
Thanks once again,
Justin
- (#15434) Justin, 17 Feb 05 07:31
after tinkering at various points throughout day i found that the fuel disapeared from the float chamber in around an hour and a half - much more quickly than i intially thought. this meant i was able to carry out a couple of tests last night and didn't have to do one a night as i first thought.
so first of all i disconnected the fuel lines and the fuel in the float chamber stayed at the correct level - so its not the carb.
i then re-connected the fuel lines and ran the engine, switched off, and removed the fuel filler cap. the fuel disapeared from the float chamber - so its not a vacuum in the tank problem.
therefore, based on these tests and whats been said above, it must be a leaky valve in the fuel pump.
i'll get on to that over the weekend, so once again, thanks very much for your help.
justin.
- (#15434) Justin, 18 Feb 05 05:39
May be worth seeing if the fuel filter is blocked, as you will be in that area anyway.
- (#15434) Clive (Bristol), 18 Feb 05 06:54
Justin, I have the same problem with my 1984 toyota torago 3y,2wd. Have you found problems with the fuel pump or the reason for the fuel loss?
paul
- (#15434) paul (western australia), 8 Mar 05 20:04