Fuel Flow problems - Update

[rajjes]

Further to my mail last week when the engine died with a collapsed fuel bulb priming pump, This weekend I went down to check the fuel lines expecting to find some blockage upstream from the bulb.

I disconnected all pipes and to my surprise everything was clear, however on testing I noticed that it takes quite an effort to blow from the tank side of the primary filter to the disconnected fuel bulb.

I am thinking that the problem was caused because the fuel tank level was down by half (for the first time) so there was less pressure, and as I have a Racor primary filter rated at 10 microns it is restricting the flow? These 2 factors seem to be generate quite an effort on the engine pump to suck fuel through to an extent that the rubber pump is collapsing and blocking the flow itself.

To address this I’m aiming to change the primary filter to 30 microns, top up the tank and remove the bulb.

Your thoughts on this are appreciated.

 

[pvb]

[ QUOTE ]
To address this I’m aiming to change the primary filter to 30 microns, top up the tank and remove the bulb.

[/ QUOTE ]I'd certainly remove the bulb. But I wouldn't top up the tank yet - your fuel system must be capable of working with an almost empty tank. As for the filter, your engine ought to be able to suck fuel through a 10 micron filter, and remember that the quantity of fuel your engine is using is very small. So, get rid of the bulb first, and see whether you still have problems.

 

[Stoaty]

I would stick with the 10 micron filter. It is a normal size and unless it is blocked with debris it should not cause a problem. The bulb being sucked flat tells you that the pump and or lift pump is working OK. I would go back to the tank and make sure the vent is not blocked and that the tank outlet is not being choked by something either floating around in the tank or in the pipe between the tank and the bulb. If you remove the bulb from the line the fuel should flow from the tank. If it does not, then the tank has debris in it. Catch the first pint in a bottle for examination. It should be clean.

 

[oldsaltoz]

Agree with above, though this sounds like a blocked filter, perhaps the tank has a pick up strainer and its partially blocked.

 

[barryhall]

Just a thought but was it unusually cold - it may be that the fuel was "thick" enough to cause a higher than normal pressure drop throught the filter and this caused the bulb to collapse, I don't think it takes a lot to suck the bulb flat and a small change in viscosity may have been enough.

Barry

 

[No Regrets]

No, that doesn't happen....(Unless you're in the arctic)

It sounds like a defective valve in the fuel priming system...?

 

[rajjes]

Well, it was cooler than usual but as I'm basedin Malta it was still some 14C /forums/images/graemlins/wink.gif

there seems to be consensus on keeping the 10 micron filter as primary. does anyone use 30 microns as primary?

 

[barryhall]

Based in Malta - forget my post then!!!

Barry

 

[morgandlm]

No, that doesn't happen....(Unless you're in the arctic)

Sorry .. but must correct this statement even though it is clearly not the problem in this case. Diesel fuel can be subject to waxing in cold temperatures that need only be a few degrees below zero. The wax appears as cloudiness and can quickly block filters. Additives are used to lower the temperature at which this occurs but you most certainly do not need arctic temperatures to experience it.
Morgan

 

[vyv_cox]

I agree, it has happened to me several times in North Wales. Diesel sold in winter is treated to reduce the waxing effect, but if you are a small consumer it is quite likely that the tank will still contain summer fuel. A pint of petrol will usually be enough to fix it. Yes, I know this is a safety hazard but it's something that truck fleets have been doing for decades.

Maltese users are undoubtedly safe from this problem.

10 microns is quite normal for a fuel filter. I still suspect that you have a problem in the filter.