Are symptoms of a fuel pump giving up slow or instant?

[benw]

Just wondering if las two engine failures are related to the fuel lift pump. After running for over several hrs no prob approaching Cherbourg engine started losing power and then gave up. Resisted tow option and sailed last mile or two in very light airs. About two hrs later using the cold start method and five attempts she ran ok getting us into a marina berth. Filters changed less than 15hrs motoring ago. Engine has done more work than normal as heading from East Cst going west with prevailing westerlies of recent week.

 

[rob2]

I can't think of any failure mode for a lift pump that would be slow to reveal itself. The only possible exception, which isn't really a pump failure, would be a slight leak somewhere in the supply line. Sometimes despite the lift pump's best efforts an imperceptible leak will allow the injector pump to suck in air which can make the engine either lose power or possibly stop. What happens next is down to the layout of the whole fuel system. If the tank is the highest part of the system, then gravity feed can refill the line and it will start OK after sufficient time for it to fill. The failed starts may have been all it needed to purge the bubbles of air out of the lines - some engines are self bleeding, others aren't.

My own experience of this type of failure (luckily had an experienced diesel user on board) was that the fuel hoses had softened under the compression of the Jubilee clips. There was no visible leak of fuel from the joint but it allowed the injector pump to suck air through! The quick fix was to cut the affected part off and remake the joint which got us home along the south coast, but I did fit new hoses to hold it off longer and allow it to be properly routed and clipped again. Before we found the problem, the stoppages were becoming increasingly frequent - involving an interesting arrival in Ramsgate harbour under sail. Even if it doesn't turn out to be the main problem, it would be good to have eliminated it as a possible cause whilst fault tracing.

Good luck,

Rob.

 

[prv]

Did you change the filter after the stop? That would always be my first step.

I know you said they were changed fifteen hours before, but when we had a tankful of sludge in Ariam they were clogging much quicker than that.

Pete

 

[nimbusgb]

Blocked breather? Gunk in tank?

 

[lw395]

Next time it's not keen to start I would crack the feed to the injector pump, if no fuel spurts out, that's your problem.
If a mix of air and fuel comes out, air is leaking in somewhere.
Yes it could be the pump, or it could be blockage elsewhere, air leak etc.

 

[KellysEye]

Could be an air leak. Put talcum powder around the bleed screw, all fuel joints, all filter bowls connections and anything else you can think of that might leak. Diesel will go through a microscopic hole and let air in. Run the engine for an hour and the check talcum, any diesel will be obvious. It's worth doing, it might prove there isn't a leak so you can rule that out.

 

[benw]

Thanks chaps for your thoughts. I have discovered the problem lifting fuel was the gauze filter was so blocked with crud and what looks like seasons upon seasons debris. Once cleaned , replaced raccor and fine filter both of which looked clear the fuel pumped brilliantly. In fact the range of the pumped increased massively. Engine started first time and sounded like an engine sipping diesel should. Feeling slightly stupid for not checking this as o noticed lifting fuel into the filter after changing before. Anyway looks like problem solved.