Diesel defeat

J

jav301

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Having finally replaced my rusty old fuel tank with a plastic one and filled with clean fuel, renewed both filter elements and connected everything up, I was expecting trouble-free motoring.

No such luck. Everything worked fine for a while, then the ominous change of pitch, revs dropping, faltering, and stopping that used to ocurr when the filters were clogged in the past.

The engine will normally start again after some time but it always happens at critical moments- of course.

The engine isn't overheating, it does emit a fair amount of white smoke at high revs, but otherwise no clues.

I am now at my wits end. Anyone got any ideas?

It is an old Petter ACW1.

Thanks
 
Possibly an air leak on the pipework
What have you used to seal the connections. This sounds like a PTFE tape break down - it should not be used near a diesel pipe!
 
I had a similar sounding problem with my Hydromarine DM12 last year. At first we thought an air leak and tightened everything up and bled it but no improvement even after bleeding quite a few times.
Then put new fuel lift pump in. Small improvement but only temporary.
Eventually went through the fuel system with great care and it started working. Our conclusion was that there was an air pocket that didn't bleed out easily and kept allowing enough air into the injectors to stop the engine.

Once it was running reliably I also used an oil flushing additive at next oil change and it is now a lot smoother too!

My conclusion is that bleeding air out of the system is not simple or reliable. You need a bit of luck too.

Hope you get it sorted
 
Also, describe your clean fuel...

Where did you get it? It is possible you could have put bad fuel back in, red diesel is notoriously variable in quality.
 
[ QUOTE ]
Also, describe your clean fuel...

Where did you get it? It is possible you could have put bad fuel back in, red diesel is notoriously variable in quality.

[/ QUOTE ]

?????? Red diesel is what ? Sorry to take you up on this - but Red is subject to Specs that ensure it is NOT notoriously variable ..... it may differ from country to country - but even then it's not as you imply with such an open ended comment !

Maybe I'm doing something wrong in my lab then that I haven't seen this ??
 
Exactly: the fuel in all marine outlets is identical, it's the quantities of water, bugs and other detritus that varies! /forums/images/graemlins/confused.gif
 
Lump of dirt in a pipe.

Normally happens with the fuel pick up pipe but any constriction in the piping will cause it. Try flushing all the pipes.

Just imagine a rough dried pea in a vertical pipe with a restriction. As you use more fuel it is pulled to the constriction and restricts the flow. Once the engine stops it falls back. Hence the normal effect of engines failing when you really need them.

There was a poor Alaskan that ended up buying a whole new engine in Spain only to find that the new engine did the same. It was a piece of flaked rust in the fuel line before the restriction of the fuel pump hose tail.
 
Had a similar problem with my brand new Yanmar 1gm10 this year - running ok 99% of the time, then dying or spluttering, followed by restarting almost immediately. It turned out that the engine fuel filter bowl wasn't completely tight and I think it was letting minute quantities of air in, but only the slightest hint of fuel was evident on the outside of the filter bowl. I (mistakenly) assumed that, being new, it would have been fitted properly. Every other screw thread on the thing is tightened to an incredible torque!
 
I had a similar problem last year - engine would run fine for upwards of an hour then gardually faulter. It turned out to be caused by a tiny pinhole in an old metal braided flexible fuel pipe - too small to let fuel escape but big enough to let tiny amounts of air in. It was a devil to find as it only actually leaked when the pipe was displaced slightly one way-I just happened to nudge the pipe with my elbow as I was operating the manual bleed pump and could actually hear the air going in under suction. Replacing with a new fuel pipe did the trick and no problem since.
 
A friends boat had same problem after he had fitted a new plastic diesel tank .The fault was that the plastic spout on the pick up pipe had a very short barb and had squashed when he fitted the jubilee clip admitting air.
Good tank but poor fittings in my opinion.
Pete
 
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