'Bleeding' diesels

[DavidJ]

\'Bleeding\' diesels

This is my first season with diesels (Sealine S37 with twin KAD43's) and although I am very competent with petrols there does seem to be an emphasis on filtration of water from the fuel.
I have a first fuel filter which is fitted to the boat and is about 2 metres from the engine and a second 'Volvo' filter on the engine.
I tweeked the little tap thing at the bottem of the first filter, nothing came out except air seemed to be sucked in. This I had to laborously bleed off at the engine end and being so far from the engine took ages.
I feel like I'm missing a trick or two. Please explain if I really have to go through this, if so how often and is it really the messy operation that I have experienced.
David

 

[pete]

Re: \'Bleeding\' diesels

Did you stop the engines before draining the water ? as the system could well be under a negative presure with the pumps running unless the fuel tank is high and producing a head of presure greater than the pumps suction.
Good luck

Pete

 

[DavidJ]

Re: \'Bleeding\' diesels

Yes the engines were stopped. You've got me thinking of where the negative pressure came from. Unfortunatly I can't remember whether the tanks were full or near empty which may have a bearing on the pressure situation
David

 

[Doffy]

Re: \'Bleeding\' diesels

If you have neg pressure in filter it means that between tank and filter you have a blockage or restriction, we had a bit of ptfe tape which acted as a flapper across a valve and stopped the engine every 5mins.

 

[hlb]

Re: \'Bleeding\' diesels

Screw thingy on bottom of first filter is to drain off water. If air comes out you have another problem which needs sorting. Only three things stop a diesel engine. Air and waterand muck. All stop the engine getting fuel. All are easy to stop.
Easy way. If a bit messy, to bleed air, is to slacken off an injector pipe or two and just turn over engine. Stick a rag over it to stop diesel going all over the place. Tighten whilst engine is still running. Course if theres still an air leak you still have a problem. Go round all the pipes with a spanner. Or it might be a knackerered olive. My last one was on the tank fitting. The only one I had not checked.

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Haydn

 

[brianrunyard]

Re: \'Bleeding\' diesels

The "tap thingy" on the bottom of the first filter is to drain off water, you should stop the engines first, otherwise, as the lift pump is causing a slight vacuum it will suck air in.
Regards,
Brian

Brian
http://homepage.ntlworld.com/brunyard

 

[c_j]

Re: \'Bleeding\' diesels

Why is it on this forum nobody reads the Effin question.

The pre fuel filters (or water seperators) have a little screw thingy on the side of the caseings (are yours glass bowls) to allow air into the system to let the water/dirty fuel out of the tap thingy on the bottom. You will get nothing (much) out of the taps if this screw thing is not undone.

No bleeding should be necessary as long as the fuel is on. If you decide to change the pre fuel filters then you MUST turn of the fuel and in my experience if you prime the filters with CLEAN fuel then no bleeding is necessary their either.

Did you make the mistake of turning off the fuel prior to turning the tap thingies?

If you did then I can see that air might be sucked in.



CJ
chris@stone.uk.com

www.stone.uk.com

 

[DavidJ]

Re: \'Bleeding\' diesels

Chris
Thanks for your reply and everyone else.
Mine are not glass bowls (which seems a great idea!) and I'll have a look for some side screw thingy. I notice from the Volvo instructions for the engine fuel filter that there is a top one which has to be undone before undoing the bottom thingy.
I didn't turn off the fuel during the operation.
David