Air still getting into fuel - please help tearing hair out

sj8070 said:
But a counter to the tank pickup possibility is that we don't see air in the bowl (though they are hard to observe as in an awkward spot...)

How much air would be visible?
Volvo Paul has never been to Barcelona
When I pump the manual lift pump to bleed it it takes a long while for fuel to come - does this not indicate there's a fair bit of air in the system ?
Click to expand...
Volvo Paul has never been to Barcelona
 
On my old boat I had issues with the engine starting to race and settle down again usually while under a bit of load, I tried all sorts to track down the problem and ended up grafting a pressure/vacuum gauge into the line after the pump (it had electric pumps), this finally told me it was going into vacuum so a blockage not a leak, a previous fuel problem I had was given away by primer bulb on the pre-filters as it was sucked hard down, that turned out to be a flake of crud partway up the pickup pipe needing rodding out.
 
my money is on a blockage - loads of pumping to prime the engine is a clue. If it was just air it usually comes through quite easily.
have you recently used a fast fill pump or moved the boat by road ? which engines do you have ?
 
kashurst said:
my money is on a blockage - loads of pumping to prime the engine is a clue. If it was just air it usually comes through quite easily.
have you recently used a fast fill pump or moved the boat by road ? which engines do you have ?
Click to expand...

hi kashurst yes we just recently moved the boat by road - we have been having the problem ever since
engines are volvo AQAD31Bs
 
Having read the thread the symptons remind me of a similar problem I had with a Volvo once and it turned out to be the lift pump, it had an internal leak and was allowing air into the system, the way I found out was when I fitted a piece of clear hose before the pump to see if air was coming through the system, it wasn.t but when I fitted the clear hose between the pump and filter it showed bubbles in the diesel, a new pump cured it.
 
spannerman said:
Having read the thread the symptons remind me of a similar problem I had with a Volvo once and it turned out to be the lift pump, it had an internal leak and was allowing air into the system, the way I found out was when I fitted a piece of clear hose before the pump to see if air was coming through the system, it wasn.t but when I fitted the clear hose between the pump and filter it showed bubbles in the diesel, a new pump cured it.
Click to expand...

We need a like button!
 
I moved a boat by road and then used a fast fill pump - starboard engine went really funny the next day, surging then stalling, hard to start etc. Got local mechanic to try and cure it. He diagnosed something in the fuel pick up pipe so he disconnected the pipe at the Racor filter and ran a stiff wire (front door bell twin wire I think) right through the pipe into the tank. That seemed to cure it for a few days. Then same problem came back at a most inconvenient moment.

Took every connection apart and the fuel shut off valves out and checked everything. Piece of metal swarf jammed inside one of the ball valves. Sorted.
 
If it's affecting both engines then it would be quite some coincidence for the filters to have sprung an air leak at the same time, ditto a problem from the tanks to the filters (am assuming you have two tanks?), so I'd be thinking it was rubbish or sludge in the bottom of the tanks/tank... if one tank was affected I think the other could easily be expected to be - yes?

also; if your filters were letting air in through the seals then once your engines are shut down that would turn into diesel seeping out and into the boat, gravity would take care of that...
 
I would still whip off the -spin on - engine 2nd ary filters to check for "double o ring "
Syndrome .
Once satisfied they are properly sealed then as others have said look for swarf /crud .

Thing is its easily done - experianced -taking a Mob call ? - or not -( double seal ) -you sometimes can,t see up inside the filter holder and if you have dumped the old one that you took off in a bag of wrag / paper etc ,
Then fitted the new canister with diligenty placed and lubed seals --without accounting for the old seals ?
One -old seal may be left behind ,but the gorilla in you just gave it some more welly as you tightened it up .
A sort of seal takes place enough to appear to not weep at stop , but air sucks in under load .

However having said the above
We ,ve only just found out about the road move .So crud climbs to the top of the diagnostic tree .Agree

I like the idea of jury rigging transparent pipping and watching for bubbles .
May as well while rodding out / flushing through the propper lines .
 
You must log in or register to reply here.

Share this page

Top