f40ehd issues

[MadMullet]

Hey Guys,

I'm sure this topic has been covered by other users in the past, (I hate to beat a drum you've already heard), but I'm having persistent and ongoing issues with some fairly new F40FEHD motors that are in commercial use...

In at least one of the motors, the problem seems to only be rectified by taking the cowling off, and in another (against my instructions) the operator cracks the Vapour separator bleed valve and the problem is temporarily resolved.

I've read here, and been told elsewhere (by very very good mechanics/marine engineers) that it's a fuel vapour lock issue....

I've carried out the following inspections/repairs

- inspect/replace water pump kit (complete)....checks ok
- inspect/test/replace thermostat (not an issue really as we're in the tropics)
- tested and passed both oil pressure sensor/temp sender.... within spec
- inspected/cleaned VSU fuel cooler (single pass on the fuel side, double on raw water.... some scale on the water side, now cleaned, but not enough to retard heat exchange in that unit)
- entire raw water system purged and checks ok...no restrictions in galleries
-fuel supply is A1

Given that I'm in PNG (not renowned for clean fuel, nor for cool weather) am I correct in assuming that , if proper shutdown procedures are not followed, that the symptoms described above are (possibly) caused by the 'vapour lock' syndrome i hear so much about?

If so, are there any other options other than equalising the pressure in the fuel line each and every time we start the buggers up? (either by the VSU bleed screw, that cool little valve under the flywheel on the starboard side, or at the fuel connection at the front of the motor)?

many thanks in advance

Mike the Mullet

[rodbolt17]

what????
never heard of a VST bleed screw.
and I really don't think your mechanics and anganeers have a clue what vapor lock actually is.

what is the motor doing and what is it supposed to do?

as your engine is not a US market motor I don't know if it has a vapor shut off valve and a charcoal canister.

but typically its either a defective valve or excess vapors being introduced to the intake via the VST vent that creates an over rich fuel mix at a hot restart.

[MadMullet]

Thanks for the reply Rod,

indeed, the motors seem to be a bit different to those on the US market, and lack the vapour shutoff valve and charcoal canister you refer to.

the VSU bleed screw i referred to is at the bottom of the float chamber, stbd side (part 6C5-14191-00), normally only used to drain fuel/water from the float chamber as far as I understand.

My own lack of knowledge, and the same lack in those actually using/servicing the outboards is the reason I'm posting on this forum.

Thanks again for your tips there....I'll see if that helps

MM

[rodbolt17]

vapor lock is when fuel boils in a line.
as the HP pump is drawing from a mini gas tank,hence VAPOR SEPERATOR, then feeds fuel to the rail under pressure vapor lock isn't really possible.
fuel under a vacuum lowers the boiling point to as lopw as 50*F at the pump intake.
on the other hand pressurized fuel boils at a much higher temp.

[MadMullet]

gotcha...


you've now got me thinking that the (I'll be honest, crappy) fuel we have access to has a slightly lower boiling point.

I'm also starting to wonder if, as I suspect, the operators aren't letting the engine run for at least a few minutes after a long run (typically an hour and a half), and instead, shutting the motor down straight away, fuel's boiling immediately in the low pressure part of the fuel system.


Back to the drawing board again [unsmiley face]

cheers again

MM

[rodbolt17]

you may wish to check the vst vent and the vst fuel cooler.

[MadMullet]

heya Rod,

Did that.. one of the first things i looked at.. removed the fuel cooler and cleaned it (no visible scale or buildup/constriction on either fuel or water side) and even swapped it out for another one from another engine... still the same symptoms.

It's starting to sound like the fuel's boiling on the LP side as you suggested. (ambient temp here is 30℃ and water temp isn't much lower).

Never had this problem on the F50's I drive at the other job.... grrr

cheers again mate

MM

[rodbolt17]

I doubt its a fuel boiling issue.
that tank(VST) holds about a qt of fuel.
that's why its called a VAPOR separator.
it allows the HP pump to draw from a vapor free source.
its why almost all modern EFI automobiles have the pump in the gas tank.

try disconnecting the vent line from the intake manifold.
if fuel vapors are percolating and entering the intake at hot shutdown it makes the fuel mixture so rich hot restarts are hard to impossible.

a quick test for this is advance the throttle to see if hot restarts are easier.
the added air will aide in an over rich intake mix.

[MadMullet]

Hey again Rod,

I'll give that crack..

cheers

MM