foaming diesel

[kurt]

Hello,

About 1 of every 2 fill ups I get foaming diesel which forces me to very gradually fill the tank.  I've checked the fuel tank vent - no problem.   Also, I do add a bit of FPPF Total Power prior to every fill.   Is there any way to mitigate this or just live with it?

Thanks,

Kurt
'88 #796 M25XP

[Stu Jackson]

Kurt, it's not unusual for the fuel to foam.  Our fuel gage has been decommissioned for the past ten years and I keep careful records of how much fuel we need based on the engine hours. See: http://c34.org/bbs/index.php/topic,3841.0.html   You need to click on the PDF file in the first message on that link to see the stats.

We've been getting better than 1/2 gallon per hour of engine run time over those ten years.  So, rather than just depending on the fuel gage to tell you when you're getting up to the top, keep track of the engine hours (20 hours = a bit less than 10 gallons) so you KNOW how much you're expecting to put into the tank. And simply slow down the nozzle when there's only a gallon left to fill it up.  We keep an absorbent pad under the vent line to contain any small spills.  Yup, it's NOT like a car fuel fill up.

[kurt]

Thanks Stu.  Good to know.   Your 1/2 gallon per our is a good conservative metric I will use.  FYI, my logs have me at about ~.3 GPH w my cruise at ~2100 rpm.  Kurt

[Steve Sayian]

With my 4 cylinder, M35Bravo, I'm consuming ~.8 - .9 GPH.  Not as economical as the M25s.  Running a 3-blade feathering Kiwi prop and boat is set-up for cruising so have everything loaded except the minivan...
In the process of removing the tank this winter due to crud build-up.  Racor water seperator was full of junk this spring.
Fuel guage is also kaput, so this is a good time to check the sending unit as well as buzz the wires.

[Stu Jackson]

ENGINE IDENTIFICATION AND FUEL CONSUMPTION

In an earlier post on fuel consumption, I put the type of engine we have in our "signature" in each post.  The larger the engine, the more fuel it uses.  Seems to max out at a bit less than a gallon an hour for the M35s.  One more piston uses up some more fuel!

[Ron Hill]

Kurt : My experience has been that the foam in from the fuel nozzle - especially if you don't engage the trigger all the way.  This is especially true with a high speed pump where you can't put the 2 1/4" nozzle in, but just over the 1 1/2" filler hole!!  This requires that you only pull the trigger part way and you'll get all kinds of foam. 

[Stu Jackson]

Good point, Ron.  At our fuel dock (in the estuary, Kurt) there are two sized nozzles on the diesel pump, one's small and the other is huge.  I choose the smaller one.  Once I got the bigger one - couldn't figure out where it was supposed to go!