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Cavitation possible from air bubbles in WVO?
The one thing that worries me about running on veggie is that sometimes I notice some small bubbles in the line. I've read that air bubbles in the line can cause cavitation to the IP which is something that can ruin a pump. I have a spare tank that I use to supply WVO to the engine. Due to the type of tank it is, it draws the fuel from the top rather than the bottom like on the Mercedes' fuel tank. I've thought about tapping a new outlet at the bottom to draw the fuel like the car's tank but the pump seems to do well enough as it is. I've also thought it advantageous to run it this way as it would avoid drawing any crud from the bottom of the tank that may settle. I haven't found any leaks in the suction line so I'm thinking the bubbles are formed when the tank gets shook from driving.
Anyone with thoughts on this?
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DJ 84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012 |
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Cavitation occurs when the velocity of a fluid causes the fluid's pressure to drop below its vapor pressure. Since the IP greatly INCREASES pressure in its function to deliver fuel to the injectors, I wouldn't worry about cavitation.
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'82 300SD - 361K mi - "Blue" "Good judgement comes from experience. Experience comes from bad judgement." listen, look, .........and duck. |
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Quote:
I'll find that info in the Bosch IP book and post it.
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Never a dull moment at Berry Hill Farm. |
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I have stated my opinion on the infopop forum, but for consistency I will state it here as well. I agree with Pete in that cavitation is probably one of the lesser worries you have when running WVO. But, everybody needs something to worry about.
The bigger question in this is where are your air bubbles coming from? Do you have a vacuum gauge in the system any where? It is possible you have a loose fitting somewhere leaking a bit of air, but it is also likely you are pulling a massive amount of vacuum on the system and that is where your bubbles are coming from. In either case, bubbles in the system aren't "normal" and should be corrected.
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Keep everything as simple as possible-but no simpler--Albert Einstein |
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Quote:
__________________
'82 300SD - 361K mi - "Blue" "Good judgement comes from experience. Experience comes from bad judgement." listen, look, .........and duck. |
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I was incorrect about free water being the cause of cavitation; Now, I don't have any idea where I picked that up at. The Bosch book's statement on cavitation leads me to believe that it is caused by the design of galleries and passages in the pump.
Here is a scan of the page from the Bosch book discussing cavitation in IPs (caution, file is 1.1 mb). Cavitation in diesel injection pumps.
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Never a dull moment at Berry Hill Farm. |
#7
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__________________
"If anyone knows other lessons I need to learn, please tell me. I'm tired of learning them the hard way". by JerryBro The Glow Plug Wait: This waiting period is a moment of silence to pay honor to Rudolph Diesel. The longer you own your diesel the more honor you will give him". by SD Blue My normal daily life; either SNAFUed- Situation Normal... All Fouled Up, or FUBARed- Fouled Up Beyond All Repair 62 UNIMOG Camper w/617 Turbo, 85 300SD daily driver- both powered by blended UCO fuels |
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__________________
"If anyone knows other lessons I need to learn, please tell me. I'm tired of learning them the hard way". by JerryBro The Glow Plug Wait: This waiting period is a moment of silence to pay honor to Rudolph Diesel. The longer you own your diesel the more honor you will give him". by SD Blue My normal daily life; either SNAFUed- Situation Normal... All Fouled Up, or FUBARed- Fouled Up Beyond All Repair 62 UNIMOG Camper w/617 Turbo, 85 300SD daily driver- both powered by blended UCO fuels |
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Quote:
__________________
'82 300SD - 361K mi - "Blue" "Good judgement comes from experience. Experience comes from bad judgement." listen, look, .........and duck. |
#10
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I must be getting a leak somewhere in my suction line, though I haven't found where it could be. Fortunately I don't have too many connections but the problem is I have my hose clamps as tight as they'll go before slipping. I've thought about changing over to fuel injection clamps but I'm not sure they'll be any better.
Lately I have had some stumbling running on my WVO that goes away when switching back to diesel so there is a leak somewhere.
__________________
DJ 84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012 |
#11
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Hose clamps can be a PITA. This is one instance where cheaper is definitely not better. The barbed fittings can make a big difference as well. Fittings such as Parker Push-Loc or similar are much easier to seal than the run of the mill hardware store variety. Not that one can't get by with cheap fittings and hose clamps, but a few dollars more for the better varieties can save a lot of headache.
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Keep everything as simple as possible-but no simpler--Albert Einstein |
#12
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I do have barbed fittings as well. I'll check out the push-locs.
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DJ 84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012 |
#13
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The Push-Lok (sorry I spelled it wrong before) fittings are barb fittings, just higher quality barb fittings. They are advertised as not needing hose clamps, but I usually put clamps on them when used on a vehicle.
__________________
Keep everything as simple as possible-but no simpler--Albert Einstein |
#14
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Are any of those barb fittings screwed into something and barb on the other side? If so, you might try plumbers goo on these treads ? Not tape, this will eventually leak air. You have to use the goo/paste.
Might try some of it on your barb before installling hose?
__________________
"If anyone knows other lessons I need to learn, please tell me. I'm tired of learning them the hard way". by JerryBro The Glow Plug Wait: This waiting period is a moment of silence to pay honor to Rudolph Diesel. The longer you own your diesel the more honor you will give him". by SD Blue My normal daily life; either SNAFUed- Situation Normal... All Fouled Up, or FUBARed- Fouled Up Beyond All Repair 62 UNIMOG Camper w/617 Turbo, 85 300SD daily driver- both powered by blended UCO fuels |
#15
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Yes I do have some threaded type of fittings. I used teflon tape on the fittings. The strange thing that started happening today was I would get a sputtering problem on hard accleration with WVO. It was like not enough fuel was getting to the pump. I thought that the filters are plugged but after switching back to diesel the problem goes away. I don't think the oil is to blame since I didn't have any trouble yesterday and it runs fine under normal acceleration.
Puzzled.
__________________
DJ 84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012 |
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