Tom,
Your right, poor design pulling fuel with a electric pump
Your right, I dont know it to be fact but ...
I think were talking about different things though, my truck still has the factory installed LP on it (bypassed) at over 120k, My IP never seen less than 10 psi wot (I had a gauge since the truck was new) and it still died the instant I asked it to double its original output. Up untill that point every thing ran great, second wot pull on 5x5 the rotor siezed. Did the rotor gall from deflection, entrained air, or just poor tolerances? My theory matters little, but after reading countless hours of DTR members storys and my own hands on I honestly think entrained air is a big problem. In stock trim how can so many of the same trucks see such vast variations in LP and IP failures? Many loose LP/IP after LP/IP yet so many more go hundreds of thousands miles failure free using the same parts?Can it be the silly tank connections, return line in the pick up, assembly QC? Then here we go adding HP and the problems show up in larger #s and sooner.
Hey how did they get the caramel in the caramilk........

 

That is a good point.....BUT line size is NOT the only reason pumps fail. There are a number of factors that are causing problems. Not only is pressure important but you must also deliver enough volume to keep the IP lubed & cool.

 

I think volume comes with the increase in line size, doesnt it? OK, maybe not EVERY failure reason is because of the fuel lines but I can bet that if you add a FASS and try to shove all that fuel through a 1/8" line you wont get much more fuel than stock. Your pressure reading might rise but the total volume will stay down. I'm sure bad VP tolerances, changing the timing of an older unit after it has run a certain way for years, air in the system, ect. all play a part.

 

Well I am glad you put up with the rant 600, I think it sparked some good conversation as well..

The line size would also play in more to the pressure drop from the test point of your gauge to the very internals of the pump. With the restrictive banjos, small diameter tubing and other factors, the pressure drop to the IP is more than anyone has good numbers for.

As far as Ratsun, I have seen the same thing happen alot with a certain vintage of VP44's. They run along just fine untill you tap the wire and whammo, its all over. I am on the band wagon of tolerances and finish of the internals where at stock conditions it was hit or miss, but anything over that was certain death. I don't know the years for sure , but it was some of the earlier pumps.

J-eh

 

Katoom,

How do you eliminate the banjo bolts??? (Katoom stated: "Tests have proved that by increasing the fuel lines to 3/8" or 1/2" and getting larger banjo's (or better yet eliminating them)") I've never heard of any way to convert to some other kind of fitting that will do the same job as the banjo's. Have I been missing something? Wow I feel like a moron asking this question.

Mike

 

It is my opinion that why the lift pumps fail has nothing to do with pulling fuel, or restrictive lines. I believe the lift pumps are failing from pressure pulsations set up by the VP44. My first lift pump failed at 20k miles. I took it apart, and the damage appeared to be totally mechanical vibration related. At first I was suspecting the mounting of the LP to the block of the engine. But after experimenting with a cheap non-liquid filled pressure gauge on the LP discharge, I noticed terrible pressure oscillations causing the needle to vibrate wildly while the engine was running, but not when the engine was off and the lift pump running. I installed a small pressure accumulator between the LP and the VP to absorb the pulsations. The cheap air filled gauge does not even flutter an ounce now. 76,000 miles later, same lift pump, same VP as all along.

As for entrained air regularly in the lines, I am struggling a bit with this concept. With a lift pump that circulates fuel from the tank to the VP and back to the tank, if your fittings are tight and dont suck air, your tank pickup stays flooded with at least several inches of fuel, and you dont leave the engine running while you fuel up the tank, how exactly does air enter the system regularly? Obviously I understand there will be air for a bit after you do a fuel filter change, or break the lines open, but with a return system, the air ultimately works its way back to the high point which is the return to tank. This is not to be confused with my earlier statement and Lil Dog's brilliant point about pulling a deep vacuum inside the VP itself and flashing dissolved air into back into suspension.


As for water separator, Cummins already took care of that and your fuel filter housing performs this function quite well with a simple concept... GRAVITY.. Water is more dense than #2 oil and just settles at the bottom of your filter housing. Thats what the coffee urn valve on it is used to drain off.. Just let her bleed a little every week.


You guys may have convinced me to get a larger lift pump, but I am more than just slightly skeptical on the FASS. A good old tried and true Holley Blue will deliver 110 GPH free flow and 65 GPH at 14 Psi all day for $108, the filter housing separates water and I am still out to lunch on the air.....



And after reading the below as the claimed benefits for the FSS:


Consistent Engine Performance

Increased Horsepower

Increased Fuel Economy (Saving 8% or more)

Drastically reduces the effects of "Hot Fuel"

Easier/Quicker Starts

Reduced Engine/Cab Noise

Improved All-Weather Performance

Drastically Reduces/Eliminates Black Smoke

Reductions in NOX and Carbon Monoxide

Excellent Cold Weather Performance

Smoother Idle and Quicker Throttle Response

Extended Fuel Filter Life

individual results may vary


I have to seriously question more than just a few of those claims, and the ‘individual results may vary’ part is cute. And when even one claim is bogus, you can’t help but question the integrity of the product/vendor.

OK Lawyers: The above statements are my personal opinions only, which by the way, in America, I am still allowed to have.



Kevin

 

Yep, Infadel, right on.. just like dissovled nitrogen flashing in a divers bloodstream on too quick an ascent to the surface, or carbon dioxide foaming when you open a pop or beer bottle too fast for that matter... hummmm I think I'll go have a beer....


Lil' Dog... you bet, great conversation indeed. I love logical techincal talk.... it arouses me !!!! lol


Kevin

 

How then do you explain why one lift pump will go 100 miles and the other 60000 miles? The pulsations from the VP-44 in both trucks will (well should) be the same. I personally dont believe thats the primary cause of dead LP's.

I stand by my contention that the air/cavitation in the system and in the fuel itself is doing more to kill LP's than most guys realize or suspect.

If you look at the Air Dog site - its a little more realistic and less self serving:

http://www.ekstamworldwide.com/fpoverview.htm

 

Ahh, yes, that site does sounds a bit more realistic. And, I like the statement they include from Cat,,, "#2 diesel fuel contains about 10% air in solution...." in solution is the key. But, as I said earlier, it is DISSOLVED O2 and/or vapor, and it wont flash out unless there is a sudden pressure drop into vacuum. As long as you dont pull the fuel into a deep vacuum, no problem....

As a matter of fact, at my power station, the generator is hydrogen cooled. The hydrogen is kept from leaking out of the shaft seals with seal oil under pressure. The seal oil absorbs a lot of the hydrogen, and for the removal of that, we have a de-entraining tank and vacuum tank. We pull a deep vacuum on the seal oil in the tank and you should see the bubbles and foaming through the sight glass!!! But again we are using 26" Hg vacuum or better to do this. Prior to the vacuum tank the oil looks as smooth and clear as can be.

Anybody ever put a vacuum or dual range gauge on the suction side of the LP and see if it is ever pulling a vacuum? Maybe it is, in which case, as several of you have mentioned, the lines from the tank to the LP are too small....

Hummmm guess what I am gonna do this weekend......



Kevin

 

Kevin, you must be an Instrument Tech....??

 

Hummmm Dr. Evil, are you a fellow Power Station guy?? Actually, I am the Chief Engineer of the station, which, as you have no doubt allready guessed, is rated 600 MW.



Kevin

 

I've checked countless numbers of VP equipped trucks and have had several that when I put my gauge on and started the truck would pull my gauge into a vacuum. They will run without a lift pump, but when it gets hot here, they won't run long.

 

Well the one kit I know of is on Scotty's site.

Scotty's 2nd Gen fuel system.

Totally eliminates the banjos from the liftpump to the injector pump.

 

I still don't understand the worry about pressure. I was taught in basic hydraulics that "pumps don't make pressure, only flow. Pressure is caused by resistance to flow" So it still seems like any positive pressure would indicate more than adequate flow. My local ******* service manager told me" ******* has no spec. for lift pump pressure, they only care about flow"
Too many questions on this for me to understand. Still think I'll get a FASS II just so I don't always worry about it.

 

Why did that happen? We aren't allowed to say *******? They made the engine we all love.