Engine/Transmission (1998.5 - 2002) Banjo Bolt "Observations" (OEM)

[Ncostello]

Since I've taken all banjo fittings out of my fuel supply equation, its easier for me to study them as time allows. Playing around with them this weekend I noticed something interesting. There are 5 bolts on a stock system. 4 are the same while the one at the VP44 is quite different. This is on a 1999 system.



The banjo bolt at the VP is shorter than the rest (no big deal) and only has 3 holes as opposed to 4 holes in the others. The holes are also centered around the circumference and are noticeably larger as shown in the photo.



The banjo fittings themselves are also not all the same. There are four equally sized fittings with the odd 5th being larger and located at the inlet of the Carter lift pump.



So what you may ask?? What does all this mean?? Well, I will show in a little while why the largest banjo fitting at the inlet of the lift pump is probably the worst of all.



Maybe... just maybe... those who offer aftermarket banjo bolts will change the way they make their replacements after they read my future posts here. Offering slightly larger holes isn't the best way to improve them. I think. You'll see what I mean later.



I'm obviously bored again as I'm starting another fuel supply thread.



The bolt on the left is the VP44 bolt (3 holes)... the right one is what the other 4 look like (4 holes).

 

[Mad Bomber]

Fuel flow

Neil, the fuel has a hard time going though a 90* turn and flow smoothly. That is why I went with A-N fittings with the sweep 90*s. The -6 make your whole system 3/8ths" all the way to the pump.

 

[Mad Bomber]

new fittings

Over on www.nwbombers.com Fish started a thread under CTD engine that goes though and gives all the summit part #s to upgrade fuel system. Fish and I even give the number of pieces needed. Eric

 

[Ncostello]

My whole fuel system is AN type fittings. They are all straight (0 degree) with only one -6AN 90 elbow at the VP44 inlet.



I understand that the fuel must make a 90 degree turn in the banjo... but I'm not exactly sure of the velocity of the average fuel drop. At some velocity the banjos would become much more restrictive than the -6 elbows.



But this thread isn't about trying to get folks to switch to AN fittings... its about a problem with the OEM banjo fittings design that makes them less efficient than they could be. I know they are bad... but there is something that makes them "real" bad and could be corrected.



I'm hoping to help those who are not going to make drastic changes to the fuel system like me and others have done. There's a large group of TDR members who might be willing to install some "better" bolts but not install an entire fuel delivery system. Thats if the bolts actually help the fuel flow situation.

 

[Ncostello]

Banjo Bolt Photo Album



The above album contains photo descriptions of the problem I believe exists.



The most restrictive banjo fitting in the stock system (I think) is the one at the lift pump inlet... . which is one place you dont want one. It is the largest of the banjo fittings on my truck by far and looks to have the greatest flow capacity as its interior volume is much greater than the others. But the bolt that is used there has four holes drilled into it. In order to get 4 holes in there they drill them offset around the bolt (ie: the holes are not lined up around the bolt). This large banjo fitting has a large flange shoulder and it blocks two of the holes.



How much does it block? I'm not sure as its hard for me to measure. But while holding the fitting, washers, and bolt all assembled up to a high intensity light... I was able to look down the tube the hose attaches to and see the holes "partially blocked" by the fitting body itself. Perhaps 1/3 blocked.



The VP44 inlet bolt is of a better design. There are three holes but they are much larger in diameter. They are also lined up around the circumference of the bolt. Thus they center themselves exactly in the center of the fitting body and flow correctly.



Perhaps the way to make banjo bolts better is to not simply drill 4 slightly larger offset holes... but to drill only 3 but much larger and centered (lined up) holes.



PS... most high flow banjos with 0. 187 holes (4) have the same cross sectional flow area as a 3/8" ID fuel hose (minus 0. 0006"). This doesn't mean they'll flow the same because of other types of friction losses... but it does mean something.



Now all I need to do is figure the flow area of the three holes in the VP44 inlet bolt.



All this and my truck doesn't even have a banjo on it!! Something is definately wrong with me. I suppose maybe its not worth anything... I'm just looking for problems in the stock fuel supply system and why lift pumps keep failing like they do. Perhaps they are having trouble pulling fuel through this restricted area and the pumps cavitate.

 

[illflem]

Does it really matter since the fuel filter will only flow about 20 gallons/hour anyways?

 

[Ncostello]

I thought the OEM 24V fuel filter was good up to around 45 gal/hour. Maybe I'm incorrect on that. If I'm right thats a decent amount of fuel to pump if its going through 4 holes less than 3/16" in diameter... two of which are partially blocked. The flow velocity has to be somewhat "rapid" through these fittings.



When strong trucks pull a good lift pump from 15psi down to 6 psi... something tells me something isn't keeping up somewhere. In fact, I have a very hard time pulling mine down below 13. 0 at any time. Used to be real easy to go below 10 on my stock setup. So loosing restriction is good for something and thats all this is about really.



My Stanadyne filters are good for 80 GPH... which is perhaps the high limit of the single Carter pump I run.



But you could be right too Illflem. I'm just havin a little fun. And if I'm wrong I apologize... I'm definately not trying to spread mis-information here.