Logo
FULL SITE MENU

Fuel line diameter

S

scott_duerring

Regular Contributor
Does anyone know the diameter of the fuel line for a 8.2 MPI Crusader engine? Getting ready to install floscans, unfortunately forgot to measure fuel lines and need to order fittings and boat is an hour's drive away. I am guessing 3/8ths???
 
That's short...i checked crusader's installation guide and they recommend 1/2" supply line and then caveat it with the 2" Hg pressure drop measured at the inlet to the fuel pump...

That being said 3/8" ID line will be adequate if the fuel system uses 1/4" NPT fittings (very common at the spin on fuel filter)...
 
Well, the actual set up was that the supply line was 1/2 inch, the return line was 3/8th inch. Just finished the install of my new floscan fuel meters. It was a pain to find 1/2 inch hose barbs that fit the 1/4 inch NPT fittings supplied with the floscan sensors but good old Kablein's True Value Hardware store came through! After trying West Marine, and several auto parts stores they were literally the only place to find the 1/2 inch 1/4 inch NTP fitting. One word of advice to anyone doing a similar project, unless your fuel lines are dangling in the air and not supported you do not need to buy the brackets for the fuel sensors that floscan sells. I have four of those dang things I didn't need after all and they ain't cheap. Did not need to buy any additional fuel hose, had to cut some out to allow for the fit of the sensors, pulsation dampers and filter.
 
Gald you got the hardware needed...with those restrictions (the 1/4" NPT connections) I'd heed Crusaders performance check and make sure the pump isn't working too hard - they aren't cheap to replace.
 
What do I need to do to do the performance check? I have a fuel pressure gauge that I can attach to the Schrader valve on the fuel rail. I know that will give me the pressure at the rail, not sure if it tells me what I need to know though.
I'll be a bit P. O.ed at Floscan if they gave me a configuration that will end up burning up my fuel pumps.
 
See post #4 ... I would interpret Crusader's data as making sure you have spec'd fuel pressure in the rail, at WOT, and, at the same time, making sure the fuel pump's inlet isn't seeing more than 2" Hg vacuum, at it's inlet...

In other words, the pump delivers enough fuel with less than 2" Hg (vacuum) thru its supply (pickup tube thru filters, flo scans, etc)...
 
I posed the issue to the support person at Floscan and here is his response. Make sense?
Hi Scott,

The Model-231 sensors used in your system have been fitted onto dozens of “Crusader Open Return EFI’s” with no issues. Additionally they have been fitted to many more Marine Power, PCM, SeaMaxx and Kodiak open return engines having similar flow rates. With hundreds of systems sold, no one has ever complained about a fuel restriction issue.

>>>In discussing this install on that forum a concern was voiced about the fact that my fuel supply line was 1/2 inch diameter and I had to use 1/4 NPT fittings for the !/2 inch hose barb

Your half inch hose has about a 0.5” ID. A half inch male hose barb x quarter inch male NPT standard brass fitting has about a 0.365” ID throughout the length of the fitting and is about 1.72” long. On each sensor you’re talking about an ID reduction of 0.135” for less than 3 and 1/2 inches. Whatever the increased pressure drop is, it’s miniscule.

NOTE: There are some HB fittings with very thick walls. If you purchased these instead of regular fittings there may be a measurable pressure drop but even those are not restrictive.

Hope this information helps.

Best Regards,
Ed
 
a vacuum gauge will tell the real story...the good news is that none of use can afford to run a pair of big blocks at WOT for a sustained period of time...the bad news is the Ed din't tell you the whole story...its the area that changed going thru the 1/4" NPT fittings and it is cut in half - he is right in that the length isn't long...

again, a measurement will tell the real story.
 
Ok, I have a vacuum gauge but never used it to check vacuum at the fuel pump. Where do I hook it up? The fuel regulator valve has a vacuum hose attached but do not know of any place on or before the fuel pump to attach it.
 
Back
Top