on My 90HP J90TSLECM Can I use 3-Port fuel pump?

[toddschubert]

I have a problem where my motor is cutting back at higher RPMs as if it were starved for fuel. I first thought it was rev limiter but it slowly started happening at less and less RPMs I cant exceed 3300 now. Pumping the primer bulb fixes the problem therefore I am assuming it is starved for fuel . My carbs are clean as a whistle and I've eliminated air and obstructed fuel flow from tank. I rebuilt the fuel pump a year ago and remembering having problems. New ones are cheap so I want to replace it.
Question: Can I use the 3 port (1-in, 2-out)fuel pump on this motor? The current one has only one port out and uses a fuel rail to distribute to 2 carbs and primer.
Thanks for any input!!!

 

[racerone]

Any input -----Some will argue , but the first thing to do is a compression test on a crossflow V-4 motor.----Post your numbers.----The fuel pumps that mount on the manifold are ultra reliable and about the only thing that goes wrong is the diaphragm.------Yes you can mount a 3 port pump with a nipple on that spot on the manifold.------One pulse port IN.-----One fuel port IN and one fuel port OUT.----I doubt that a 3 port pump will work any better than a 2 port pump !

 

[toddschubert]

Thank you. I have to go get a compression gauge to check that. I will do that this week.
The problem really had me scratching my head. I thought for shire I was sucking air in on my fuel line from tank but I ran a line straight from a gas can eliminating my filter/hose and still had the problem. It will run perfectly for about 20 seconds WOT then dies down. If I back off throttle for about 15-20 seconds I can run again for 20 seconds. It?s as if the carb bowls empty out and if I let them catch up it runs again.
I?ll probably stay with the single out Port pump and manifold.

 

[racerone]

Accept this fact !---Both pumps have ONE fuel port in.-------Both of these pumps only have ONE port for fuel to come out.

 

[Fed]

Don't forget there's a screen filter inside the pump but seeing as you had problems when you rebuilt it last year I'd go for a new genuine replacement for peace of mind.
Read & understand racerone's posts, I don't think you have quite got it yet.

 

[Chris1956]

Did you clean or remove the antisiphon valve from the fuel tank? Some have screens which partially clog. Did you check the fuel tank vent? A known-good portable fuel tank removes the built in tank from the test circuit.

 

[toddschubert]

Yes...As I stated I have run with a line to a gas can eliminating all tank, line, filter possibilities....it did the same thing.

 

[toddschubert]

I get that the fuel pump with two out ports still only pumps the same amount of fuel. I was just trying to eliminate the manifold. However, I would still need to come off with something for the Primer solenoid so I'll just keep it like it is.

 

[racerone]

???---Why do you insist that one of those pumps has 2 fuel outlet ports ?----Because it simply is not so !

 

[toddschubert]

No Title

would you kindly explain to me what the second brass nipple is for?

 

[toddschubert]

Im going to start a new thread about original engine problem....cutting out at higher RPMs

 

[racerone]

The pumps need a pulse signal from the crankcase !!----A + pressure and a slight negative pulse to be exact.----One pump gets that pulse by mounting directly over the hole in the manifold.----The 3 hose pumps get the pulse to the diaphragm via that second brass nipple !!----Read post # 2 again I guess.

 

[Fed]

I reckon when the penny drops I'll hear it from here.

 

[toddschubert]

That is what I needed! An explanation as to what the 3rd port did. Sorry I didn't pick that up in post#2. I didn't know there were pumps that didn't draw pulse from back-side.
Thanks!

 

[racerone]

Read and heed I say.