Logo
FULL SITE MENU

Intermittent fuel starvation on 454

N

northern_lights

Member
Boy I am struggling with this.

Boy I am struggling with this. To set the background; 34 Tollycraft 1986 with twin 454's Crusaders. Setup is Holly Carbs and Racor 500 MAM fuel filters. I have developed a "fuel starvation" intermittent at around 2000 - 2500 rpms. (does not appear at lower rpms) I also notice that when the crossover valve is open (dual 100-gal tanks) its does not happen. Plus I notice the one tank is always down about 10% or more than the other. My belief is that I have something in the tank partially clogging the fuel pick-up tube...and it draws from the opposite tank to feed the engine. Make sense??? The racor bowl is clean and the 2-micron filter show no indication of sludge. I was thinking of putting a "T" flow meter on top of the Racor and watch that when this occurrs. Will that tell me what I need to know? I will have the tank pumped dry this week to see if perhaps a piece of absorbant fell in and thats my culprit. Is their anything else I should be thinking? I have lazer temp both carbs at 1000 to 2500 rpms and don't believe its vapor lock or something along those lines. Am I on the right track? Both engines have exactly the same set up.
 
"Why don't you start by pu

"Why don't you start by pulling the anti-siphon and dip tube and taking a look at them, It just might answer your questions. The anti-siphon could be stuck and the dip tube may have a screen on the bottom which may be obstructed as well.

Good luck,
Rick"
 
"You can put a vaccum gauge on

"You can put a vaccum gauge on the racor to see what its pressure drop is, too. With that 2 micron filter, if there's any quantity of crud in the tank, it won't take long for it to "get full""
 
"A 2 micron filter! That'

"A 2 micron filter! That's insanely fine, and even it's positioned AFTER the fuel pump (which I assume it is not!)

Frankly, if you haven't burnt a piston by now you're darn lucky! I suspect that playing with the tank selector switch is tricking you into thinking THAT is the problem, when that 2 micron deal is what's causing your fuel starvation.

The accepted rule of the thumb on gas filtration is this: 25 to 30 micron junk removal strainer/ water separator BEFORE the pump, and a 10 micron fine filter AFTER the pump.

Jeff

PS: The questionable fuel quality of gas sold at marinas, combined with "Evil-Nol" in our fuel, have made proper filtration more important than ever."
 
"Well now I have learned somet

"Well now I have learned something new!! Of the three mechanics I have used over the years... This is the first time anyone has mentioned that Micron 2 are too fine and is my likely culprit.

I know the fuel tank vent is not clogged...but will check to see if their is a screen on the end of the pickup tube.

However, my set up has nothing after the fuel pump??? What I have is fuel tank - Racor filter - fuel cannister on engine - fuel pump - line to carb. Are you suggesting I should have an inline fuel filter?? That will be a little tricky since I have stainless steel fuel line from pump to carb.

So am apolgizing inadvance if I have somehow have missed the "boat" here on the correct setup."
 
"You should measure the pressu

"You should measure the pressure drop in the "suction" side of your fuel delivery system.

Your fuel pump is pulling fuel thru a lot of stuff to deliver it to the carb. the lower the pressure in a fuel container, the easier it turns to vapor (that's the carbs job).

I'd seriously get a vacuum gauge out and sample your line while the engine is running under load. I'd also cycle the crossover valve during the measurement to quantify its impact.

I think you'll be surprised at what you will find."
 
"Richard:

I never do this,

"Richard:

I never do this, but I GUARANTEE that your present fuel set up is causing fuel starvation. I'm even willing to bet a steak dinner on it!

Jeff"
 
Roger That! You have not stee

Roger That! You have not steered me wrong yet...so I won't take that bet. But you make it to California and I WILL take you out for the biggest steak you can eat! I appreciate the expert advice always.
 
Back
Top