fuel pressure loss

[bassmaster893]

 i have a 94' Nitro 190DC with a 150 XRI Merc, it has dual gas tanks, one is main (32gal) one is aux(17.5gal) i only used the main one this summer, the aux is empty, but i noticed a pin hole in my primer bulb so i put a new one on it. it was losing fuel pressure and i thought that might be the issue but its not, still losing fuel pressure, the fuel pump is working because i can hear it, but ill pump the bulb, it will get hard, but not super hard, the new bulb is stiff as it is, but after i get on plane, and go down the lake it loses fuel pressure and dies. i looked at my lines, they all are old but dint see any leaks? i thought about filling the aux tank up and switching to that but i dint know if that will fix the problem or not, it was only doing it at a slow idle and would be fine on plane but now its all the time? i just dint know what it could be! 

[Mike Cork]

since it's progressively getting worse it could be a fuel pump going bad. Seals inside it are letting pressure off back towards the tank.

If you had a pressure gauge you could verify that the fuel pump was holding pressure.

You said you put a new bulb on, verify it's installed in the right direction. Also the check valve in the bulb could be going bad. Pump it up and let it sit without running the engine and see if it holds pressure.

[Redleg62]

The fuel line lining on my 99 merc 90hp disintegrated,  turned to what looked like coffee grounds, and clogged everything from the pick-up, to the fuel pump itself .    Just a thought.  I will be installing a fuel water seperator filter soon.

[Mike Cork]

Very good thought, a disintegrating fuel line will clog a fuel filter creating the exact same problem and would explain it getting worse over time.

Good Call

[bassmaster893]

i checked the fuel filter and its not clogged, i hate to take it in and spend 125 dollars an hour for somthing that could be simple! if its the fuel pump, (which i have looked at and is a mechanical on the side of the motor,) could i put and electric pump on it? or would i be better off with a rebuild kit for it? i still gotta find time, hopefully tomorrow, to test the aux tank and see if it makes a diffrence, if it does ill know its a bad fuel line. 

[Mike Cork]

The mechanical pumps are usually quite sufficient. I wouldn't suggest and electric unless you're running a supped up motor.

Fuel filter clean, is a good thing. However, your fuel lines could still be deteriorating and collapsing under pressure. It would be excellent to pressure, vacuum test them.

I don't think there could be much with the tank, unless there is a vent problem, but it will be interesting to see if the other works fine. If you're having a vent problem, check for mud dobbers.

[bassmaster893]

well im gonna test it sunday, its raining today and the Funny Car nationals are in town and i love me some race fuel! so hopefully sunday i can do a little test and tune on it, all else fails. ill be buying new lines.

[Redleg62]

Good luck.   Let us hear about it