The Boating Forum - primer ball deflates

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View Full Version : primer ball deflates


dmart990
05-06-2006, 09:53 PM
we boat on a ten mile lake, we can run full throttle for upwards of 15 minutes or so. next thing you know, the motor boggs then stalls, and the primer ball is deflated... so i disconnect the gas line at the tank, and the ball refills, and it restarts fine.....
why is the ball defalating

its a 77 marquis nassau / 70 hp evenrude

thanks


capemariner
05-06-2006, 10:11 PM
Is it going soft? or is it actually colapsing?

Whiteowl
05-06-2006, 10:16 PM
dmart, sounds to me like the fuel tank vent is clogged or if it is a portable tank then the vent may be screwed shut. It it is a portable, the vent is usually in the top to the fuel tank cap and can be unscrewed. If it is a permanent tank you will have to start at the overboard vent and work back. As a test to this theory, you can try running the boat with the fuel tank cap loose so the tank does not develop a vacuum. If the problem still occurs, I will once again be incorrect.


witchcraft
05-06-2006, 10:25 PM
The check valve inside the ball can go bad or break apart. The valve will work it's way around until it blocks the gas line. You can take the primer ball off and shake it, if it rattles thats probally it.

prockvoan
05-07-2006, 05:27 AM
Vent the tank!Once the tank is vented,the fuel ball should be able to pump up hard,if not,the check valve is bad in the ball.Built in tank,check to see if a dirt diver didn't build a nest in the vent line or any other bug.

jethro1
05-07-2006, 04:53 PM
A normal primer ball is soft but not deflated. In any event, the motor should never starve for fuel. You need to get this fixed since fuel starvation can cause the engine to run lean and this can cause a lot of bad things to your motor.

It is a clog somehere upstream from the ball. Here is a list of possibilities, some of which have already been mentioned:

Bad inlet check valve in ball
Kinks in fuel line
Internal collapse of fuel line
Failed anti-siphon valve (if not needed throw it away and don't replace)
Clogged fuel tank pick up tube screen (if equipped)
Block fuel tank vent

Good luck and let us know what you find. We need more feed back than we are getting.

fourdfish
05-07-2006, 08:35 PM
I have had the check valve go bad in a new primer bulb and bulb deflate. Dealer says it happens occasionly!

sleddermxz
05-07-2006, 09:28 PM
Check your fuel lines inside the cowling also. I had the same problem last year. Turned out to be a loose fuel line that I had recently replaced. Tightened back up and problem solved.

RIC
05-07-2006, 10:57 PM
jethro1 - 5/7/2006 4:53 PM

A normal primer ball is soft but not deflated. In any event, the motor should never starve for fuel. You need to get this fixed since fuel starvation can cause the engine to run lean and this can cause a lot of bad things to your motor.

It is a clog somehere upstream from the ball. Here is a list of possibilities, some of which have already been mentioned:

Bad inlet check valve in ball
Kinks in fuel line
Internal collapse of fuel line
Failed anti-siphon valve (if not needed throw it away and don't replace)
Clogged fuel tank pick up tube screen (if equipped)
Block fuel tank vent

Good luck and let us know what you find. We need more feed back than we are getting.

pay attention to this advice......i can attest to it from experience in the last month. one internally collapsed fuel line while at full throttle on a calm day and there goes a cylinder. i had noticed for about 6 months that the ball would never get hard but it always ran great so i didnt do anything about it.....in fact it ran perfectly right up until it died. one factory reman powerhead ($5500.00) later and you can bet i wont make that mistake again.

dont let it run lean

Mumblerone
05-08-2006, 01:59 PM
"Failed anti-siphon valve (if not needed throw it away and don't replace)." This is a safety devise; it prevents the tank from dumping gas into the bilge if the gas hose should fail. If the little ball is sticking...I would replace anti-siphon valve Vs elimating. ;)

KevinM
05-08-2006, 02:53 PM
Do you use portable fuel tanks? If so open the vent valve!

jethro1
05-08-2006, 06:18 PM
Mumblerone, I specifically said "if not needed". If the fuel hose runs from the top of the fuel tank to the the motor there is no way for a siphon to occur and an anti-siphon valve is not needed, nor is it a requirement. If the hose breaks, the fuel on the tank side of the hose will simply run back to the tank. To have a siphon take place the free end of the hose must be at or below the level of fuel in the tank (whatever that level may be).

Here is the specific section of CFR 33 that addresses this matter:

Sec. 183.568 Anti-siphon protection.

Each fuel line from the fuel tank to the fuel inlet connection on
the carburetor must:
(a) Be above the level of the tank top; or
(b) Have an anti-siphon device or an electrically operated fuel stop
valve:


My comment still stands. If an anti-siphon valve is NOT needed then why have it? One less thing to fail and this thing can and does fail. At the best the failure is an inconvenience. At the worst it can destroy a motor.



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