how to check for a bad fuel pump, or an air leak?

last year my motor would starve for gas every minute or so for the first 15 minutes , then it seemed it would be fine. i would just pump the primer bulb when i heard the motor die a little, and she would rev back up and wed be going again...

I didnt use the boat much this summer but, i went out yesterday and i have to squeeze the primer bulb every minute the who trip!!! and I was alone!! so id have to throttle back and put it into nuetral while i walked to the back or the front of the boat to prime( i have two gas tanks up front each with a primer bulb, and I have another right at the engine!)

I know I have a long run for the gas..and i have a manual diverting valve under the console to switch from one tank to the other, and I have a water seperator and an inline fuel filter in the stern about 6 feet of gas line before the engine. I have always thought the run was long and have heard that it might put a strain on my fuel pump...

but I have also heard that i may have an air leak.. I have visually check all the connections, they seem fine.

what tests are there to check the fuel pump? and or for an air leak?

I think i read i could install a clear line right before the motor to check for air bubbles...are there any others??

the tanks both have quick dissconnect gas fittings, so i can pull the tanks and fill and or clean as needed.

all other connections are hose clamped. I have 3/8th" ID gas line.

the motor is a 1995 ocean runner 115 hp. the oil side is closed off and i pre mix.

thanks

bob

Re: how to check for a bad fuel pump, or an air leak?

bad fuel pump. rebuild it or replace it.

Re: how to check for a bad fuel pump, or an air leak?

does primer bulb stay hard,until you start it? if bulb stays hard 4-5 minutes,then its safe to say no air leak. then i would say fuel pump. i ran another test the other day, i took fuel line off from pumps to carbs and ran a volume test.if you have steady stream and about a cup of gas while running5-6 seconds. that should be good for a low volume pump. I haven't been able to find specs on pumps

Re: how to check for a bad fuel pump, or an air leak?

If you have a portable tank and hose without all the filters you can try that to verify no air leaks. However I am afraid your fuel pump is done.

Re: how to check for a bad fuel pump, or an air leak?

stylesabu said:

does primer bulb stay hard,until you start it? if bulb stays hard 4-5 minutes,then its safe to say no air leak. then i would say fuel pump. i ran another test the other day, i took fuel line off from pumps to carbs and ran a volume test.if you have steady stream and about a cup of gas while running5-6 seconds. that should be good for a low volume pump. I haven't been able to find specs on pumps

Click to expand...

Ill check that at home tonight!!

i did notice that when i primed the bulb to good and firm , and then waited because i was tidying up a little before getting under way, i noticed that a gas stain was forming on the water where the lower unit entered..


I have two spare motors, one with a slight low compression in one cylinder, and another totally re machined and ready for assembly, including a rebuilt fuel bracket and a working fuel pump that was waiting to go on the rebuilt motor.

i also have rebuilt carbs waiting...so i guess....if the pump is bad , i have incentive to change it all over at the same time.


going forward...is this 20 foot of gas line in 3/8th " dia too long a run for this style fuel pump???

should I install a "helper" electric pump...or should sorten the gas run?

or can I go with this set up??



a non oil mixing fuel pump set up on a 1997 125 hp evinrude


bob

Re: how to check for a bad fuel pump, or an air leak?

You won't ever get a steady stream from a vacuum driven pump. You will get spurts. Tee a pressure gauge into the pump outlet. You should see 3 to 6 psig. You can also check by cranking the motor with the outlet hose disconnected. You should get strong, steady spurts of gas. Make sure the motor CAN'T START when you do this (i.e. use a remote starter switch with the ignition off.)