Fuel pressure runs low 96 150.

[budsbud662]

Im having a fuel pressure problem with my 1996 150 (not fast strike).
I Went throught most the system today and i havnt found any leaky hoses or any reasons why the fuel pressure gets low.

but everytime i start my motor i have to pump the primer bulb to hard or the motor wont start..

recently ive had to pump the bulb while i drive to keep it running at 100%. or the motor will starve and gradually die..

Along with this problem my "no oil" light will buzz. but when i pump the bulb and restart the motor.. there are no alarms or warnings..

Im kinda scared? what should i check first.. can i drive the boat if i maintain fuel pressure manuelly?

 

[Chris1956]

Re: Fuel pressure runs low 96 150.

Bud, Start by checking (or removing) teh anti siphon valve in the fuel tank. Next is the primer bulb itself, as well as all connections in th fuel line. How old is the watrer seperator (if you have one)?

 

[budsbud662]

Re: Fuel pressure runs low 96 150.

Should i run the 150 motor off my 6 gal tank. Wont this diagnosis if the problem is tank or motor related?

 

[Chris1956]

Re: Fuel pressure runs low 96 150.

Running off the 6 gal tank can assist in diagnosis. Make sure you understand teh common parts and unique parts (ie if you use a seperate fuel line for the 6 gal tank, you have not just isolated the main tank)

 

[budsbud662]

Re: Fuel pressure runs low 96 150.

where is the anti-siphon valve commonly located?
the boat is a 1999 warrior 1891 its a walleye fishing boat.

it had duel fuel pickups but i blocked off the pickup designed for a kicker motor.
i blocked it off by the tank making sure all connections are leak proof.

I am gonna take the boat out running on the 6gal tank and see if it holds good pressure, The tank holds excellent pressure with my 25hp.. so i will figure if it doesnt its a motor based problem..

 

[Silvertip]

Re: Fuel pressure runs low 96 150.

The anti-siphon valve is the fitting on the tank where the fuel line attaches. If you take off that fitting and look inside, you will see a check ball. These things can stick and restrict fuel flow. Having to pump the primer bulb to keep the motor running is a classis symptom of a bad fuel pump or a fuel restriction. If it is a fuel restriction between the primer bulb and the tank, the bulb will typically be sucked flat so I think you may be experiencing a fuel pump failure. Running on the six gallon tank will prove or disprove that. Your fuel system does not develop fuel "pressure". Fuel is being sucked through the fuel line so the only time there is any pressure in that part of the system is when you initially squeeze the primer bulb. Once the engine starts, the pressure drops to zero and even goes into a vacuum due to the sucking of the fuel pump.

 

[budsbud662]

Re: Fuel pressure runs low 96 150.

Ok, that was an awsome post, im about to go out and do some more diagnosing but befor i do would like to make a few comments.

if it is the check valve (anti siphon) i should be able to switch to the other pickup (and block off the other one) and the problem should be solved, correct?

However, I dont know if this is a fuel pressure related problem or not. but it seems to me that it is, and may give you guys a clue to whats going on... ok The motor has a great cold start.. i can pump the primer and it starts right up, no coughs. however once the motor is warmed up and we have been out in the sun fishing for a 2 hours, i go to start the motor and it coughs and dies. so i got to get on the throttle and it dies agan. if i set the idle up a little bit. to 2k for a minute im able to get on the throttle and then it will agan run good. but once its warm, its like it has a "bad cold" it coughs often and then dies..

The motor is a 1996, but i bought it from a guy that seldom used it, The motor has less then 100 hrs on it, he replaced it with an etec because of fuel cosumtion, loudness and he just wanted to get a new etec. however he states that it also coughed for him..

Do u think this cough could be a clue to fuel pump unable to supply enough fuel to the carbs? or would you bieleve its more carb related??

overall ive had the motor for 3 months and at WOT it runs perfect.. (until i had start priming the bulb)

thanks, any input or side comments are very helpful..

 

[budsbud662]

Re: Fuel pressure runs low 96 150.

I ran the motor 3 10 minute increments on the 6 gal tank and let it sit for an hour..

the 6gallon tank remained holding good pressure throught the test. and after it sat for an hour..


so im assuming there are no leaks to the motor.

could it still be the fuel pump?

 

[budsbud662]

Re: Fuel pressure runs low 96 150.

Ok, one more thing, i dont mean to be lengthy, but the other fuel inlet is a bit larger. i just measured Inside diameters of the fittings and the kicker fitting im assuming is a bit larger, 3/8 ID the one ive been running the main motor off is 1/4 ID... im assuming the other one is built for a fuel injected or 4 stroke kicker that requires a higher amount of fuel pressure?


is it ok if i run the main motor off the big fitting?

 

[budsbud662]

Re: Fuel pressure runs low 96 150.

The VRO pump was changed new last year by the former owner.

Anyone got any ideas? i bieleve the fuel and VRO pump are the same?

 

[Chris1956]

Re: Fuel pressure runs low 96 150.

Bud, Both fuel tank pickups should have antisiphon valves. You need to have a 3/8 fitting for that motor. Since it ran OK on the portable tank, the main tank is likely the culprit. Pull the 3/8 fuel pickup and remove the A-S valve. Double check all connections and the tank vent to make sure they operate properly.

 

[budsbud662]

Re: Fuel pressure runs low 96 150.

Interesting, i found a hose that i could pull off leading to the drivers side fuel rail for the carbs. i was thinking that there should be no hose that you can easily pull off, when the hose pulled off there was fuel coming out "pressureized" so i put a good hose clamp on it.. im gonna have to get it on the water to try it out..


Once i get the fuel pressure figured out, we are gonna have to figure out the low idle miss.. i dont think the problem is related to the fuel pressure.