BAD-HABIT

Fuel pressure reads 6.5-7.5 lbs at startup (after sitting several hours) After sometime running the pressure will drop slowly but surely to 1.5-3.5lbs. Sometimes the drop will only be to about 4.5-5.5 lbs. RPM's do not effect this. Seems like this takes place after the motor runs for awhile. WHY? I have replaced the fuel pump and changed the fuel pressure guage four times. For some reason the Dry guage seemed to indicate the more steady pressure reading. The rest of the guages and the current guage are liquid filled. The drop from the initial pressure reading usually takes place after about 5 minutes or so. At that point it usually reads about 4-5lbs. Then after running for 20minutes or so the pressure will drop lower. This final drop (from 5lbs) does not happen all the time. Confused here any suggestions?


BH

mopower

Sounds like you found the cause of your performance problem(low fuel pressure). Now just find the cause of the low fuel pressure . You said you changed the pump and guage. How about the water sep. filter and did you check the pickup in the tank. That fuel pressure is dropping way too low.
It sounds as though after running a while you are collecting crap on the filter , which will settle off of the filter after being off for a awhile. Then after restarting it will be picked up onto the filter element again as time goes by.


PS my pressure never moves

RumRunner

The liquid filled gauges are filled with glyceron, and are heat sensitive. The hotter the gauge gets, the thinner the liquid, and the lower the reading will be.

BAD-HABIT

That would explain why the dry guage read different Have you run into this personally? Do you have any recomendations for dry guages?

BH

mopower

Faria

Turbojack

When pressure goes down remove you gas cap & see if that lets the pressure come back up. Might be a clogged vent line

formulaF302

I had a blockage a few years back in the pickup tube that went into the fuel tank. Seems the manufacturer left pieces of crap from the floor carpet in the tank and they slowly blocked up the screen at the bottom of the pickup tube, but cleared themselves after shutting off only to clog it up again later (whenever). I had a buddy that had his clogged up with a white waxy substance that supposedly came from him having used pump gas from a local gas station on land that had gasohol instead of pure gas. It reacted with the aluminum fuel tank and created the white waxy stuff that clogged up the intake screen and left deposits inside the carb. I got rid of the screen and let the other fuel filters do their job and it worked...good luck... Glenn

BAD-HABIT

Well I have gotten a new fuel pressure guage. I bought a Autometer DRY guage. Reads 6.5 at startup (ROCK STEADY). I didn't have a chance to run very long last Sunday but did notice the pressure drop as usual but only to about 4.5lbs.. I pulled the tank pickup and it doesn't have a screen. It was clear as a whistle..I removed the anti-syphon valve and it did have some junk in the side that goes from the ball to the fuel filter. Not enough to keep the ball from moving with a screwdriver or compressed air...Had some crud and what looked like a piece of plastic or something yellow.. I cleaned it out and ran compressed air thru it. I have a question though. The ball seemed like it had a magnet pulling it back towards the tank fitting. You had to suck or blow(No comments from the peanut gallery) to get it to move. Is this normal? I thought it was supposed to have a spring or something. Anyways got that on and changed the water/fuel seperator. The gas that came out of the filter looked fine...Well hopefully I will get out Thursday and find out if I have taken care of the problem...THOUGHTS ANYONE?????

Bad-Habit

BAD-HABIT

Well took the boat out and saw some marked improvement in getting the pressure to stabilize....Now its 7lbs at startup and 5.5 after running for awhile....Funny thing now is sometimes it goes back up to 7lbs...Didn't do that before! But the lowest the pressure drop is 5.5.lbs. I have started a new thread about trying a using a regulator called "Fuel Pressure Regulators" Hoping that will help me out..

BH

tbird

I had a similar problem last year and I found a loose connection from the fuel line at the Pick up tube, after driving the vibration must have causes a slight air leak and my pressure dropped right down, then it would come back. Simple solution but maybe it will help.
Jim