Hello all, I have searched here and cannot find an answer here or elsewhere on the web regarding actual fuel pressure should be when running.
I have read Mercruiser Service Bulletin 2004-06, which addresses fuel pressures, and all it say is that if when in key-on, engine-off mode the fuel pressure is above 44psi replace the cool fuel module. Well, with my non calibrated gauge in that condition I get 46psi...so really close but not exactly on the spec.
The problem is that when I start the engine and run at idle the gauge increases up to about 82psi over a period of 30 seconds, then stays there. When I disconnect the fuel pressure regulator the pressure goes up to 84-86psi. The vacuum line to the regulator is free of obstructions, and the regulator responds to the loss of vacuum so I believe the regulator is OK, however I think the fuel pressure is too high as on automotive fuel systems 30-40 psi is the normal running fuel pressure.
I did rev the engine up to about 1800RPM in neutral and the pressure remained at +/-82psi. When I stopped the engine it fell immediately to 30psi and has held there for several minutes.
What started all this is that I completed the annual service several weeks ago (replaced the fuel filter too), and ran the boat on the muffs, no problem. Took the boat out for a day, ran at various speeds (idle-planing) no problems, and went through about 15 gallons of fuel. Filled up a couple days later, putted around the lake and the engine started to misfire, and drop idle from 800RPM down below idle. I checked what I could while floating (there was fuel in the filter housing, had good battery voltage, and the pump would trigger when I went key-on for a few seconds as it should. I got the engine re-started a few times, but eventually it just ran out of fuel. The next day when at the dock I went and fired it up, no problems and ran well. I putted over to the boat launch (200 yds) and trailered the boat, no problem. My issue is that I don't want to go trial it until I get to the bottom of the problem.
Of course this was an intermittent no-run condition that hasn't re-occured, now turns into a question of where should I be on fuel pressure.
Anyone here have any ideas, or a copy of the correct portion of a service manual that gives pressures?
Thanks!
I have read Mercruiser Service Bulletin 2004-06, which addresses fuel pressures, and all it say is that if when in key-on, engine-off mode the fuel pressure is above 44psi replace the cool fuel module. Well, with my non calibrated gauge in that condition I get 46psi...so really close but not exactly on the spec.
The problem is that when I start the engine and run at idle the gauge increases up to about 82psi over a period of 30 seconds, then stays there. When I disconnect the fuel pressure regulator the pressure goes up to 84-86psi. The vacuum line to the regulator is free of obstructions, and the regulator responds to the loss of vacuum so I believe the regulator is OK, however I think the fuel pressure is too high as on automotive fuel systems 30-40 psi is the normal running fuel pressure.
I did rev the engine up to about 1800RPM in neutral and the pressure remained at +/-82psi. When I stopped the engine it fell immediately to 30psi and has held there for several minutes.
What started all this is that I completed the annual service several weeks ago (replaced the fuel filter too), and ran the boat on the muffs, no problem. Took the boat out for a day, ran at various speeds (idle-planing) no problems, and went through about 15 gallons of fuel. Filled up a couple days later, putted around the lake and the engine started to misfire, and drop idle from 800RPM down below idle. I checked what I could while floating (there was fuel in the filter housing, had good battery voltage, and the pump would trigger when I went key-on for a few seconds as it should. I got the engine re-started a few times, but eventually it just ran out of fuel. The next day when at the dock I went and fired it up, no problems and ran well. I putted over to the boat launch (200 yds) and trailered the boat, no problem. My issue is that I don't want to go trial it until I get to the bottom of the problem.
Of course this was an intermittent no-run condition that hasn't re-occured, now turns into a question of where should I be on fuel pressure.
Anyone here have any ideas, or a copy of the correct portion of a service manual that gives pressures?
Thanks!
