Fuel presure on 496 ho
 

Need a litle help Re over presure on one of my 496 Ho motors.
Started the motor on the hose and noticed F / presure was at 60 psi after running for a while , they only go up to 60 so it could be higher .
Changed the presure reg on the cool fuel pump gen || and took boat out for a run this weekend while idling about the presure stays around 35 ish but once I get on it its up to the max on the gauge 60 psi .
New fuel filters and boat seems to run ok and low presure pumps are new .
Any help at what I should look at first motors are 2001 Thanks Paul

I don't know where your pulling from. I check at the fitting on the rail. Key on. Motor not running and I like to see 43-45. I don't know if this is correct. But it's what I use and keep as my baseline

.


I have new Gaffrig Gauges / electric which I have hooked up at the fuel rail ,
Will go down to boat this Friday and hook up a hand held F / presure gauge and see what I get
Both gauges read the same motor not running key on pumps energised just over 30psi

Pu t a hand help fuel /P gauge and only got 33 psi motor running At idle , rev motor and it drops to about 29/30 psi . Put the boat in water go for a run lift hatch hand held is at. 70 psi ??
Has any one modified the fuel system on the 496 Ho , different pumps , tank return instead of cool fuel , inline regulater .

There is a non adjustable regulator already

43 psi + or - 2 psi

2001 fuel pressure reg is mounted into the gen 2 cool fuel assembly

I know , I have changed the FPR on both motors

Did you inspect/change the little filter screen under the regulator? If it clogged, you can get high fuel pressure. Item number 16, http://www.iboats.com/Fuel-Pump-And-...iew_id.1693114

Hi yes the regulater come with a new screen , iam getting below desired presure at idle ,when I rev motor to say 2500 it drops to just below 30psi this is boat on trailer and hose , but when I take it for a run my gauge is at 70 psi same on in dash gauge
At first I thought it might be the gauge as I only fitted them this year , so I went and bought a hand held and it does the same with that . Can pumps over presure ? Thanks for any advise .

the tiny o ring seal is very important as well make sure that is new and not deformed when installed in between the FPR. Also did you install the correct FPR for this app ?

Did you install a new GEN II cool fuel KIT ? There is 3 different cool fuel kitys to choose from just saying.

Yes Bup I fitted the correct one Thanks for your Input .
I will have to go through the whole fuel line , filter , pumps. .

I am not even sure these pumps can produce 70 PSI? The max pressure they can produce is in absence of vacuum at the regulator, so start the motor and pull the vacuum line from regulator...most I get is 43-45 PSI on Gen II systems.

All I can say is 30 ish when idling and after a run the Gafrig was pined at 60 so I bought a hand held from a auto shop and that was reading 70 psi after a run .

Only fuel system I 've seen do this is an ATIsupercharger system that uses an FMU.

Hi SB yes this is a strange one , I do have the fmu on a D1 on a well built 383 .
I will have a proper look at it next week

Fuel psi at idle with the vacuum hose disconnected should be same fuel psi as WOT at top rpm with vac hose connected to fpr.

Ok I have changed both the FPR on the cool 2 but what about the ones on the fuel rail ,
I have heard these called dampers but the book callers them Fuel/P R ??

Paul your referring to the device where the fuel line attaches to the rail? You are correct it is a pulse dampener and they manage fuel pulsing and limit noise, will have no affect on rail pressure.

many people think thats FPR on the fuel rails - I have been saying its the DAMPER for years up here - and I have posted this before (the Merc SB) as to what it is exactly.

http://ww2.justanswer.com/uploads/ke...5804_EN_09.pdf

A symptom of a delaminated cool fuel housing is high fuel pressure from what I have read. Might be worth pulling the rail and inspecting for paint.

I had high fuel pressure and starving for fuel on a 2008 496 mag removed the regulator on the fuel pump and you could see where the paint was coming off the inside of the fuel pump. Removed the injectors and they had chips of paint on the screens. Ended up putting a new fuel pump on flushing the fuel lines and replacing the injectors. Problem fixed.

I think this is just a Gen 3 problem isn't it?

It is a Gen 3. Don't know about the others.

the OP has Gen 2 and yes its the GEN 3 that peels paint internally. find paint in the injectors all the time form the GEN 3 cool fuel systems. The GEN 2 cool fuel does not have internal paint.

The 496 can have really bad corrosion internally of the fuel rails and the damper. See that alot as well.

You have to make sure there is no restrictions under the FPR and that tiny screen and o ring seal is very clean and installed properly / correctly.

I have seen high fuel pressure readings when that passage is restricted and or the screen and or bad installed o ring seal.

Thanks everybody for your help I will go through the fuel system and get back here when I've fixed it and let you no the prob .