496/Raylar HO600 fuel questions
 

Good evening from the UK, I hope you are all well.

I bought a Donzi 26 with a Raylar HO600 engine (OW317280) last year and I have a few questions if anyone can help.

Ater the boat runs out of fuel is it normal for the whole fuel system to need stripping down and priming up to the fuel rail? I have a Racor pre filter that we filled with fuel to help but the cool fuel filter and pump chambers on the engine also had to be filled with fuel before it would start. We primed several times with the key without starting but this didnt help so are they not strong enough to self prime or do I maybe have a failing pump? Hose runs uphill from tank to racor pre filter around 2ft total length then 1ft downhill from filter to cool fuel on engine. Racor and cool fuel filter and screen filter are brand new, no evidence of any flaking paint inside them.

Also what should the fuel pressure be on the Raylar HO600 engine at the fuel rail? My mechanic has struggled to get hold of anyone at Raylar to ask, I had an Oring blow out of one of the round connectors on the crossover pipe, although this wasnt disturbed in the previous issue with the priming. Im worried the pressure may be set too high as the engine is running rich and we cant see why as there are no faults when scanned.

Thanks for any help.

That's totally normal once you run out of fuel. Your should be as far as I know 3-4 psi over stock. So 46-47 psi key on engine not running.

Ok thats a big help, thanks. I should be back down there this week so will see what its running.

You might need to prime the system but I find it hard to believe. If it doesnt stay primed and ready, that's another issue, air is getting in somewhere.

Do you have the stock regulator? You should be 1-2 PSI over stock. 43-44 PSI You really need to get an O2 sensor even after you are at 42-43 PSI. At that point you can run the boat, However, you really should ditch the stock regulator and put in an Aeromotive, They are more consistent and more accurate. You can take your fuel rail off and weld on a AN fitting, replace and plumb in the new regulator. It is 10 times more reliable for $150.000

Do you have the stock ECU program? Whos program is on the ECU? Raylar or Whipple? Stage 1, 2 or 3?

Unsure if I have a stock regulator in the cool fuel, the engine was bought by one of the previous owners of the boat from Raylar as a complete engine before they stopped doing them and just sold the kits.

As for the ECU Im pretty sure it is the correct Raylar HO600 going by an additional sticker on it that has almost faded. When it was scanned we found it was programmed by Whipple which seems to confirm it is not the stock program.

I like the sound of the more simple regulator and return line setup and will look at that if I cant get the current system right.

Thanks for the replies.

Here was the way we did it on mine. Simple.

Supposedly the Raylar program is slightly more conservative. Not knowing if it was a Whipple Stage 2 or 3 makes it a little difficult. Whipple did have specific programs for the Raylar 600 engine. What I can tell you is that even only 1.5 to 2 PSI over stock was very rich. The problem is that it varies greatly through the RPM range. For example, mine is spot on 12.8 AF at 5200, 5400 5600 but is rich idle through about 3000. Yes, this can be fixed but it took a month of fooling around to get it here. The program can be tweaked but the best way to figure any of it out is to just get an O2 sensor and be done.

Thats a neat install and some great information thanks. Sounds like a lot to look into but I dont mind spending the time to figure it out. Il look into the O2 sensor but my headers arent set up for them yet. Il chat to the mechanic this week.

I was under the impression the stock merc cool fuel setup was not up to the task of feeding the HO600? I've seen it recommended by Raylar to eliminate the merc setup and go Aeromotive and return to tank like Keith has done.

When checking your fuel pressures engine running make sure to have the rubber vaccumn hose unhooked from the regulator.

Another reason for fuel pressure bleed down is a stuck open and or injector(s) the pintle can not fully seat close.

Or a fuel pump check valve issue