525 Vapor Lock
 

My port engine (525 EFI) vapor locks when I run the engine for 15 minutes or longer and then shut it off for 15 minutes. it will eventually start, usually about 5 minutes once I try and start it, My fuel pressure gauge will show 90 psi when I turn the key to prime the pump. The starboard engine show the same pressure, It doesn't matter how many times I cycle the key, I have to wait 5-10 minutes. I intermittently turn the engine over during this time. When cold it fires up perfectly, and once it does fire when warm, its instant, so the engine is not flooding out.

Before I dig into the cool fuel system and see if the heat sync compound is still around the pump, does anyone have any other suggestions. Also if I go so far, as to repack the fuel pump, I'm thinking about just replacing the entire pump incase the check valve in it is bad.

Any suggestions on this? I hooked up my Rinda, and it is not throwing any codes.

This weekend the port engine completely stopped running after getting warm and turning it off. 3 hours later, it still wouldn't fire up. Checked spark, and plugs were firing. So then I stated working my way through the fuel system, When I removed the water separator, the gasket didn't look right, so I replaced it. Went back to the helm, turned the key and once the fuel pressure reached 90 PSI, I turned the key and the engine fire up instantly. I then took the boat for a test run, to get the engine warm. An hour after turning it off, it fired up. The next day, same, no issues at all.

So, if anyone has a 525, and experiences this, change the water separator. You may be lucky and have it solve your problem.

Thanks for the tip.

I tried keeping the lid open, running the blowers, as well as the throttle in different positions, nothing worked. I'm hoping it was some, one off situation, with the fuel/water separator. You can find lots of posts on the 500 EFI having these issues, but very few with the 525 EFI.

The only time it's 90 psi is when I cycle the key (engine not running), as soon as the engine starts, it drops to 45 psi and stays there no matter what the RPM is. Both engines do the same thing. 90 psi, with a cycled key and 45 psi once started. I've not verified these numbers with my scan tool.

BUMP on this thread.

I believe I had the same problem this past weekend as OP described. Both my 525's flopped at the exact same time after a run, then anchored for cpl hours, fired up fine, past the no wake zone, throttle down, about 3000 RPMs, the both fell flat on their face. Wouldn't start. Fired up and idled fine on trailer at ramp next morning and 42ish fuel PSI.

I too will be changing my Fuel/Water separators and doing the various tips and tricks that many describe given the increase in Ethanol in today's fuels.

Thanks for the intel.

Ian

it's for my 350s, but most should apply.

Intermittent No Start - but then works fine - then doesn't

TLDR: replaced IAC, replaced fuel pump, replaced fuel pressure regulator.

Engines now start much easier, key only, hot or cold. Start and stay running.

The 525 is unique in that it has an electric fuel pump to pressurize the fuel system before starting; Then the mechanical pump takes over. That's why you have to turn the key on, wait for the pump to stop running and then start the engine. It also has a fuel cooler.

yep, its a sound you cant miss, and I never start the engine till several seconds after the electric fuel pump stops. Good point.

this is completely incorrect. The mechanical pump pushes fuel to the electric and aids in priming. Just follow the fuel lines. First stop after the filter is the mechanical pump

I have vapor lock issues on one of my 1997 502MPI's with VST. Anyone know a way to "purge" the vapor quickly to get fuel back in the rail and get going without waiting 1.5hrs to cool down?

Hey Mike, did you ever have this problem reoccur? Ive been experiencing this problem every now and then for about a month now. Fires up cold every time but after it sits for an hour or more she doesnt want to start for 5-10 minutes until I push the vapor out of the fuel system. Port motor still, Starboard motor fires right up every time.

I had a huge thread on myike issues, after changing almost everything, it was the fuel line from tank to mechanical fuel pump. Port was 100% blocked, srbd was 70.

see if there is a shrader valve on the fuel rail towards the middle of the intake

After I changed the fuel filter, I did have it vapor lock one more time. So I'm not positive that the fuel filter was the issue.