Limp/Guardian Mode Woes in 1999 2100i

[mtchanc]

I'm getting the popular intermittent and extremely frustrating limp/guardian mode buzzer for like 20 or so secs and then the boat will shut down. Most of the time this occurs when warm but not always. If I wait for like 30min to an hour it will usually start right back up and run like a champ. This usually happens 3 or 4 times a weekend and always at the worst times . Fuel pump is gtg/fairly new. Water pump/impeller is new so no over heating. Wiring under dash and grounds are my primary suspicion but so hard to research for a non electrical type. The dealer is like 3 hours away in Atlanta, so I'm trying to avoid a trip if at all possible. Any suggestions?

[boatwakes]

That would be a merc 315HP Mag MPI and there is no limp mode on those engines. The beep only goes off for one of three reasons: 1) low oil pressure 2) high engine cooling system temperature 3) high transmission temperature. There also is no safety shut down so if the engine is shutting itself off, it's for a different reason. I would guess high cooling temp where internal combustion temps would be high enough to cause the system to either vapor lock or stall from some other high temp condition. Check engine temps when it happens, new impeller or not, thermostat could be stuck, trans cooler could be blocked with old impeller pieces (located right next to starter), any number of things. Fix it before the block cracks or the heads warp and you have a really major issue. Keep us posted.

[mtchanc]

Thanks. Good to know, but know that there is no limp mode on the 315 MPI.

I would guess high cooling temp where internal combustion temps would be high enough to cause the system to either vapor lock or stall from some other high temp condition.

The last time this occurred it had been sitting for 3 hours, at night, and it wouldn't start. Walked back to our camp site (at midnight!), came back in the morning and it started fine and we boarded for a few hours no issues.

I've taken it to a local, non-Tige, Merc Certified mechanic but he cannot recreate the problem. He came up to the lake with me once and we drove around for an hour but of course the problem would not present itself. It occurs selectively and only at the worst times . Temps are always fairly normal according to the gauge. So, very wierd and frustrating.

If here is a vapor lock how is that released and were does that occur?

[boatwakes]

Have you tried applying throttle when it won't start? Don't put more than 25% throttle position above neutral because the ECM will not supply fuel to the injectors above that level during a start. This test will help determine if it's spark, air or fuel related by opening the throttle plate to bypass the idle air control valve. If you have access to a fuel pressure gauge, the test port is at the front of the motor, port side at the end of the fuel rail and has a black metal cap on it. It looks like a bike tire valve (schrader valve). Fuel pressure should be 30-32psi running or cranking. Also, a spark checker installed inline between the plug wire and spark plug (auto parts store for $4) will tell you if there's spark when it happens. Because it's intermittent, I think it's electrical and spark related, maybe the ignition sensor inside the distributor. Do those tests to determine where to go from here.

[mtchanc]

Boatwakes,
When I try to start with 25 or less % throttle what exactly am I looking for to test the air control valve? Engine to start?

Fuel pressure should be a constant, so an intermittent problem shouldn't be related, right? Or could the ECM be shutting down the fuel pump? Just want to ask before I go out and buy a fuel pressure gauge.

I can't find a spark plug checker online. Is there another name?

Sorry for the 101 level questions. This is all new to me.

[boatwakes]

No worries. Remember, there are no stupid questions, just stupid people. If the engine starts with throttle applied, the idle air control valve is the likely culprit. Bypassing that valve with the throttle plate open helps determine this without a computer. Fuel pressure SHOULD be a constant but I ran into an issue with a customer's boat earlier this week where the fuel pump relay would activate but not open the solenoid on the fuel tank (Sea-Ray exclusive design). What I want you to look for with fuel pressure is: 1) Is it making it? and 2) If not or too low, why? Anti-siphon, fuel pressure regulator, fuel pump etc., are all paths to follow next.
http://www.oreillyauto.com/site/c/de...0665&ppt=C0103, spark plug tester. As for the pressure gauge, I have one we use for diagnostics, but I installed one in the fuel rail on the Tige as seen in the photo. Easy to do and allows anytime monitoring.

[mtchanc]

Boat ran great all day today! I had the inline spark plug tester and the fuel pressure tester ready to go, but no - Prob a good thing since I had lots of friends out . The only thing I did was replace wing nuts on batter for some nylon lock nuts. We may be out again tomorrow more to follow as I have it...

[boatwakes]

Good to hear!