4.3 Mercruiser MPI Wouldn't Stay Running (IAC??)

[rcflyyer1]

Hello,

Quite a strange problem I experienced on my 280 Sundancer a few days ago. Both engines were replaced (long blocks) a few months ago and after the repairs were finished, I had to let it sit for a month.

When I went to start up the engines at the marina, they both started right up and ran perfectly fine for 20 minutes just idling at the dock with periodic revs in neutral. Restarted them about an hour later and, again, perfect running engines. The next time I went to start them up, about another hour later, starboard ran perfectly while the port would start up but then stop a few seconds later. Tried restarting the port ~5 times all with the same result. I call over a mechanic and he is able to get the engine started after giving it some gas. He lets it run at 3000 RPM for a little while before letting it idle back down. After that, it idled perfectly, but with the new addition of a loud alarm the beeps twice every minute. We let it idle for around 10 minutes until shutting it down. The alarm was active the entire time, even though the engine idled perfectly.

I commonly see the IAC valve being a common culprit in this situation. I had the symptoms of it at first, but then after giving the engine a good workout, the run ability problem went away though the alarm still kept going off. At this point, I just really want the alarm to stop going off. Will the alarm still beep if the IAC was failing but then corrected itself later on?

Thanks

 

[CaptRonn]

Did you do an engine scan to see what code is showing?

 

[scoflaw]

Do you know what ecm you have ? the 555 came out in late 2002 early 2003. The predecessor was the Mefi-3 and much simpler to trouble shoot without the scanner.

 

[rcflyyer1]

Did you do an engine scan to see what code is showing?

The mechanic said that a scan wouldn't really do anything since my particular engines don't throw codes pertaining to the alarm (??). I believe that's what he meant.

Do you know what ecm you have ? the 555 came out in late 2002 early 2003. The predecessor was the Mefi-3 and much simpler to trouble shoot without the scanner.

Not too sure on my ECM model, but I know the engine model is 4.3L MPI A1 (T-220 PHP) according to the literature that came with the boat. My boat was built before the 555 came out according to that time frame.

Could it be my gear oil? Right now, I can't get my engine hatch open for some reason so I can't check it, but my engine manual says the only thing that would cause intermittent beeps is gear oil. Does this seem correct? The only reason I suspected the IAC is because of the engine stopping problem I was having.

 

[scoflaw]

Yes, unplug the sensor near the bottle. Oil and overtemp would give a constant alarm. Although a sensor failure, of which there are just a few could give that intermittent alarm

 

[rcflyyer1]

Finally got the engine hatch open to begin tacking this issue. Only had enough time to look at things on a wash rack so I didn't get to start the engines. First thing I looked at was the gear oil reservoir and the port side was full and starboard side was about 3/4 in. below full but well above the low line. Strange since the alarm started after we got the port side running. I'm starting to think that maybe gear oil level might not be it unless running the engines in neutral causes fluid levels in the reservoir to change.

Yes, unplug the sensor near the bottle. Oil and overtemp would give a constant alarm. Although a sensor failure, of which there are just a few could give that intermittent alarm

Pardon my ignorance, but what will unplugging the sensor tell me? Will it stop beeping if it doesn't receive a signal from the sensor? Do you think my sensor could be malfunctioning?

Thanks

 

[scoflaw]

Floats sticking in the bottle is a common issue

 

[rcflyyer1]

Floats sticking in the bottle is a common issue

I tried working more on the issue today. It seems that when the fluid is full, the float is out of sight, so I tried using my finger to find the float but didn't have any luck. I cleaned an Allen wrench and stuck it down in there and felt something but couldn't find a float. I gave the outside of both bottles some hard taps to hopefully free a stuck float.

Next time, should I suck the fluid out so I can manipulate the float? Maybe I could mistakenly introduce unwanted air into the system?

Thanks

 

[Wanderer 290]

The way the float system works is when the system is low on oil the float grounds and causes the alarm. By unplugging the the float it can not ground.

 

[scoflaw]

Best to take it off the engine and give it a good cleaning. That oil turns to gunk at the bottom.

 

[Wanderer 290]

Best to take it off the engine and give it a good cleaning. That oil turns to gunk at the bottom.

Agreed

 

[rcflyyer1]

Decided I would update this thread. I was working on the boat today and looked at both lube bottles. Turns out neither of the sensor wires on both bottles were attached to begin with. Could this be causing the alarm?

Meanwhile, coming in to dock, both engines are having issues with stalling out (especially when shifting from R to N. This doesn't happen all the time, maybe 1 in 5 shifts. I have a new IAC I will put in to see if the problem goes away.

Since I recall both engines having this behavior, I'll install the IAC on the starboard engine first to see if the issue goes away. Also, it gives me a better chance of retaining my power steering since it's powered off that engine.

I'll update when this is solved.