Mercruiser 5.0L MPI stalls during cold start

[troman9]

I think I might have the same problem as another poster from a different thread, but taking a moderator's advice I thought I'd try and start my own.

I have a 2006 Maxum 2600SE with a Mercruiser 5.0L MPI engine and a Bravo 3 sterndrive. I bought it in Feb 2010, and it ran fine all last season. The engine now has about 80 hours. When I first started it this season, the idle RPMs oscillated up and down in the 400 to 600 range. I had it in the shop for another reason, and they checked the computer and there were no fault codes. I had it on the water last week, and when I tried to start the engine in the morning it turned over but could only run for a few seconds and then stalled when the RPM was low. This happened a few times until I ran the throttle up a bit, and then it was able to stay running. Once it was warm it had no problem at the normal idle RPM of 600.

I was advised that this was probably an idle air controller (IAC) and I should clean it with carborator cleaner. I did that today, but it didn't help. So I'm ordering a new one, but that won't be here for awhile.

Is there anything else that could cause this? Nauticool already tried to replace the IAC and it didn't help in his case. But, there is anecdotal evidence that IAC failures are common with this particular engine (see link below).

Any and all sage advice is greatly appreciated!

Tom

http://www.boatingwinnebago.com/forums/mechanical-service-prop-talk/merc-mpi-engine-does-not-start-idle-or-is-beeping-twice-every-minute/

 

[dubs283]

Re: Mercruiser 5.0L MPI stalls during cold start

a faulty IAC will give a code and a warning horn

if it is stuck, any technician worth their salt will see on the data monitor of a CDS that there is an issue with it

cleaning it with carb cleaner?? never heard of that, they either work or they don't

seeing as how your engine idles fine at warm temps indicates the IAC is doing what is supposed to

often times when waking up these mpi engine from winter sleep i see this same behavior, they've been stored for six months, take her out for a nice hard run, get the juices flowing and the problem will more than likely go away

 

[Pete104]

Re: Mercruiser 5.0L MPI stalls during cold start

If this is a continuing problem, that's bad! There is/are "drivers" in the PCM that control what the IAC does. If IAC motor "freezes" or "locks up" the drivers have given up. You have options: http://www.pmefi.com/

Contact them, they may want to talk to your tech but they set ECM's & PCM's up that need a little TLC!

 

[dubs283]

Re: Mercruiser 5.0L MPI stalls during cold start

If IAC motor "freezes" or "locks up" the drivers have given up

hmmm...never heard that one

if an IAC fails, it fails - it will not feed back to the ecm/pcm and cause damage

yes drivers in the ecm/pcm do fail but not as often as IACs themselves fail - not even close

and that website, according the the pictures of the ecms they have only deals with MEFI 1,2,3 not ECM/PCM 555 like what this fella has

 

[Don S]

Re: Mercruiser 5.0L MPI stalls during cold start

You need to get it hooked up to a diagnostic computer and compare all the outputs from the sensors to what they should be. Not just look for trouble codes. something simple, like the ECT temp sender, could be showing a warm engine temp when in fact the engine is cold. It wouldn't show a code, because it just thinks the engine is warm, which is not a problem. Until you check everything, you are just guessing and throwing parts $$$$$ at a problem and hoping for the best.

 

[troman9]

Re: Mercruiser 5.0L MPI stalls during cold start

Thanks for all the feedback. A few answers:

dubs: Carb cleaner was suggested by an auto mechanic, who has seen IACs in cars get "sticky". When they get "sticky", he says, they don't always throw codes.

I've had the boat on the water 4 times this season, for a total of about 6 hours, so I don't think the problem will just go away with use.

Pete: I looked at that website and maybe I'm dense but I don't see the connection. Are you saying they can reprogram the ECM to solve a problem like this?

Don S: A couple of months ago I took it to a mechanic to fix a high fuel consumption problem. He checked the fault codes as part of diagnosing that and said there were none. That turned out to be the fuel pressure regulator. I noticed the idle issue at the time, but didn't know it was a separate problem.

I agree the ideal way to find the problem is with a diagnostic computer, but I don't have one (yet) and it's a bit of a hassle to get the boat to a shop. The IAC is only about $90, and it's a 5 minute job to replace, so it seemed like it was worth a try.

 

[Don S]

Re: Mercruiser 5.0L MPI stalls during cold start

Pete: I looked at that website and maybe I'm dense but I don't see the connection. Are you saying they can reprogram the ECM to solve a problem like this?

NO!, you can't reprogram an ECM to cure a problem. Places like that may be able to fix a problem in the ECM if there is a problem in the ECM, but it can't program the thing to cure an engine or sensor or wiring problem.

 

[troman9]

Re: Mercruiser 5.0L MPI stalls during cold start

NO!, you can't reprogram an ECM to cure a problem. Places like that may be able to fix a problem in the ECM if there is a problem in the ECM, but it can't program the thing to cure an engine or sensor or wiring problem.

OK I see, if the ECM is bad maybe they can fix it vs replacing it. This is a 5 year old engine with 80 hours, so I'm thinking the odds of the ECM being bad are pretty low, but I'll keep that in mind.

 

[dubs283]

Re: Mercruiser 5.0L MPI stalls during cold start

Carb cleaner was suggested by an auto mechanic, who has seen IACs in cars get "sticky". When they get "sticky", he says, they don't always throw codes.

thats one auto mechanics opinion - and its fine if you want to follow their advice, i'm just telling you what i have seen many times in the past, on boats

as far as a code, i did state that a good tech will note on the DATA MONITOR of the CDS that there could be an issue with the IAC, not neccissarily a code

BTW - be sure to get a gasket with the new IAC - they don't come with one

 

[troman9]

Re: Mercruiser 5.0L MPI stalls during cold start

dubs:
yes, good point about the gasket... I ordered one. Strange thing, when I cleaned the IAC yesterday, there was no gasket! I wonder if that could be part of the problem...

 

[nauticool]

Re: Mercruiser 5.0L MPI stalls during cold start

Hi Tom,

Noticed your reply on my thread. Yes we seem to have exactly the same engine with exactly the same problem.

I fitted a new iac with gasket and muffler and this has not solved the problem. See my thread to see what else ive tried, mostly as part of a service. Have you checked your iac muffler? Mine was really bad and often overlooked on a service. This will not solve your problem but is worth bearing in mind. It is located under the flame aresstor on the end of one of the pipes from the iac. pull it out with long nose pliers and change. they are white when new, i expect yours is black like mine was, it will prelong the life of your new iac valve if nothing else.

I may have the dealer come to look at mine soon, with much regret.

If you find a fix please PM me and obviously i will do the same

Good luck!

Glenn

 

[nauticool]

Re: Mercruiser 5.0L MPI stalls during cold start

btw about the laying up thought. My boat is in the water all year round, except for three weeks of the year, and is run every two weeks without fail. So i dont think this is the issue...

I have also heard someone saying it could be fuel pump issue. im not sure as it runs fine all other times. Does yours make a dry whine sort of noise when you first turn ignition on, and then when started? i can hear my pump over the sound of engine, kind of sounds like an engine bay vent fan...

 

[troman9]

Re: Mercruiser 5.0L MPI stalls during cold start

Glenn,
Thanks for the reply. Yes I did see the things you've already tried so I'm not hugely optimistic that the IAC will do the trick. I'll be installing it on Saturday, so we'll see what happens. I did order a new muffler along with the IAC and gasket.

If it's not the IAC, I'm not sure what I'll do next. Like yours, my engine idles fine when it's warm. There must be a sensor that tells the computer that the engine is cold or warm, and the IAC must be controlled based on that. Maybe the sensor is bad, and telling the computer that the engine is warm when it's really cold?

I might just break down and tow it to the shop, but I'm really hoping there is something that is simple to replace that would fix this. If/when I figure this out I'll be sure and let you know.

Thanks,
Tom

 

[emilsr]

Re: Mercruiser 5.0L MPI stalls during cold start

Don S has given good advice; get it to a Mercruiser mechanic (NOT an automotive mechanic) and have it scanned. The other option is to buy your own Rinda and scan it yourself, but unless you're an experienced marine mechanic with the proper training and tools you're better off going to a pro. Either way you're just going to be throwing parts at it until you do so....and that gets expensive, not to mention frustrating. In the end, going to a competent mechanic is probably going to be the cheapest option as well.

 

[Don S]

Re: Mercruiser 5.0L MPI stalls during cold start

There must be a sensor that tells the computer that the engine is cold or warm,

Go back and read reply #5.

but I'm really hoping there is something that is simple to replace that would fix this.

There may be, the problem is finding it and knowing what to fix. But how many parts are you going to throw at it hoping to fix it and it doesn't work. It's also possible you have a problem with the wiring itself, a loose pin in a connector, a bit of corrosion, etc. in which case a new part will do nothing to fix the problem.

Here is a link to the OEM manual for your EFI system,
http://www.4shared.com/document/FWwx1Vs7/Service_Manual_36_Rev_1_SBC.html
With that manual, a DVM, and the Rinda Scan Tool, a fuel pressure gauge, a test light, and some work, you should be able to track down the problem

 

[troman9]

Re: Mercruiser 5.0L MPI stalls during cold start

Emilsr & Don S: your advice regarding diagnostic scanning is duly noted. I agree that replacing parts based on guessing is not the way to go. I have though, read alot of accounts that the IACs are prone to failure on my engine, and some folks say they go as far as keeping a spare onboard in case it fails on the water. So if my IAC turns out to be OK, I will use it as a spare.

DonS: Thanks for all of the reference info, that's going to be a great help. I'd like to take a crack at diagnosing this myself. I'm not a mechanic, but I am an engineer, so I'm used to troubleshooting complex problems. Regarding the scan tool, Rinda also has something called Diacom which runs on a laptop, and seems to have more capability. It's a few hundred $ more, but if I'm going down that road maybe it makes sense. I'd be interested in your take on that.

Thanks for your help,
Tom

 

[emilsr]

Re: Mercruiser 5.0L MPI stalls during cold start

I'll be curious to here what the problem turns out to be. All 3 times I've experienced IAC failure (twice on my boats, once on a friend's boat) it threw a code and set off the soft alarm (2 beeps every minute).

Not a mechanic, but like you I'm overly curious. Good luck!

 

[Don S]

Re: Mercruiser 5.0L MPI stalls during cold start

Rinda also has something called Diacom which runs on a laptop, and seems to have more capability.

It's a good program, have had both, but for working on boats outside in the sun and/or rain, forget the laptop. You just can't see anything on those screens in the sun, and rain is a no-no. Plus laptops suffer damage a lot easier than the scan tool. The scan tool will tell you everything the laptop will, just takes a bit more button pushing, it's also only $400.

 

[nauticool]

Re: Mercruiser 5.0L MPI stalls during cold start

I would say that replacing parts on guessing only is a bad way to go but isant that what these forums are for? A bit of an educated guess? The amount of money i have saved using forums for auto and boat repairs warrants a few wasted ? or $ (In the long run its not really wasted)

The sort of engineers in my area would have come to have a look at the boat, 1 hour travel, plugged in and found nothing, 1 hour labour, said they need to order an iac valve, muffler and gasket at rrp prices. Then return, 1 hour travel, 1 hour labour to fit ( at this point i owe them approx ?400 ) then to hear them say its a process of elimination! these are mercruiser dealers. I know this because ive been down this road before.... its a long story.
I spent a total of ?100 by ordering my iac valve, gasket and muffler from the states, waiting for delivery and fitting myself. It would have cost about ?200 to purchase here in the UK for some reason. I think Mercruiser assume we are all loaded here

note; i am not saying all engineers are like this. This is my area and my experience and im saying some people need these forums for any ideas and yes we win some and we loose some but i dont think any money is lost overall. Definatly not in my case.

I cant bear all this modern technology, sensor this, switch that, buy this and plug in for this model. What happens when you sell and end up with a volvo or cat etc. I miss carburettors

Maybe i should start a new thead on this? Im not bitter just feel for Tom as im in the same situation

Glenn

 

[Don S]

Re: Mercruiser 5.0L MPI stalls during cold start

I would say that replacing parts on guessing only is a bad way to go but isant that what these forums are for? A bit of an educated guess?

No, or at least it shouldn't be. MOST people come here to get answers, not guesses. Guesses is what most of them tried and it didn't work.
That is why some of us give troubleshooting information, manual links, and actual things that help find the problem. INSTEAD of just guessing.

I cant bear all this modern technology,

Yes, but carbs don't make the EPA happy anymore. They want cleaner. Same thing happened with cars. Do you remember seeing a carb on a new car lately? Hasn't happened in years.
The days of easy to work on is gone, you learn to use the tools and procedures to make your job easier.
The engines aren't even automotive engines used in todays cars and trucks. They are marine now.