Port engine dies after first cold start

Alex D

Alex D

Active Member
Oct 2, 2006
1,408
Smith Mountain Lake, VA
Boat Info
2004 240 Sundeck
Engines
Mercruiser 5.0 MPI B3
Now that it is getting colder, my port engine dies after the first cold start after the boat has set for a week. I know it's not the fuel pump 'cause its pre-priming the system fine. After that first start up and died, the engine starts fine, runs and idles just fine without a hitch. The SB engine does not do this.

I could see that the IAC motor and/or valve could be the culprit and maybe slow to react ... they're easy to get to and clean or change.

Frank et al ... any other ideeas what could cause this and what I should check??
 
Alex:

Are you getting any alarms on your smart craft..???
 
Alex,

The 5.0 MPI on my 240SD always acted the same way as yours from the first day I took delivery. I thought the IAC was the culprit too. But one summer day my IAC completley failed and was replaced. But when cool weather returned my start/stalling problem remained the same. I just looked at the problem as an "annoyance" and lived with it.
 
Dom, no there is no SC alarm and no systems panel alarm going off.

The fuel pump pre-primes the system just fine, then the engine starts also fine, but the idle goes down from the initial 1000 rpm until it dies slowly within about three to four seconds after start up. I hit the start switch again and she immediately fires up on the first revolution cranking and idles just fine.

If I start her after just sitting for a night this also doesn't happen, only when she sits for a longer period, like a week.

It didn't do it in the summer and the SB engine does not do this at all, summer or fall.
 
Alex, I have the exact same problem with my port engine as well. The engine fires up fine and then dies after a few seconds. On restart, I have to keep the RPMs up a bit for a minute or two, then its OK. Not sure if its because the air temps have fallen or because I'm using the boat less frequently since the temps stared to fall. Warm restarts are fine. Stbd is fine too. Both fine all summer. No alarms either. My dealer is going to check it out. I'll let you know what they / we find.
 
WHEW .. now I don't feel so bad if even a 2006 dancer is doing it ... juuust kidding.

WL ... mine starts fine after thee first stall and doesn't need any throttle jockeying to stay running. If your does I would highly recommend to inspect and clean the IAC since it seems your engine stall because of lack of air, which is controlled by the IAC. It sits on top of the manifold towards the bow of the boat. Keep in mind that if needle and pintle are clean, the actuator motor could still be the culprit.

I am going to take mine off and check it out sometime this fall.
 
This type of problem happened to me three or four times at the end of last year. I removed the IAC and cleaned it, but it still stalled once more after starting it for winterizing. I did have to throttle up slightly for a few seconds only to keep it running once, and other times I just re-started it.

Do you guys think that if it is the IAC it would have set a code? I do not have a scanner, but a local merc guy will scan it for me in my driveway for some $$. I am not sure if this condition will even be evident in a computer scan.

Please let me know what you think.

Thanks

Mark
 
Alex D, my port motor used to do the exact same thing. Now it does not. I have no idea why in either case.
 
As we got later into the winter, both of my engines did it. I am pretty sure that as things warm up, this is going away ...
 
i dont think i have an IAC (not sure what that is but it sounds new and electronic). but if it makes you feel any better, both my engines do this each and every cold start, spring summer or fall. actually, the boat has to sit for more than a couple of days for this to happen. starts like a japanese car when warm, even a day or two later. any more than that, i'm pumping and grinding just to keep em from sputtering. i'll probably pull a muscle trying to get them started this weekend on land (first start since october). talk about a cold start!

i just chalk it up to still another joy of owning an OLD boat :smt013
 
Rodds -- The IAC is electronic. It is a device for fuel injected motors which adjusts the idle (Idle air control - I think). I just read my merc manual and found out how to test it, but the motor needs to be running. No-one answered about it setting a "code" so I will wait until I "summerize" my boat and run the tests in the manual. Normally this motor starts almost without cranking!. I love fuel injection....
 
boatrboy said:
Rodds -- The IAC is electronic. It is a device for fuel injected motors which adjusts the idle (Idle air control - I think). I just read my merc manual and found out how to test it, but the motor needs to be running. No-one answered about it setting a "code" so I will wait until I "summerize" my boat and run the tests in the manual. Normally this motor starts almost without cranking!. I love fuel injection....
Click to expand...

Idle rpm are determined by idle air allowed to pass this little pintle valve since the throttle blade closes 100% shut on an FI engine. The computer controls this valve based on the rpm it reads and based on the coolant temp. The valve can gunk up with black stuff and residue and move hard, so the computer cannot compensate and the engine dies. It even can become entirely stuck at which point you may lose idle alltogether and the engine stalls all the time. this valve is extremely easy to exchange. It is most often on top of the manifold held with two allen head bolts and has a water proof harness connector. You can exchange it in 10 minutes.

Carbed engines do not have them as they control idle speed via a idle mixture or idle air screw in the carb that basically does the same. Old. old carbs have a throttle blade stop screw controlling idle with keeping the throttle blade open just a hair. The other circuit controlling idle air on a carbed engine while warming up is the choke.
 
Thanks Alex. I removed the valve last year and sprayed it with carb cleaner, but without actually activating it in my hand, I could not tell if it works properly. After I re-installed it I had the same same problem once, a couple of days later. I priced it out out at around 95 bucks, but I want to diagnose it properly. The manual gives specific tests to perform once the boat is running. I was hoping a code in the computer would be set because I could read this with out starting the engine, and replace the IAC if that was the problem. Oh well, I will just wait a few more weeks till I summerize..

Thanks again - Mark
 
boatrboy said:
Thanks Alex. I removed the valve last year and sprayed it with carb cleaner, but without actually activating it in my hand, I could not tell if it works properly. After I re-installed it I had the same same problem once, a couple of days later. I priced it out out at around 95 bucks, but I want to diagnose it properly. The manual gives specific tests to perform once the boat is running. I was hoping a code in the computer would be set because I could read this with out starting the engine, and replace the IAC if that was the problem. Oh well, I will just wait a few more weeks till I summerize..

Thanks again - Mark
Click to expand...

If you have a good SR dealer they can diagnose it with their SR diagnosis tool or they might have a "tester" IAC around since IAC faults and failures are actually very common. So they should be able to determine the issue. If yours hasn't failed yet it might only be a question of time. I had three friends with Merc power packages replace theirs last two years.
 
You must log in or register to reply here.

Forum statistics

Threads
113,143
Messages
1,427,149
Members
61,056
Latest member
Rafael Saraiva
Back
Top