2004 Mercruiser 5.0 MPI Starting/Stalling Issues

[jwilson_46143]

Need some help troubleshooting my 2004 Chaparral Mercruiser 5.0MPI with Alpha 1 drive. The engine serial number is 0W029452. The engine has had intermittent starting and stalling issues for several seasons, but the problems have recently become significantly worse. The starting issue tends to be after sitting for a few hours or multiple days....cranking but not firing. It has always eventually started in the end, but it's becoming a chore to get it going. Once started it runs fine and will restart without issue. The stalling issue generally happens when I come off plane and idle in. The first time I shift into neutral the engine occasionally sputters and dies. I have already replaced the IAC valve and the fuel filter. I ran a can of Seafoam through the tank. Neither of those replacements helped my issues. The battery is a starting version, 2-3 years old, Interstate Brand.

Are these two issues even related? Suggestions for next steps to try? Many thanks for your suggestions!

 

[Bondo]

Ayuh,..... Have ya taken a peek at the spark plugs, 'n the distributor contacts,..??

Was there anything but clean fresh gasoline in the old fuel filter,..??

 

[QBhoy]

Start with the distributor and rotor, if you’re sure your fuel is good. By far, the most common cause of issues like this. You have the flat cap unit that’s now become notorious for failure and random running issues off all sorts you can imagine. But check your fuel for its condition first off. Empty the fuel filter out into a glass and let it settle. See what she has in her after a half hour or hour. That will tell the story. If that’s definitely good. Most would have a sure fire bet on the distributor being too blame. And if it isn’t now…it soon will be. Can bet your bottom dollar on it.

 

[alldodge]

Check fuel pressure - 43 psi at 1800 rpm
Is idle at 600 rpm?

 

[jwilson_46143]

Start with the distributor and rotor, if you’re sure your fuel is good. By far, the most common cause of issues like this. You have the flat cap unit that’s now become notorious for failure and random running issues off all sorts you can imagine. But check your fuel for its condition first off. Empty the fuel filter out into a glass and let it settle. See what she has in her after a half hour or hour. That will tell the story. If that’s definitely good. Most would have a sure fire bet on the distributor being too blame. And if it isn’t now…it soon will be. Can bet your bottom dollar on it.

Thanks for the suggestion. I ordered a new OEM cap and rotor and will put it on this weekend. Unfortunately I dumped the contents of the fuel filter before I thought of examining it in a bottle for water content.

 

[jwilson_46143]

Check fuel pressure - 43 psi at 1800 rpm
Is idle at 600 rpm?

Thanks for the spec on fuel pressure. I'll check when I have a chance. The neutral idle does tend to be a bit flaky. Sometimes idles in normal range at 600rpm or so. Other times it wants to idle at 800-1200rpm. Does that point toward any potential issue?

 

[alldodge]

The 800 to 1200 would have me looking at the IAC and TPS. Noted you just replaced IAC and did you clean or replace the IAC muffler (foam rubber piece in TB)?

At idle the TPS voltage should read about 0.5V

Most likely your going to need to get some readings to determine what's going on. Scanner is best but many checks can be done with a voltmeter

Might have a vacuum leak

 

[jwilson_46143]

The 800 to 1200 would have me looking at the IAC and TPS. Noted you just replaced IAC and did you clean or replace the IAC muffler (foam rubber piece in TB)?

At idle the TPS voltage should read about 0.5V

Most likely your going to need to get some readings to determine what's going on. Scanner is best but many checks can be done with a voltmeter

Might have a vacuum leak

I'll check on the muffler condition and the TPS voltage....thanks

 

[jwilson_46143]

Thanks for the help and suggestions here. I cleaned the IAC muffler and replaced the rotor and distributor cap. The old cap was quite corroded. My starting issue is now fixed! It started on the first crank all weekend. I'm still fighting an occasional stalling issue when I come off plane and shift to neutral. Is this likely caused by a stretched shift cable like I have read about?

 

[QBhoy]

Thanks for the help and suggestions here. I cleaned the IAC muffler and replaced the rotor and distributor cap. The old cap was quite corroded. My starting issue is now fixed! It started on the first crank all weekend. I'm still fighting an occasional stalling issue when I come off plane and shift to neutral. Is this likely caused by a stretched shift cable like I have read about?

Excellent. So common.