Vapor Lock or something else?

[bengaltiger14]

Hello all,
I have a 2005 Sea Ray with a Mercruiser 5.0L MPI engine. Cold starts off the trailer perfectly every time. I shut the engine off after running for a little while, getting the engine up to operating temperature. I sit for a half hour up to 1.5 hours and try to crank up but it will not start. It turns over just fine but will not start unless I rev the engine up while cranking. Also, this happened last week after just running the boat at idle for 5 minutes. I don't believe it ever reached operating temperature. I changed the engine mounted fuel/water separating filter and saw no signs of water. Checked the fuel pressure and it was at 40-43 psi.

Now, yesterday, the boat cranked just fine off the trailer but then shut off when trying to put it in forward. This has not happened before. It would not crank back up at all unless I revved the engine. I had to rev the engine (at low rpms) for about 10-12 seconds in order to keep it running.

I did notice that when cranking, some type of alarm goes off briefly (approx. 2 seconds). It is not the low oil pressure alarm that goes off when turning the key. It happens when turning the key to start the engine.

 

[alldodge]

Hello all,
I have a 2005 Sea Ray with a Mercruiser 5.0L MPI engine. Cold starts off the trailer perfectly every time. I shut the engine off after running for a little while, getting the engine up to operating temperature. I sit for a half hour up to 1.5 hours and try to crank up but it will not start. It turns over just fine but will not start unless I rev the engine up while cranking. Also, this happened last week after just running the boat at idle for 5 minutes. I don't believe it ever reached operating temperature. I changed the engine mounted fuel/water separating filter and saw no signs of water. Checked the fuel pressure and it was at 40-43 psi.

Now, yesterday, the boat cranked just fine off the trailer but then shut off when trying to put it in forward. This has not happened before. It would not crank back up at all unless I revved the engine. I had to rev the engine (at low rpms) for about 10-12 seconds in order to keep it running.

I did notice that when cranking, some type of alarm goes off briefly (approx. 2 seconds). It is not the low oil pressure alarm that goes off when turning the key. It happens when turning the key to start the engine.

Do you have an Alpha or Bravo drive?

Could use a bit more explanation on what kind of alarm your hearing. Is it a solid beep, 2 beeps, something different?

If you can give it a bit of throttle and she fires up, you need to remove and clean your Idle Air Control (IAC) valve, Check to see if a vacuum hose/line came off or is cracked. If you have a vacuum gauge, get the engine running and see what the reading is at idle.

 

[bengaltiger14]

Do you have an Alpha or Bravo drive?

Could use a bit more explanation on what kind of alarm your hearing. Is it a solid beep, 2 beeps, something different?

If you can give it a bit of throttle and she fires up, you need to remove and clean your Idle Air Control (IAC) valve, Check to see if a vacuum hose/line came off or is cracked. If you have a vacuum gauge, get the engine running and see what the reading is at idle.

Bravo 3 drive. The alarms is when cranking and its a solid beep. It is brief. Maybe 1.5-2 seconds long. I have a spare IAC valve that I am going to put on this afternoon to see what it does. I'll report back tonight.

 

[alldodge]

Bravo 3 drive. The alarms is when cranking and its a solid beep. It is brief. Maybe 1.5-2 seconds long. I have a spare IAC valve that I am going to put on this afternoon to see what it does. I'll report back tonight.

If you hear the solid beep when trying to start the engine, it could be the low oil pressure alarm. There is a delay in the oil alarm when you first try to start, but if you crack a bit, stop and try again, the delay goes off and the alarm sounds. If this is the case then no worries

 

[Fun Times]

Also it has been reported by many owners that the IAC muffler sometime found inside your throttle body...If it's real dirty it will affect the starting and warning horn on these engine models. We'd need your engine serial number to see what IAC design you have though. And yes it could be the IAC as well as the IAC muffler.

Low battery voltage during engine cranking would sound the warning horn too along with a big list of other possibilities but the ones mentioned are more common.

 

[bengaltiger14]

If you hear the solid beep when trying to start the engine, it could be the low oil pressure alarm. There is a delay in the oil alarm when you first try to start, but if you crack a bit, stop and try again, the delay goes off and the alarm sounds. If this is the case then no worries

I've always heard the low oil pressure alarm when turning the key from OFF to RUN (or whatever the first position clockwise is). I've never gotten an alarm when going from RUN to START until recently. I did swap out the IAC valve last night but that did not solve the problem. I don't have my engine serial number right off hand but can get it later.

 

[bengaltiger14]

Replaced inline fuel filter last night. Have to rev the engine to start when cold now. The alarm from RUN to START is now gone. After starting the engine, If I return the throttle back to neutral immediately or within a few seconds after the engine starts it will shut off. I have to keep the rpms up for 15-20 seconds before returning to neutral position. It does idle a little rough for the first few minutes after getting started. Once running and engine warms up, it runs great like normal and idles like normal. Could this be a fuel injection problem?

 

[alldodge]

Replaced inline fuel filter last night. Have to rev the engine to start when cold now. The alarm from RUN to START is now gone. After starting the engine, If I return the throttle back to neutral immediately or within a few seconds after the engine starts it will shut off. I have to keep the rpms up for 15-20 seconds before returning to neutral position. It does idle a little rough for the first few minutes after getting started. Once running and engine warms up, it runs great like normal and idles like normal. Could this be a fuel injection problem?

Could sue use that engine serial number.

The symptoms you have in most cases is the IAC, but could be a fuel pressure problem. Only thing that keeps me from thinking fuel pressure is you have not mentioned having an issue at high rpm. Look for the vacuum line going from the intake to the fuel pressure regulator to see if it is loose, cracked or disconnected

 

[bengaltiger14]

I believe the serial number begins with 0W5....... I will write it down today.

I checked fuel pressure at the fuel rail and it reads 43 psi. The boat runs perfectly at high rpm also. I have doing some research today and it appears that it could be the IAC muffler? I am going to remove it and see what happens. Also, I just installed a brand new IAC valve installed.

 

[Fun Times]

While you're removing the IAC muffler, Check and clean the inside of throttle body, both sides of the throttle plate and flame arrestor as those being dirty would cause running problems such as your description.

 

[bengaltiger14]

I figured out the problem. It was the IAC muffler. I took it out, cleaned it and now all problems solved.

 

[alldodge]

I figured out the problem. It was the IAC muffler. I took it out, cleaned it and now all problems solved.

Sounds good, looks like Fun Times got it in post 5