Mercruiser 5.0 EFI intermittent starting problem

[hcove7]

Hi,

I have a 2000 SeaRay with the Mercruiser 5.0 EFI Alpha One. I can start it when it's cold, but sometimes I can't restart it after letting it sit. If I try restarting right away or 2 hour later, it will probably start. But if I let it sit for about 30 minutes, it will not start.

When it doesn't start, it immedidately revs up and down for a few seconds, and then stops. I usually have to wait another half hour or longer to get it to restart. I have taken the boat to 2 different boat shops, and nobody can find any trouble codes. I do have spark

Another user (kbetts) on this site described the same problem as mine. He checked every connection, changed the rotor cap, fuel/water filter, fuel pump, etc and still had the problem. He was going to check the IAC next, but he didn't post the results.

How likely is it that the IAC is the culprit? If that doesn't end up being the problem, what do I do next?

 

[Silvertip]

Re: Mercruiser 5.0 EFI intermittent starting problem

Hey Mods, would you please move this to the I/O section?

 

[QC]

Re: Mercruiser 5.0 EFI intermittent starting problem

Hey Mods, would you please move this to the I/O section?

Good idea Silvertip.

And welcome aboard hcove!! We'll get you some more focused help over here. Good luck

 

[642mx]

Re: Mercruiser 5.0 EFI intermittent starting problem

Hi,

I have a 2000 SeaRay with the Mercruiser 5.0 EFI Alpha One. I can start it when it's cold, but sometimes I can't restart it after letting it sit. If I try restarting right away or 2 hour later, it will probably start. But if I let it sit for about 30 minutes, it will not start.

When it doesn't start, it immedidately revs up and down for a few seconds, and then stops. I usually have to wait another half hour or longer to get it to restart. I have taken the boat to 2 different boat shops, and nobody can find any trouble codes. I do have spark

Another user (kbetts) on this site described the same problem as mine. He checked every connection, changed the rotor cap, fuel/water filter, fuel pump, etc and still had the problem. He was going to check the IAC next, but he didn't post the results.

How likely is it that the IAC is the culprit? If that doesn't end up being the problem, what do I do next?

It almost sounds like vapor lock. Are you running the blower all the time? If not, try it. My boat will vapor lock the fuel rail if you run it hard, then stop, then try and start it within the next 1.5 hours. I also lift my hatch a little bit to help circulate some air when we pull up to the beach. Since I've been lifting the hatch and running the blower all the time, my problem went away.

 

[QC]

Re: Mercruiser 5.0 EFI intermittent starting problem

I think 642mx is on to something. I too have recently had a similar issue and also believe it is vapor lock. Mine's a 2001 6.2.

PM your email addy and I can send you the Merc Service letter that has me convinced . . .

 

[642mx]

Re: Mercruiser 5.0 EFI intermittent starting problem

I think 642mx is on to something. I too have recently had a similar issue and also believe it is vapor lock. Mine's a 2001 6.2.

PM your email addy and I can send you the Merc Service letter that has me convinced . . .

I've got the same service letter from Merc. Seems like a common issue thats been going on for a very long time.

My engine is a 2000 454 mpi.

 

[hcove7]

Re: Mercruiser 5.0 EFI intermittent starting problem

Thanks for all of the responses thus far. I run the blower for about 4 minutes before restarting. This is the same procedure that I've used for the last 10 years. Would something have changed? Maybe the hot weather?

I do have the service bulletin that addresses vapor lock. Not sure I understand it all, though.

 

[QC]

Re: Mercruiser 5.0 EFI intermittent starting problem

Mine happened for the first time a few weeks back, I think for me it was a combination of a weak water pump, very high ambient air and 10% ethanol.

 

[NHGuy]

Re: Mercruiser 5.0 EFI intermittent starting problem

HC, you want to run the blower all the time that you are just idling around to keep the engine compartment air as cool as possible. Then when you stop lift the cover to let it cool passively. Vapor lock is when your fuel turns from liquid to gas from the heat. I hope that is your problem because it's a no money fix.

 

[642mx]

Re: Mercruiser 5.0 EFI intermittent starting problem

Thanks for all of the responses thus far. I run the blower for about 4 minutes before restarting. This is the same procedure that I've used for the last 10 years. Would something have changed? Maybe the hot weather?

I run the blower a couple minutes before starting and restarting.... but I also run it anytime the engine is running. And then after a long run, I keep the blower on for 10-20 minutes after I shut the engine off. Blowers are designed to suck fumes from the engine compartment, but they also are very good at sucking the heat out too.

Fuel quality changes everytime you fill up.... some fuels will vapor lock quicker than others, but this extreme heat most of us are getting doesn't help the problem either.

 

[JohnnyH]

Re: Mercruiser 5.0 EFI intermittent starting problem

Hi, I had same problem.It appeares as VAPOR LOCK.I checked just about everything and talked to a marine mechanic and he told me that he had encountered the same problem several times.The gas outlet fitting at the gas tank pickup has a anti flow back check ball which will stick closed at times,which will cut off gas flow.After setting for a while the check ball will release and engine will run fine untill engine is cut off again and it will not stay running which will appear as vapor lock. this fitting is aluminium and check ball is steel and after closing and opening for a long period of time it will cause a seat in aluminium which makes it stay shut. Removed fitting and replaced it with a brass fitting. Runs fine now.Try this it will cost about $2. JohnnyH

 

[hcove7]

Re: Mercruiser 5.0 EFI intermittent starting problem

I will run the heck out of the blower this week-end when I have it out again. I'm located on the Potomac River about 50 miles south of D.C. at a place called Fairivew Beach, VA. I'll report back.

One mechanic pointed out that my exhaust baffle had come loose from the outdrive. I meant for him to fix it, but it is still loose. I don't know if the baffle was loose before or after my starting problems began.

When the outdrive is raised, it seems like water could leak back into the exhaust line. I don't recall if the outdrive was rasied or not when I couldn't start the engine. I'll take better notes. Could the loose baffle have anything to do with the reving up and down when I try to start the engine?

 

[hcove7]

Re: Mercruiser 5.0 EFI intermittent starting problem

I think I have resolved my starting problem. I wanted to follow up on this thread so that I might help someone else with this same problem.

After eliminating so many possibilities, I thought the only thing left was the pickup valve (anti syphon). My mechanic suggested that I hook up a portable 6.6 gallon contain of gas, which would bypass the boat gas tank, the boat gas, the pickup valve, fuel line, vent line, and gas cap.

Once I hooked up the portable tank, I never had any problems starting the boat. So I had isolated the problem quite a bit. I decided to go ahead and replace the pickup valve.

I was surprised to find out that the old pickup valve did not have a ball in it. The mechanic said it never did have a ball. That was (and still is) a mystery. Can anyone explain that? We went ahead and installed a new pickup valve with ball. After one test, the starting problem came back. I was concerned that performance might deterioate now that I had a ball in the pickup valve, but that was not a problem.

What's left? Could it be the gas cap? My boat has the Perko Self Venting Gas Cap. Unlike most other boats, the vent line outlet is "blocked" by the gas cap. The cap has 4 slits that serve as exits for the vapor. We cleared those out with compressed air. I have tested the boat hard, and I have not had the restarting problem.

In short, my self venting gas cap caused my boat to have an intermittent starting problem in which the engine would rev up and down and then cut off. I hope this helps somebody else.