Mercruiser won't start after warm-up

[Conoloway Dave]

Year 1999, Model MCM 5.0L EFI, 305 CID..I have been dealing with this problem for 3 years now and need help. This is an intermittent issue whereby after running the boat for a couple hours on water and turning off, she sometimes fails to start back up. I can hear the fuel pump priming, and after removing the flame arrestor, I can see the fuel injectors spraying gas into throttle body (not a strong spay), the engine fires for about a second and then stalls out. After sitting sometimes up to 2 hours, it starts up. Once it starts, I'm golden with no hesitations at idle, full throttle, etc...... It only happens after I turn it off. I have taken this boat in a couple times but the mechanics can't get it to fail to determine the problem (no codes as well). I have been told so it's the fuel pump, fuel cooler, distributor, coil, ECM, bad ground wire, etc... I can't afford to throw parts at this problem. Any ideas?????

 

[acuraguy81]

Re: Mercruiser won't start after warm-up

do u see fuel when its dieing or died after u try to start it?

 

[Conoloway Dave]

Re: Mercruiser won't start after warm-up

Once it dies, the fuel stops, however after firing for a second there is a small spray of fuel coming from both injectors but it doesn't look like a strong stream that comes out when it actually starts.

 

[acuraguy81]

Re: Mercruiser won't start after warm-up

maybe a fuel pump is it electric or manual. electric can get warm and loose pressure as a manual seems to go out fast but both can get warm and have an affect.

 

[Conoloway Dave]

Re: Mercruiser won't start after warm-up

It is electric, but VERY expensive as you probably know from a parts and labor standpoint. I was leaning towards a new fuel pump as well but wanted to be sure. Some have said that the pump would either work or not work.

 

[speedhik05]

Re: Mercruiser won't start after warm-up

I am having the same sort of issue with a 2000 5.0 mercruiser, the only difference is mine is carb instead of efi. a few people have told me that the fuel pump can have issues once it is warm. to be sure that it is fuel pump i would put a fuel pressue guage on the fuel line and note the pressue when its running and when it wont run. that is what i am going to try next to rule out things as cheaply as possible.

 

[solar7647]

Re: Mercruiser won't start after warm-up

It sounds like vapor lock to me. Once the engine has been running for a while and is hot, it also warms up the fuel line. While its running it dosnt cause any issue because the fuel is moveing through the line and dosnt heat up, but once the engine is stopped the fuel just sits in the line, and everything in there is still hot including the fuel line. This causes the gas to vapor in the line creating an air pocket. It is more commen issue on carbs with mech fuel pumps but not on heard of on an EFI.

I would try to insolate the line so that it dosnt get heated as much, or re rout it so its farther from the block and picks up less heat.

If that dosnt work then look for bad parts.

 

[Conoloway Dave]

Re: Mercruiser won't start after warm-up

What type/kind of insulation would I use and where would I buy it... I want to put a gauge somewhere on the gas line to sit there permanently until I have this problem again. Can anyone tell me the type guage to get that will fit and how to install? What is the expected pressure readings at start-up, and idle?

 

[Kschimm]

Hello: I am having the same problywith 5.0l efi, 2003. Runs good but when I stop to swim or got lunch, it won’t keep running after being started. We wait 10 minutes and it runs great. I tuned it up but still doing it. Did you ever find a solution to your problem?

 

[GA_Boater]

Hello: I am having the same problywith 5.0l efi, 2003. Runs good but when I stop to swim or got lunch, it won’t keep running after being started. We wait 10 minutes and it runs great. I tuned it up but still doing it. Did you ever find a solution to your problem?

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