Intermittent No Start - 2002 5.7L MPI After Sitting Warm

[Skelley]

It's happened twice this season. Starts fine cold and has normal smooth performance. After sitting for 15-30 min, It'll try to start but won't stay running. Additional time allows it to start fine. It's at the repair shop now. Dlr says they are seeing 45 psi fuel pressure at idle and it should be 38-42. Also says there's is a Mercruiser tech bulletin for the fuel/cooler module. Something about paint being eaten away by ethanol that may have contaminated the fuel system and may require compltet injector replacement. Engine has 565 hrs. Fuel is fresh name brand 89 octane with proper mix of Starbrite Enzyme fuel treatment. Has had processor replaced 3 yrs ago and idle air control replaced last yr. other than that, it's been running great. Anybody got any experience here?

 

[alldodge]

If it was paint it wouldn't run fine and then start doing this after sitting for a time. Also the paint was dealing with the cool fuel boxes, which contained both the fuel pump and the filter in one box. Not knowing your serial number I cannot check.

If this happens after running for a wile, you stop and sit for a while and then get going later, it could very well be vapor lock. You crank the motor and it tries to start but will not, maybe cough a bit.

I don't see an issue with 45 psi, now if it was 55 or 60 then yes. Tell us more about what or how it started and any other info which may help

 

[Skelley]

Thank you AllDodge. Serial number is OM326560. Dlr says they found paint flakes in fuel rail and are calling Mercruiser tech service back today to report and ask further direction. The last time the intermittent no start occurred the engine would crank and sounded to me like it would run for a split second and then die. This repeated for 5-6 attempts. We let sit for about 30 min and tried again and it fired up the first attempt and ran fine. I agree it sounds more like vapor lock, but what would cause this all of a sudden other than possibly bad fuel? Most of all the fuel in the tank is fresh within the past 60 days from two different stations. Also, I'm aware my engine has a cold water check valve after the steering cooler and before the fuel module/cooler. I had some cooling issues and remember reading advice to add another check valve after the fuel module to reduce vapor lock. I've not done this. There isn't much space to do this either. I have the Std cooling system (easy drain).

 

[alldodge]

Your serial number does not have the fuel pump/filter box which had the issue with paint. So if (and I do mean IF) the dealer actually found paint then my next question would be where did it come from? You do not have anything which would even begin to introduce paint to the lines. Merc has had lots of problems with vapor lock and your motor was changed starting serial number 0M336102. This is where they installed a boost pump to help stop it.

Vapor lock is caused not by old or new fuel, its caused by heat soaking into the fuel lines which causes fuel to boil. So if you have made a nice run, stopped to swim or relax, then take off after 30 minutes to a few hours it may not start. If you use the blower to keep the engine cooler, this helps. The best fix is to route the return fuel line going back to the filter, and route it back to the tank.

 

[Skelley]

Thanks, AllDodge. My dealer came back and acknowledged that our boat doesn't technically have the components related to the paint issue as you noted. They did find some crap in the fuel rail, so the plan on Friday was to clean everything, bench flow/test all the injectors and put everything back together and retest idle fuel pressure. I don't have the results of that yet, but hope to tomorrow first thing. After further calls to Mercruiser tech service, they are onto the tech bulletins related to vapor lock and the recommended kits that are evidentially offered by Mercruiser. I believe this one is what they are going by: https://www.perfprotech.com/blog/articles/mercruiser-vapor-lock

Like you stated, the article discusses running the bilge blower to exhaust hot air in the engine compartment as well as letting the boat idle for 3-5 min after a good run before shutting off. The Mercruiser p/n of the fuel pump kit with anti-siphon valve and check valve is 862264A 7. Do you know of anyone using this along with the suggested practices and solving their no-start issues?

Can you restate how you're suggesting to re-route the fuel? The line to the fuel filter goes where now? Would this avoid the expensive kit?

 

[alldodge]

That's the booster pump check valve fix. Any a lot of cases it does work, so long as you still let it idle a bit to cool down after a run. The theory is to keep the pressure up so it takes more heat for the fuel to boil. The check valve is to keep the pressure in, once built up to remain.

The fix that other manufactures are using is to return the fuel line back to the tank. For yours its like this

 

[Skelley]

Perfect, now I understand. Thank you very much!