01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

[budnowicki]

HI, I have '01 5.7 merc in a 22 searay and have had some fuel problems( i Think) sometimes at cold start, starts and runs great (small stumble) after about 10- 15 min starts to pop and backfire thru TB- if i shut down, hard restart, no power, can coax it up on plane but really hard. SO, i looked at seperator / filter , replaced and dumped it out. NO water. took a long time to see spray out of TB injectors. pulled filter, saw was only 1/2 full of fuel??!!. I cycled key to prime system and finally I saw some spray from injectors and it started but same problem, no power. SOO, i figured fuel pump. BIG deal, nasty job, but..got it done and same thing, great cold, no power 10 min later. I changed the filter again, even though i saw no signs of contamination during pump change. ( on the screens). can injectors work intermittently if bad? could it be oil pressure? (seems to be ok) could it be a bad pickup? could I have 50 gallons of gas/ethonol/water sludge ?(startron no help to date) could I have some electronic problem? could my kill sw/ lanyard be controlled by my ex-wife? AHHHHHH! help! Oh, how about pressure regulator? its part of that nifty, fuel "cooler/ pump $400.00 gem" that isnt included in the rebuild kit. (accidentally on purpose?) ANY help would be appreciated. THANKS

 

[Don S]

Re: 01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

http://forums.iboats.com/showthread.php?t=167561

 

[APPALOOSA2]

Re: 01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

Sorry I don't do DARES.......

 

[budnowicki]

Re: 01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

thanks Don, I read this after doing research on this forum before asking. Its a great start but not a cure all, and it certainly doesn't apply to all fuel problems. I hope there is someone with a similar problem, who is just as frustrated with the troubleshooting process. It would help to know if there are any "other" filters that could have become clogged or if a TB injector can work intermittently as i see no other way to troubleshoot it other than replacing it.

 

[budnowicki]

Re: 01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

Could this be related to the throttle position switch?

 

[rodbolt]

Re: 01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

first lets run over what can create a backfire in the intake manifold.
1 way overadvanced ign timing. not likly as it doesnt do it all the time but very easy to check.
2 stuck open intake valve. there again as its mechanical not likly as your not describing a solid failure.
and still easy to test.
3 low fuel presure due to a restriction,defective pump or a bad pressure regulator in the TBI unit,not real hard to test.
4 restricted filters on the injector, not hard to check but will require a filter gasket kit.
now for the last one,defective riser/manifold/riser gasket allowing water intrusion into the exhaust, easy to find as it leaves water marks on the spark plugs.

these are the normal causes of backfire with a TBI setup.
as with any other running issue a careful plan of attack coupled with a bit of understanding how and why each part of the ign and fuel subsystems work can cut down on troubleshooting time and drastically reduce the amount of cash used by parts tossing.
some of the testing you can do yourself with a digital multi meter,some need an analog meter and others will simply require the scan tool.
you will also need a fuel pressure test guage and the correct adapters to insure the TBI has adequate fuel pressure.
you will need the scan tool to test the IAC reset function to insure the IAC is working.
a mechanically stuck IAC on the system can cause hard starting and everything from unstable idle to 1800RPM+ idle and the ecu wont see it on that model.

 

[newport dave]

Re: 01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

I dare you to buy some diagnostic equipment and a service manual.

 

[budnowicki]

Re: 01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

Thanks Newport Dave! A manual!!?? What a great idea! But then I wouldn't get to hear all your snappy witty comments when you haven't got anything else to offer while trolling through other peoples troubles! I've got a manual, dave, but unlike a 8' john boat with a 9.9 OB like you, manufacturers sometimes change things a bit. I appreciate the help from the other guys that understand what a "forum" is for. Go help someone else with your particular
Brand of sunshine on this great holiday weekend when you should be on the water.

 

[budnowicki]

Re: 01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

thanks rodbolt, I checked and there were no trouble codes, gonna check the injectors next, fuel pressure seems fine but I'm troubled by how long it takes for the fuel filter to fill up. Is that normal? Never noticed it before

 

[piratedude]

Re: 01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

Ill Take Your Dare- Put A Carb On It!!! Another F/i Bites The Dust!

 

[Uraijit]

Re: 01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

Not familiar with BOAT efi systems, so I don't know what system it's got on it. Throttle Position Sensor, Idle Air Control Valve, Manifold Absolute Pressure sensor, coolant temp sensor.

Check 'em all, according to the manual's specs. Fuel injectors usually work, or they don't, not likely that your issue is the injectors. You probably just have a bad sensor somewhere. I'd start with TPS.

 

[chiefalen]

Re: 01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

So you did pull the fuel pickup tube to check the screen, and checked the anti-siphon valve?

You did check the vent to see if it were clear and no nasty spiders or bees nest/ bird nest in there?

You did do a fuel pump pressure test?

You did clean the connections and grounds on the electrical system?

 

[sumdood]

Re: 01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

I have been troubleshooting my fuel system recently and installed a water separator filter. My filter fills up quickly when I start the engine, I would suspect the intake in the tank or the anti siphon valve

 

[pyland2006]

Re: 01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

HI, I have '01 5.7 merc in a 22 searay and have had some fuel problems( i Think) sometimes at cold start, starts and runs great (small stumble) after about 10- 15 min starts to pop and backfire thru TB- if i shut down, hard restart, no power, can coax it up on plane but really hard. SO, i looked at seperator / filter , replaced and dumped it out. NO water. took a long time to see spray out of TB injectors. pulled filter, saw was only 1/2 full of fuel??!!. I cycled key to prime system and finally I saw some spray from injectors and it started but same problem, no power. SOO, i figured fuel pump. BIG deal, nasty job, but..got it done and same thing, great cold, no power 10 min later. I changed the filter again, even though i saw no signs of contamination during pump change. ( on the screens). can injectors work intermittently if bad? could it be oil pressure? (seems to be ok) could it be a bad pickup? could I have 50 gallons of gas/ethonol/water sludge ?(startron no help to date) could I have some electronic problem? could my kill sw/ lanyard be controlled by my ex-wife? AHHHHHH! help! Oh, how about pressure regulator? its part of that nifty, fuel "cooler/ pump $400.00 gem" that isnt included in the rebuild kit. (accidentally on purpose?) ANY help would be appreciated. THANKS

hi
there is a module in the distributor that supplies a signal to the fuel system.
it can cause the symptoms that you describe.

 

[JustJason]

Re: 01 Mercruiser 5.7 EFI fuel prob (I DARE YOU TO SOLVE IT)

Welcome to Iboats plyand2006.

You'll notice that every post is dated in the upper left hand corner. You replied to a thread that is over a year old and one in which we never heard an outcome from the original poster. Instead of digging up old threads, try and share your knowledge with more current threads.