Mercruiser 5.7 tbi injector issue?

[jrc1986cruisersholiday26]

5.7 merc tbi issue... Noticed that at lower rpm, one injector has very distinct uniform cone pattern- other seems to be pouring excessive fuel in a stream. Engine runs quite rich at low-mid rpm range and can be troublesome on warm starts. Also, after shutdown, some fuel drips for several minutes from what I believe is the overflow (small diameter brass? tube that directs into throttle body)- probably not supposed to happen? Just to clarify- I've done basic tune up (plugs, cap, rotor, wires, fuel filter) with no effect on this issue. I simply want to be sure that both injectors should operate identically to one another- both with distinct cone pattern of very fine fuel droplets and is the dripping after shutdown normal? Also, where should my course of action begin? What is most likely culprit, and thus, remedy? Maybe fuel pressure issue or leaking gasket, or similar? Injectors look to be EXPENSIVE! Any options if that is the likely culprit? Thank you all so much in advance!
-Jeff

 

[Bondo]

Re: Mercruiser 5.7 tbi injector issue?

5.7 merc tbi issue... Noticed that at lower rpm, one injector has very distinct uniform cone pattern- other seems to be pouring excessive fuel in a stream. Engine runs quite rich at low-mid rpm range and can be troublesome on warm starts. Also, after shutdown, some fuel drips for several minutes from what I believe is the overflow (small diameter brass? tube that directs into throttle body)- probably not supposed to happen? Just to clarify- I've done basic tune up (plugs, cap, rotor, wires, fuel filter) with no effect on this issue. I simply want to be sure that both injectors should operate identically to one another- both with distinct cone pattern of very fine fuel droplets and is the dripping after shutdown normal? Also, where should my course of action begin? What is most likely culprit, and thus, remedy? Maybe fuel pressure issue or leaking gasket, or similar? Injectors look to be EXPENSIVE! Any options if that is the likely culprit? Thank you all so much in advance!
-Jeff

Ayuh,.... Welcome Aboard,... Most likely Culprit is Dirty Fuel,...

The Cure is to supply good fresh clean fuel through fresh filters,...
'n of course, completely Clean the contaminated fuel/ induction system,...

I've seen a guy pull those injectors, completely disassemble, clean, reassemble 'em, 'n they worked Perfectly,...
But it ain't a typical Diy'er thing to do either,...

 

[Don S]

Re: Mercruiser 5.7 tbi injector issue?

Could be the injectors need sent out, cleaned and adjusted. number of places that do that. Google injector cleaning.
Have you checked your fuel filter lately to see what was in it? You should do that every time you replace your filter (yearly) so you know if a problem is developing or not.

 

[jrc1986cruisersholiday26]

Re: Mercruiser 5.7 tbi injector issue?

I recently did fuel filter change and I emptied contents of fuel filter into mason jar, thoroughly inspected- no signs of water or contamination (and ran my commercial lawn mower like a charm after). Fuel is fresh from marina as well. Don, you think best bet is send injectors out to be serviced as opposed to replace? I found oem replacement injectors with top plate and gaskets for $249 (+ $100 core). In any case, does it seem that injectors themselves are most likely the issue or a diaphragm, gasket, ECM, etc? Again, thank you very much gentlemen- it is greatly appreciated!
-Jeff

 

[Don S]

Re: Mercruiser 5.7 tbi injector issue?

Cleaning the injectors are $25-$50 each and they come back like new. Then all you need is gaskets. You can do the math after finding how much the gaskets alone are. Then decide which is best for you.

Usually when an injector is stuck open, they will dribble and leak fuel into the engine any time the fuel pump is running.

 

[jrc1986cruisersholiday26]

Re: Mercruiser 5.7 tbi injector issue?

Thanks Don! I'll definitely explore that option for sure! Any thoughts on the fuel dripping from small tube back into throttle body? Related or separate issue or normal? Does this for about 4 mins after shutdown at an approximate rate of one drop per 7-8 seconds... Thanks again!

 

[jrc1986cruisersholiday26]

Re: Mercruiser 5.7 tbi injector issue?

Thank you so much gentlemen. The boat is running perfectly again! Swapped out the bad injector with one I picked up from a local marine salvage, supply and service provider (my first experience with the place, great people- guy sold me injector that is like brand new for $60- he says they bought it brand new as part of a pair and turns out the injectors were not the problem so they pulled them back off and out on shelf). I only wish they still had the other one as well so I could have switched the pair and keep a good spare on board. I also changed the fuel pressure regulator as well since diaphram on mine looked a bit distorted, probably from ethanol. In any case, thank you very much and fair winds for now, fellahs!