I think I need new injectors, how to tell for sure

[Charlie D.]

Checked my plugs today and 5 out of 8 were fouled, ( fluffy black ) on my '02 350 Mag MPI S/N 0M320855 with a Bravo III. I've noticed that she's been hard to start lately, and leaving black soot on the transom after a day on the water. Put on fuel pressure gauge to check pressure, with engine running or not the pressure is up to spec. but I noticed the pressure drops from 43 psi. to about 9 psi. rather quickly when the engine is shut off. When I say rather quickly I mean it takes less than a minute for the 9 psi. reading. Is this pressure drop in this amount of time normal? By the way I have checked the plug wires, coil, and have new plugs, and no faults on the scanner, does it sound like I'm on the right path? If this points to the injectors can I use Delphi injectors from my local GM dealer? Does anyone know the part numbers? Thanks.

 

[Don S]

Re: I think I need new injectors, how to tell for sure

I seriously doubt you have to replace the injectors. Have you followed the troubleshooting insturctions for your engine using the OEM manual? Have you tested the injectors? ............ Have you priced injectors????? 200 bucks each from Merc, you need 8.
There are too many very expensive possibilities to go replacing parts and hoping you find the problem.

 

[Robj]

Re: I think I need new injectors, how to tell for sure

While I am not an expert on fuel injectors, I would suggest having them cleaned first. I would think that a Merc shop would be able to do this by running the engine on a fuel/injector cleaner mix, same idea as with cars. You may also try one of those additives in your fuel.

Have a great day,

Rob.

 

[Windykid]

Re: I think I need new injectors, how to tell for sure

May also want to check and troubleshoot fuel pressure regulator.

 

[Windykid]

Re: I think I need new injectors, how to tell for sure

Also may want to borrow some noid lights and test injector pulse.

 

[SuperNova]

Re: I think I need new injectors, how to tell for sure

If you suspect leaky injectors, the easiest way to check them is to unbolt the fuel rail from the intake and pull it and the injectors up. Cycle the key so the fuel pump runs and pressurizes the fuel rail, then look and see if any injectors are leaking. If not then look elsewhere for your problem. (coolant temp sensor). And Don is right, a logical approach to fault-tracing beats out the "replace parts until you fix it" any day, so I would start by getting the appropriate service manual and follow the diagnostic tree they provide.
--
Stan

 

[Tail_Gunner]

Re: I think I need new injectors, how to tell for sure

I take it the ecm cannot read the exhasut gases as in a car, feeble fuel supply would readily detected.

 

[bruceb58]

Re: I think I need new injectors, how to tell for sure

There are no O2 sensors if that is what you mean.

 

[Charlie D.]

Re: I think I need new injectors, how to tell for sure

Super Nova thanks for your suggestion, got in from work tonight and pulled the fuel rail. After pressurizing, fuel was spraying everywhere, some light mist, and some big tear drops. Who would have thought that 5 out of 8 injectors would be bad. I wonder if they can be cleaned, no one local for me I'm afraid. I sort of thought that I would get more positive than negative replys. Don S. your serious doubt was in doubt, bad injectors. Perhaps I didn't word my post correctly or I should have wrote a couple of pages on the steps that brought me to the injector decision. I just figured a MPI engine that's flooding AFTER shut down was self explanatory and I was looking in the wrong place for some assurance of my conclusion. I have all of the OEM Manuals for my unit and I find Mercury shop manuals leaving alot to be desired in many places concerning troubleshooting. My old Clymer has better literature and details for half the price, it's just what you get used to I guess. For technique, tools, and spec's I do turn to the OEM manuals.
Had to vent on all the half a** replies I recieved, except for you Super Nova, you DA Man. I think alot of these guys just want to add to their post count.

 

[SuperNova]

Re: I think I need new injectors, how to tell for sure

Better watch it, or you'll give me a big head. Thanks for telling us what you found the problem to be, it helps everyone.
--
Stan

 

[Robj]

Re: I think I need new injectors, how to tell for sure

Again not a fuel injection expert, but would cleaning them help? Could be they are gummed up and that is why they are leaking. You don't have much to lose and I think it would be worth a try.

Have a great day,

Rob.

 

[Silvertip]

Re: I think I need new injectors, how to tell for sure

Start the engine and let it idle for short time (just a minute or two). Stop the engine. Pull the line off the pressure regulator and shake it. If fuel comes out you found the problem. A pinhole in the diaphram sucks fuel into the intake.

 

[SuperNova]

Re: I think I need new injectors, how to tell for sure

He already found the problem Silvertip--leaky injectors. I have never personally seen cleaning the injectors fix leaky ones, only clogged, poorly spraying ones were made better. But as I have said before, I have far from seen it all.
--
Stan

 

[Limited-Time]

Re: I think I need new injectors, how to tell for sure

Who would have thought that 5 out of 8 injectors would be bad.

You may have more than bad injectors. Any injector failure on an 02 engine seems premature, how many hours are on the engine? And to fail 5 out of eight?? You need to find what caused the injectors to fail.

 

[SuperNova]

Re: I think I need new injectors, how to tell for sure

An '02 engine is already 6 model years old, and anyone who works in a new car dealership can tell you how many injectors they've replace on engines younger than that. But you are right 5 out of eight is an awful lot. We usually get one or two on a single engine. But it may have been a bad lot, too.
A little somethin' somethin' put in the fuel tank would do it, too. Do you have any enemies??
--
Stan

 

[Charlie D.]

Re: I think I need new injectors, how to tell for sure

No enemies to date. I bought this boat second hand one year old 44 hrs on the clock with the raw water impellar destroyed, pump locked up destroyed. That tells me the guy I bought it from really knows his stuff. Fried the impellar even warped the pump housing, that's hot, trying to flush the engine after salt water use. I got the boat 25K under loan value so I couldn't pass it up. He probably never even picked up a bottle of gas treatment/injector cleaner. It's like brand new, has 244 hrs on it now and with these trashed injectors was getting 2.7 mpg cruising 33 mph. It's a Chaparral Signature 240 and we really have enjoyed it. It can only get better from here on out. Thanks guys for all the reply's. And yes I keep fuel presservative in the tank but will take a closer look at my brand and make sure it also cleans the injectors.

 

[Coors]

Re: I think I need new injectors, how to tell for sure

You are happy with all the half a***ed replies?

 

[Limited-Time]

Re: I think I need new injectors, how to tell for sure

An '02 engine is already 6 model years old, and anyone who works in a new car dealership can tell you how many injectors they've replace on engines younger than that. But you are right 5 out of eight is an awful lot. We usually get one or two on a single engine. But it may have been a bad lot, too.
A little somethin' somethin' put in the fuel tank would do it, too. Do you have any enemies??
--
Stan

My post was in regards to the now even more quick (less than 250 hours) demise of the original injectors. I'd hate to see Charlie trash another set in short order. Only to find the originals were trashed by sheet in the gas tank, or some thing equally as correctable.