2004 Mercury 115 HP 4 Stroke -- Injector Voltage

[Qack]

Hi --

The question is, what voltage is used to energize the fuel injectors?

Background:

Condition: The engine has 287 hours on it and ran fine before I stored it last year. I put in gas stabilizer, ran the fuel down and oiled the cylinders. Now the motor runs rough and hesitates when accelerating. It does not have enough power to even get on plane.

After checking/replacing the following:

all new gas
battery is strong
checked fuel pressure at 1500 RPM- steady 41 psi
checked spark - strong on all four plugs and steady timing
checked and reseated connecters for the electronic Control Module - OK
replaced spark plugs
replaced external fuel filter
replaced internal fuel filter
verified primary and secondary resistance for both coils - all good
cleaned the HP fuel-pump filter and VST - not very dirty

Since I don't have a voltmeter with a direct voltage adapter, I can't do some of the electrical tests identified in the manual.

I'm going to clean the injectors. Since I have access to a heated ultrasonic tank, I'm going to do that myself. In order to best clean the injectors, I need to energize them while they are in the tank. that's why I need the voltage.

Thanks,

Qack

 

[impatico]

Re: 2004 Mercury 115 HP 4 Stroke -- Injector Voltage

12V should energize the injectors....

long write up on a testing rig, but he used 12V to energize them

http://www.ecs.fullerton.edu/~sowell/jag/fuelingsys/testrig/InjectorTestRig.pdf

 

[Faztbullet]

Re: 2004 Mercury 115 HP 4 Stroke -- Injector Voltage

I would send them to Brucato and have cleaned ,flowed and balanced. You can "clean" one and it still not correctly flow. Have you checked it to see if it has any troble codes? It like a OBD1 computer and you count the lamp flashes and it sounds like it may be in a safe mode. I got to ask ...did you check oil level and are you getting the beep alarm when turned on?

 

[Qack]

Re: 2004 Mercury 115 HP 4 Stroke -- Injector Voltage

I would send them to Brucato and have cleaned ,flowed and balanced. You can "clean" one and it still not correctly flow. Have you checked it to see if it has any troble codes? It like a OBD1 computer and you count the lamp flashes and it sounds like it may be in a safe mode. I got to ask ...did you check oil level and are you getting the beep alarm when turned on?

I did check for trouble codes ... none present. The oil level is where is should be ( I checked it several times!) and I do not get any warning beep when I start the engine. I'm sure this isn't safe mode ... it runs poorly all of the time and stumbles and sometimes stalls when it accelerates.

I have already built a test stand and plan on flow checking and verifying the spray pattern for the injectors.

 

[Qack]

Re: 2004 Mercury 115 HP 4 Stroke -- Injector Voltage

The boat now runs like a champ. It again will tach out at 6,000 RPM which is where it used to be and where the spec says it should be. The engine runs very smoothly.

Here is what I found out and what I did, in case you want to do it as well.


1. The voltage at which the injectors operate is five (5) volts. If you use twelve (12) volts you will likely burn them out. I found that out from a local Mercury service place.

3. I purchased a Sharpertek model SH80-2L, half gallon, heated ultrasonic cleaning tank. It's a great little unit, and American made.

4. I purchased Sharpertek's "Varnish and Shellac Cleaner" which is the product they recommended for fuel injectors.

5. I built an injector bench -- see picture attached. I shut the valve supplying the hose, then poured in some of the cleaning solution using the fill cap. With the fill cap tightened down, I then attached my air compressor, which was set at 40 PSI. Next I inserted one fuel injector into the high pressure 3/8" hose and clamped it in with a hose clamp.

I had jerry-rigged a 5 volt power supply with an intermittent switch, and attached that to the fuel injector. The little electrical spade connectors used for speaker wire worked just fine to attach to the injector.

After preheating the ultrasonic cleaner to 150 degrees, I immersed the injector into the bath without getting the electrical connectors wet. I held the injector in the tank for ten minutes, energizing the connector at frequent but short intervals to help out.

Notes:

(1) I had originally tested the bench to 60 psi while wearing very protective clothing so I knew it was OK.

(2) I used the bench to flow test the injectors before and after their cleaning. I couldn't do a quantitative test yet, as that would require a precision timer on the electrical circuit. However, during my qualitative test, all four injectors flowed low, and two were really low. When I tested them after the cleaning, they all flowed the same and they were all almost 40% higher than the high injector before cleaning.

(3) I purchased the professional cleaning solution as I had no way to experiment on cleaning solutions to "get it right". However, with virtually everything else, I have and will continue make my own.

(4) I have since tested my ultrasonic tank with various other items. My wife's engagement ring sparkles again (washing soda formula) and the heavily-rusted pair of pliers is no longer rusty, and after only 20 minutes in an oxalic acid formula.

(5) Everything for my injector bench came from Lowes except for the high pressure hose, and that came from Autozone.

(6) Although Mercury's Service Manual says you have to remove the intake manifold to get to the injectors, that is incorrect. All you have to do is to 1) remove the high pressure fuel line from the bottom of the fuel rail, and 2) remove the three bolts holding the fuel rail to the intake manifold. To get the injectors, pull off the electrical wire harness connector, gently pull/rotate the fuel rail away from the intake manifold, and pull/twist each injector.

I did remove the lower cover on the port side of the engine to give myself a little more clearance although it was not necessary, but it's only eight small bolts and pull.

 

[theoldwizard1]

Great post !

I'll be doing this during the off season as I have been dealing with intermittent misses on my infrequently used 2001 115 4 stroke EFI.

I also plan on suctioning the tank dry and "rinsing" with fresh fuel.

 

[theoldwizard1]

Thinking about my situation more ...

Does anyone think it is worth the effort to remove the vapor perpetrator (which holds the high pressure pump) and clean the inside, especially the sock filter ?

 

[Qack]

Thinking about my situation more ...

Does anyone think it is worth the effort to remove the vapor perpetrator (which holds the high pressure pump) and clean the inside, especially the sock filter ?

I think you have to do it just to be sure. When I did that, I found everything very clean but your results may vary.. That was two years ago, but I remember it was a PITA. I didn't have to do everything the shop manual said to do, however, to gain access.