MAP sensor question?

[spankzilla]

Sporster I did take the boat out today after putting prop back on. The rpm speed issue is fixed but it was def rich at idle. After getting it back home on the hose I disconnected the map sensor vacuum line while running and it made no difference at all. I then put vaccum to the sensor via a hand vaccum pump and still no change. I also unhooked the air temp sensor and didn't make a chance either. I unhooked the port temp sensor and it immediately idle down real rough until I hooked it back up.

 

[Sportster-2001-951C-Stock]

Good work testing, man! I think it's possible based on no change MAP and air temp sensor it might not use these sensors at idle (just a guess). I know these motors do use the block temp for fueling though, a sensor out of calibration makes them rich and hard to restart hot (gotta open the throttle for some air on the restart).

I would measure the resistance in ohms of that port temp sensor and match it to the table that should be in the manual. (I guess you've done this already).

Let me think a bit more..... Still leaning towards nothing really wrong but also now I'm thinking about that temp sensor.

Not mistaking rich idling with too much oil? Some owners have complained about too much oil at idle but I wonder if it's not too rich from the temp sensor (ECU thinks engine is cold thus adds fuel).

I'll keep thinking about this, beginning to run out of ideas.....

 

[Waterluvr]

Gentleman, you guys are on the right track with your diagnosis the air temp sensor does levy an input to the ECU on the idle circuit but it's almost impossible to nail down without a little help from technology more than what a meter can do for you. These get expensive to the point of throwing a man's wallet into the lake buying parts after doing all you can to try and pinpoint the issues without some real diagnostic tools available to you.

Fingers crossed, the mad scientist think tank at CandooPro have been hard at prototyping and testing the Mercury/Mercruiser diagnostic option for their system and it's slated for release soon. By soon, I mean any day now soon their homeowner/DIY level diagnostic tool for Sea Doo's is well know and represents an incredible value to anyone turning their own wrench to save some $$$ and this will be a blessing for all the guy's struggling with these EFI's that have aged to the point where they need constant help every season.

Most industry professionals are pretty apprehensive to even try and help people fix Merc EFI's on these forums for the simple reason we don't want them wasting their hard earned money changing expensive parts without a positive outcome. I've had two of these come in already this year after the owner's spent a small fortune at the parts counter buying every input sensor on the powerhead and installing them with no change.

You hook into these and get rid of that hard stored code language in the ECU and they seem to clean up and run very well inside of 5-10 minutes of water testing. I grilled my Merc rep's over and over about that and never got a straight answer, but there is something in that code language that does not respond immediately to proper sensory input until the stored code trash get's written out of the ECU by the programmer and it get's a little run time in under a load.

The CDP tool is going to give Mercury EFI owner's a much needed ability to work on these at home and get it right the first time around and you can get it right here from [MENTION=2]hfgreg[/MENTION] or [MENTION=1]JoeZ[/MENTION] when it's released.

 

[DomsX20]

Hey Spank, Any luck on this? It is funny that you are posting on this because I find myself in the exact same situation you are in... My idle is rough... very rough... I have even had to increase the idle screw (opens the butterfly) to keep it running. I have followed almost the exact same troubleshooting steps you have with the same results. TPS / Port Head Temp / Compress Check.... Like you, I pulled my MAP sensor tube, put a vacuum on it with no change (Should lean it out). I also disconnected, and shorted the Air Temp with no change.

I have noticed that the idle will smooth out if I run the boat until it warms up. I suspect that is because the EFI will start to lean out the motor once the head temperature increases.

I am afraid it is the EFI but they are SO expensive. A new ECU is almost $1800. Right now I am considering an aftermarket PCU from Brucato (brucatosvs.com) but I would hate to make the investment if it is not the problem. I am really hoping to learn from your troubleshooting.

It would be great if someone with a working motor could do a little test and disconnect their air temp to see if it changes anything.

 

[spankzilla]

I'm gonna try to get it I. The water this weekend to see if the rich idle start was a fluke or a real problem. I'm gonna run the exhaust fan longer before I try to start it this time. Sounds to me yours is doing exactly what mine was doing when I unhooked the head sensor. You might try unhooking it while running and see if the idle gets rougher than it already is.

 

[Sportster-2001-951C-Stock]

Meanwhile I'll keep tossing out ideas:

Not sure if that one has the knock sensor as I was unable to locate a manual that goes back further than OG303046. Have you guys disabled knock detection as a test to see if that effects the low speed idle mixture? It's possible there could be false knock detection causing a rich offset and possibly retarded ignition as well. Note: If the knock circuit was not disabled when setting up ignition advance (I haven't checked the procedure) a malfunctioning knock circuit would change the initial ignition timing and if the circuit is malfunctioning then that would need to be rechecked.

Under normal conditions when knock is not occurring, the knock sensor circuit advances ignition by 6*..... If knock is detected it retards 8*, thus if disconnected there is no 6* advance from initial mechanical advance. So if you disconnect while running you should notice a 6* later ignition timing. Also, fuel mixture is increased when knock circuit detects knocking.

So start with the sensor itself, is it properly fastened to the block and/or was it damaged (possibly by over torquing at some point)? Then move on to eliminate the knock sense circuit as a potential issue (by disconnecting the wire as described).

"DETONATION CONTROL SYSTEM FUNCTION
1. Combustion noise (or vibration) excites the
piezoelectric circuit located inside the detonation
sensor, which transmits a voltage to the control
module.
2. When cylinder number two ignition primary fires,
it signals the controller to look at a one
millisecond window of sensor output, which it
retains as a reference level of combustion
“background noise.”
3. When “background noise” reaches a measurable
value, usually between 2500 and 3500 RPM (it is
dependent on load), the ignition timing is
advanced 6 degrees beyond what the
mechanical timing is set at. Timing advance is
accomplished by lowering the bias voltage.
4. The controller continues to monitor sensor output.
If the output exceeds a pre-determined
threshold level over the “background noise”
(which is indicative knock is occurring) ignition
timing is retarded by up to 8 degrees and fuel flow
is enriched by up to 15% until the sensor output
is reduced below the threshold level.
The detonation control system actually acts as an
ignition advance module, when knock occurs it takes
away the advance. Ignition timing will not advance if:
a. Knock sensor fails.
b. BLUE/WHITE wire becomes disconnected.
c. BLACK wire has poor ground connection.
d. PURPLE power wire becomes disconnected.
NOTE: Disconnected GRAY/WHITE wire will not
affect ignition timing and will not allow fuel
enrichment.

 

[Sportster-2001-951C-Stock]

The Temperature sensor resistance should correspond to the ambient temperature of the engine in the bilge. No need to remove sensor if possible to measure resistance, a reading that corresponds to ambient is enough to have confidence the sensor is functioning.

The Warning module is item #4 of the electrical drawing. If this is disconnected, does the red indicator on the help still illuminate? If no, then check the sensor signal inputs to the warning module.

 

[spankzilla]

Mine doesn't have the knock sensor . I'll check the wire colors of the warning module you posted and see if it matches mine thanks

 

[Sportster-2001-951C-Stock]

Mine doesn't have the knock sensor . I'll check the wire colors of the warning module you posted and see if it matches mine thanks

Sorry I was forced to cut off the bottom half of that drawing to make it large enough to see, so here's the bottom half. It looks to me the warning module accepts a few signals (water/oil) outputs green to switch box for limp? The signal from the warning module looks like it comes out on the tan/blue wire and populates the engine connector pin 3 is for the horn?

I don't see the LED light signal in this harness (still looking)?

So here's the remainder of that drawing, sorry it's so chopped up.

 

[Sportster-2001-951C-Stock]

I'm also wondering if you have the idle stabilizer, this might be retarding your ignition timing at idle and I think it's an unnecessary part anyway. Might try disconnecting it and see if that improves the idle.

 

[Sportster-2001-951C-Stock]

And check this guy out, he tunes Merc ECU's:

http://brucatosvs.com/acu.html

 

[Sportster-2001-951C-Stock]

Is your warm restart too rich, or would you prefer to have manual control over choke enrichment? Mercury EFI ECU's have an enrichment function for cold starts. This function is enabled when the YEL/RED wire from the ECU harness "sees" +12v. On most EFI motors, the factory connects this wire to the starter solenoid where the corresponding RED/YEL wire from the keyswitch also connects. This causes the ECU to feed the injectors an extra-rich mix while the engine is cranking.

Releasing the key returns the ECU to normal mode. Sometimes a cold motor will stall at this point. Turn the key and it starts again. Repeat till warm. Annoying! Later on, re-starting a warm motor may emit quite a puff of smoke or foul a plug.

To move this automatic function up to the helm switch you can use the spare yel/blk wire in the engine harness, just disconnect the yel/red wire from the starter solenoid and connect it to the yel/blk wire that runs in the engine harness up to the helm for your manual choke switch.

Maybe your boat is already wired this way?

 

[spankzilla]

The idle stabilizer opens another can if worms. I have asked several times and no one can tell me where its located . Manual tells me to uhook it to set the timing but I can't find it. It may have been removed and my timing would be wrong if so. Only boxes my motor has is the two black boxes attached on top of each other on top of motor. My merc manual calls them the rev limiter and control module. I've been told the rev box is also the stabilizer but cant confirm this.

 

[spankzilla]

My warm restarts are fine. Its just the cold starts in the water that suck. Cold start out of water is fine. But I may not be running the fan long enough to clear the fumes do I'll try that first chance I get

 

[Sportster-2001-951C-Stock]

My warm restarts are fine. Its just the cold starts in the water that suck. Cold start out of water is fine. But I may not be running the fan long enough to clear the fumes do I'll try that first chance I get

Yeah, I was looking at that wiring diagram and suddenly remembered mercury wired the choke command signal to the ECU off of the starter solenoid so there's no enrichment unless the starter is cranking. Soon as the cranking stops so does enrichment. When we were rigging those we'd move the command signal to the ECU up to the helm switch so the operator could choke it as he pleased, b/c sometimes you need to give it a bit of choke if they began to lean sneeze when cold.

Distant memories....

On the idle stabilizer, I'm not sure if it should be disconnected or connected for setting the ignition timing but maybe you can trace through the wires to find if it's still there. Oh yeah, you're right now I remember something about the stabilizer has some effect on timing that needs to be accounted for during setup if the stabilizer is removed. Not sure anybody does this though, stabilizer actives at low speed? I also recall seeing a lot of corroded wires, as well. Hopefully not for you though.

 

[DomsX20]

I certainly do not want to hi-jack your thread but since we are facing similar problems, I will piggy back off of you...

Like you, my problems appear to be mostly related to Cold Starts. The engine is very rough and idles very low at cold temps. Once it warms up, the RPMs go up and everything smooths out. I suspect this is because the EFI is decreasing fuel output. I say decreasing the fuel because the engine seems to be getting too much fuel at cold temps. The only way to increase RPM is to advance the timing or open the butterfly by hand increasing air flow. The engine also smokes a LOT at cold temps.

Also, when I disconnected the Port Head Temp (or TPS), the engine lowers RPMs and further bogs down. This is because the EFI sees an open circuit and increases fuel flow (by 40%) according to the manual.

Basically, by manipulating the sensors, I have found this...

Disconnect TPS = More Fuel, RPMs drop
Disconnect Port Head Temp = More Fuel, RPMs Drop
Disconnect Air Temp = No change (should cause rich condition by increasing fuel by 10%)
Short Air Temp = No Change (Should cause lean condition by decreasing fuel by 10%)
Create Vacuum on MAP sensor = No Change (Should create a lean condition by decreasing fuel)

Because of the lack of change in engine performance when the MAP and Air temp are manipulated, I have made the decision to have my ECU checked out and sent it off to Simon Motorsports last night. I will let you know what there diagnosis is.

 

[spankzilla]

OK let me know your results thanks

 

[Sportster-2001-951C-Stock]

Because of the lack of change in engine performance when the MAP and Air temp are manipulated, I have made the decision to have my ECU checked out and sent it off to Simon Motorsports last night. I will let you know what there diagnosis is.

I wouldn't be terribly surprised to discover MAP and AIR sensor aren't used by the ECU under certain circumstances. IF for example, the head temp sensor is outside of normal operating range (ie:cold or overheating engine, or defective head temp sensor). Were the tests you performed executed precisely according to a defined diagnostic procedure?

 

[DomsX20]

OK let me know your results thanks

UPDATE: Simon Motorsports tested my ECU and verified the Air Temp and MAP sensor are working perfect. The only problems they identified were the #5 and #6 fuel injector drivers were loose. They went ahead and replaced all of the injector drivers and sent it back to me.

As a courtesy, they called and gave me some advise which I thought was very professional. The technician said that 240 EFI motor was the largest to use this specific ECU. That is why a person will see little change when disconnecting the Air Temp or putting a vacuum on the MAP. This is because the ECU is programmed to almost put out max fuel possible. The next size up motor uses a different ECU. He recommended to check the Stator and ignition controller.

When I got the ECU back, I double checked EVERYTHING. All of the sensors and resistance value through the STATOR. Everything checked good. I went ahead and replaced the TPS (even though it checked ok) with no change in performance. Then I replaced the ignition controller with no change again.

The end result was going back through ALL of the throttle linkage, idle set screw and timing. Once I "tweaked" everything, she is back to running perfect (out of the water) and sounding better than ever. We will check on the water but I feel pretty good.

 

[spankzilla]

Thanks for the update.