Alarm problem. 4.3l Mercruiser TKS Carb 2004

[qben8]

Alarm problem. 4.3l mercruiser TKS carb 2004

Hi,

​My first post so please bear with me. I have the following problem. I have just had her annual service done and subsequent start and engine test resulted in the alarm coming on randomly once reaching operating temp. Advancing the throttle to above 2000rpm sometimes stops the warning. Other times it remains on until I turn the ignition off. Re start engine straight away, no warning for a few minutes then comes on again. Sometimes it doesn't come on at all. Very random!
​Faultfinding. I have read the wiring diagram and see that the alarm is triggered by sensor on the thermostat (overheat condition), oil pressure (low oil pressure condition) and drive oil (low quantity/pressure condition). I have disconnected sensors one by one to eliminate source with no success. Even with all sensors removed the alarm still sounds.
Oil quantity fine. Oil pressure 40-50 psi.
Drive oil. Between the bands.
​Eng temp. Steady at 175 deg. Risers cool. Water flowing indicating impeller working. (it was just replaced during service).
So its got me stumped!
​Questions for the gurus.
​1. Could it be a faulty ignition switch? It looks like the switch is part of the circuit as horn sound during start up pre ignition (I assume due to low oil pressure)
​2. Could it be a faulty alarm? Seems unlikely as it looks to be in reasonable condition.
​3. Could it be my worst nightmare and there is some ground in the circuit causing the alarm to trigger? If so could some knowledgeable chap pls explain how this would cause the horn to sound in relation to on/off conditions in the sensors. That would help me with further fault finding.
4. Is there anything else it could be that is not associated with the above? The boat engine operates fine within all specifications but the high pitched horn is rather annoying and has caused a subsequent high pitched whining from my wife and kids. Copping it in both ears so not my idea of a fun day on the water.
​Thanks in advance for any advice given.
P.S. I have read nearly every associated thread on this matter but they don't address my exact issue.

Cheers,

 

[qben8]

Further fault finding with the ignition system reveals the following. Removing the purple wire from the back of the ignition switch stops the alarm but also stops the engine. I'm guessing this is normal. Removing the purple wire from the back of the alarm stops the alarm. I'm guessing this is normal as the purple wire is the power wire. Also after many runs, its now a constant problem with the alarm going off a few minutes after start, but ceases when I increase throttle to above 2000 rpm. This last part still has me suspicious as oil px increases from 40 to 50psi as rpm increases. I'm not sure at what psi the low pressure alarm triggers but 40 psi seems normal to me unless the gauge or oil px sender is also malfunctioning. (I think that this is unlikely). I also considered low water pressure sensor malfunction but I don't think this engine is fitted with one as its not a closed system. Basically I'm now out of ideas other than to start changing components. I'd prefer not to do trial and error with component changes just yet so any advice is greatly appreciated.

 

[qben8]

Hi,

​My first post so please bear with me. I have the following problem. I have just had her annual service done and subsequent start and engine test resulted in the alarm coming on randomly once reaching operating temp. Advancing the throttle to above 2000rpm sometimes stops the warning. Other times it remains on until I turn the ignition off. Re start engine straight away, no warning for a few minutes then comes on again. Sometimes it doesn't come on at all. Very random!
​Faultfinding. I have read the wiring diagram and see that the alarm is triggered by sensor on the thermostat (overheat condition), oil pressure (low oil pressure condition) and drive oil (low quantity/pressure condition). I have disconnected sensors one by one to eliminate source with no success. Even with all sensors removed the alarm still sounds.
Oil quantity fine. Oil pressure 40-50 psi.
Drive oil. Between the bands.
​Eng temp. Steady at 175 deg. Risers cool. Water flowing indicating impeller working. (it was just replaced during service).
So its got me stumped!
​Questions for the gurus.
​1. Could it be a faulty ignition switch? It looks like the switch is part of the circuit as horn sound during start up pre ignition (I assume due to low oil pressure)
​2. Could it be a faulty alarm? Seems unlikely as it looks to be in reasonable condition.
​3. Could it be my worst nightmare and there is some ground in the circuit causing the alarm to trigger? If so could some knowledgeable chap pls explain how this would cause the horn to sound in relation to on/off conditions in the sensors. That would help me with further fault finding.
4. Is there anything else it could be that is not associated with the above? The boat engine operates fine within all specifications but the high pitched horn is rather annoying and has caused a subsequent high pitched whining from my wife and kids. Copping it in both ears so not my idea of a fun day on the water.
​Thanks in advance for any advice given.
P.S. I have read nearly every associated thread on this matter but they don't address my exact issue.

Cheers,

 

[qben8]

Further fault finding with the ignition system reveals the following. Removing the purple wire from the back of the ignition switch stops the alarm but also stops the engine. I'm guessing this is normal. Removing the purple wire from the back of the alarm stops the alarm. I'm guessing this is normal as the purple wire is the power wire. Also after many runs, its now a constant problem with the alarm going off a few minutes after start, but ceases when I increase throttle to above 2000 rpm. This last part still has me suspicious as oil px increases from 40 to 50psi as rpm increases. I'm not sure at what psi the low pressure alarm triggers but 40 psi seems normal to me unless the gauge or oil px sender is also malfunctioning. (I think that this is unlikely). I also considered low water pressure sensor malfunction but I don't think this engine is fitted with one as its not a closed system. Basically I'm now out of ideas other than to start changing components. I'd prefer not to do trial and error with component changes just yet so any advice is greatly appreciated.

 

[ModernRifle]

I have a 2006 Trophy with the 4.3l carb, I have looked at the alarm circuit just for fun, never a problem tho.

While I don't have my wiring diagram in front of me, I remember a few things.
The most important (on my rig) is that the alarm sensor for oil (Oil Pressure Switch) is a separate unit from the Oil Pressure Sending Unit for the gauge on the dash.

I would have to look to see if the other sensors are separate units also, but I remember the built in Alarm system is basicly stand alone for the engine.

The point of this discussion is to highlight that, although you have oil pressure showing on the gauge, the alarm side (or oil pressure switch) may be bad.

Hope this allows you to continue you search....

Glenn

 

[qben8]

Thanks for that. Yes they are separate and self contained systems but disconnecting the oil px sensor doesn't stop the alarm. I assume this rules out this sensor, but I do say ASSUME! Do you know if the oil sensor switch is an on switch as a normal condition or an off switch?

 

[QBhoy]

Given your description...if this isn't an electrical gremlin, it does sound like a mechanical oil pressure related problem, especially given the info on when you rev the engine it goes away.
I'd start with verifying the genuine oil pressure and temps to make sure, then have a look at electrical earths
A low voltage may also cause this alarm...get a meter on the alternator and make sure she is charging around 14v.

 

[QBhoy]

Check the obvious....leaking at oil filter etc...

 

[QBhoy]

And oil pressure sender unit (situated at oil filter casing)

 

[qben8]

Thanks QBhoy. Checked oil px pressure sender. Seems ok, no leaks. When sender disconnected oil guage drops to zero as it should. When re connected oil px guage reads back to 40-50psi. This also seems normal. Oil filter was changed and oil was replaced during service only 5 days ago. Oil colour looks good. Oil quantity looks fine. No oil leaks anywhere. Haven't checked genuine oil px as I don't have the tools. Will now check voltage across alternator although on the guage it reads approx. 13V. Where would you start looking for electical shorts / grounding?

 

[qben8]

Ok. Checked alternator. Voltage fine. Re run of engine. Now alarm comes on 16 secs after start and remains on irrespective of RPM.

 

[alldodge]

It's always best to provide the engine serial number to verify what you have. In any case look at the shift pale and see if you have a gear shift switch. If its there the alarm will sound above 2000 rpm (motor thinks its in neutral). If its there disconnect it

 

[qben8]

Eng serial number is OW303577. Family is 4M9XM04.32VC. I'll have a look for the gear switch.

 

[qben8]

Ok. Check the gear shift plate assembly and it only has one switch so I'm assuming its the switch interrupter. Thanks for the idea though.

 

[Four Winns Fanatic]

Possibly check Mercruiser part 87-805605A1 audio warning alarm oil pressure sendor sensor switch located behind distributor .A single wire pushes on or attaches to threaded stud .

 

[qben8]

Checked that. Oil guage works correctly from the sender. Isolated oil px sensor and alarm still sounded.

 

[alldodge]

Well scratch that one.
Have another possibility, with the TKS carb the oil pressure switch is used to supply power to the TKS module and will no longer supply a ground to sound the alarm. The Tan/Lt Blue wire goes to the Lube Bottle, Temp switch and TB-V module. If there is a short grounding the wire or internally to the TBV module the alarm will sound

 

[Four Winns Fanatic]

On my 2007 5.0 l mercruiser tks I have oil sender to pressure gauge and low oil pressure switch on lower portion of block near oil filter .I also have a low oil audible alarm switch that has 1 wire going to it , it is screwed into block located on top of engine behind the distributor , I wonder if you have that too.It is OEM Mervruiser 87 805605A1 .

 

[qben8]

Thanks folks for all the info. I'll study up on that diagram AllDodge and see what I come up with. I'll also look for that low oil alarm switch FWF. Just out of interest I took the boat out today as I was pretty confident that it was an indication problem not an actual engine problem. Eng ran fine for 2 hrs straight at various speeds. (I disconnected the alarm but kept a weather eye on the gauges.) I also went through a fair bit of chop which jolted the boat around with the intention of maybe shifting the wires slightly if they were grounded. Sure enough at the end of the session I reconnected the alarm and now the alarm works as it is supposed to. So I'm definitely suspecting a ground somewhere. The big question is where? Thanks once again for all the replies. Great forum!

 

[qben8]

Sorry, one more question ALLDodge. What is the TBV module?