Knock sensors for 502 mag mpi
01-19-2015, 08:10 PM
#1
Registered
VIP MemberThread Starter
Knock sensors for 502 mag mpi
On 1999 502 mag mpi motors. These motors came used with knock sensors put on the blocks, but I looked in the actual mercruiser factory manual for that s/n motor and it says that external knock sensors are NOT used on this motor. It is controlled just buy the brain. Figured I could trust the manual but you never know. Any surefire knowledge of this. By the way there is a wire on the harness for the sensor but that means nothing as there are always extra wires for things. I have tapped on various places on the block with a hammer with no changes in timing.
01-19-2015, 08:50 PM
#3
Banned
iTrader: (9)
Manual 23 had 2 versions as you have the latest version of it as it was updated by merc in march of 1999. The older 454/502 service manual # 23 version was Sept 1997. There was no mentioned of this in the 1997 version hence a lot of updates were added in the 1999 your version service manual # 23 plus it should be a 2 manual set sections 1-4 and sections 5-9 so is this what you have ? Just want to be on the same page here.
next you are correct about the brain part but per Merc in the manual it should state not using knock sensors external hooked to a knock sensor module for MEFI 3 big blocks but before I go any further with this you need to post your engine serial serial # along with what ECM you have. MEFI 1 and 2 used the KNOCK sensor modules hooked to knock sensors.. Knock sensors used a dark blue wire connection here. Engine serial # will really tell the story for your app and what ECM was used. I can careless the year model of your hull that means nothing me to or anyone working on the engine professionally.
next you are correct about the brain part but per Merc in the manual it should state not using knock sensors external hooked to a knock sensor module for MEFI 3 big blocks but before I go any further with this you need to post your engine serial serial # along with what ECM you have. MEFI 1 and 2 used the KNOCK sensor modules hooked to knock sensors.. Knock sensors used a dark blue wire connection here. Engine serial # will really tell the story for your app and what ECM was used. I can careless the year model of your hull that means nothing me to or anyone working on the engine professionally.
Last edited by BUP; 01-20-2015 at 01:08 AM.
01-19-2015, 09:36 PM
#4
Registered
VIP MemberThread Starter
BUP - I have the book 1 of 2, sect 1-4. Don't have the other. what does it cover?
Engines: s/n OLO315551/565
ECM MEFI 3 square type, not the longer rectangular one.
I don't have the boat here at the moment to look at the wire color.
Can you recommend a shop that can do a top notch job on reflashing it for better fuel ratio and timing. This Sutphen runs a true 74 with two people and half gas with completely stock motors even before I just rebuilt one -
but the timing is 34 cruising but goes down to only 18 at mid range when hit throttle, then about 20 -22 at wot at 4700/4800 with no vac. Both motors identical and steady timing, just low timing at top end. Have checked all ignition and seems in good shape. Timing set properly at 8btdc with the shorting tool. THis low timing be a detonation OVER-precaution by mercruiser, but cant be making a lot of power at 19 degrees. I run nothing but premium. Seen too many detonate but probably from gas on motor not set up properly.
appreciate your time. nothing like experience.
Engines: s/n OLO315551/565
ECM MEFI 3 square type, not the longer rectangular one.
I don't have the boat here at the moment to look at the wire color.
Can you recommend a shop that can do a top notch job on reflashing it for better fuel ratio and timing. This Sutphen runs a true 74 with two people and half gas with completely stock motors even before I just rebuilt one -
but the timing is 34 cruising but goes down to only 18 at mid range when hit throttle, then about 20 -22 at wot at 4700/4800 with no vac. Both motors identical and steady timing, just low timing at top end. Have checked all ignition and seems in good shape. Timing set properly at 8btdc with the shorting tool. THis low timing be a detonation OVER-precaution by mercruiser, but cant be making a lot of power at 19 degrees. I run nothing but premium. Seen too many detonate but probably from gas on motor not set up properly.
appreciate your time. nothing like experience.
01-19-2015, 09:48 PM
#5
Registered
iTrader: (1)
8 and 22 = 30.
01-19-2015, 10:11 PM
#7
Registered
iTrader: (1)
BUP - I have the book 1 of 2, sect 1-4. Don't have the other. what does it cover?
Engines: s/n OLO315551/565
ECM MEFI 3 square type, not the longer rectangular one.
I don't have the boat here at the moment to look at the wire color.
Can you recommend a shop that can do a top notch job on reflashing it for better fuel ratio and timing. This Sutphen runs a true 74 with two people and half gas with completely stock motors even before I just rebuilt one -
but the timing is 34 cruising but goes down to only 18 at mid range when hit throttle, then about 20 -22 at wot at 4700/4800 with no vac. Both motors identical and steady timing, just low timing at top end. Have checked all ignition and seems in good shape. Timing set properly at 8btdc with the shorting tool. THis low timing be a detonation OVER-precaution by mercruiser, but cant be making a lot of power at 19 degrees. I run nothing but premium. Seen too many detonate but probably from gas on motor not set up properly.
appreciate your time. nothing like experience.
Engines: s/n OLO315551/565
ECM MEFI 3 square type, not the longer rectangular one.
I don't have the boat here at the moment to look at the wire color.
Can you recommend a shop that can do a top notch job on reflashing it for better fuel ratio and timing. This Sutphen runs a true 74 with two people and half gas with completely stock motors even before I just rebuilt one -
but the timing is 34 cruising but goes down to only 18 at mid range when hit throttle, then about 20 -22 at wot at 4700/4800 with no vac. Both motors identical and steady timing, just low timing at top end. Have checked all ignition and seems in good shape. Timing set properly at 8btdc with the shorting tool. THis low timing be a detonation OVER-precaution by mercruiser, but cant be making a lot of power at 19 degrees. I run nothing but premium. Seen too many detonate but probably from gas on motor not set up properly.
appreciate your time. nothing like experience.
01-19-2015, 11:21 PM
#8
Banned
iTrader: (9)
Hey I will look into your serial #'s when I get a chance tomorrow. Man I had a zillion questions and very long phone calls all freakin day so really mostly all boated out for the whole day. Recorrected post # 3, it was incomplete and not a very good post on my part so reread it. Anyways here is more and hopefully pin point some sort of problem with your engine(s)
In my best opinion I do not like reflashing the ECM's as here I am shipping it to you in mail / reflash it and send it back to me YOU ARE GOOD TO GO. Anyways I deal with one person and one person only who either does it on a dyno with that motor or he flys in and we go boating for the day with all of our diagnostic equipment and his retuning / reflashing skills.
Next - your manual in your hands then should say NUMBER 23 and at the bottom should say "BOOK 2 of 2" and below that should say "Sections 5 thru 9" is this correct ?
Next - book one for this set should say Book 1 of 2 and below that should say Sections 1 thru 4.
Sections 1 thru 4 in order
1. Important information -
2. Removal and Installation
3. Engine ----- IMO important to have if you are working on your app and have not torn into these many of times to go off your head
4. Electrical systems -------------- IMO can be important if you have work on this stuff only a very few times.
Next you bought the manual(s) how in the world are U missing the other half ? Just guessing here its missing
Next if you have a scan tool to hook and read MEFI 3 -whether its the DDT, Diacom or (whomever) OTC with Merc cartridges (MEFI). Scan the motor and see if CODE / FAULT CODE 43 or especially CODE 44 shows up or any other codes show up for a piece of mind and true diagnostics..
CODE 44 means NO KNOCK or CAN NOT DETECT KNOCK ACTIVITY - conditions this take place - after 513 TDC knock free events with RPMS greater than 3000 and MAP greater than 70 and filter noise less than 0.14 volts means any one of these or all -FAULTY KNOCK SENSOR or DISCONNECTED KNOCK SENSOR or OPEN or BROKEN CIRCUIT
CODE 43 means CONTINUOUS KNOCK - meaning not good for your engine. Conditions this takes place when you HAVE CONTINUOUS KNOCK RETARD FOR 30 SECONDS or MORE. means anyone of these, bad fuel - low octane fuel, INCORRECT TIMING, BAD or FAULTY IGNITION or FAULTY KNOCK SENSOR or KNOCK CURCUIT - Believe it or not I have seen very worn / lose / stretched timing chains set this as well.
OK post some jist of this for an FYI . will hit again tomorrow or after that. I tried to cap the words that are important.
Again FYI - knock sensor(s) used a dark blue wire connection. AND Lastly your knock sensor needs to be connected IMO is your problem retarding the timing. I went back over my post above as I think faster than I can type.
I recorrected it and read your 1st post thought your were stating knock sensor to no external knock module. My bad totally.. Its knock sensor to ECM is correct and should be connected..
If I recall correctly the big block L29 engines (MEFI) used 2 knock sensors, the rest of the big blocks use one knock sensors and MEFI 3 does not use a knock module 4 sure, MEFI 1 & 2 did use the knock module. Hope this clears all of this up. Sorry for my incomplete post above. It is corrected now. That's what I get trying to do to many things at once plus its hard to write these story books to make sense for everyone. I have a lot more info about this - later and will follow up.
In my best opinion I do not like reflashing the ECM's as here I am shipping it to you in mail / reflash it and send it back to me YOU ARE GOOD TO GO. Anyways I deal with one person and one person only who either does it on a dyno with that motor or he flys in and we go boating for the day with all of our diagnostic equipment and his retuning / reflashing skills.
Next - your manual in your hands then should say NUMBER 23 and at the bottom should say "BOOK 2 of 2" and below that should say "Sections 5 thru 9" is this correct ?
Next - book one for this set should say Book 1 of 2 and below that should say Sections 1 thru 4.
Sections 1 thru 4 in order
1. Important information -
2. Removal and Installation
3. Engine ----- IMO important to have if you are working on your app and have not torn into these many of times to go off your head
4. Electrical systems -------------- IMO can be important if you have work on this stuff only a very few times.
Next you bought the manual(s) how in the world are U missing the other half ? Just guessing here its missing
Next if you have a scan tool to hook and read MEFI 3 -whether its the DDT, Diacom or (whomever) OTC with Merc cartridges (MEFI). Scan the motor and see if CODE / FAULT CODE 43 or especially CODE 44 shows up or any other codes show up for a piece of mind and true diagnostics..
CODE 44 means NO KNOCK or CAN NOT DETECT KNOCK ACTIVITY - conditions this take place - after 513 TDC knock free events with RPMS greater than 3000 and MAP greater than 70 and filter noise less than 0.14 volts means any one of these or all -FAULTY KNOCK SENSOR or DISCONNECTED KNOCK SENSOR or OPEN or BROKEN CIRCUIT
CODE 43 means CONTINUOUS KNOCK - meaning not good for your engine. Conditions this takes place when you HAVE CONTINUOUS KNOCK RETARD FOR 30 SECONDS or MORE. means anyone of these, bad fuel - low octane fuel, INCORRECT TIMING, BAD or FAULTY IGNITION or FAULTY KNOCK SENSOR or KNOCK CURCUIT - Believe it or not I have seen very worn / lose / stretched timing chains set this as well.
OK post some jist of this for an FYI . will hit again tomorrow or after that. I tried to cap the words that are important.
Again FYI - knock sensor(s) used a dark blue wire connection. AND Lastly your knock sensor needs to be connected IMO is your problem retarding the timing. I went back over my post above as I think faster than I can type.
I recorrected it and read your 1st post thought your were stating knock sensor to no external knock module. My bad totally.. Its knock sensor to ECM is correct and should be connected..
If I recall correctly the big block L29 engines (MEFI) used 2 knock sensors, the rest of the big blocks use one knock sensors and MEFI 3 does not use a knock module 4 sure, MEFI 1 & 2 did use the knock module. Hope this clears all of this up. Sorry for my incomplete post above. It is corrected now. That's what I get trying to do to many things at once plus its hard to write these story books to make sense for everyone. I have a lot more info about this - later and will follow up.
Last edited by BUP; 01-20-2015 at 01:04 AM.
01-20-2015, 07:45 AM
#10
Registered
VIP MemberThread Starter
Merc Manual - I do have the book #1 you state. A friend gave it to me that's why I don’t have book two.
It has never shown any fault codes on either motor. The knock sensor on both motors were replaced with no changes or codes on either one. I always run fresh Premium gas.
Maybe Merc has it cut back to 20 degrees (actual total not just the advance) at low vac for detonation reasons for the general public.
It is the MEFI 3. I have seen that come up on the computer.
It does have a knock sensor wire although im not there to check color. I have always run with it connected to the sensors on both motors.
QUESTION IS - SHOULD THIS WIRE BE CONNECTED ON THE MEFI3 ???
The timing is identical on both motors. Over 30 at cruising, drops to 18 instantly when hit the throttle and then slowly climbs up a couple degrees to about 20 when hit 4800 which is WOT. With more timing and thus HP, it should reach 5000 im sure.
DO YOU KNOW WHAT THE TIMING CURVE IS FOR THIS MOTOR. THAT WOULD BE A TREMENDOUS HELP.
Who do you use for a tuner BUP?
It has never shown any fault codes on either motor. The knock sensor on both motors were replaced with no changes or codes on either one. I always run fresh Premium gas.
Maybe Merc has it cut back to 20 degrees (actual total not just the advance) at low vac for detonation reasons for the general public.
It is the MEFI 3. I have seen that come up on the computer.
It does have a knock sensor wire although im not there to check color. I have always run with it connected to the sensors on both motors.
QUESTION IS - SHOULD THIS WIRE BE CONNECTED ON THE MEFI3 ???
The timing is identical on both motors. Over 30 at cruising, drops to 18 instantly when hit the throttle and then slowly climbs up a couple degrees to about 20 when hit 4800 which is WOT. With more timing and thus HP, it should reach 5000 im sure.
DO YOU KNOW WHAT THE TIMING CURVE IS FOR THIS MOTOR. THAT WOULD BE A TREMENDOUS HELP.
Who do you use for a tuner BUP?
