tgorbett

Hi guys,

Hoping someone who has been down this road before has some advice.

I had an idle issue on the motor that I believe recently resolved by changing the TPS and cleaning the IAC motor.

While diagnosing the idle issue, I borrowed a scanner and codes 42, 43 and 21 are active. Codes were reset but came back immediately. Hopefully 21 has been resolved by changing the TPS but I have not confirmed this yet as I changed it a few days later after borrowing the scanner. I have since purchased a scanner and will continue troubleshooting this weekend.

The motor runs good but seems to lack punch out of the hole. It will pull max RPM under load (5500 rpm) It seems to rev up quickly under load which doesn't feel quite right but that could be in my head. It is a fresh rebuild (upper and lower) by a respectable builder with about 20 hours on it. Mild modifications (cam and heads) Compression and fuel pressure look good.

My question is: With codes 42 (Spark Control) and 43 (Knock Control) active, is my ignition advance being controlled by the IC module as opposed to the ECM? How would I verify this? Can I view total advance with the scanner while under way? Total Advance should be 35* according to my build sheet. Base timing has been confirmed with a timing light at 8*

Will code 43 "cause" code 42? Any advice on how to resolve the two codes would be appreciated. I have the manual and flow charts on how to troubleshoot the codes and plan on going through them soon.

Thanks.

tgorbett

Still looking for advice from the pros

tgorbett

ttt

Here you go BUP.

BUP

iTrader: (9)

Oh I see and I see. Anyways I have questions

5500 rpms ?? Not stock mercruiser app ?

Stock ECM ?? And NOT recal ??

Ignition set UP ?? what do you have - stock or what ??

What TPS did you install ? Where did you buy it ?

Do you have a print out of your first scan ?

And what are the fault codes and scan parameters after working on things 2nd scan ??

What is your fuel pressure readings thru out all rpms ??

Can you give me your engine serial number as I can run it

Super busy might not get back to this possible Sunday

tgorbett

Different cam, springs, valves, etc...
Stock ECM MEFI-1. Tyler Crocket Dyno tune on ECM. I believe he flashed it after upgrades to motor.
Stock Merc. Ignition
TPS from NAPA---appeared to be the same and is working fine.
Have not had a chance to get back to the boat as have been out of town.
Fuel pressure pretty solid at 38-40 psi
serial number is OF764154

My main question: How do I confirm whether my ignition advance curve is being handled by the ECM or the Ignition Module?

Thanks BUP and no rush.

articfriends

iTrader: (1)

The timing is controlled mainly by map sensor and rpms so to verify its using timing tables in ecu IF you held it at 3600 w set back timing light and unplugged map sensor timing would go from the 40/50 map table at 40 or so degrees of timing to about 28 or 30, motor would spit out a black cloud of fuel but it would tell you if timings being controlled by timing table in tune!

BUP

iTrader: (9)

Address the codes here for jist. Man I am bet up this week.

21 TPS High (open) or TPS low (short)
42 IC or Bypass circuit = circuit open or shorted to ground
43 knock circuit failure or continuous knock detected

BUP

iTrader: (9)

hopefully this is understandable as how to write all of this.

So you have stock Ignition

ECM / EST operation there is various modes of operation. skipping to engine running mode also reffered to ECM control mode.

The rpm of the engine reaches a value of 300 rpms the ECM see this as the engine is running so the ECM applies 5 volts on the bypass line of the EST MODULE. At that point the rely is energized and causes the points from the pick up coil. Also the grounding points for the IC line to open. ( IC = Ingition Control). At that time it will connect the IC line to the base of the power transistor and by passes the ignition module timing control. The EST system is then controlled by the IC signal from the ECM and the time at which spark occurs can be determine by a variable time circuit in the ECM. That is called ECM control mode.

IC circuit (source of REF HI SIGNAL ) circuit 430 purple and white wire is where the distributor REF HI (rpm) signal is sent to the ECM.

When the system is running on the ign module or even for the cranking mode, there is no voltage on the by pass 424 circuit and the ign module grounds IC circuit 423. The ECM should detect low voltage on circuit 423 IC; if the ECM sees higher voltage than it should, it will set code 42.

When the rpm for IC is reached around that 300 rpm and circuit 424 by pass voltage applied - circuit 423 IC should no longer be grounded in the ign module and that voltage should be varying. If circuit 424 is open or grounded, the ignition module will not switch to the IC mode, Circuit 423 IC voltage will be too low and code 42 will be set. If cicuit 423 IC stays grounded, the IC module will switch to IC mode but because the line is grounded there will not be an IC singnal and again code 42 will be set.

The TPS provides a voltage signal that changes when the throttle blades open and close. Signal voltage should vary from around half a volt at idle to about 4.5 volts at WOT. The TP signal is very important as its inputs are widely used by the ECM to produce the correct oputs for fueling along with most of the ECM controlled outputs.

BUP

iTrader: (9)

FWIW and last bit of reading material. Read it AND READ ALL OF IT.

Merc service bulletin. I knew about this SB way back then and found it.

http://www.boatfix.com/merc/bullet/94/94_12.PDF

tgorbett

Smitty,

Not sure I understand your method for this but this is due to my inexperience with ignition timing. You mention 40 degrees of timing and I guess that's what is throwing me. I have never used a set back light. If you care to do so and have the time maybe you could enlighten me. Thanks.
How is Tyler doing?