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TOPIC: Setting Ignition Timing for a Mercruiser 5.0L MPI engine

Setting Ignition Timing for a Mercruiser 5.0L MPI engine 29 Aug 2017 03:27 #1

  • iceman11
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I apologize in advance for having to ask what should be a basic question. I've set timing in cars before they had computers, so that's my reference knowledge. (Connect timing light, Loosen the distributor, rotate based on markings down on the crankshaft flywheel etc)

I would like to check and adjust if necessary the timing for my 2006 Mercruiser 5.0L MPI engine. I have older Mercruiser service manuals and they seem to conflict.

Service manual #31 which includes the 5.0L MPI engine, circa Oct 2001, has no procedure listed for setting timing.

Service Manual #24, which also covers the 5.0L MPI/EFI engine but is older (circa 1999), has the procedure copied below.

So my first question is: is the older procedure correct for my engine? Or is there no need to adjust timing on newer engines? If the procedure is right, why do I need to connect a "Scan Tool" to the engine. Is this to disable the computer so that it doesn't try to compensate for rotations of the distributor? I had heard there might be a lead somewhere that has to be connected to ground to disable the computer, but this is not mentioned.

Thanks in advance for any insights!

Tom

EFI / MPI Models
1. Connect timing light to number 1 spark plug wire.
2. Start engine and run at 1300 rpm until it reaches normal operating temperature.
3. Stop engine and connect the scan tool or timing tool to the DLC connector on the EFI/ MPI wiring harness.
4. Start engine, allow rpm to stabilize.
NOTE: MEFI-1 models only, manually adjust remote control throttle lever to get 1200 engine rpm.
NOTE: MEFI-2 and MEFI-3 models only, ECM will automatically adjust engine rpm to approximately 1200 rpm when put in the service mode on a scan tool or when using the timing tool.
5. Check ignition timing. If incorrect, rotate the distributor until timing is correct. Torque clamping screw to 18 lb-ft (25 Nm).
6. Recheck ignition timing.
7. Disconnect scan tool or timing tool from DLC connector.
8. If required, return remote control throttle lever to idle position and shut off engine.
9. Restart engine, increase rpm to 1300 then return to idle position slowly. Ensure that engine returns to idle rpm. Readjust throttle cable, if required.
10. Shut engine off.

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2006 Maxum 2600SE with Merc 5.0L MPI/Bravo III

Setting Ignition Timing for a Mercruiser 5.0L MPI engine 29 Aug 2017 15:08 #2

  • Pcpete
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I'm having to go from some feeble memory as to wire color, however, on my 2001 4.3's (same engine less two cylinders) the process was to warm the engine, shut it down, ground the ignition, install the timing light, start the engine and set the timing. Shut it down, disconnect the timing light and ground, clean up and go for a ride. The ground, I think, is a purple wire you will probably find laying on the intake manifold just in front of the carburetor kinda near the starboard valve cover. It may have a black rubber plug in the round connector.
I stepped up and bought a timing light with a built in tach
www.amazon.com/gp/product/B002SSDUOA/ref...01_s00?ie=UTF8&psc=1
It was one of the better tool decisions because I could also set the rpm without climbing out of the engine bay to look at the tach then go back and forth. Course now I have diesels and MSD on my muscle car so it's collecting dust right now, but I'm sure I'm going to use it in the future.
As far as having to have the scanner, I'm not sure on that one and I have real issues with the games manufacturers play so that owners have to go to their special shops. Oddly enough, when the technology gets to the user sector, they figure out how to get more power and performance and, mostly, stay within the EPA guidelines. Rant on that over.

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Setting Ignition Timing for a Mercruiser 5.0L MPI engine 29 Aug 2017 16:18 #3

  • Nauti Mike
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See instructions for TB V timing. You must install a jumper to set the ECM for base timing in order to be able to set it. Under operation the ECM manages the timing advance.

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1997 Maxum 2400 SCR 5.7LX Bravo II

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Setting Ignition Timing for a Mercruiser 5.0L MPI engine 29 Aug 2017 17:15 #4

  • iceman11
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Yeah I saw that Mike, but I've got an EFI/MPI engine. That's the procedure after the Thunderbolt procedure. But again, the newer manual for serial numbers starting at OM300000 (mine is OW365...) has no procedure.

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2006 Maxum 2600SE with Merc 5.0L MPI/Bravo III

Setting Ignition Timing for a Mercruiser 5.0L MPI engine 29 Aug 2017 18:12 #5

  • Ruffryder
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post #2 #3 are for a TB V module carbed engine.
ON an EFI engine, you don't ground out a PUR/WHT.
Will need to put it in base timing by either using one of the SCAN tools,
Or By finding your data link connector and jumping two wires from the connector on most DElphi MEFIs.
You should have a ECM 555... DLC method may not work.

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Last Edit: by Ruffryder.

Setting Ignition Timing for a Mercruiser 5.0L MPI engine 29 Aug 2017 18:56 #6

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Ruffryder, yes I do have a PCM(ECM)-555. I do have a Diacomm scan system. There is a test menu, and for the MEFI engines there is an option to "Activate Base Timing Mode". There is no such option for the PCM-555.

Which leads me back to.... is it possible with this ECM no timing adjustment is necessary?

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2006 Maxum 2600SE with Merc 5.0L MPI/Bravo III

Setting Ignition Timing for a Mercruiser 5.0L MPI engine 29 Aug 2017 19:22 #7

  • Ruffryder
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YES, that is why...
Base timing is NOT adjustable on your engine ECM 555.
but it does need to be properly aligned for correct rotor phasing.

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Setting Ignition Timing for a Mercruiser 5.0L MPI engine 29 Aug 2017 21:01 #8

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OK thanks RuffRyder. I contacted Rinda, which makes the Diacom scanner, and they confirmed that spark timing cannot be adjusted on an ECM 555, and that it is set by Crank and Cam sensors. There is no base timing mode.

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2006 Maxum 2600SE with Merc 5.0L MPI/Bravo III

Setting Ignition Timing for a Mercruiser 5.0L MPI engine 31 Aug 2017 17:35 #9

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iceman11 wrote: OK thanks RuffRyder. I contacted Rinda, which makes the Diacom scanner, and they confirmed that spark timing cannot be adjusted on an ECM 555, and that it is set by Crank and Cam sensors. There is no base timing mode.


That is correct!

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