ECM for 1999 Mercruiser MCM 5.0L EFI / 305 CID

[ToboFan]

Yes, that's it

You need manual 24,

To set timing motor must be placed in base timing mode. To do this find the DLC (Data Link Connector). It will have a plastic cover on it that is removed to gain access to the pins. Take a paper clip or small wire and jump pins A and B which places motor in base timing.

Awesome, thank you for your time!

 

[alldodge]

The MEFI can be scanned for codes using a paper clip and 12V resistor LED. In place of the LED can also use a digital multimeter with tone option.

Connect paper clip and led then turn key ON and count flashes

 

[ToboFan]

The MEFI can be scanned for codes using a paper clip and 12V resistor LED. In place of the LED can also use a digital multimeter with tone option.

Connect paper clip and led then turn key ON and count flashes

Thank you very much

 

[ToboFan]

As Scott mention fuel pressure may be out of spec, should be 30 psi at 1800 RPM

You have EST ignition, might have an issue with the modules (item 8 or 9). Have you tested the items?

https://www.mercruiserparts.com/bam/subassembly/31844/2704/70

Thank you, I have looked for these two parts, I don't have them in my configuration. I have two wires going from the distributor directly to the ECM (MEFI 3). I have attached a photo.

 

[ToboFan]

Thank you, I have looked for these two parts, I don't have them in my configuration. I have two wires going from the distributor directly to the ECM (MEFI 3). I have attached a photo.

I have a Thunderbolt V ignition system and EFI/ MPI MEFI 3 ECM model (or possibly MEFI 4) My distributor looks exactly like the attached drawing

 

[alldodge]

I have a Thunderbolt V ignition system and EFI/ MPI MEFI 3 ECM model (or possibly MEFI 4) My distributor looks exactly like the attached drawing
View attachment 378292

Go figure, I plug in your serial number and it takes me to an older model and does show it's not in your series. Websites, have to double check them also, and it's coming from Merc

OK TB5, TBI and MEFI 3

Need to get the motor timed, then see it that fixes the issue

 

[ToboFan]

I am wondering if this is really a EFI. I have found photos of the 5.0L MPI that look like my engine. Please see the photo below of my engine. Can anyone help me? Many thanks!

 

[ToboFan]

Go figure, I plug in your serial number and it takes me to an older model and does show it's not in your series. Websites, have to double check them also, and it's coming from Merc

OK TB5, TBI and MEFI 3

Need to get the motor timed, then see it that fixes the issue

Alldodge,
When you say TB5, TBI and MEFI 3, does that mean I do not have an EFI? I am asking because EFI was printed on the cover of my flame arrestor.
Thank you for your guidance!

 

[alldodge]

Alldodge,
When you say TB5, TBI and MEFI 3, does that mean I do not have an EFI? I am asking because EFI was printed on the cover of my flame arrestor.
Thank you for your guidance!

Yes you have a EFI (Electronic Fuel Injection) motor, it's TBI (Throttle Body Injection) with TB5 (Thunderbolt 5) ignition

 

[ToboFan]

Yes you have a EFI (Electronic Fuel Injection) motor, it's TBI (Throttle Body Injection) with TB5 (Thunderbolt 5) ignition

Thank you very much! For me, this is all new, and I really try to understand. Your help is appreciated! Have a good evening

 

[ToboFan]

Yes you have a EFI (Electronic Fuel Injection) motor, it's TBI (Throttle Body Injection) with TB5 (Thunderbolt 5) ignition

I am currently trying to time the engine. I looked up the manual and there are two alternatives for the timing procedure. One for TB5 and one for EFI. Which one should I follow? I tried the EFI procedures using a paper clip. I bought an 8 inch timing tape for Chevrolet 305 engines, and adjusted to 8 degrees BTDC, assuming the mark on the balancer wheel was the 0. Engine in idle now drops every 30 seconds from 900 Rpm to 500 Rpm (almost turns off) but recovers and jumps back to 900. Any guidance from you guys? As always, I appreciated your help. Thank you!

 

[alldodge]

Does the rpm automatically increase to 1300 rpm when jumper is installed?

 

[ToboFan]

Does the rpm automatically increase to 1300 rpm when jumper is installed?

Almost, to about 1200 rpm

 

[alldodge]

ok
Your timing tape, when looking at the balancer, BTDC will be to the right of the center mrk and ATDC will be to the left

 

[alldodge]

Also are you using the correct tape for your size damper?

 

[ToboFan]

ok
Your timing tape, when looking at the balancer, BTDC will be to the right of the center mrk and ATDC will be to the left

Yes, correct!

 

[ToboFan]

Also are you using the correct tape for your size damper?

I don’t know what a damper is, but the “balancer wheel” on my motor is 8 inch in diameter.

 

[alldodge]

Don't see it yet to be a ECM issue, but maybe a timing issue.

Connect timing light and watch BTDC degrees and 8* and distributor is clamped down

Shut motor down and remove jumper
Restart motor and let idle

Watch timing and increase rpm. Does it advance timing increase or stay the same?

 

[ToboFan]

Don't see it yet to be a ECM issue, but maybe a timing issue.

Connect timing light and watch BTDC degrees and 8* and distributor is clamped down

Shut motor down and remove jumper
Restart motor and let idle

Watch timing and increase rpm. Does it advance timing increase or stay the same?

I’ll check. I am pretty sure it did remain at 8 degrees. In your opinion, is 900 rpm right for idle? Shifting in gear is pretty aggressive! And: should I follow the timing procedure of ECM or the TB5 procedure? I am lost…

 

[ToboFan]

I’ll check. I am pretty sure it did remain at 8 degrees. In your opinion, is 900 rpm right for idle? Shifting in gear is pretty aggressive! And: should I follow the timing procedure of ECM or the TB5 procedure? I am lost…

I also bought a winky dinky led tester. I am only getting faults for low temps, low pressure when engine is cold. The controller seems to work!