Limp mode

[unbtabl]

I’ve got a 99 Larson 226 LXI with the tbi 305. Does this year model have “limp mode” built in? I’ve replaced all ignition components, both fuel pumps, and injectors. All Volvo penta branded. The motor will rev good on the ears, but will not get over 8-9 mph on the water. As I give it gas, if bogs down and backfires.

 

[alldodge]

The motor is a 5.0 what (Gsi, Gi, other)?

Did the motor ever run ok?

How is the compression?

What is timing set at, and does it advance as rpm increases?

What is the fuel pressure?

 

[unbtabl]

The motor is a 5.0 what (Gsi, Gi, other)?

Did the motor ever run ok?

How is the compression?

What is timing set at, and does it advance as rpm increases?

What is the fuel pressure?

It’s a gi pwtr
I bought the boat with this condition thinking I could get it figured out. It fires right up and idles great.

8 degrees
Compression is good at around 150 per cylinder
7 psi on low pump, 51 on high pump

 

[alldodge]

If your ECM is a MEFI-4 then there is a power reduction mode that does not let rpm's go above 2500. MEFI-3 does not

I'm seeing part numbers but I'm unable to determine if it's a MEFI 3 or 4
3858863
3801310
Replaced by
3860614
7749063
21242085
21242092
21242089
3832370
948211

 

[unbtabl]

If your ECM is a MEFI-4 then there is a power reduction mode that does not let rpm's go above 2500. MEFI-3 does not

I'm seeing part numbers but I'm unable to determine if it's a MEFI 3 or 4
3858863
3801310
Replaced by
3860614
7749063
21242085
21242092
21242089
3832370
948211

Not to sound like a dummy, but I’m a dummy when it comes to boat motors… where can I find the ecm on these?

 

[alldodge]

It's on top of the motor and looks like the middle one. Look on the back side for a part number

 

[unbtabl]

Not to sound like a dummy, but I’m a dummy when it comes to boat motors… where can I find the ecm on

 

[unbtabl]

I’ll take a look shortly. If it is a mefi 4, is there a way to trick it into seeing oil pressure?
Thank you for your help on that

 

[unbtabl]

I’ll take a look shortly. If it is a mefi 4, is there a way to trick it into seeing oil pressure?
Thank you for your help on that

I’m grasping at straws because I’ve replaced everything that normally causes this issue. My oil pressure gauge isn’t showing pressure… so, I’m thinking the sending unit is bad causing the ecm to go into limp mode

 

[alldodge]

I’ll take a look shortly. If it is a mefi 4, is there a way to trick it into seeing oil pressure?
Thank you for your help on that

Would need to check for codes. Can check by using a digital multimeter with a tone built in, or a 12V resistor LED

Put meter or LED across pins E and F of the DLC connector (on top motor near ECM with a cap on it). Put paper clip or other wire across A and B. Turn key ON (do not start) and count flashes. Flash, pause, flash, flash, etc

I’m grasping at straws because I’ve replaced everything that normally causes this issue. My oil pressure gauge isn’t showing pressure… so, I’m thinking the sending unit is bad causing the ecm to go into limp mode

The oil gauge uses a sender which has nothing to do with the ECM. There is another sender which does not go to the gauge but does go to ECM. Both senders are normally connected together with a Tee fitting, on the block next to where remote oil filter is connected

Have you verified oil pressure with a mechanical hand held gauge?

 

[unbtabl]

Would need to check for codes. Can check by using a digital multimeter with a tone built in, or a 12V resistor LED

Put meter or LED across pins E and F of the DLC connector (on top motor near ECM with a cap on it). Put paper clip or other wire across A and B. Turn key ON (do not start) and count flashes. Flash, pause, flash, flash, etc



View attachment 380166


The oil gauge uses a sender which has nothing to do with the ECM. There is another sender which does not go to the gauge but does go to ECM. Both senders are normally connected together with a Tee fitting, on the block next to where remote oil filter is connected

Have you verified oil pressure with a mechanical hand held gauge?

I haven’t yet. We got all of what’s listed replaced and took it out yesterday to find it doing the same thing. Thank you for all the info. I’ll start looking at those things today

 

[Horigan]

Note that the ECM receives inputs for limp mode from both temperature and oil SWITCHES, not sensors. The switches open at high coolant temp or low oil pressure. Find the switches and ground each connector to the block to determine which is one not closing at normal temps/pressures.

 

[unbtabl]

Would need to check for codes. Can check by using a digital multimeter with a tone built in, or a 12V resistor LED

Put meter or LED across pins E and F of the DLC connector (on top motor near ECM with a cap on it). Put paper clip or other wire across A and B. Turn key ON (do not start) and count flashes. Flash, pause, flash, flash, etc



View attachment 380166


The oil gauge uses a sender which has nothing to do with the ECM. There is another sender which does not go to the gauge but does go to ECM. Both senders are normally connected together with a Tee fitting, on the block next to where remote oil filter is connected

Have you verified oil pressure with a mechanical hand held gauge?

Only code it flashed was 12.

 

[alldodge]

Only code it flashed was 12.

ok no codes

Some codes don't set, some re only active when running, would need scanner for that

 

[unbtabl]

ok no codes

Some codes don't set, some re only active when running, would need scanner for that

Is there any way to check the map sensor? A new one is $200 plus. I don’t want to just throw parts at it

 

[alldodge]

MAP sensor will not put motor in limp mode

BTW when you set the timing did you jump pins A and B to put it in base timing mode?

 

[unbtabl]

MAP sensor will not put motor in limp mode

BTW when you set the timing did you jump pins A and B to put it in base timing mode?

I think it’s the mefi 3 based off of the info I can find. This is all the info that was on the tag. So, I pulled up the parts on Volvo penta site based off of the engine info… it said it came with 3, but is replaced with 4 when needing replacement. This includes an added harness to make the change. I paid a shop to check timing as I was unsure how to do so on these boats. I’m just grasping at any straw at this point. It’ll rev to any rpm on the ears… just not under a load on the water.

 

[alldodge]

MEFI 3 no power reduction
Need fuel pressure reading
Would also be good to know if the timing is advancing as rpm's increase, need timing light

 

[unbtabl]

MEFI 3 no power reduction
Need fuel pressure reading
Would also be good to know if the timing is advancing as rpm's increase, need timing light

Would I check the timing advancing under load or can it be done on ears? I’m 2 hours from a body of water big enough

 

[alldodge]

Ears are fine, point light at balancer and increase rpm. See how much it does