Absolutely frustrated with this Mercruiser engine

Scott215 said:
Hopelite can you have somebody watch the fuel pressure gauge or the fuel pressure at wide open throttle just to see if it drops it's a shot in the dark but at this point I would take anything
Click to expand...

Did that already, pressure holds at 37 psi. I'm certain it's electrical but what. As far as I can tell everything is plugged in correctly and testing that its within spec if I follow the reference data in the SEALOC repair manual. It's also not throwing any fault codes.
 
While the MEFI1 does not itself have a "limp mode" there are fail safes designed into the system.
There are any number of ECM and component "failure modes" that may be true yet not "set a code".

I do not completely understand the reluctance to by the Rinda software. I would do the DIACOM PC based version it captures more information. If you have access to a laptop. You need to know the real time sensor data and modes of operation while it running.

You can also rent one from several companies search ebay about $50 plus shipping
https://www.ebay.com/itm/2757468129...uid=_dTdNC2dSCu&widget_ver=artemis&media=COPY

Here is a possible ECM-wiring-Distibutor problem that will not always set a code in the ECM.
Surprisingly it is all under the fuel injection section.

DISTRIBUTOR MODULE MODE (MEFI 1 ONLY)
The ignition system operates independent of the ECM. The distributor module module in
the distributor maintains a base ignition timing and is able to advance timing to a total of 27
degrees. This mode is in control when a Code 42 is detected while engine is running and
will have a noticeable effect on engine operation.

The code 42 may not set if any of a number of faults or wiring issues are present- Patrick

Results of Incorrect Operation
Open IC Line from the ECM to the Distributor Module - While the engine is cranking, the
ECM expects to see the IC signal pulled to virtually zero because it is grounded in the distributor
module. Since the IC line is open, it cannot be grounded by the module and the IC signal
will be able to rise and fall, or do what is called toggling. The ECM recognizes the toggling
as an abnormal condition, and will not apply bypass voltage to the distributor module when
the engine reaches run rpm.
Since bypass voltage is not applied to the relay, it remains open and the engine continues
to run on the pickup coil triggering in the ignition module timing mode.
If this condition occurs while the engine is running, the engine will stop, but it will restart and
run in the ignition module timing mode with reduced power.

Grounded IC Line - During cranking, the IC voltage is at virtually zero so the ECM does
not recognize a problem. When engine rpm reaches the value for the run condition, the ECM
applies bypass voltage to the distributor module. Bypass voltage on the module switches
the distributor power transistor to the IC line. Because the IC line is grounded, it will have
no voltage applied so it cannot operate the power transistor to enter the IC mode.
If the IC line becomes grounded while the engine is being operated, the engine will stop and
will be difficult to restart.
An open or ground in the IC or bypass will cause the engine to run on the distributor module
timing. This will cause reduced performance, poor fuel economy and erratic idle.
 
hughespat57 said:
While the MEFI1 does not itself have a "limp mode" there are fail safes designed into the system.
There are any number of ECM and component "failure modes" that may be true yet not "set a code".

I do not completely understand the reluctance to by the Rinda software. I would do the DIACOM PC based version it captures more information. If you have access to a laptop. You need to know the real time sensor data and modes of operation while it running.

You can also rent one from several companies search ebay about $50 plus shipping
https://www.ebay.com/itm/2757468129...uid=_dTdNC2dSCu&widget_ver=artemis&media=COPY

Here is a possible ECM-wiring-Distibutor problem that will not always set a code in the ECM.
Surprisingly it is all under the fuel injection section.

DISTRIBUTOR MODULE MODE (MEFI 1 ONLY)
The ignition system operates independent of the ECM. The distributor module module in
the distributor maintains a base ignition timing and is able to advance timing to a total of 27
degrees. This mode is in control when a Code 42 is detected while engine is running and
will have a noticeable effect on engine operation.

The code 42 may not set if any of a number of faults or wiring issues are present- Patrick

Results of Incorrect Operation
Open IC Line from the ECM to the Distributor Module - While the engine is cranking, the
ECM expects to see the IC signal pulled to virtually zero because it is grounded in the distributor
module. Since the IC line is open, it cannot be grounded by the module and the IC signal
will be able to rise and fall, or do what is called toggling. The ECM recognizes the toggling
as an abnormal condition, and will not apply bypass voltage to the distributor module when
the engine reaches run rpm.
Since bypass voltage is not applied to the relay, it remains open and the engine continues
to run on the pickup coil triggering in the ignition module timing mode.
If this condition occurs while the engine is running, the engine will stop, but it will restart and
run in the ignition module timing mode with reduced power.

Grounded IC Line - During cranking, the IC voltage is at virtually zero so the ECM does
not recognize a problem. When engine rpm reaches the value for the run condition, the ECM
applies bypass voltage to the distributor module. Bypass voltage on the module switches
the distributor power transistor to the IC line. Because the IC line is grounded, it will have
no voltage applied so it cannot operate the power transistor to enter the IC mode.
If the IC line becomes grounded while the engine is being operated, the engine will stop and
will be difficult to restart.
An open or ground in the IC or bypass will cause the engine to run on the distributor module
timing. This will cause reduced performance, poor fuel economy and erratic idle.
Click to expand...
Mister Wizard has spoken! That's another one for my scrap book. Thanks for posting that!
 
hughespat57 said:
While the MEFI1 does not itself have a "limp mode" there are fail safes designed into the system.
There are any number of ECM and component "failure modes" that may be true yet not "set a code".

I do not completely understand the reluctance to by the Rinda software. I would do the DIACOM PC based version it captures more information. If you have access to a laptop. You need to know the real time sensor data and modes of operation while it running.

You can also rent one from several companies search ebay about $50 plus shipping
https://www.ebay.com/itm/2757468129...uid=_dTdNC2dSCu&widget_ver=artemis&media=COPY

Here is a possible ECM-wiring-Distibutor problem that will not always set a code in the ECM.
Surprisingly it is all under the fuel injection section.

DISTRIBUTOR MODULE MODE (MEFI 1 ONLY)
The ignition system operates independent of the ECM. The distributor module module in
the distributor maintains a base ignition timing and is able to advance timing to a total of 27
degrees. This mode is in control when a Code 42 is detected while engine is running and
will have a noticeable effect on engine operation.

The code 42 may not set if any of a number of faults or wiring issues are present- Patrick

Results of Incorrect Operation
Open IC Line from the ECM to the Distributor Module - While the engine is cranking, the
ECM expects to see the IC signal pulled to virtually zero because it is grounded in the distributor
module. Since the IC line is open, it cannot be grounded by the module and the IC signal
will be able to rise and fall, or do what is called toggling. The ECM recognizes the toggling
as an abnormal condition, and will not apply bypass voltage to the distributor module when
the engine reaches run rpm.
Since bypass voltage is not applied to the relay, it remains open and the engine continues
to run on the pickup coil triggering in the ignition module timing mode.
If this condition occurs while the engine is running, the engine will stop, but it will restart and
run in the ignition module timing mode with reduced power.

Grounded IC Line - During cranking, the IC voltage is at virtually zero so the ECM does
not recognize a problem. When engine rpm reaches the value for the run condition, the ECM
applies bypass voltage to the distributor module. Bypass voltage on the module switches
the distributor power transistor to the IC line. Because the IC line is grounded, it will have
no voltage applied so it cannot operate the power transistor to enter the IC mode.
If the IC line becomes grounded while the engine is being operated, the engine will stop and
will be difficult to restart.
An open or ground in the IC or bypass will cause the engine to run on the distributor module
timing. This will cause reduced performance, poor fuel economy and erratic idle.
Click to expand...

That was awesome. Thank you. Saved this. Don't have an MEFI1, but may run into this with someone else.
 
A minor two cents from a limited knowledge guy. After reading the entire thread, I cant help to think its two fold, injector related and electrical. Independent of each other maybe. THe electrical - The failure to run above 2000 RPM-feels like a sensor kicking in because its not rough running, stumbling, backfiring, it just wont go past. As others have stated, this is like guardian limp mode which is caused by a poor sensor signal to ECM in newer Mercruiser systems like my former 2002 6.2L MX,s. My system went similar limp due to IAC problem. Not a complete IAC failure but rather partial failure. This carries an soft alarm with newer OBDII systems key here is SOFT alarm- Maybe not with older OBDI systems or OBDI soft codes dont register, dont know. Further, I recall the IACs have a filter screen that can get sucked into the manifold that can also create great gobs of different issues. Do these older MEFI's have the same kind or IAC filters? If the filter sucked into the manifold this wouldnt necessarily cause a fault code would it?. Many other electrical points of contention are now mentioned by Hughespat57 - When he speaks I listen for sure. Definetly things to check. Of course, the central system for electrical is the ECM and you need a really GOOD diacom diagnostic tool to troubleshoot this (Ie the on-island master tech with the correct tool you have already tried to find).

Regarding the injectors-Ebay, yea, cheap but never a good idea in my book. As noted above, if you use other than a quicksilver or mercruiser IAC you could be asking for headaches. I suppose the same holds for injectors.

I want to see this problem resolved as I too am an owner of a 97 BBC with bravo 3 system that has been sitting for two years and I learn troubleshooting through these forums.

Keep us posted Hoplite808
 
Hoplite808 said:
I have been trying to fix this engine for over a year now with no success. I’ve tried to find a professional mechanic to fix it and the only two I could get to come look at it both just said they don’t know what’s wrong with it and good luck. It’s a 1996 Mercruiser 7.4LX MPI (Gen V) with a Bravo 3 stern drive mounted in a 270 Sundancer.

So far I’ve replaced the cylinder heads, exhaust manifolds, the spark plugs, spark plug wires, cap, rotor, distributor, ignition coil, ignition module, air temp sensor, MAP sensor, IAC, throttle position sensor, mechanical fuel pump, the electric pump in the vapor separator tank, the alternator, raw water impeller and housing, the heat exchangers, thermostat and housing, engine temp sender, oil pressure sender, the entire outdrive, and repaired or replaced wiring. I have quadruple checked the timing and fuel pressure. All is set exactly as it should. Fuel in the tank has been flushed and replaced with new. Oil is fresh and pressure is good. Engine coolant temperature is fine. Compression in all 8 cylinders is 120 psi and testing for spark at all 8 cylinders showed no problems.

But still it has a hard time starting when cold and it will not throttle past 2000 rpm’s under load. Fuel pressure remains at 37 at the rail when under load and adjusting the timing either more retarded or advanced makes no difference. If I had to guess I’d say it almost feels like it’s running to lean but the plugs look normal.

I am at a complete loss as to what’s wrong with this motor. Has anyone ever run into something like this? If so what was the issue and how did you fix it?
Click to expand...

Any one of those new parts could be defective. New fuel pump didn’t work. Alternator, starter, injectors, even the damn ignition.

You sir are chasing a ghost. Retrace all prior systems and double check soundness.
 
89P270 said:
A minor two cents from a limited knowledge guy. After reading the entire thread, I cant help to think its two fold, injector related and electrical. Independent of each other maybe. THe electrical - The failure to run above 2000 RPM-feels like a sensor kicking in because its not rough running, stumbling, backfiring, it just wont go past. As others have stated, this is like guardian limp mode which is caused by a poor sensor signal to ECM in newer Mercruiser systems like my former 2002 6.2L MX,s. My system went similar limp due to IAC problem. Not a complete IAC failure but rather partial failure. This carries an soft alarm with newer OBDII systems key here is SOFT alarm- Maybe not with older OBDI systems or OBDI soft codes dont register, dont know. Further, I recall the IACs have a filter screen that can get sucked into the manifold that can also create great gobs of different issues. Do these older MEFI's have the same kind or IAC filters? If the filter sucked into the manifold this wouldnt necessarily cause a fault code would it?. Many other electrical points of contention are now mentioned by Hughespat57 - When he speaks I listen for sure. Definetly things to check. Of course, the central system for electrical is the ECM and you need a really GOOD diacom diagnostic tool to troubleshoot this (Ie the on-island master tech with the correct tool you have already tried to find).

Regarding the injectors-Ebay, yea, cheap but never a good idea in my book. As noted above, if you use other than a quicksilver or mercruiser IAC you could be asking for headaches. I suppose the same holds for injectors.

I want to see this problem resolved as I too am an owner of a 97 BBC with bravo 3 system that has been sitting for two years and I learn troubleshooting through these forums.

Keep us posted Hoplite808
Click to expand...


I purchased the IAC I replaced off of amazon. I can't remember if it was a legit mercruiser part or not but it very well could be a knock off. However there is no code being thrown. I would think if the IAC was the issue there would be a code.
 
For those following for updates. I've been reading the MEFI 1 manual located here as well as being busy with life in general between days I can work on it:

https://marinepowerusa.com/wp-conte...NJECTION-MEFI-1-2-5.7L-350CID-8.2L-502CID.pdf

on page 25 it mentions a discrete switch input which if it gets one of these inputs it will activate a engine protection feature that will cause the engine to not exceed 2000 RPM's. It looks like it does actually have a early version of "safe mode". Further reading in this manual has indicated the solution is likely buried deep in whatever computer coding and sensor readings it's getting and the only way I'll figure it out for sure is learning to decipher all of that. I've been trying to get a local mechanic to come out and plug a computer into it but they are saying $500 to run the diagnostic. Which of course costs as much as me just buying the computer myself. Now the question is which RINDA thing do I buy.
 
Hoplite808 said:
For those following for updates. I've been reading the MEFI 1 manual located here as well as being busy with life in general between days I can work on it:

https://marinepowerusa.com/wp-conte...NJECTION-MEFI-1-2-5.7L-350CID-8.2L-502CID.pdf

on page 25 it mentions a discrete switch input which if it gets one of these inputs it will activate a engine protection feature that will cause the engine to not exceed 2000 RPM's. It looks like it does actually have a early version of "safe mode". Further reading in this manual has indicated the solution is likely buried deep in whatever computer coding and sensor readings it's getting and the only way I'll figure it out for sure is learning to decipher all of that. I've been trying to get a local mechanic to come out and plug a computer into it but they are saying $500 to run the diagnostic. Which of course costs as much as me just buying the computer myself. Now the question is which RINDA thing do I buy.
Click to expand...
Tell him you will only pay if he can fix it.
 
Hoplite808 said:
For those following for updates. I've been reading the MEFI 1 manual located here as well as being busy with life in general between days I can work on it:

https://marinepowerusa.com/wp-conte...NJECTION-MEFI-1-2-5.7L-350CID-8.2L-502CID.pdf

on page 25 it mentions a discrete switch input which if it gets one of these inputs it will activate a engine protection feature that will cause the engine to not exceed 2000 RPM's. It looks like it does actually have a early version of "safe mode". Further reading in this manual has indicated the solution is likely buried deep in whatever computer coding and sensor readings it's getting and the only way I'll figure it out for sure is learning to decipher all of that. I've been trying to get a local mechanic to come out and plug a computer into it but they are saying $500 to run the diagnostic. Which of course costs as much as me just buying the computer myself. Now the question is which RINDA thing do I buy.
Click to expand...

Start a private conversation with me. I will send you a Fox Gateway for MEFI-1 to hook up. You will need the app on your phone/tablet to read the bluetooth. That way you don't need a MFD to see what's going on.
 
Time for another update. Last week I had a mechanic come out to the boat that a friend recommended and he begins by having me start the engine and he listens to it for a minute and tells me to shut it down. Then proceeds to tell me he had an injury that caused hearing loss in one ear and now he hears low frequency noises really well, almost like a super power he claimed. He then says that he can hear a galloping noise from the bottom of the block and recommends a full engine replacement. I can't hear any such noise nor can I think of what on earth would make a "galloping" noise from the crank which he assures me only his special hearing ability would be able to hear. I asked him if he'd perhaps like to try plugging in some diagnostic equipment and he stated he could but that would cost $500 and he wouldn't be able to do that for another month or two since he didn't bring any of his equipment with him. So I decided not to use his services further. Then another friend recommended another mechanic who asked for a photo of my engine before he would entertain a trouble call. Upon seeing the photo he simply related he wasn't interested in working on this motor as he's never seen this model of engine before. Finally, today I got a competent mechanic to come out with a professional grade diagnostic computer. He plugged it in and we ran the engine for about an hour going back and forth in the lagoon while he checked all the readings and even sent reset signals to everything. What we found was that all sensors were working and there were no codes being thrown. The engine is not in limp mode and everything was giving readings that related that absolutely nothing was wrong with the engine whatsoever. However the engine still will not rev past 2000 RPM's while under load. The diagnostic thankfully only cost about $300 but still I have no idea what is wrong with this engine. I'm thinking of hiring a priest to perform and exorcism on the boat perhaps as the next step.

(The photo I had shared with the second mechanic.)
Engine LX MPI Gen V.jpg
 
At this point it seems that the simplest things must be reconsidered. The compression is low. It would be great to see the numbers for each cylinder. All of the other options have been exhausted. Have the cylinders been looked at with a bore scope? Has the fuel pressure been tested? Is there a hot spark? Re-evaluate the obvious problems. This engine may be shot. How long do you kick a dead horse? Summer is coming.
 
Lazy Daze said:
Did you get the injectors properly/reliably rebuilt?
Click to expand...

I took them to a shop and paid for them and a set of the Chinese ones from ebay I got for $150 to get tested. The shop said all 8 Mercruiser injectors were bad and the Chinese ones were tested OK. I installed the Chinese junk ones and the engine won't even try to run on them. It will however start and run well up to 2000 RPM's on the old Mercruiser ones. I am looking for another shop that actually knows what they are doing to test them. In the SEALOC repair manual it said to test for resistance across the terminals of each injector to see if they are ok and you should get a reading of 12 ohms +/- 0.04 if they are ok. I tested this and all 8 read 12 ohms exactly. I then took a 9volt battery and used it to trigger each injector while I sprayed carb cleaner through each injector and all 8 appeared to spray well. I know thats a janky thing to do but I'm trying everything at this point. The Mercruiser brand replacement injectors are between $300-400 each and 8 of them at this time would break the bank for me right now. If I can't find another shop that can test them properly then I'm going to have to wait until I can save up enough money to just buy 8 new ones.
 
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