5.7 efi no power/WOT

[Macrae99]

Hi guys. New to the forum with a slight problem.
I've posted on another site but thought I'd see what you guys think.

I've got a 1995 mercruiser 5.7 efi s/n 0F431832, Delco est ignition
So this season, end of last I couldn't get WOT and now only getting 3200 revs roughly, cant even get up on plane really. No real power at all, in fact since I've had the boat it's never been great.
Compression is good 170-180 psi, new fuel and pressure is 30psi, so it's not a fuel problem.
I checked for codes and got 42 so went through the diagnostic cheks in the manual, I wasn't getting the right ohms on the ignition module so got a new one but it hasn't helped and actually I seem to be getting worse results so might be a bad module I don't know, got another module on the way.
So I checked knock module today following diagnostic in manual and where I should be getting 8-10 volts I'm only getting roughly 4v. Are the ignition module and knock module linked or could I have a bad knock module also?
Also timing was at 12/13* BTDC so I've now put that at 8* btdc

Any input would be appreciated, can't seem to find anyone with same problem which is a bit strange!!

 

[Don S]

Re: 5.7 efi no power/WOT

That engine serial number is for a 1995 TBI engine, not a 2007. A 2007 engine would have had MPI.

I checked for codes and got 42 so went through the diagnostic cheks in the manual,

And what manual are you using? I assume 42 is the code number and not the number of instances?

 

[Macrae99]

Re: 5.7 efi no power/WOT

Oops sorry, its a 1997 engine or so I thought with a new block in 2006. Don't know why I put 2007!!!
I got fault code 42 ignition control circuit, I'm using manual 24. I believe that to be correct?

 

[Don S]

Re: 5.7 efi no power/WOT

It might be a 97 boat, but it's a 95 engine by the serial number. You should also be using manual #17 for that engine. 24 was for the 98 to 01 engines.

Here is from manual 17 for code 42. I didn't check to see if it was the same as 24.

View attachment #17 GM V8 305-350 93-97 650.pdf

 

[Macrae99]

Re: 5.7 efi no power/WOT

Thanks for the info, I'll get myself #17.

Ye it's almost the same just laid out a bit different, that's why I came to the decision it was a faulty ignition module. I got a new ICM and still have the same problem so I might have got a new faulty module. I have ordered another one just to make sure. Do you know if a faulty ICM would cause the knock module to appear faulty. As I used the diagnosis from #24 manual on the knock module and where it should have 8-10 volts it's only got about 4v and I'm not sure if it could be linked?

 

[Don S]

Re: 5.7 efi no power/WOT

Everything has to work at the same time for it to run right. If you don't have the proper voltage, then something is wrong.
You do know how to proper test voltages don't you? I ask because about half the people with electrical problems on forums aren't testing things properly.

 

[achris]

Re: 5.7 efi no power/WOT

...I've got a 2007 mercruiser 5.7 efi s/n 0F431832, Delco est ignition
...
So I checked knock module today following diagnostic in manual and where I should be getting 8-10 volts I'm only getting roughly 4v. Are the ignition module and knock module linked or could I have a bad knock module also?
Also timing was at 12/13* BTDC so I've now put that at 8* btdc...

A Delco EST ignition system is not the factory issue system. You can't use the factory book to fault find non-factory systems. Get onto Delco and get the service manual for their system and use that...

Chris...

 

[Macrae99]

Re: 5.7 efi no power/WOT

ye i know how to test the electrics so thats not the problem, i might just have to wait till i get the other ICM before i can go any further.

thanks Chris i'll try find one for that.

 

[Don S]

Re: 5.7 efi no power/WOT

A Delco EST ignition system is not the factory issue system. You can't use the factory book to fault find non-factory systems. Get onto Delco and get the service manual for their system and use that...

Chris...

\

The Delco EST is the OEM ignition system on his engine.

 

[achris]

Re: 5.7 efi no power/WOT

\

The Delco EST is the OEM ignition system on his engine.

View attachment 169578

Sorry, I was looking at the TB-V picture... :facepalm:

 

[Fun Times]

Re: 5.7 efi no power/WOT

So I checked knock module today following diagnostic in manual and where I should be getting 8-10 volts I'm only getting roughly 4v. Are the ignition module and knock module linked Also timing was at 12/13* BTDC so I've now put that at 8* btdc

Yes they can be linked by both power and ground. They share the same ground wire to the stud on the back of the engine, if corroded, etc, then yes you could show low volts. Same concept for 12.6v power as well.

Also is your battery fully charged? what does it show for volts at various spots on the engine? the same volts as battery?

The KS module terminal B is powered by 12 volts from the ignition switch thru system relay. If the 12 volt power source is not present, the KS module cannot send an 8-10 volt signal to the ECM.

The ground circuit for the KS module is connected to terminal D. If the ground circuit opens, the KS module will not be able to remove the 8-10 volt signal to the ECM and spark knock cannot be controlled.

How did you reset ignition timing on this engine? do you have a scan tool?

Have you check to see if your ignition timing is varying at idle then check to see if it's advancing up to around 27 degrees at around 3000+ rpm.

 

[Macrae99]

Re: 5.7 efi no power/WOT

Thanks for the replies,
Checked the grounds, all fine but cleaned anyway, power into the KS module is 12v. Batteries are fully charged. Checked the KS module again today with another ignition module I have and it's now getting 10v however I tried tapping engine and also repeatedly touching KS harness with test light but never noticed any fluctuation in rpm.
I took the boat for a spin to check a few things, it's definitely firing on all 8 and getting about 3600 rpm.
I have a LED and jumper cable to read, reset codes and set timing but not a proper scan tool.
Can some point me in the direction of timing curve for delco ignition as I can only see TB systems.
I seem to be getting 38* btdc by 2500 rpm which I know is too high which makes me think something's wrong with ignition module?? As base timing is set at 8* btdc, idle is roughly 12* btdc but does vary until warm.
15* @ 1000 rpm
20* @ 1500 rpm
26* @ 2000 rpm
38* @ 2500 rpm
Next boat is going to be twin engine so I can just swap bits over!!

 

[Don S]

Re: 5.7 efi no power/WOT

Next boat is going to be twin engine so I can just swap bits over!!

Get yourself a proper scan tool if you plan on sticking with EFI, you got to have the tools to work on this stuff or you end up buying a bunch of un-needed parts. http://www.rinda.com/marine/mtspec.htm#techmate and this

 

[Glastron_V210]

Re: 5.7 efi no power/WOT

The things I coudl think of were:

1) Fuel filter. You said you have 30psi, but is this at WOT? Without load on the engine it means very little!
2) MAP sensor. Although it would generally run rough, a bad sensor or a vacuum leak near the sensor can later the signal, and therefore the fueling
3) You have checked the compression, so check ALL the spark plug firing. With a V8, without a good ear, you could have dropped a cylinder and no know it. 1 way to determine this is to pull 1 spark plug lead a time at idle and see if there is a drop of rpm each time. Use insulated pliers ! (Zap...Ha ha!)
4) Intake or exhaust blockage. Low air flow through the engine will kill your power. This is the least likely issue though.

The advance was done without load right? 38* is way too high for a loaded engine. the ecm could have it this high with no load though. I'd load it up (in smooth water) and check it under load as well. I'd expect more like 30-32 btdc.


Chay

 

[Macrae99]

Re: 5.7 efi no power/WOT

Haven't been on for a few days as it was raining and only just got another new ignition module. Still exactly the same though. I keep getting fault code 42 appearing.
I go through the test procedure as in the mercruiser service manual!! And it keeps pointing to the module but it can't be. When checking the ohms across the IC module I get about 9000 ohms, manual asks if it's above 3000 ohms so that fine. However if I put a 12v test light on ckt 424 is should drop below 1000 ohms, both of my new modules don't they increase very slightly! My old module would decrease from 5000 to roughly 2000 ohms
Does anyone knows what values you are getting, testing resistance on ckt 423 to ground then attaching test light to ckt 424 and reading value again?

The fuel pressure was with ignition on as I was told this would be enough, spray pattern from injectors seem fine.
I disconnected the map sensor harness today and it ran rough, quite a bit of white/grey smoke. So stopped checked for codes and code 33 appeared.
It's 100% firing on all 8 as I checked and doubled checked that a couple of times.
Intake is fine and have replaced exhaust risers and manifolds lately plus leg was off just over a year ago and no blockages then.
I need to find why code 42 keeps reappearing, what's the chances of a faulty ECM? Does anyone know how to test one?
Also with timing advance I checked it under load also and when accelerating it's about 32* btdc but does go to about 36/37* btdc when reducing throttle. Need to test this again just to double check though.
One last question with ignition on and testing knock module I put 12v test light on the knock sensor harnes and the voltage into the ECM drops for a second then stays about 10v which it was before testing, any know if that is correct or if it should drop and stay lower???
Thanks for the help guys

 

[Tail_Gunner]

Re: 5.7 efi no power/WOT

There is a serial number and model number on your ecu post that if you will. If you have a mefi system there is no igntion module the ecu controls the timing. It seems your knock module is telling the ecu your engine is detonating and retarding the timing. Fun time's post is on track if if is a mefi. Thats a old system and if your knock is only getting 4v that's your issue..being old leads to intermitnet signal processing be patient and follow the power lead to a point where it show's the correct voltage.

As to timing you need to post the model and serial number of your ecu

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.
Spark Plugs

So you did not use a shunt.....what is a timing tool? Below is a shunt

And the EFI timing tool...The shunt connects to the dist and the timing tool connects to the ecm or data link

 

[Macrae99]

Re: 5.7 efi no power/WOT

I have a MEFI-1 serial number 16189069
The knock module is getting 12v and the ground is also good, it's output to the ECM is 10v and when connecting 12v to the KS harness it quickly drops then returns to 10v again.
The shunt cable your showing above is that for the thunderbolt system? I have the delco hei system.
Apart from that the way I did the timing was to the book, it was set about 12/13* btdc before I re-timed it to 8* btdc.

 

[Tail_Gunner]

Re: 5.7 efi no power/WOT

Even mefi 1 has built in timing timing tables. No timing module comes into play. So you use the timing tool not a shunt. I havnt played with a mefi one wait for Don but i would be astounded if you short the dist..that would be incredible. Did you use the shunt or the timing tool. You should have hooked up to the data link not the dist.

IGNITION “OFF.”
• DISCONNECT ECM CONNECTORS.
• IGNITION “ON.”
• USE DVM WITH SELECTOR IN OHMS RANGE.
• PROBE ECM HARNESS CONNECTOR CKT 423 WITH
DVM TO GROUND.
IT SHOULD READ MORE THAN 3000 OHMS.
DOES IT?
YES

 

[Macrae99]

Re: 5.7 efi no power/WOT

Yup I hooked up to the datalink and that put it into base mode.

 

[Tail_Gunner]

Re: 5.7 efi no power/WOT

Ok the mefi 1 has a seperate knock module and it does read out 10v so you monitor the 10v signal if it drops then the ecm retards the timing..So while the engine is running does the 10v signal jump around? You may have to vary rpm or run it under a load to see if it's intermittent.