Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

[Don S]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

If you are planning on sticking with EFI engines and doing your own work, time to invest in some tools. I have access to laptops and the fancier scan tool, but this one just works, always, and is about as inexpensive as they come with the ability to do it all.

http://www.rinda.com/marine/mtspec.htm

Without it, you just spend a lot of time guessing.

 

[vegasphotoman]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

I agree with Don
TOOLS

fuel pressure gauge for sure.... also a test light is the cheapest handy tool ever $1.99 at HarborFreight

you could cut the wires to the fuel pump, hook it to the battery, if it runs continuously its good or atleast working, best if you can check the pressure reading at the same time, should be atleast 15lbs to 30 lbs range, sometimes those high pressure pumps fail, cost around $100....
my brotherinlaws boat recently had the pump go out...it was intermittant and was bad especially once the motor was warmed up

took him 3 tow ins over time before he fixed it...not fun and not smart....

 

[Fun Times]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

Not familiar with the term "Switch" back, could you explain? And, I'm not axactly sure you you have never seen go bad ...... ECM or oil pressure switch. I have replaced both.

Well if A 1998 5.0 carbed engine does use a oil pressure switch/Sensor to turn on and off the power to the fuel pump, That is what I was trying to say about the switch Or sensor, [Depending on what index of part's you are looking at]. And form what I can remember I myself have never seen one go bad to where I had to replace the Switch/Sensor to get the fuel pump to work again, And to be honest I for got the Switch/Sensor was even used back in the 90's "Back then" to me anyway's. I only recalled seeing this oil pressure switch/Sensor on newer style engines for some reason:redface: After I had seen it in a service manaul some place, Then one day I unpluged one for a oil change one time and it would not stay running till I pluged it back in.

As far as Back Then, "The 90's" The only switch/Sensor I could find that would controll the power to the fuel pump by oil pressure for a 5.0 carbed engine is #11 in this next link, It's kind of hard to make out in the photo, But I believe this is the only thing mounted to A 1998, 5.0 carbed engine that would turn on and off the power to the fuel pump. Also I'm not to sure of the part to the right of #12, I can't make it out really but it could be a diffrent style switch?
http://www.mercruiserparts.com/Show...desc=Wiring+Harness+And+Electrical+Components

Now in this next link, http://www.mercruiserparts.com/Show...g&inbr=2704&bnbr=60&bdesc=SENDERS+AND+SENSORS. Will be for the senders for this engine we are talking about in this thread, He has a 5.0 TBI engine set up, And I can not find a Oil pressure switch/Sensor to turn on or off the fuel pump For a fuel injected engine, Because i believe It is done by the ECM in the older style engines, But also I'm pretty sure the newer style EFI engines have the oil pressure switch/sensor to controll the fuel pump power by oil pressure, Now See # 16 in this next link for the switch/Sensor to controll fuel pump power by oil pressuer on newer style EFI & carbed engines. http://www.mercruiserparts.com/Show...bdesc=Cylinder+Block(Camshaft+and+Crankshaft)


Now the reason I keep saying Switch/Sensor is because of the links I keep pulling up and they all say different things for the same thing. Example See #16 in this link. http://www.mercruiserparts.com/Show...bdesc=Cylinder+Block(Camshaft+and+Crankshaft) Now see #16 in this link. http://www.mercruiserparts.com/Show...bdesc=Cylinder+Block(Camshaft+and+Crankshaft)
And now see #11 in this link.http://www.mercruiserparts.com/Show...desc=Wiring+Harness+And+Electrical+Components

 

[Don S]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

Like I said before, EFI doesn't use the oil pressure switch to control the fuel pump. That is done by the ECM.
Next, don't go by a parts catalog. Mercruiser uses the same catalog for Carbed and EFI at times. Besides, with the catalog you have shown, I have no clue what it's for.

Study the manual (#24 if you want to download it from the adults only sticky), not a parts diagram.

 

[dryan117]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

I think I'll try the $40 noid lights before the $500 dollar software for the laptop. More good money after good money. Boats are just a hole in the water you throw money into!

Better yet, It's almost time to get to know a boat mechanic...

 

[JustJason]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

you don't need the software for the laptop, you need a $399 techmate. It will show live data just 1 line at a time.

 

[dubs283]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

I have replaced all ignition system parts, with the exception of the pickup coil - but that ohm'd out fine.

just because the ignition sensor passes an ohms test does not mean it isn't bad

an ohms test only allows you to see resistance through the component when in a static state, i.e. not connected and operational in the system

i have seen ignition sensors that pass an ohms test but ended up being the culprit when connected in a "running" system

the ONLY ignition sensor i trust to work properly is the latest, solid black, one piece, potted sensor from MERCRUISER

as said before, if the sensor is original or anything other than the latest OEM merc part, replace it. the ignition sensor is the number one part to fail in the ignition system in my experience

 

[lucky7]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

is there any chance that you got the plug wires crossed? that might make a knock.

 

[Don S]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

the ONLY ignition sensor i trust to work properly is the latest, solid black, one piece, potted sensor from MERCRUISER

He doesn't have a Thunderbolt ignition with the black sensor, he has an EST distributor with an ignition module (they are white). There is NO resistance tests on it, at all. NONE. He has made up his own test for some reason and it is meaningless.
There are testing procedures in the #24 manual. It requiers reading, and actual testing per the specs, with the proper tools.
Hammer, screwdrive, and a cresent wrench and the desire to fix it, just doesn't get the job done anymore.

 

[dryan117]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

I was performing the resistance check on the pickup coil, per the merc service manual 24, page 4B-28. Step 2. "Connect an ohmmeter to both pickup coil leads. Flex the leads by hand at the coil and the connector to locate any intermittent opens. The ohmmeter should read a constant unchanging value in the 500-1500 ohm range. If NOT, replace the pickup coil."

I observed an 809 ohm measurement. It plugs into the back of the ignition module, and I believe you need to remove the distributor and disassemble the shaft assy from the housing to get to it... so I assumed it was good.

Anywho. I got the noid tester. Folks at the auto parts store had no clue what is was, until I called it a fuel injector light test kit. That made the computer happy. It was right next to the guy on a shelf behind the register in plain sight.

Here are the results of the noid light test. I observed a faint continuous blinking light on both injectors, which at first I thought was indicative of a weak power pulse to the injectors. So I measured the supply voltage - solid 12v, which will light the injector test bulb if I tie the drk blue / drk green wires to ground with a jumper wire. So I have 12volts strong getting to the injectors.

I assume the ECM pulses the injectors by intermittantly connecting the drk blue / drk green wires to ground via the ECM, so I pulled the J1 and J2 ECM connectors and checked J1-14, J1-30 and J2-15, J2-20 to ground, verifying near zero consistant resistance. So I think I have a good ground. Could be a failed ECM.

Thinking about it some more, I am not sure the faintness of the light was all that abnormal, given the injector power pulse is probably only about 100 milliseconds, so the bulb really didn't have time to light up brightly.

So if that is correct, I believe I have now verified that I have adequate consistant power pulses to the injectors, along with steady fuel pressure measured at the input to the TBI housing, so I am now thinking about going after clogged throttle body unit or non-functioning fuel injectors.

Thoughts?

 

[Don S]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

Pour a little gas (a shot glass full will work) down the throttle body and see if it fires.

 

[dryan117]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

Yep. Fires right up. Injectors still intermittent during event.

 

[Don S]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

Well, now you know it's a fuel delivery issue, not spark, timing, compression or anything like that.
It fuel delivery either to the injecters or from them. There are tests for that.

Earlier you mentioned water. Are you spraying water from the injectors or gas??????

 

[dryan117]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

When the injectors do pulse, it is gas. I believe the boat had crap gas in it at the start of the season, and in the process of running it out, the throttle body and/or injectors either plugged up, corroded or whatever. I am ready pull them out and inspect for contamination.

I pulled the fuel supply line from the back of the throttle body and ran the pump, got about a gallon of ok fuel out of the tank, which ran fine in the leaf blower. No water, stank or crud in it after letting it settle out.

When pressure tested I am getting 30 psi at the end of the line.

The injectors are getting electrical pulses, but the fuel is just not coming out!

 

[Don S]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

Injectors can get plugged up and not work, even though the ECM tells it to work. Old gas, crud, varnish will all kill an injector. They can be sent out and reconditioned, but the rest of the system has to be cleaned as well. From the tank to the injectors.

 

[dryan117]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

I just pulled the fuel injectors, and I have to say, they are quite clean and free of debris. If I use a 12v power supply, they click and I can see the pintle moving up and down through the fuel supply hole on the body of the injector. I could still have a plugged injector nozzle, or the ball could be stuck on the seat, but I am now second guessing whether the ECM is providing the correct power pulses to the injector.

So to prove things out, I am going to put them back in the boat as is, and with fuel pressure on, put power to one of the injectors and see if it flows with a good ~1 second pulse.

If it does, it's time for a new ECM.

 

[Don S]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

Have fun throwing parts at it. I will stop bothering you.

 

[JustJason]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

Hmmmmm A $1500 ECM that is designed for 1 engine that is not returnable and hardly re-saleable... Or a $400 scan tool that works on many a boat, and will tell you what you have going on.

 

[dryan117]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

Just to close out this thread.... It was a faulty pickup sensor in the distributor that ohmed out fine, along with some rusty screws that held down the ignition control module. The 400 dollar scan tool and 2 trips to the dealer (they had to call in the merc master mechanic) could not diagnose this... it was intermittent start no start. Everyone gave up and said I needed a new ECM... but my research indicated the ECMs rarely go bad, and never intermittent.

Thanks to the smart dudes at http://www.michaelstractors.com/forum/topic.asp?TOPIC_ID=199

They understand how this efi system really works, and the Mercury Service Manual #24 belongs in the garbage.

Luckily, I only borrowed the scan tool, had "honest" dealers who didn't charge me for not confirming the problem, and I refused to spend 1500 bucks for a "guess". I spent 32 dollars on a pickup coil and wire-wheeled some tiny screws for free after getting good advice from a real mechanic....

P.S. Dubs283 was right and Don S was not.

 

[Bondo]

Re: Mercruiser 5.0 - Won't Start, Continuous Knock Code 43

Just to close out this thread.... It was a faulty pickup sensor in the distributor that ohmed out fine, along with some rusty screws that held down the ignition control module. The 400 dollar scan tool and 2 trips to the dealer (they had to call in the merc master mechanic) could not diagnose this... it was intermittent start no start. Everyone gave up and said I needed a new ECM... but my research indicated the ECMs rarely go bad, and never intermittent.

Thanks to the smart dudes at http://www.michaelstractors.com/forum/topic.asp?TOPIC_ID=199

They understand how this efi system really works, and the Mercury Service Manual #24 belongs in the garbage.

Luckily, I only borrowed the scan tool, had "honest" dealers who didn't charge me for not confirming the problem, and I refused to spend 1500 bucks for a "guess". I spent 32 dollars on a pickup coil and wire-wheeled some tiny screws for free after getting good advice from a real mechanic....

P.S. Dubs283 was right and Don S was not.

Ayuh,.... Glad to hear ya got the darn thing sorted out,.... 'n Thanks for the up-date....

On a side note,... I just checked,... dubs hasn't posted since April, this year,... I hope all is well with dubs...