2001 6.2 Merc Skips, Gas Smell, No Power When Cold

[Pacfanweb]

So I have a 2001 Ebbtide Mystique. 6.2L. Bravo 3. 629 hours.

I have an odd problem, that I thought I had fixed but it happened again yesterday:

Bought this recently in another state. Had the marina where it was stored do a "buyer's checklist" checkout on it so I'd know more about it. Compression was good in all cylinders, so the base engine should be okay.
They mentioned it "ran a little rough when first started cold".

Okay, that could be anything. When I went to buy it, it started and ran fine on the test drive.

Pulled it home: Went to the lake the next weekend, and when I backed off the trailer, it ran like crap. Tried to ease it around the lake while the wife parked the truck and it ran like a 3-legged dog. No power at all, skipped, shook, and lots of raw gas smell.
So I'm thinking something must have shaken loose on the trip home, right? I checked every connector I could find, and nothing.
Back to basics: I'm a mechanic, and this is a Small Block Chevy, so how hard can it be? Well, you don't have to stand on your head to work on most cars, lol.

Found the cap badly corroded. Sanded the terminals pretty good (I was parked on the beach next to the ramp) and it ran like a champ. Ran the next day like a champ. Next week, it ran bad for a minute or two, but I had bought a new cap/rotor and had it with me, so back to the beach and I put it on right there. Ran perfect several more trips over the next few weeks. I figured that MUST have been the cause of the "ran rough cold" the inspection sheet mentioned.

Yesterday: It's sat almost 2 weeks. Backed off the trailer, and same thing...skipping, no power, (won't rev) raw fuel smell. I cruised around the lake a few minutes to see if it got better, but it mostly didn't...maybe slightly, but still ran bad.
Beached it. Cap and rotor can't be bad already, but I checked it anyway. Okay. Wiggled all the plug wires to make sure nothing was loose, all seemed okay.

Also had noticed a rattling or tapping/knocking noise at the same time all this happened yesterday. I assume it's from the drive area...not sure if it was actually something else wrong, or if the motor was just running so badly it was causing it.

So after checking the cap/rotor and wiring again, I decided run it a few more minutes to see if I had helped it, and Lo and Behold, it's running better. Felt like it was mostly okay, maybe missing on one cylinder only. Drove it around with a slight skip, and decided we'd run it that afternoon regardless. Came back in to pick up guests (was my son's B-day party) and when I took them for a ride, it ran pretty darn good. No skip anymore.
Ran good the rest of the day.

However, I have no illusions that I have fixed it. I fully expect it to be back next time out, but I do think it might be something related to engine temp, since it gets better as you drive it more. Oh, and there was no more knocking/tapping noise after it started running better as well.

Been reading up some, have found something about the IAC air filter, and how that can cause it to idle rough if it's clogged. Haven't checked it yet, but seems plausible....up until the point where I remember the engine had no power at all under full throttle. Wouldn't the IAC be rendered irrelevant once you crack the gas open?

I haven't ruled out more basics like plugs and wires, but those things don't tend to be "only when cold" type of issues. But not ruled out.

I've read of someone having a bad FPR causing this.

I guess I'm looking for common issues with these engines, or maybe if anyone else has had a similar issue?

Just going on the symptoms, it doesn't seem like a fuel delivery problem because of the raw gas smell...but then there's that "it won't rev" issue, too, so maybe it is?

Thanks for any advice here

It's also got some wonky shifter issue as well, but I figure I'll work through that when I get it running correctly.

 

[achris]

Get a timing light and check each lead for spark... That will tell you more about whether it's MISSING due to spark or fuel. Also, an engine serial number would help us out a lot here...

Chris........

 

[alldodge]

What is the serial number of the motor?

The MPI motor has many things going on, and need to start with the basics.
Remove the fuel filter and dump contents into a clear container to see if there is anything but clean gas

Measure fuel pressure at the rail, should be 43 psi at 1800 rpm. Keep the pressure gauge on the rail and see what it does throughout entire rpm range under load

What do the plugs look like?

New to you boat maintenance
Replace, fuel filter, impeller, gear lube
Check drive alignment

 

[Pacfanweb]

Get a timing light and check each lead for spark... That will tell you more about whether it's MISSING due to spark or fuel. Also, an engine serial number would help us out a lot here...

Chris........

Skipping, missing, same thing, lol.


I will get the serial number shortly.

Okay, 0M012275 is the S/N for the motor.

 

[Pacfanweb]

0M012275 is the S/N for the motor

 

[alldodge]

Thanks for the s/n, I'm seeing a MEFI-3 so this can make finding codes a bit easier

Your motor has a fuel pressure sensor (item 14) and a shrader valve (item 6) to test pressure. Would like to know what the fuel pressure is


https://www.mercruiserparts.com/bam/...31953/5725/100

If you get a resistor 12V diode and a paper clip you can read if there are any codes at the DLC connector. Or can buy a test connector already made (CodeMate)

https://www.rinda.com/marine/marine.htm

To read codes the led and paper clip is installed, turn key ON and then count the flashes. If there are no codes it will flash 12. Read flash then short pause, then flash, flash then longer pause. It will repeat 3 times. If there are codes then other 2 digit numbers will show

 

[QBhoy]

Never rule out that diz cap. Even when new.
Other than that...
crank sensor and fuel pump/fuel pump relay would be on my list.

Of course all the above only if you have ruled out the simple things like fuel quality, leads and the all important MPI iridium plugs are fitted.

 

[Pacfanweb]

Thanks for the s/n, I'm seeing a MEFI-3 so this can make finding codes a bit easier

Your motor has a fuel pressure sensor (item 14) and a shrader valve (item 6) to test pressure. Would like to know what the fuel pressure is


https://www.mercruiserparts.com/bam/...31953/5725/100

If you get a resistor 12V diode and a paper clip you can read if there are any codes at the DLC connector. Or can buy a test connector already made (CodeMate)

https://www.rinda.com/marine/marine.htm

To read codes the led and paper clip is installed, turn key ON and then count the flashes. If there are no codes it will flash 12. Read flash then short pause, then flash, flash then longer pause. It will repeat 3 times. If there are codes then other 2 digit numbers will show

So it's been awhile. I put the boat away last year and didn't worry about it.

New battery this year. Still no start. At first, it turns over and you can hear it fire on a cylinder here and there, but it never "catches" and starts completely. Eventually it'll stop doing that and just crank, no start.

I have fire. At the cap and at the plugs.

Replaced the filter. Fuel poured out of it was perfect. No trash, no water. Put it in my mower and burned it, in fact.

I pulled a few plugs and none of them were wet, which tells me it's probably not getting fuel.

No codes. I rigged a tester with the paper clip and test light.

Fuel pressure: Not a lot. When you turn the key, it comes up to about 20-ish. If you crank it over it rises to about 25, then when you stop cranking it it might get up to 30 and that's it.

So that seems to be the problem, but now the question is, why?

It does have a sensor on the back right (facing the motor) rail, under all the "Merc Cathode" stuff and 50a breaker. Don't know what genius thought it was a good idea to put all that right on top of each other, but whatever.

I can say that the pump is kind of loud. But where is it? I don't see it, but can certainly hear it. Doesn't seem to have one of those "pump/cooler assy" things that I can tell. The filter is on the left. (facing the motor, again)

What's my next move? Could the sensor on the rail cause this or is it the pump?

I had thrown up my hands and had a mobile guy come out to look at it. Turned out he was clueless and I'm not sure he knows much more than I do. He bailed and I am back to trying to do it myself or just taking it somewhere.

 

[alldodge]

No codes. I rigged a tester with the paper clip and test light.

You cannot use a test light it has to be a "resistor LED" only. There is only 5V on the wires and a test light won't work

Fuel pressure: Not a lot. When you turn the key, it comes up to about 20-ish

The fuel pump is behind the port side motor mount and under neath a black plastic cover. There is a pressure issue but sounds like the injectors are not working

Can you see the tachometer go up to around 300 rpm when cranking?

 

[Pacfanweb]

You cannot use a test light it has to be a "resistor LED" only. There is only 5V on the wires and a test light won't work


The fuel pump is behind the port side motor mount and under neath a black plastic cover. There is a pressure issue but sounds like the injectors are not working

Can you see the tachometer go up to around 300 rpm when cranking?

Tach hasn't worked since we got it

 

[alldodge]

Make sure the tach has been disconnected, do this at the tach behind the helm, its a gray wire. If tach is shorting out there will be no spark.

Might be possible to get a loaner tach from the local auto parts store. If so connect it to negative side of coil and ground

 

[Pacfanweb]

I know I have spark. But I will check that tach wire. Might be a few days it supposed to rain here this week a good bit.

 

[alldodge]

The reason there needs to see a tach signal is because the ECM looks for it before it fires the injectors. If the ECM doesn't see the signal from the distributor the injectors stay off.

Does the Thunderbolt distributor have the 2 wire or newer 3 wire sensor?
The sensor have had problems with intermittent issues do to grounding problems, so Merc add a ground wire

 

[Pacfanweb]

Okay weather finally cleared up. Sitting on the boat right now, two wires going to the distributor.

And just to verify that my fuel pressure gauge was correct, I hooked it to my wife's Suburban and it popped right up to 50 psi, which is about what it should be.

I also checked codes again, with my test light which works just fine, and all I have is a code 12.

 

[alldodge]

To recap
Have spark on all cyl, yet pouring gas down does nothing
Fuel pressure is at 20 to 25 psi

 

[Fun Times]

Also seems as if you have 2 issues now almost a year later...Went from running rough at times to now a no start and run at all after sitting.

Your engine model/design doesn't utilize the IAC air filter.

The fuel psi on these engines (serial number range) often seem to be reported low... Like down in low to mid 20/25ish range but they still seem to run. Your regulator is supposed to be a 30 psi setting....Also at some point while the engine is/becomes "running", try disconnecting the vacuum line hose at the regulator or up-top of the engine all the while inspecting the vacuum line hose for any possible damage like mentioned from a past member had found, https://forums.iboats.com/forum/eng...i-fuel-pressure-problem?p=6840489#post6840489

If the engine still isn't starting or running right now then try opening up and then pumping the throttle anywhere between 1/4 to full throttle while cranking the engine over.

If you find that you are or begin to smell heavy raw fuel while running or starting, etc. and/or get a to rich of fuel look/smoke out of the exhaust water system then one of the main usual suspects (of many) to consider not working correctly would be the MAP sensor 8M0054726.
Have a few touchy, push down on it/tap on it movement moment with the MAP sensor to see if maybe it changes its state any before cranking the engine over and while it's running too just to see if you get lucky on engine running changes as I have in the past.

Check and replace all spark plugs especially after you see/smell raw fuel...If only checking a few plugs especially while out on the water then be prepared to check both side of the rear of the engine cylinders (8 & 7) along with cylinder # 6 too...But it's time for new plugs no matter what.

Make sure all the power and ground battery cables at the engine side too area clean and tight.

Make sure the whole distributor assembly is seated down correctly, is tight and not turning and free of any types of debris.

Also make the cap and rotor, plug wires are seated correctly as sometimes they can be installed cockeyed.

Also be sure the high tension coil wire at the coil isn't leaking spark as that is often an issue with these.

Shake/inspect the main 10 pin cannon plug wiring harness at the engine to see if anything helps changes the state of starting the engine while watching the gauges at the helm.

Again, disconnect the gray wire at the tachometer gauge to see if it helps any.

Here's your parts guide to this engine model, https://www.mercruiserparts.com/mx-6-2l-mpi-bravo-0l680003-thru-0m2999

 

[Pacfanweb]

So today: Had my son spin the engine over and I poured gas down the throttle body. Cracked it open a bit as well. Doesn't hit a lick. Not one cylinder fires.
Put my spark tester on #1 and on the coil wire: It blinks.
I know there's compression, I know there's fuel...the one thing I don't know for a fact: How MUCH fire? And is it sparking actually at the plug?
Although I seriously doubt all 8 plugs just went bad at once.

Here's another thing I found awhile back: The coil wire and the female terminal on the coil itself were badly corroded....almost a green gel was in it. I cleaned the coil terminal out thoroughly, and fixed the coil wire. But don't know if that was anything other than corrosion from age.

I think I can definitely say it's a fire issue, since I added the fuel manually now.

Have not disconnected the gray wire at the tach, it's a bear to get to.

 

[alldodge]

Assuming there is only one wire on the - side of the coil, remove it.
Remove coil wire from distributor and leave it in the coil. Place wire in spark tester to ground

Take a jumper wire and attach to the - side of the coil, then turn key ON. Strike jumper wire to ground and the coil should spark


Test Sensor

1. Disconnect the two sensor wires from the wiring harness to distributor.
2. Using an Ohmmeter, check for an ohm reading between the two sensor wires. If reading
is less than 100 ohms, replace sensor.

 

[QBhoy]

Hi
id do the following to rule some things out

The crank sensor is suspect. Test it
The temp sensor may cause it to run Rich, but not cause cold starting issue
Still not going to look past the diz cap here.
Really doubt it’s the IAC but might throw in it may be a crappy battery, whilst I’m at the list of usual MPi issues.

 

[Pacfanweb]

Only had a few minutes today before the rain started again. The two wires to the distributor have infinite resistance.

And the battery is brand new, literally just replaced it like 2 weeks ago after I ran the old one down