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Ignition problems 2001 4.3

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yzinger5126

New member
"hello
I have a 2001 Merc 4.3
I was boating fine until it died and i had to be towed in.diagnosed that it was the ignition sensor.boat runs and idles great but when i add throttle the timing starts to jump everywhere and it starts backfiring through the carb at 1800 rpm.i have replaced plugs,wires,cap,rotor,ignition sensor,drained fuel tank(worried about water in fuel),coil and rebuilt the carb.could it be a bad ignition sensor or something else??? thanks in advance for the help.
Clay"
 
no i have not. is that a easy

no i have not. is that a easy thing to do???i dont want to make more problems for myself. is there an easy way to check them??
 
Disconnect the tachometer and

Disconnect the tachometer and try the engine. Bad tachs will screw up your electronic ignition.
 
clay carr
It generally involv

clay carr
It generally involves removing the distributor. You could just try and check for side way slop on the rotor shaft with the distributor still in the engine. That might show some problem on the upper bushing but not the lower one.
Bert
 
"After you try everything abov

"After you try everything above, yank the timing chain cover, chain stretched, skipped a tooth ?

But usually it's dist. or a timing problem with your symptoms."
 
"Did you remove the rotor asse

"Did you remove the rotor assembly?

If so did you push it all the way down when you reinstalled it?

When did you replace the plugs and wires, before or after the sensor was installed?
Either way double check the firing order, Sounds like a crosed plug wire to me.

Lets keep this simple!! A bad dist bushing is a far reach at this point.

If it was running good and just died and the sensor was the root cause then the initial problem was fixed. He then threw the kitchen sink at it but he does not specify when the sink was thrown..............before or after the sensor diagnosis.

Also if all was done in the correct order and no mistakes were made the next item up for bids would be the ignition/timing module."
 
morning

engine has never be

morning

engine has never been opened up so i would assume the valves are fine???like i said previosly it ran great then just died???never had any overheating issues either. the boat was completely dead wouldnt fire until i replaced sensor this other problem happened after i replaced sensor. no crossed wires or rotor issues either
 
"<[img]"http://www.marineengin

"
uhoh.gif
I bet it's the tachometer or module."
 
"Clay

I will ask you again

"Clay

I will ask you again to answer each of my questions.

Just telling us WHO ARE NOT THERE that this or that is ok without saying why, does not tell us it is OK.

Example:

Question!
""""Did you remove the rotor assembly?

If so did you push it all the way down when you reinstalled it? """"

ANSWER: Yes I pulled the rotor ASSEMBLY off to get at the sensor and reinstalled it all the way back on the distributor shaft as far as it would go, it was a bitch to get off but went back on ok.


This is what we need to see in order to fully understand what may be wrong.

You say the wires are ok?

I have replaced hundreds of wire sets and you know what I still mess up from time to time and cross one. How do we know they are correct? if you would explain it to us we will have a better understanding.

Just saying.........."
 
"I WOULD SAY CHECK YOUR ENGINE

"I WOULD SAY CHECK YOUR ENGINE CONTROL AS WELL.
MY BOAT I HAVE NOW DID THE SAME EXACT THING.
I CHANGED SO MANY THINGS.
HECK I EVEN TOOK IT IN TO A BOAT SHOP N THEY COULDNT FIGURE IT OUT.
THEY SAID IT SEEM LIKED MY VALVES WERE CLOSING INSTEAD OF OPENING WEN I HAVE THE THROTTLE OPEN??
HAHA.
BUT YEA. MY GM 305 DID THE SAME EXACT THING.
STARTS UP FINE WITH THE WATER HOSE, BUT ONCE ITS IN THE WATER, COULDNT GET IT PAST 1500 RPM IN GEAR.
AFTER CHANGING SO MUCH ENGINE RELATED STUFF, ONE DAY MY BROS TOOK IT OUT, ALL OF A SUDDEN THE ENGINE CONTROL CAME LOSE.
THEY DOCKED IT, FEW DAYS LATER MY BRO GOT A NEW ONE. PUT IT ON.
TOOK IT OUT. AND EVERYTHING WORKED.
AND HAS BEEN GREAT SINCE.
I NEVER WOULD OF THOUGHT IT WAS THE ENGINE CONTROL ITSELF TOO SINCE IT STARTS UP AND IDLES AND GOES INTO GEAR FINE.
BUT YEA, CHECK YOUR ENGINE CONTROL. THATS JUS MY SUGGESTION."
 
"thanks again to all the answe

"thanks again to all the answers. a long day at work,ghost i can confirm rotor is in place because yes it was a bitch to put back in and wires are not crossed because i did them individualy and yes the starboard side center is ugly due to the cooling hose that gets in the way . all is good there. i am going to try the unhook of the tach today . thank you all again .i will let all know. cheers clay"
 
whats the easiest way to unhoo

whats the easiest way to unhook the tach??? i thought it would be a simple process with a diagram or label but i cannot figure out how with all the wires in one plug behind the dash. or is it easier at the motor??? thanks again
 
"GREY wire, one goes to the ne

"GREY wire, one goes to the negative side of the coil the other end goes to the signal side of the guage, the guage should have three or four wires,
Purple = ignition on
Black = ground
Grey = tach input
Blue = guage light"
 
thx ghost

i will reply asap

thx ghost

i will reply asap it started freezing here again and have to pull the plug... i live 20 minutes from where the olympics were.... amazing that it snows now...... hopefully within a day or two.. cheers clay
 
I sure would look real close a

I sure would look real close at the dist cap. First and easiest place to look and sure would cause your problem. Look for a carbon track from one contact to any other. If in doubt replace the cap and rotor.
 
afternoon to all helpers
I un

afternoon to all helpers
I unhooked the tach and boat wouldnt even fire up.
as soon as i hooked up grey wire back to coil she fired right up?????
 
Then you unhooked the wrong wi

Then you unhooked the wrong wire.....

The tach lead is an OUTPUT from the coil to the tachometer. If the tach shorts out internally it will also short out the coil.

If you disconnected it the the ONLY thing that should have happened is the tach did not work.

Double check what color the wire you removed was.

Also what side of the coil was it connected to?

+ or -
 
hi ghost
the grey wire on the

hi ghost
the grey wire on the negative side i removed
the positive side is purple that i did not touch.
boat would not start at all until i hooked grey wire back up????. is there supposed to be more wires on coil other than the high tension lead and the purple and grey??2 16 guage wires total 1 on each side is all i have here.thanks again
 
"The schematic shows two grey

"The schematic shows two grey wires, one goes to the tach the other is the "tach" lead to the inginiton control module attached to the distributor housing SEE PIC.

There may only be ONE wire at the distributor but somewhere it splits or is joined with the tach lead and the ignition control module lead.


377382.jpg
"
 
hey ghost
thanks for the pic

hey ghost
thanks for the pic
before i say anything i am really confused my module is on the water manifold and that makes me wonder if the info is incorrect. all that is near distributor is inside with the ignition sensor.i do appreciate all the info and ideas
 
"Your first post said 2001, th

"Your first post said 2001, that image is out of the 2001 V6 manual # 23 I beleieve

Here is another image from a Earlier version.

There are two ignitions, Thunderbolt IV or V for carbureted engines. EFI have a different ignition set up.

They are the same for the most part with some of the differences being a knock sensor and distributor mounted timing controll module.

So the wiring shown on this image says the grey wire goes to the ignition module/timing module and the tach from the coil.

It is still the same just drawn differently.

My advice to you if you are unfamiliar with any or all of this is to get a service manual with schematics.

377397.jpg
"
 
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