2800 SCR 4.3 V6 ignition problem

[marcucho]

I am copying this post from my post on Mercrusier FB.. looking for help

First part
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Working 4.3 v6 vortec just stop ..turning no running…
My faithful (port side) engine just stopped working at the ramp. It started for 3 or 5 second and then died. Could not get to start again.
Let me start saying that I replaced coil, distributor cap, rotor, ignition sensor (distributor), spark plug cables. It actually ran fine with the water hose on the trailer .. no problem at all.. it was just when it got to the real deal on the water

1) Plenty of Gas. I can even see gas getting to the carburetor .. even used starting fluid.. turning but not running.
2) Checked the following

1. Kill safety switch (I replaced with a new one .. I had a spare one)
2. I checked on current at the key switch, then following to the kill safety switch and check at the ignition coil. 12V all the way
3. Tried the ignition module from my starboard engine … no luck.
4. Tried another ignition coil. no luck
5. changed the ignition sensor in the distributor to the old one .. no luck
   
6. I checked on the grey cable (for the tachometer) it is connected .. so, it is not grounded
7. I check on the green/white cable from the ignition module (12V) no problem from there... Like I said before I even tried with a known working ignition module.
8. What I cannot find is the Neutral Safety switch that supposes to be at the gear linkage This is a Bravo 2 I think that the switch is on the level control itself

I also checked on the 50 Amp breaker if it was triggered.. nothing there either
Getting a tester to connect to the spark plug to check if I have spark .. if I have spark .. well that it’s something … but I believe that I will not have spark…

suggestion…?


PS. Plenty of Gas, no gas problem. fuel filter clogged, fresh gas. Fuel/ water filter new .. The problem is electric

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PART 2 (updated from last weekend)
************************************************** ******
Ok last Sunday results.

1 All connection from the ignition key switch to the coil were rechecked. 12 Vol all the way to the Coil
2) Checked the spark from the coil to distributor = Strong spark
3) Checked the spark from distributor to the sparkplugs = Strong spark.
4) Checked all connection cables from distributors to ignition module = Everything is plugged right and the correct sparkplugs.
5) Checked pressure cylinder #1 and set TDC = Pressure 120 and made sure that Cylinder 1 was TDC
6) Opened NEW distributor cap to check were the NEW rotor is pointing at TDC. It was pointing to cylinder 6
7) How the time got moved just because replacing new sensors, distributor cap and spark plugs cables … Do not know …
8) This engine was the faithful one never had problem with it, actually started fine after I put the new parts (rotator, distributor cap, ignition sensor and cables) , problem started after it hit the water
9) Set the time back to 1 when TDC .. I can tell the bolt at the distributor was tight as hell so it did not move ..
10) tried to start the engine and just turn over, gasoline getting to the carburetor (actually sparkplug was gasoline wet when I pull the spark plug for Setting TDC ).

Going to turn the engine few times to check if at TDC the rotor still set at location #1 at the distributor .. if not we may assume the timing chain jumped?
Crazy thing is that this engine only have 248 hours.. for a timing chain to jump.. any other suggestion ?

I checked on the 50 AMP breaker, but I think that if the breaker is triggered nothing would work on the engine .. meaning I would not be able to get spark on any sparkplugs ..

For a engine to work just need spark and gasoline and I have both .. I also checked on the oil sensor unit that may shut down the fuel pump .. but I do get gasoline so oil sensor unit theory out the door..

I do not have the neutral switch like alfa1 , I have it on the helm level unit ..and I assume that if the neutral safety switch is bad I would not be able to get spark at the coil and sparkplugs …

Any Idea that is not kill switch (tested), ignition module (tested), coil (tested), sparkplug cables(tested), ignition sensor at distributor (tested) ? Does the mercrusier 4.3 v6 have any other fuses of switch that may create this situation .. ? I am open for any suggestion at this moment ..

Thank you guys

[jrsick]

Marcucho, I just had same problem. The cause of my no-start was a weak starter. It was making the sounds like it was really cranking, but was actually turning the engine at 16 rpm. The slow crank speed resulted in my plugs wet-fouling. I determined it was 16 rpm by recording my spark plug tester with my ipad and realized I had 2 sparks in 15 second starter cycle.
My suggestion:
1. Pull a couple of plugs and see if they are fouled, black, wet, or smell like gas. They should be dry.
2. Count engine rpm for your starter
3. Couldn't hurt to check battery at least 12.4 volts and see what it drops to during start cycle. If it drops below 10V then you may have a starter or ground problem.
4. Try disconnecting wire harness from tach.
Are your carb or EFI? If carb, make sure that fuel squirts from discharge holes in carb venturi when you pump the throttle.

I messed with my problem for 3 weeks. I got lots more suggestions if these first four don't work for you.

[marcucho]

Marcucho, I just had same problem. The cause of my no-start was a weak starter. It was making the sounds like it was really cranking, but was actually turning the engine at 16 rpm. The slow crank speed resulted in my plugs wet-fouling. I determined it was 16 rpm by recording my spark plug tester with my ipad and realized I had 2 sparks in 15 second starter cycle.
My suggestion:
1. Pull a couple of plugs and see if they are fouled, black, wet, or smell like gas. They should be dry.
2. Count engine rpm for your starter
3. Couldn't hurt to check battery at least 12.4 volts and see what it drops to during start cycle. If it drops below 10V then you may have a starter or ground problem.
4. Try disconnecting wire harness from tach.

Originally Posted by jrsick

Are your carb or EFI? If carb, make sure that fuel squirts from discharge holes in carb venturi when you pump the throttle.

I messed with my problem for 3 weeks. I got lots more suggestions if these first four don't work for you.

Engine carburated .. 2 barrel rochester. Battery 13 volts reading. I have a video but I do not know how to upload a video here .. I am going to check again at this point I am taking any suggestion.. thank you .. I checked the battery and shows good voltage .. At this moment going over everything ..

[mmwjr]

You do have a neutral safety switch which if open would prevent the engine from cranking. What the Bravo doesn’t use is the shift interrupt switch.

If you are getting gas and have spark then it must be a timing issue. To see if the timing chain jumped remove the port valve cover and turn 5he crank until the marker is on zero, both valves on cylinder 1 should be closed and the rotor on post 1.

[marcucho]

That is the plan for Sunday..take the cover off to check on the valves piston 1.. when is tdc. Actually, planning to get it back to tdc pointing on 1 and try again to rotate the engine and check if the rotor holds the set on 1 when piston 1 is tdc..

Ok if timing chain did not jump... then what else?

[mmwjr]

Originally Posted by marcucho

That is the plan for Sunday..take the cover off to check on the valves piston 1.. when is tdc. Actually, planning to get it back to tdc pointing on 1 and try again to rotate the engine and check if the rotor holds the set on 1 when piston 1 is tdc..

Ok if timing chain did not jump... then what else?

Remember the cam makes one full rotation per every two full rotations of the crank and the distributor is driven by the cam. I.e. so if you start at TDC and the rotor is on plug one you need to make two full rotations of the crank for the rotor to be back on plug one.

Have you verified the plug wires are in the correct firing order?

[marcucho]

Sparkplugs cables were checked twice , my brother and myself to make sure that we were not missing anything. Planning to check on the Tach cable again ( I made sure that it was not grounded) , but it does not hurt to disconnect the grey cable from the gauge . Planning to recheck on the timing ..

The weird thing is that the engine just stop working after 3 or 4 second when it started on the water... one good faithful engine. I already checked fuel .. we can see fuel at carburetor so oil sensor is working and its no killing the fuel pump. Sparkplug you can tell they are getting fuel. Thats why the suggestion #1 made by jrsick got me curious.

at this moment I am open for any kind of Suggestions.. and Mike I will be making sure that 2 turn on the engine (twice on TDC ) with the valves rested to make sure that it is on TDC.. Then I will turn the engine again and check on the distributor that rotor still pointing to #1.. If not we can tell timing chain needs to be replaced.. crazy thing is that I talked to a mechanic and he told me that on all his years he has never seen an broken or slip time chain on that particular Chevy engine specially with only 283 hours . Oh well there is always a first time.. :-(

Than you guys .. keep them coming any suggestion

[jrsick]

I apologize, I did not read the "last sunday's results" in your post, I thought it was a quote.
So timing is off by one cylinder. Your firing order is 1-6-5-4-3-2 and rotor points to 6 when you are at TDC.
Your timing chain would need to be really loose for it to jump timing. If it were loose, then you should see timing gradually getting worse vice suddenly jumping.
You should be able to fix this by getting back to basics:
- Are you sure you put the rotor on correctly? I just replaced my rotor and had to heat up the new one to get it on the shaft. It would not go on cold. Are you sure it's the right rotor?
- Distributor cap in correct position? It should have a notch on the cap that you line up with the base. What is the numbering on top of the new distributor?
- How are you determining TDC? A technique to determine compression stroke is to cover spark plug hole with your finger.
Let us know results of timing chain check. On my 5.0, the deflection limit is 1/2 inch and replace at 3/4 inch deflection.
What part of NC do you boat out of? I operate mostly out of Southern Shores.

[mmwjr]

I to will be surprised if the timing jumped. It's hard to provide much more insight over the WEB, if you have fuel and spark it must be a timing issue. Unless there is no compression.

[marcucho]

Originally Posted by jrsick

Marcucho, I just had same problem. The cause of my no-start was a weak starter. It was making the sounds like it was really cranking, but was actually turning the engine at 16 rpm. The slow crank speed resulted in my plugs wet-fouling. I determined it was 16 rpm by recording my spark plug tester with my ipad and realized I had 2 sparks in 15 second starter cycle.
My suggestion:
1. Pull a couple of plugs and see if they are fouled, black, wet, or smell like gas. They should be dry.
2. Count engine rpm for your starter
3. Couldn't hurt to check battery at least 12.4 volts and see what it drops to during start cycle. If it drops below 10V then you may have a starter or ground problem.
4. Try disconnecting wire harness from tach.
Are your carb or EFI? If carb, make sure that fuel squirts from discharge holes in carb venturi when you pump the throttle.

I messed with my problem for 3 weeks. I got lots more suggestions if these first four don't work for you.

Originally Posted by jrsick

I apologize, I did not read the "last sunday's results" in your post, I thought it was a quote.
So timing is off by one cylinder. Your firing order is 1-6-5-4-3-2 and rotor points to 6 when you are at TDC.
Your timing chain would need to be really loose for it to jump timing. If it were loose, then you should see timing gradually getting worse vice suddenly jumping.
You should be able to fix this by getting back to basics:
- Are you sure you put the rotor on correctly? I just replaced my rotor and had to heat up the new one to get it on the shaft. It would not go on cold. Are you sure it's the right rotor?
- Distributor cap in correct position? It should have a notch on the cap that you line up with the base. What is the numbering on top of the new distributor?
- How are you determining TDC? A technique to determine compression stroke is to cover spark plug hole with your finger.
Let us know results of timing chain check. On my 5.0, the deflection limit is 1/2 inch and replace at 3/4 inch deflection.
What part of NC do you boat out of? I operate mostly out of Southern Shores.

I used a cylinder pressure test tool (120 on Cylinder 1) to determine TDC. I bough the same tuning kit and installed on the starboard engine (which used to be my problematic one ) and its working like a champ. All the part are the same . I even reinstalled the old distributor ignition sensor back just for in case the new one was bad .. and did not make any different . Anyways. I am just waiting for this Sunday that going back to the boat to redo the TDC checking on the valves that both of them we set at rest and pressure on the
piston #1 is back to 120 .. (2 turns on the engine) get the distributor rotor back to position #1 ( I am glad that I have distributor location marked well on the engine area that meet the distributor ) because it has to go up and down very careful to set the rotor back to position 1..

After the rotor is set on 1 with TDC.. I will turn the engine 2 or 4 times to see if the rotor keep the position 1 at TDC .. if the rotor moved after 4 turns on the engine will indicate that timing chain is jumping. BUT

Here is the question what about is everything stay the same .. in other words rotor still at position 1 @ TDC..?

If that the case that timing chain is OK.. then I will go to remove the tachometer connection from the gauge ... try again and if the problem still there .. then I will change the ignition switch with the starboard one that iots working just fine ... I read somewhere that a person was having problem with the engine no working even getting 12V at the ignition coil, but he replaced the ignition switch and problem solve.. Well I am long way to get there and it is hard to believe , BUT at this point I will try everything .

Another think that I would do if even with the ignition key switch does not work ,,then I would replace the oil sensor unit.. which may cut off the gasoline pump for safety ... I doubt the oil sensor is the issue because I can see the gas flowing at the carburetor... Engine did not even start with starting fluid .. but guys I getting out of options so I have to try with anything that I can ...

I was in Beaufort area last year but I moved boat back to Raleigh due to Florence, now I could not find a place in the marina where my boat was due to the storm and they have not fixed the docks yet .. so I had to bring the boat to Kerr Lake.. I do not even know the lake yet .. because the engine decide to quit as soon as it hit the lake water .. maybe its complaining hehehe


Thank you guys for all the help ..

[mmwjr]

A better way to see if the timing chain has too much slack is to rotate the engine clockwise until it’s on TDC then rotate it counterclockwise and see how many degrees the crank moves before the rotor turns. Should be no more than a degree.

When starting the fuel pump gets power from the starter soleniod and the oil pressure switch doesn’t come in to play until the engine is running.

[marcucho]

Originally Posted by mmwjr

A better way to see if the timing chain has too much slack is to rotate the engine clockwise until it’s on TDC then rotate it counterclockwise and see how many degrees the crank moves before the rotor turns. Should be no more than a degree.

When starting the fuel pump gets power from the starter soleniod and the oil pressure switch doesn’t come in to play until the engine is running.

Mike ,

Thank you for the tip on the timing chain .. Will use it this Sunday

[marcucho]

Ok This was my Father's day ...back from the boat ..

1) Checked timing = TDC on piston #1 and rotor kept position on #1, Piston pressure 120.
2) Great to know that timing chain did not jump. Beside the pressure test I had to remove the valve cover to make sure that both valve were set .
3) Check spark from the coil to distributor (STRONG spark),
4) Check for spark on each spark = GOOD spark
5) disconnect the tach from the gauge = did not make a different
6) changed ignition switch with my working engine (starboard side) did not make a different ( I knew that it was not the ignition switch because I have power at the coil and good spark, but no leaving anything to test
7) remove the + cable from the coil, I jumped the coil straight from the battery positive + to the coil. Still no run .
8) Fuel is plenty coming to carburetor
9) used starting fluid no luck
10) No play on the timing chain … THANK GOD
11) set on BOTH battery switch to get full power from 2 good working power to start the engine … no luck
12) pulled distributor out to check on the gear ( it is fine)
13) check in the camshaft for broken gear parts ( I have endoscope camera … no broken part )


Now only thing left is ... oil sensor unit. I know that would kill the fuel pump if there is not oil pressure , but that it is after the engine started.. would the oil sensor unit .. (actually 2 on the 4.3 L .) one close to the oil filter at the block and another one behind the distributor would cause the engine not to run ?

I do not have anything else to test .. PLust I have spark , fuel and good compression so I do not know what else to look for ...

Thank you guys ..

[jrsick]

Did you take a look at each spark plug? Were any wet or black? Were they all dry?
If plugs are good, then I rec you check the fuel. One way to check fuel is to disconnect the fuel inlet at the carb and connect a hose to the fuel line. Cycle the starter and pump some fuel into a clear jar and let it sit overnight. If you have water in jar the next day then fuel in tank is contaminated.
If you don't have any water in the jar, then get another jar and pour approx. the same amount of water in the second jar as you have fuel in the first jar. Mark the water level with a marker, then pour the fuel into the second jar. Shake this up really well and let it sit overnight. If water level is above the mark on the jar then you have water in the fuel. I hope this makes sense.
I'm thinking your problem is either spark plugs or bad fuel. Since it suddenly stopped working, I"m leaning toward fuel.
Starter turning the engine good?

[mmwjr]

The oil pressure sensor near the distributor is for the helm gauge and the sensor by the filter is the oil pressure switch that provides power to the fuel pump once the engine is running. Again the fuel pump gets power from the engine starter when cranking. You say plenty of fuel, could it be too much flooding the engine? Try advancing the throttle all the way open and leave it there then try to start the engine. If the carb is flooding the wide open throttle will help lean the mixture out. You can try swapping carbs.

[marcucho]

Originally Posted by jrsick

Did you take a look at each spark plug? Were any wet or black? Were they all dry?
If plugs are good, then I rec you check the fuel. One way to check fuel is to disconnect the fuel inlet at the carb and connect a hose to the fuel line. Cycle the starter and pump some fuel into a clear jar and let it sit overnight. If you have water in jar the next day then fuel in tank is contaminated.
If you don't have any water in the jar, then get another jar and pour approx. the same amount of water in the second jar as you have fuel in the first jar. Mark the water level with a marker, then pour the fuel into the second jar. Shake this up really well and let it sit overnight. If water level is above the mark on the jar then you have water in the fuel. I hope this makes sense.
I'm thinking your problem is either spark plugs or bad fuel. Since it suddenly stopped working, I"m leaning toward fuel.
Starter turning the engine good?

I just filled up the gas tank with fresh fuel.. I will do the test no matter what .. weird thing is that my other engine which is getting fuel from the same tank is running fine .. oh well. At this point I am doing anything that may help me to find the fix.. Planning to remove the sparkplugs to let them dry because every time that I turned the engine I am sure that I have fuel on the piston so the sparkplugs are going to be wet .. need to let them drive..

[jrsick]

After you dry the plugs, try starting with the throttle in neutral. Don't pump it at all.
If it doesn't start, check your plugs again. If they are wet then likely time for carb rebuild.

[marcucho]

Ok. Checked again on sparks.. I do have spark at the sparkplugs as I checked again. I also noticed that my oil gauge was not working. I replaced both oil sensors a the oil filter area. I got now good oil pressure reading. Then I tried to run the engine and it just crank and nothing to start ... I disconnected the cable to the ignition module for who knows .. maybe it needed to be reset so it learns the new signal from the oils sensors I replaced... (guys I just doing stuff here and there because this situation has logic) .. so I connected the ignition module and nothing still crank and not starting ..

I use starting fluid .. I know that there is plenty of gas , but Hey.. I want it to start.. with the starting fluid still the same. I checked the sparkplugs .. they were dry and clean . I was expecting to find them wet , but not there were dry and of course if you smell them, they do smell like gas .

I checked all the cables around the distributor and they are connected. K=Lik I said I have sparks.

So I have sparks and using starting fluid ( just talking craziness here because I know that the fuel pump is working) the engine should star at least for few seconds...

Tomorrow I will switch the Ignition module from my starboard engine to see if the engine start ... I did that before swapping ignition module and did not make a different , but I had the bad oil sensors unit that time so now I am doing it again with good oil pressure reading.

I also move my level forward and reverse to make sure that if there is any neutral safety switch on the level box could be reset. I also now that the neutral safety switch would not allow to crank if it is activated. So we could assume the switch is good.

P.S. the oil sensors picture is upside down

[mmwjr]

Since you have spark the run/stop (kill) switch must be in the run position but try cycling it anyway to ensure it's in the run (on) position.

[jrsick]

Thanks for the update. I appreciate your frustration, I've been there.
What I would do:
- Replace the spark plugs. Make sure new ones are gapped correctly and check gap of old plugs just for info. Try two 15-second start cycles with new plugs. If that doesn't work:
- Loosen distributor bolt and try a 30-second start cycle while moving distributor from current to old setting. Be sure to mark current setting. If that doesn't work:
- Switch carbs and try to start with known working carb.
Your spark plug looks like you have a rich fuel mixture or weak ignition.
You could have potentially started with a carb problem, then added an ignition problem with the timing adjustment.
Have you tried an HEI tester, or are you using spark plug electrodes to determine there is spark?