Mercruiser 3.0 LX wont start after turning engine off. Video

[Berget80]

Hi.
Swedish so excuse my bad english.
Was out on a trip for a couple of hours. Engine ran fine. Then after i turned it off it did not start again. Had to be towed back. I know nothing about engines but ive hade some friends look at it. There is fuel coming up to the carb. When you loosen the fuel line and pump you see fuel coming out of the pipe. Ive changed the sparkplugs and I got a spark on all four plugs. Can it be The ignition coil?
Any ideas on how to move forward would be appriciated. The summer is to short in sweden.
View attachment received_791521175885982.mp4

 

[Berget80]

Forgot to mention it doesnt start with starter fluid either.

 

[Scott06]

Do you have spark coming off the coil? Take wire from coil of center of distributor cap and put near a ground and crank? Do you have spark? If you do have spark take distributor cap off and see if cap and rotor are ok.

Look down carb when you pump the throttle does it shot gas in?

 

[PosessionSound26PC]

I just dealt with something VERY similar on my 4.3 LX - I went to winterize, warmed up my engine, turned it off because I forgot the fogging oil, came back and couldn't start it again for months as I was trouble-shooting it during the winter. I also had spark and gas and I tested the resistance of my coil across its terminals to make sure it was within specs. My specs were here:

Sierra 18-5438 Ignition Coil | Wholesale Marine

Sierra 18-5438 Ignition Coil available at Wholesale Marine. We offer Sierra Marine products at lowest prices with superior service.

www.wholesalemarine.com

For me it turned out to be a somewhat clogged/dirty carb or fuel filters. My boat has been sitting for a couple of years and even though I put Stabil in the gas tank, I think the carb and filters get dirty/gummy regardless. I noticed that when cranking, the motor WANTED to start sometimes - you could tell some gas was getting in there and was igniting. Does yours do that or is there no sign of combustion? You can watch your tach and see if it's slightly higher some times vs others.

Usually, I give the throttle a little bump before cranking so I decided to also open up the throttle to 1/4 when cranking. I immediately noticed that the RPMs during cranking were HIGHER! It wanted to start even more. I opened up the throttle to 1/3 and it almost started and at 1/2 it started. I had to be careful to quickly pull the throttle back once it started up. I haven't FIXED the problem yet completely because I still have the old gas in there and haven't replaced the filters yet but at least I know how to start it. Maybe check yours for similar.

 

[Berget80]

Do you have spark coming off the coil? Take wire from coil of center of distributor cap and put near a ground and crank? Do you have spark? If you do have spark take distributor cap off and see if cap and rotor are ok.

Look down carb when you pump the throttle does it shot gas in?

Forgor to mention. We tried a friends rotor and cap who had The same engine. My cap really looked like it needs a replacement. But it Was no difference with his. Im also starting to suspect that The carb is clogged. The fuel filter looked ok but there Was alot of dirt in The cap that holds it.

 

[Scott06]

Forgor to mention. We tried a friends rotor and cap who had The same engine. My cap really looked like it needs a replacement. But it Was no difference with his. Im also starting to suspect that The carb is clogged. The fuel filter looked ok but there Was alot of dirt in The cap that holds it.

Ok check for spark off of coil. if you dont have it look for 12v on positive side of coil when cranking. Would be more likely that the ignition module is bad than the coil is.

This is the Delco EST troubleshooting guide https://f01.justanswer.com/oldnewenglandmarine/814bd65a-9279-41cd-a8bc-1a5f5bb74266_Delco+EST.pdf

 

[Berget80]

Thx alot guys. Will check your suggestions tomorrow.

 

[1985 Century Mustang]

Did you pull your plugs and inspect them? They could be fouled.

 

[Berget80]

Did you pull your plugs and inspect them? They could be fouled.

Yeah i changed all the plugs.

 

[PosessionSound26PC]

Yeah i changed all the plugs.

Not sure about your boat but mine has two filters - one at the mechanical fuel pump (maybe yours is electric?) and one at the carb where the metal fuel line goes in. They are both cheap and easy to replace - haven't done mine yet but have them and will do soon. Good luck!

 

[Berget80]

Update.
Engine is still dead.
Tried another ignition coil, ignition module and replaced the pickup coil.
Did a compression test and that was ok.
Disconnected the gear switch.
Feels like the only thing left is to set The timing from scratch.
But seems strange that it would go bad from one minute to another.
But i got fuel and spark, still doesnt start on starter fluid either.

Any ideas anyone?
Im runnning out of them.

 

[Scott06]

Update.
Engine is still dead.
Tried another ignition coil, ignition module and replaced the pickup coil.
Did a compression test and that was ok.
Disconnected the gear switch.
Feels like the only thing left is to set The timing from scratch.
But seems strange that it would go bad from one minute to another.
But i got fuel and spark, still doesnt start on starter fluid either.

Any ideas anyone?
Im runnning out of them.

Would think you have a weak spark or no compression

As a sanity check do a cold compression check to make sure there are no dead cylinders

Also check with spark gap tester that you are not loading spark from coil to distributor to plugs

You can retime it by putting at tdc on 1 cylinder or at least turn the engine to see timing is in the ballpark but would think if timing is off yiu would get a cough or backfire

Not lighting on starter fluid tells me the spark is too weak

 

[Berget80]

I did a compression test and all cylinders was close to eachother.
What do you think could cause a weak spark? Feels like ive tried everything in ignition way.

 

[Scott Danforth]

It's never the coil

 

[Scott06]

I did a compression test and all cylinders was close to eachother.
What do you think could cause a weak spark? Feels like ive tried everything in ignition way.

if you have compression, fuel, and spark i should cough or run momentarily… especially if u dump a little gas down carb , or starting fluid like u tried. So im thinking spark is too weak to fire it off.
get a cheap spark gap tester like this. https://www.amazon.com/Lisle-20700-...ocphy=9007343&hvtargid=pla-570785920751&psc=1

test on hi voltage wire coming off coil, should jump 1/4” if not 3/8 “ and be blue not orange or yellow. Test on each plug see if you are loosing spark in distributor .

if you have compression, dump gas down carb, if there is spark even if timing is off you would get a cough or backfire. Getting nothing makes me think you dont have spark or have spark at coil but are loosing it in distributor.can also try turning distributor while cranking to play with timing , mark it you can always put it back where it was

 

[Berget80]

Todays update.
IF I pull one of the plugs out the engine starts with no problem. Works with all combinations, 124, 134, 234 etc. But not with all the plugs in. Tried to screw in The last plug with engine running but then The engine dies again. That might be a bad idea, i know. IF it didnt die when puttning the fourth in i would suspect that the starter is bad and dont have power to crank with all plugs in.

 

[Scott06]

Todays update.
IF I pull one of the plugs out the engine starts with no problem. Works with all combinations, 124, 134, 234 etc. But not with all the plugs in. Tried to screw in The last plug with engine running but then The engine dies again. That might be a bad idea, i know. IF it didnt die when puttning the fourth in i would suspect that the starter is bad and dont have power to crank with all plugs in.

Probably not the starter but more likely the battery and condition of the cables both positive and negative.

So it cranks slow unless you leave a plug out?

 

[Berget80]

Probably not the starter but more likely the battery and condition of the cables both positive and negative.

So it cranks slow unless you leave a plug out?

In the boat now. Atm i got 3 batteries connected.

 

[Scott Danforth]

Check the block ground

 

[ba5e]

Definitely sounds like voltage drop, how many CCA’s has your starter battery? If you have a multimeter, measure the voltage drop when cranking