Mercruiser 5.0 v8 no ignition

[dlogvine]

I got mercruiser 5.0 v8 engine completely rebuild and installed it on Larson 93 boat. Connected the battery and cranked it. It turns, but no spark or ignition. I installed a new distributor cap, spark plugs and spark plug wires. What should I check to see if there any spark happening? Thx

 

[bruceb58]

Did you check your man overboard switch?

 

[dlogvine]

yep I was pushing it all the time, but there was no spark and you can hear this. The engine turns but no ignition. Will try to drop a little gas tommorow, currently im recharging the battery, will start over tomorrow again.

 

[achris]

You can't 'hear' no spark. Confirm you have no spark, then troubleshoot it. To help, read THIS document.

 

[dlogvine]

Actually, even in your troubleshooting guide it says: A good spark if a health blue one that you can hear go 'crack'. A yellow spark is weak and may not fire a fuel charge properly.
But thank you very much, I'll go through the troubleshooting steps.

 

[Bt Doctur]

stick your tongue on it, you`ll know for sure if you have any spark.
You forgot a key component in the rebuild?

Is there 12v at the + side of the coil?
Does the motor turn in the proper direction
Is the firing order correct and was the dist installed with #1 at TDC compression
Are all the harness wires connected

 

[achris]

Actually, even in your troubleshooting guide it says: A good spark if a health blue one that you can hear go 'crack'. A yellow spark is weak and may not fire a fuel charge properly.
But thank you very much, I'll go through the troubleshooting steps.

That reference is to a spark plug laying on top of the engine, not buried inside a combustion chamber.

 

[dlogvine]

I tested the spark plug outside,there was nothing...

 

[bruceb58]

I tested the spark plug outside,there was nothing...

You have the spark plug grounded?

 

[Fishermark]

I'm surprised no one has asked yet - what are you working on - what ignition system? Points? Electronic?

 

[bruceb58]

I'm surprised no one has asked yet - what are you working on - what ignition system? Points? Electronic?

Since it's his 1993 Larson, I am guessing it's the original TB4.

 

[dlogvine]

Got it running, there were a couple problems. The main problem was a bad alternator, it was shutting the circuit breaker, so I replaced the alternator and started cranking. Secondly, the fuel lines to the fuel pump were loose and was sucking some air and after tightening the connectors, got fuel into the carburator. Still had to adjust the rocker arms, Olsen them up a couple turns and there it was, coughing and ready to go. Still had to adjust the distributor a little and it is purring like a big happy cat. All thanx to my friend and his lucky touch.

 

[dlogvine]

crap, checked out the oil in the heads, was all milky, getting water in. Suspect it coming from the riser elbow gasket, was kinda old looking in an old wrinkled cover when I got it online. drained the oil from the pan, tried to clean and flush the engine with the diesel fuel. the oil in the pan was not too milky and we checked out the compression, every cylinder was at 150psi, so looks like we dodged the bullet. Question is, what can I use to clean up the engine from the remaining watered oil? We are planning to let the diesel all drain till tomorrow, fill the engine with the new oil, put a bew filter, unplug the water hoses from the manifold, keep the water only to the intake and let it run a little to see if there is any water leak left. if there is, then we will look for the intake gaskets and possible head cracks. also the head cracks are unlikely, since one was checked at the shop and the other was replaced at the same shop. if there is no water, than it means the riser elbow gasket was bad and we will flush the oil, use the engine flush and seafood, change the gaskets and put the engine back together.

 

[Scott06]

In addition to what you mentioned - If you reused the intake they can rot out under the thermostat, head bolts may also need sealant. Did you find water in the combustion chambers? If risers were leaking you'd see water on the spark plugs. Would be worth dong a cooling system pressure test drive to se if you can isolate where it's leaking..

 

[Bondo]

crap, checked out the oil in the heads, was all milky, getting water in. Suspect it coming from the riser elbow gasket, was kinda old looking in an old wrinkled cover when I got it online. drained the oil from the pan, tried to clean and flush the engine with the diesel fuel. the oil in the pan was not too milky and we checked out the compression, every cylinder was at 150psi, so looks like we dodged the bullet. Question is, what can I use to clean up the engine from the remaining watered oil? We are planning to let the diesel all drain till tomorrow, fill the engine with the new oil, put a bew filter, unplug the water hoses from the manifold, keep the water only to the intake and let it run a little to see if there is any water leak left. if there is, then we will look for the intake gaskets and possible head cracks. also the head cracks are unlikely, since one was checked at the shop and the other was replaced at the same shop. if there is no water, than it means the riser elbow gasket was bad and we will flush the oil, use the engine flush and seafood, change the gaskets and put the engine back together.

Ayuh,.... Milky snot under the valve covers is condensation from runnin' a cold motor,....

Runnin' up to temp will steam it off,... No more problem,...

If there's no water in the oil pan, 'n the oil level ain't risin', ya Don't have a leak,....
If it were the exhaust riser gaskets, it'd blow out the exhaust, not get into the oil of a runnin' motor,...
That leak can only fill the oil pan, after the motor has been run, 'n shut down for along enough time for the water to leak past the piston rings,...

'n Don't run the motor without water goin' into the exhaust,....
It'll run Way hot, 'n burn up all the rubber parts in the exhaust system, like shutters, 'n boots,....

 

[dlogvine]

Ayuh,.... Milky snot under the valve covers is condensation from runnin' a cold motor,....

Runnin' up to temp will steam it off,... No more problem,...

If there's no water in the oil pan, 'n the oil level ain't risin', ya Don't have a leak,....
If it were the exhaust riser gaskets, it'd blow out the exhaust, not get into the oil of a runnin' motor,...
That leak can only fill the oil pan, after the motor has been run, 'n shut down for along enough time for the water to leak past the piston rings,...

'n Don't run the motor without water goin' into the exhaust,....
It'll run Way hot, 'n burn up all the rubber parts in the exhaust system, like shutters, 'n boots,....

The problem was definitely in the water leaking inside of the intake. There was some water in combustion chambers and when we removed the spark plugs and cranked the engine, the water was pushed through the spark plug gaps. There was not much water ion the oil pan though. Btw, according to the cooling system diagram (I can make a pic and post) leaking water from the elbow/riser manifold gasket goes into the intake and not into the oil pan.
We ran the engine with the exhaust manifolds hooked up but no elbows, all the water going through the engine went into the boat and drained through the drain hole. Oil remained clean and no spots. So the suspected problem remained in the manifold/elbow gaskets. Yesterday I resurfaced and polished the edges of both and put the gasket on the permanent gasket maker. Assembled the risers, tightened the bolts, will check today.

 

[Bondo]

Btw, according to the cooling system diagram (I can make a pic and post) leaking water from the elbow/riser manifold gasket goes into the intake and not into the oil pan.

Ayuh,.... 'n that doesn't put it in the valve covers,....

 

[dlogvine]

Ran the engine today, no water in the oil, oil clean and nice. Also fixed the oil pressure warning. The shop put the plug in the place of a sensor and I plugged the second oil pressure sensor instead of the plugged hole into some lug hole an inch higher. Wasn't getting any reading from this sensor obviously. Instead we're getting a warning beep. Had to use a powerful flashlight and discovered my mistake. Now the engine runs as well as a new one, which it essentially is. One problem left is in the tachometer gauge, shows no life. Will take it out tomorrow and take it to the shop to test. If it is good will have to go through the wires and find the broken link.

 

[QBhoy]

Risers and manifolds leaking water will definitely result in milky emulsified crud under the valve covers.

 

[dlogvine]

Finally got it all together! Runs like a clock, nice and strong