1996 5.7LX sputters but wont start!!!!

[Marada20]

Hi, I am back to boating after a few years off. I have a 1996 Mercruiser 5.7LX ser#OF769749 and Alpha gen 2 Ser#6957281. Just bought this boat, Lake tested adn it ran great, but it was very dirty. So I power washed everything. I did stay away from the engine and cleaned it by hand. I also replaced the impeller. After shop Vacuuming up excess water in the carpet and bilge It started right up and pumped water like it should.

It ran at idle for about a minuet and died. I did not fill the upper reservoir with drive oil so the alarm was on and I was trying to figure that out when it died. Filled the reservoir up and alarm off when cranking but it wont start. It seems to fire and spit up thru the carb when I stop cranking.

Being a new boat to me I then check and cleaned all electrical connections I could find. Under the distributor cap was clean and dry. I don't know where to go from here. This may be unrelated but in cleaning the bilge the bilge pump came apart and does not work anymore.

Thanks for any help and advice you can give me.

Doug

 

[Don S]

Re: 1996 5.7LX sputters but wont start!!!!

Look on the block just above the oil filter block mount. there should be a pressure switch there that controls the fuel pump. See if the wires may have been knocked off or corroded off the switch.

 

[Marada20]

Re: 1996 5.7LX sputters but wont start!!!!

Fuel pump wire is ok.

No voltage at coil with key in on position or cranking, but I get 11.7 volts when I stop cranking for just a second. Probably why it tries to start at the end of cranking.

I have two grey wires on the negative side and two purple on the positive side of coil (Thunderbolt V ignition). I removed the hours meter wire (purple) and no change. The other purple wire has 12v with the key on but not when connected to the coil??? The negative side does not appear to have continuity with engine ground.

Where to go from here??

Doug

 

[Marada20]

Re: 1996 5.7LX sputters but wont start!!!!

I cleaned more wires and connections. There was a lot of corrosion at several connectors.

I now have 10.5 volts at the coil before cranking, and 8.5 while cranking.(currently charging the battery). still no change. I will check the plugs as the engine probably flooded trying to start so many times.

Any other advice???

Thanks Doug

 

[dubs283]

Re: 1996 5.7LX sputters but wont start!!!!

Any other advice???

check for spark at the coil tower while cranking, when your battery is fully charged of course

 

[Marada20]

Re: 1996 5.7LX sputters but wont start!!!!

I am going thru the Thunderbolt V flow chart for troubleshooting.

I have 11.4 volts at the coil (key on w/good battery)

10.2 volts at the red and white wire going into the distributor (key on w/good battery).

12v at the battery. Are these voltages too low???

How do you properly check for spark at the coil tower?

Plugs are black and sooty but not wet with gas.

Thanks Doug

 

[dubs283]

Re: 1996 5.7LX sputters but wont start!!!!

How do you properly check for spark at the coil tower?

with a spark tester between the coil tower and a good ground - if you don't have one probably a good idea to purchase one, shoudl be able to track down at an auto parts store or online

the shade tree method is to just hold the cap end of the coil wire close to a good ground and crank the motor, see if a spark jumps the gap

those voltages are probably okay, you are looking for zero volts or less than 1 volt at those locations to indicate a problem

 

[Marada20]

Re: 1996 5.7LX sputters but wont start!!!!

Raining again. can't get any work done. Plugs are bad two were cracked and rusted.

1/2 way to replacing when it down poured.

I do have spark at the old plugs.

Try again once rain stops.

Thanks Doug

 

[Marada20]

Re: 1996 5.7LX sputters but wont start!!!!

Ok, new plugs in, and found purple and yellow wire that broke loose down by the alternator.
The loose wire was joined together with a purple wire using a blue (what I call trailer connector. 2 into 1 wire). Both wires connected to the black wire going into the alternator.

Boat started and ran like a Harley only firing on just a few cylinders.

Instead of removing just the purple and yellow wire, I disconnected both the purple and yellow and the solid purple wire from the black wire coming out of the bottom of the alternator.

The motor cranked 1 revolution and started immediately and idled smooth??? Great, my battery shows 13.6v and appears to be charging.

My alternator got wet during the cleaning, as the carpet next to it was very dirty.

Does anyone know why disconnecting the black alternator wire would make my engine run so well??

Thanks

Doug

 

[Marada20]

Re: 1996 5.7LX sputters but wont start!!!!

I do not have an electric fuel pump. My fuel tank sits beside the engine and the fuel line goes thru the fuel filter to a fuel pump mounted on the front starboard side of the engine below the fuel filter mounted to the block (no wires to it). My alternator does not look like the diagram. I have only a red and black wire a the bottom both going in at a black connector, and an orange wire.
Some where between the lake test and picking the boat up the next day the purple unused wire got plugged into the black alternator wire, and the I stupidly added the purple yellow wire because it was right there and stripped. I think the connector was for just the purple to purple yellow. They are not connected at this time and the boat runs great. The black alternator wire is not connected to anything. Should I just cap these wire off?? Thanks for your help. Doug