5.7 has spark question

[achris]

Sounds like the coil or a bad ground somewhere.

The sensor is basically an ON/OFF switch. If the sensor fails, no spark at all. It can't 'half fail'. . Very easy to swap the coils across the engines, so that's definitely what I'd do first. It could be the ignition amplifier (the switch box), but unlikely as they usually work or not work. Poor spark can also be a bad rotor (which you have replaced. BTW, it's not a bad design. The rotor is loctited in to reduce vertical float. They very very rarely fail). Bad contacts on the distributor cap (also replaced) or a bad wire (did you replace the coil -> cap lead?)...

Chris.......

 

[Mild 85]

Well, I set spark gap tester at 7/16" plugged it into couple different plug wires and grounded other end to block. It sparked white but wasn't consistant.

 

[alldodge]

Well, I set spark gap tester at 7/16" plugged it into couple different plug wires and grounded other end to block. It sparked white but wasn't consistant.

Even with that the motor should hit, even for a moment, and with either there would be no doubt. You said both engines get fuel from the same tank and same connection. Same connection tells me a Tee of some sort. I'm thinking fuel supply, but then again no hit with either

 

[Mild 85]

I've worked on engines in machinery and in Gas compressors in nuclear power plants all my life and never seen anything like this. Im a ford guy so in the back of my mind I keep thinking god is punishing me for buying a GM product

 

[alldodge]

Guess it's time to sell the boat and buy one with Indmar motors, but they are all ski/wake boats. Find a real old boat with Ford motors, or go all out and go diesels

 

[Mild 85]

Guess it's time to sell the boat and buy one with Indmar motors, but they are all ski/wake boats. Find a real old boat with Ford motors, or go all out and go diesels

I cant give up that easily.

 

[alldodge]

I cant give up that easily.

That's the sprit, come over to the dark side, it's real nice over here :flame: :tape2:

 

[Mild 85]

The only thing I haven't done is swap coils. I will do that this evening

 

[Scott Danforth]

I would pull the plugs and check if they are wet or oil fouled. if so, dry them off or replace.

 

[Mild 85]

can a coil from a automotive engine be used if it is bad?

 

[Mild 85]

Swapped coils and high tension lead

Nothing

 

[alldodge]

I'm still with fuel supply

 

[alldodge]

If you would humor me, take a rag or paper towel and stick it partly down the throat of the carb. Pump the throttle a few times and then take the rag off the boat. First smell the gas and see if it smells like gas. Take the rag/towel and lay on the ground then take a lighted match/lighter and see how close you can take the flame before it ignites.

Only reason I'm saying this is the motor will not fire with either, and you have spark. just does not add up

 

[Mild 85]

I went to get some wings I will when I get back to boat

 

[Mild 85]

Rag lit when lighter was 1/2" away

 

[alldodge]

Can you agree
The gas smelled like gas
There is only one feed which feeds both engines

Compression while maybe a bit low should not be an issue. Even either does not change anything. There is spark, while may not be real steady the motor just cranks, does not even try to hit once,

If all this is true, I got nothing, it does not add up.

If you were within 2 hours of me I would drive down to help, but your an all day drive in one direction

 

[Mild 85]

It does sound like it trying a little but very faint. Do marine engines have any kill switch, knock sensor shut off. Odd ground feed that I could jumper or test?

 

[alldodge]

It does sound like it trying a little but very faint. Do marine engines have any kill switch, knock sensor shut off. Odd ground feed that I could jumper or test?

If a kill switch was involve it would crank but there would be no spark, you said your getting spark.

 

[Mild 85]

The port side engine dose turn over slightly slower when cranking starter. Could it be that?

 

[thumpar]

Since you have twins you can swap parts. If the timing was off you would still get something. It could be 180 degrees out and still make a bang. Compare the 2 engines. Do they both have the same spark at the plug (not tester)?