Carbureted 5.7 merc, no fire

[dirtbagchaser]

Hello all. Have a 1993 carburated 5.7 with thunderbolt 4 ignition that is in a searay 220 br. Last weekend had it out and ran great. Shut off at the dock waiting to trailer and then would not start. Worked on for a while out of water, still no start. Changed Coil, cap/Rotor, pickup sensor. Wires and plugs. Getting spark to all 8 cylinders. Getting fuel and obviously air flow with the breather off. Cranks just fine, but getting no fire at all. Any help to diagnose would be great! Engine serial number: 0F012178

 

[alldodge]

Getting spark to all 8 cylinders. Getting fuel and obviously air flow with the breather off.

Takes fuel, spark and compression for motor to run. State your getting all and motor will not run.

Your not getting one of the 3

If you are getting spark then it's either flooding or bad fuel.

 

[dirtbagchaser]

Takes fuel, spark and compression for motor to run. State your getting all and motor will not run.

Your not getting one of the 3

If you are getting spark then it's either flooding or bad fuel.

Tested spark at Coil, distributor and wires. Forgot to pull and check each plug for spark but will do that tomorrow evening. Plugs are brand new and gapped at .035. Can see fuel going into carb and also tried ether. Still no fire. Any thoughts on timing maybe?

 

[Scott06]

Tested spark at Coil, distributor and wires. Forgot to pull and check each plug for spark but will do that tomorrow evening. Plugs are brand new and gapped at .035. Can see fuel going into carb and also tried ether. Still no fire. Any thoughts on timing maybe?

can the spark jump a 3/8" gap on a simple spark tester? if it doesn't cough on ether would suspect you don't have a strong enough spark. Rarley the coil but would ohm it out.

You say you had spark at wires do you mean wires coming out of cap? Are you sure you are not loosing spark inside distributor? good connection between rotor and cap?

Checked compression on all 8 cylinders?

 

[alldodge]

Can see fuel going into carb and also tried ether.

Your not getting spark

Any thoughts on timing maybe?

It's not timing, if it was off it would fire or back fire but either way their would be some kind of combustion

Try a cheap spark gap tester and/or run through this test

 

[dirtbagchaser]

Your not getting spark


It's not timing, if it was off it would fire or back fire but either way their would be some kind of combustion

Try a cheap spark gap tester and/or run through this test
View attachment 379850

Yeah I'm getting no fire at all. We initially thought it was Coil because all ran just fine until shut down. Since then I've changed almost all ignition components. Appreciate the flow chart and feedback..i will hit that list tomorrow evening and report back

 

[dirtbagchaser]

Yeah I'm getting no fire at all. We initially thought it was Coil because all ran just fine until shut down. Since then I've changed almost all ignition components. Appreciate the flow chart and feedback..i will hit that list tomorrow evening and report back

alldodge had the correct answer. After further investigation and some assistance from someone who knows more of what they are doing, we determined that it was flooding. We were able to get started only by opening throttle wide open to get more air. Once excess fuel burned off she ran just fine. We plan to adjust fuel air mixture this weekend and see how things go before rebuilding carb. Thanks to all for the responses, it helped narrow some things down!

 

[Scott06]

When you are running at idle look down carb bores to see if fuel is weeping off the booster or bowl is over flowing. Either would be indicative of needle/seat/float issues or too much fuel pressure.