motor will not start - need help

[aggie9498]

I have replaced the coil, points, condenser, spark plugs, battery, battery cables and ignition switch. It does have fuel getting to the plugs and there is compression, it just will not fire up.

I have a 140 hp mercruiser 4-cylinder '83 Galaxy I/O.

[sbsboats]

I don't know your particular engine ...however all engines have the same basic needs ....fuel ...which you have...air...clean filter unblocked intake and carb...and spark
you have replaced a lot of ignition components ...have you checked for spark?? and have you checked for spark at the appropriate time? TDC?

take out a plug ...ground it and crank the motor ...tell me what you see at the spark plug gap

[TerryKing]

Originally Posted by sbsboats

take out a plug ...ground it and crank the motor ...tell me what you see at the spark plug gap

Aggie, if you definitely have spark at the plugs like sbsboats said, and fuel , and it doesn't even cough, then there's something very unusual happening. Like the distributor gear has jumped, or the timing chain has jumped. I've only seen this rarely, in cars. You may have to go back to square one, turn the engine to Top Dead Center on cylinder one, and check that the valves are closed, and the distributor is pointed right at cylinder one's wire etc.

[Fanie]

I agree with Terry - if there's spark, fuel and the timing is right to the nearest lamp pole the engine MUST start.

[USCGRET/E8]

Originally Posted by aggie9498

I have replaced the coil, points, condenser, spark plugs, battery, battery cables and ignition switch. It does have fuel getting to the plugs and there is compression, it just will not fire up.

I have a 140 hp mercruiser 4-cylinder '83 Galaxy I/O.

If it doesn't have spark, check your shift cut out switch. If you don't know what that is, bring this site up: http://forums.iboats.com/showthread.php?t=158082

[FAST FRED]

Its dangerous as heck , but what I do in a gas engine is give a squirt of ether , and see if she fires.

If it does fire its a fuel problem , if not look again at the ignition system.

DANGER !! Be really careful.

FF

[Petros]

there are two basic reasons a gas engine will not run. No spark or no fuel.

If you have fuel it could be getting too much or too little but you usually get a few pops. Sometimes the carb out of adjustment or crap in the carb, will make it too rich or too lean to run, but it still appears you are getting fuel to the pistons. A real wet spark plug can indicate too much fuel, often too wet and you will not even get a pop.

If no spark you have to follow the current from the battery, through each component and then to the spark plug, with a volt meter. And then verify that the timing is close enough so it will run. Also make sure you got all of the connectors and wires hooked up to the correct places, you will need a engine wiring diagram, and if it has electronic ignition perhaps even a system logic diagram. Even if the timing it is way off you usually get a few pops or backfires, you can "eye ball" the timing (with no. 1 piston at top dead center) so it will start.

Also do not assume that because all those parts are new that they are good. I have found with car and trailer parts that anywhere from 10 to 30 percent of new parts are junk right out of the box, even "factory" parts (which just come from some overseas supplier more times than not).

Good luck

[marcpiery]

There is an old saying amongst shade tree mechanics: 90% of all carburation problems are in the distributer. First, check that the connections are all correct and tight with your new points and condenser. Then, check that the point gap is correct. Next, check the distributer cap and rotor. As cheap as they are, just get new ones and change them. A crack in the distributer cap can cause the electricity to just flow out. Quite impressive in the dark. Also, a bad rotor will not make the proper contacts in the distributer. Make sure that you lubricate the rotor with electrolytic grease. Next, check the lock bolt for the distributer and make sure it is nice and tight. If it is loose, it will have moved if the timing was adjusted. Also, as Petros said above, the parts themselves may be suspect. One more thing as I am thinking about distributers, make sure that the cylinder firing order is correct coming off the distributer cap to the plugs--that one can cause quite a bit of frustration if everything else is good.
Good Luck
Marc
P.S. Remember that Mercruiser and Mercury Marine are GM products, and it is probably a good idea to stick with GM parts.

[dough]

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