1994 mercruiser 5.0 LX carbureted ran fine, barely fired, now no start

[Neverdie38]

New to forum, own a 1994 Mercruiser 5.0 LX carbureted by Rochester quadrajet 4bbl. new mechanical fuel pump, fuel lines, plugs, wires, cap, rotor, and battery last year. new carb kit this winter. good fuel. battery reading 13 volts while cranking.

started normally and ran fine about 2 months ago, then i changed the impeller about 5 weeks ago and it has sat. today i went out to start and it did the normal randomly fire but never started. I let it sit for a few minutes and tried again but never fired. attempted start with starting fluid and new fuel yet still no fire. seems like a spark issue to me.

have not pulled plugs or verified spark yet. seems odd that it wanted to start but then it stopped firing. i have never had an issue with starting even before i replaced all of the parts mentioned above. could i have flooded it? maybe charge battery and retry? open to any suggestions

 

[Portofino]

Check for spark first then report back .

Was it running immediately after the impeller change ie eliminating you knocking / disturbing any wires around the coil and it’s capacitor if its got those you haven’t said ? and dizzy ? Or alternatively electronic ignition unit if it’s got one ? Did any of this tackle get inadvertently soaked ?

Is there a gearbox interlock …..necessitating it’s needs to be in N to fire up ?

 

[bowler]

Is there a gearbox interlock …..necessitating it’s needs to be in N to fire up ?

This. Or kill switch perhaps?

 

[Neverdie38]

Will verify spark after work today. I did not attempt to start after impeller change. It’s an outboard drive so no work was done in engine bay prior to this no start issue. As far as i know there are no other starting requirements other than neutral and kill switch in on position (i even cycled kill switch a few times and verified in ON position)

 

[James jameson]

Electric fuel pumps ? Can you hear them running ?
Interlinked on the back of the alternator on some of the V8s

 

[Neverdie38]

Mechanical fuel pump only. Family was not home so I was unable to verify spark, but I pulled all of the plugs and they were wet. Replaced with new plugs. It tried to fire once and then could not get any fire after that. Anyone know of an easy way to check kill switch? I ordered a coil replacement as next step

 

[Neverdie38]

I hooked a spark plug to the wire, coming from the coil to the distributor cap. I sanded off a piece of metal on the motor and grounded, the spark plug and cranked the motor over. No spark through the plug. Is that a correct way to identify a bad coil?

 

[bowler]

You can just remove the kill switch from the equation by bypassing it. I had one go bad last year and bridged the wires to and from it to verify. Easy check to rule it out. Can't speak for the coil.

Hang in there!

 

[dpb]

When you say spark plugs wet, you mean petrol or water?

 

[Neverdie38]

Bypass the kill switch by hooking both wires together? Wet plugs meaning fuel, i could smell it on the plug and from the cylinder when i removed the plug….i’ve replaced plugs, wires, cap, and rotor and have a coil ordered. Are there any other ignition elements to recommend replacing?

 

[bowler]

Bypass the kill switch by hooking both wires together? Wet plugs meaning fuel, i could smell it on the plug and from the cylinder when i removed the plug….i’ve replaced plugs, wires, cap, and rotor and have a coil ordered. Are there any other ignition elements to recommend replacing?

Yup, just join them. Could be an easy fix. Mine stopped working with immediate effect, no symptoms beforehand.

Have you tried starting with throttle wide open?

 

[Neverdie38]

Ok i will try that. I did try with wide open throttle. I tried my normal startup procedure of three throttle pumps the. 1 tick over. Coil arrives tomorrow but will try kill switch idea first. Thanks

 

[bowler]

Did you try starting with the throttle held wide open? No pumps etc.

 

[Neverdie38]

Yes attempted wide open throttle. And let it sit with throttle forward to air out in caae flooded. I’m assuming it is lack of spark at this point, new coil arrives tomorrow. Will update after it is installed

 

[spannerman]

Does the rev counter flicker when you crank, if not then check you have 12v on the purple wire on the coil + if yes then connect a test light between the coil - grey wire and crank, if the light flickers then the ignition module is working and there should be a spark from the coil king lead, if not then either the coil is open circuit or the module is faulty. Check the coil with an ohm meter before buying a module. Some older Mercruiser modules are no longer in production but I have found several for customers on the net in the USA.

 

[Neverdie38]

I did not watch the ribs counter while cranking. It is raining in my area today, but if it clears up, I will check the purple wire. Thanks for the suggestion

 

[Portofino]

 

[Neverdie38]

Great video, thanks

 

[Neverdie38]

No power to purple wire at coil. Coil resistance measured within spec

 

[Neverdie38]

Also have continuity through kill switch. And I stand corrected. Now I have -12.5 V at the coil on the purple wire and continuity, i’m not sure how I have that, but maybe I had a bad ground first. The only thing I did differently was remove the ignition switch and check those wires and connections. I attempted to get spark at wire running from coil to distributor with no spark. Are used three different good ground sources on motor to verify. So I with power to the coil at the purple wire, but no spark from it that would point to the coil, correct?