No start condition Mercrusier 4.3 L

[Watkinsj]

Hello all!

I hope I can get some help with a no start condition on my Mercrusier 4.3 L. This engine is on an old 1991 Celebritie 181. It has a Mercarb 3304-9565 on it that I just rebuilt and installed tonight. Tried starting it and it turns over but will not start. I can smell gas so know it’s getting to the carb.

A little history on the boat, I am extremely new to this and been having trouble with it dying on me while on the water. At first I found the ignition coil was arcing to ground, so I changed out that with a new one. Took it out on the water last week and was running great, stopped on the beach for 3 hrs, tried starting it and no dice. We got towed in and I noticed the little plastic safety gas return line had melted. So I figured got something in the carb, so tore the carb down and cleaned it. Installed it tonight and tried starting it and no luck! Would anyone know what else to check?

Any help would be greatly appreciated!

 

[Chris51280]

do you have a mechanical or electrical fuel pump? one mounted to the side of the block that gets actuated by a push rod? maybe its your fuel pump. when that one fails, it squirts gas into the carb to shut it off.
do you get good spark? check the distributor and spark at the plugs.
when you prime the carb (pushing the throttle all the way down), you need to see 2 streams squirting on top of the flaps

 

[QBhoy]

Sounds like the old auto choke sticking.

 

[Watkinsj]

Hello Chris and thank you for replying!

It is a mechanical fuel pump and I did just replace that as well. I originally thought that was plugged up before I found the ignition coil arcing.

I am not not sure about the spark though, how would I check for spark on the plugs and cap? Sorry new to this.

I don’t see fuel coming out of the carb flaps when I throttle down on it but smell gas. I first noticed the gas line from the pump to the carb was leaking gas so tightened that up. The inline fuel strainer was dirty so replaced that. Did I screw up the carb rebuild!?

 

[Watkinsj]

Thank you QBhoy! If the auto choke is sticking what should I do to help it clear out? I stripped the screw holding the lever, dumb move on my part!

 

[QBhoy]

Thank you QBhoy! If the auto choke is sticking what should I do to help it clear out? I stripped the screw holding the lever, dumb move on my part!

Hi
many will disagree with me, but on every single gm carb engine I’ve ever had, merc and VP...the choke has caused issues like this. The result is that on every single one...I’ve taken the end off the actuator and wound it to the choke off position and locked it there...then replaced the cap. Pump throttle about 8-10 times on cold start...catch it on the throttle when it fires. Then hold it at a high idle for 20-30 secs then wind it back to tick over. Never an issue since.

 

[Watkinsj]

Thank you QBhoy, I may need walked through that task haha. So you remove the cap off the electric choke. Move the lever all the way to choke off position, tighten screw down and put cap back on. Do you rotate it to rich or lean?

 

[QBhoy]

Thank you QBhoy, I may need walked through that task haha. So you remove the cap off the electric choke. Move the lever all the way to choke off position, tighten screw down and put cap back on. Do you rotate it to rich or lean?

Rotate it until the flap is full open and lock it off so the thermo electric can’t move it.
I can feel the critics coming already. The local merc dealer showed me about 20 years ago. He is 50 years in the game and does it to almost all of the carbs that’s ever been here on the Loch in Scotland. Never an issue once you get the idea.

 

[ajent]

It will save you a lot of frustration if you start from the basics. You need fuel, compression and spark to run.
Leave compression to last. Do you have spark, do you have fuel. Both are easy. Pull a plug, lay it on something metal. Look for BLUE spark
If you have spark after testing at least half of the cylinders, move to fuel.
Put some brake clean or ether down the carb. Crank the throttle open halfway. Lock open the choke as mentioned above. It should sputter

Also
Permanently disabling the choke is a bit of a patch job, fixing the underlying problem is favorable.
If the choke needs to be wired open, something is wrong.

 

[Watkinsj]

Thank you all for the fast responses, you all are awesome . I will change out the main wire and ignition coil to see if I have spark and then try the choke adjustment today! I’ll give an update later!

 

[Watkinsj]

Man not sure what I am doing here. I replaced the ignition coil with a new one again and replaced the main coil wire. Did the choke trick pumped the gas, saw it pour out in the carb and tried turning it over and nothing but chug chug chug chug. Everything is turning but just won’t fire. I know fuel is getting to the carb so not sure what is happening. How do I check spark on the wires? Do I need to be turning the engine over while putting each wire on metal?

 

[QBhoy]

Have a look at the ignition sensor on or near the dizzy
make sure it’s getting a signal to fire when key is turned.

 

[Watkinsj]

Thank you again QBhoy! I replaced the ignition sensor and swapped 3 ignition coils every time I tried to start the engine, the same thing, it’s cranking over but nothing is getting the engine to start. I might just drill a hole in the bottom of the boat, tie an anchor to it and walk away.

Would it crank over and not start if only one one or two spark plug wires are bad?

 

[Chris51280]

Yes, mine ran on 4 cylinders because i had 1 and 5 swapped. no back fire, just low power.
Take a spark plug out and put it in a boot, then hold it against the the block. (risers,elbows....) Something that has ground to it. It should spark from 1/2" away. Do this on every one to be sure. You don't have to take all the plugs out, just one and take each wire off the plug and put it on the loose plug, then hold it against the block or ground. This way you can test that each cylinder fires.
Sounds like you have fuel but no spark.
Check all the wiring to be sure you have no broken wires somewhere. I believe you can crank but that doesn't mean you get a spark. You can bypass all the wiring if all fails and just jump the pig tail with 2 wires. but lets just check for spark for now

 

[Chris51280]

you can also check if your timing may be off. I believe it is 8 degrees before TDC on cylinder 1. check the distributor if it is cleaned and the contacts still look good.

 

[wahlejim]

Stop swapping coils. It is rarely the coil on these things. I would check distributor, rotor and wires and new spark plugs. You have probably fouled the set you have by now. Also check timing and adjust if needed.

 

[Watkinsj]

Thank you Chris,

With the timing off would that cause the engine to not start at all? I am finally getting a chance to work on the boat tonight so I will update you all on what I find after testing for spark and tearing apart the fuel lines. I still can not find the fuel pick up line strainer that is suppose to be in the tank. I pull the anti-siphon valve off and no tube attached, I can see gas up to the top of the line though. Anyone have to fish this strainer out?

 

[Watkinsj]

Okay, checked a lot of things, I am not getting 12 volts to the coil even. What could that be?

 

[achris]

Lots of information flying around in this thread, but the most important facts seems to be missing...

Let's start with the engine serial number, engine year and a few other facts... Is it a mechanical fuel pump or an electric? 2 bbl carb or 4bbl?

Also, you seem to be going in circles with your troubleshooting. You're just throwing parts at it hoping that one of them will 'fix the problem'... It rarely does.

So, let's get all the original parts back on the engine and start with some basics... Do a compression test. Do a spark check, do a timing check. If all those are ok, then pull the carb and strip it down, clean it and rebuild it following the book.

If you're not getting 12 on the coil+ with the key on, then troubleshoot (not throw parts at it) the ignition electric circuit. Do you have an engine wiring diagram? (BTW, without the factory manual, fixing anything is going to be difficult. You need to have all the resources at your fingertips, and the factory manual is number 1 on that list)....

Chris.........

 

[Watkinsj]

Thanks Chris for making me feel even worse haha jk! I did just that, put original ignition coil back on, pulled one spark plug and used it to check all wires. Not a single spark from any of the 7 wires. The main wire off the ignition coil didn’t even have a spark. So this led me to check the power coming into the ignition coil.

The coil + side to ground on the motor was 12 volts. When I put the negative lead on the coil negative and positive lead to the coil positive, I had nothing. Key was turned to on.

Sorry i will pull the serial number off the engine tomorrow and post it. The engine is a 1991 4.3 L Mercrusier with thunderbolt IV ignition. Plenty of fuel to carb from what I am seeing, I now know I have a spark issue.