1985 merc 340 not starting. backfires through carb

[jo8330]

Hey guys. Have a 1985 cris craft commander 333 flybridge with two 454 mercs. They are fwc. I am having ignition problems (I think). The boat has been layed up for two years. It wants to start, but lets out a puff of smoke from the flame arrestor. I tested voltage at the coil, I have 11.6. I know thats little low, but should be enought to fire it off. So im thinking its the pick up sensor in the distributor. Would this cause a weak spark ? Causing a no start condition ? Im also going to check the inlet filter on the carb to make sure a lean condition isnt present, causing ths backfire. The plugs, wires, rotor, and cap are new.

Here is the weird part. Hopefully someone can tell me what this means. When I checked voltage at the coil, the only way I can get a reading is if I ground on something other than the post on the coil. What could that mean ????

Also, we removed the pick up sensor out of the distributor to clean the contacts, when we put it back in the motor wouldnt even sputter anymore. Lost all signs of spark. Could we have screwed it up somehow ? Im thinking it was faulty to begin with. Need to get this motor running .....

I also have 11.6 volts at the red/white wire coming off the dist.

Thanks jeff

 

[jo8330]

Battery is putting out 12.3v. Key on...not cranking. Didnt have two people there to test that

 

[Scott Danforth]

with the boat sitting for 2 years, have you completely (and I mean completely) drained, and cleaned the fuel system?

after 2 years the fuel will have completely turned to crap. the tank(s) need to be drained. the fuel system cleaned, the lines cleaned, and most of all, the carbs need to be cleaned.

After that, you need to change the oil, pull the distributors and prime the oil system. then crank each engine about 20-30 times to get a good oil film back on all the internal parts. then reinstall the distributor and time the motor

then perform a compression test to make sure that you do not have a bad cylinder from it sitting (rusted rings, rusted valves, etc.)

then change out the plugs, cap and rotor at a minimum.

then put in fuel and try to start.

 

[jo8330]

Fuel tanks were drained and cleaned before layup. And a few weeks ago just for good measure. Lines and carbs were run dry. Cap, plugs, wires, and rotor are new. Also I took the valve covers off and coated everything with kroil and squirted some oil in the cylinders. Also cranked it a few times until I saw oil coming out of the return line for the oil filter. So its got fresh gas and filters.

 

[jo8330]

Oh compression is anywhere from 130-140. So its within specs

 

[NHGuy]

drop an ounce of fuel in the carb and she if she lights.

 

[jo8330]

I did, she wants to go, but just wont catch. I really think its that pick up sensor in the distributor since I have voltage everywhere else.... plus shes squirting fuel when I pump the throttle.

 

[tfret]

when my ignition sensor failed the engine wouldn't hit at all. Just crank and crank but not fire what so ever. I think they either work or not. No "weak" signal in between. At least that's my experience. If yours is kicking but just won't lite, I think your sensor is ok. What about your choke. My 350 is a stubborn cuss when the choke get off by just a little.

 

[tank1949]

Someone lied?????? Both engines acting like this then common is fuel. Disconnect fuel line and put it into a good can of good gas and with batteries fully charged and disconnected, pull top of carbs off and look for crap inside. If no crap, reconnect batteries and turn each motor over. If this doesn't work, look for a common ground that is "green." or corroded. This may be why you don't get 13 volts????????? Iwent through hell with boat that had laued up with fuel in tanks for over a year. I mean hell!!!!!!!

 

[jo8330]

Both engines arent doing this. The port motor runs pike a top. Ive been running them off a 5 gallon can. A line straight from the fuel pump into the can. My wires all look ok.

 

[NHGuy]

Well then diagnose the ignition system. Check for spark, if there's spark, check timing. You can borrow parts off the other engine too.

 

[Stamey]

My first thought is timing. It could be just a few degrees, adjustable by normal timing procedures, or the chain could have jumped a tooth which is a more involved repair.
For me, initial check would be to get it to the timing mark and see where the distributor rotor is pointing. If 180 out, rotate crank 360 degrees to the timing mark, and look again. If the rotor is not just before the location of plug wire one then the timing is way off. If it is just before number one plug wire's location then timing hasn't jumped, proceed with fuel checks then once engine is running adjust timing with light per spec.
Yes, you can have a weak coil. Swap coil with running engine to diagnose.

Chris

 

[jo8330]

Wow, its 330 am here. I got up, lit a cigarette and had an epiphany. Ive only owned tue boat maybe two months now, ive been thinking since I woke up a minute ago, im a dumbass, counter rotating engine. Its my starboard engine im having issues with that WOULD be the engine thats rh. I changed plugs and WIRES........think about that. ....plugs amd WIRES !!!!!!! Holy crap ive been racking my brain with this motor. I now feel like a complete tard. Ive never owned a twin engine boat before. If logic serves me correctly that should completely reverse my firimg order correct ? This has to be it. Ive double checked everything else........I feel so stupid. Glad this came to me though....

 

[NHGuy]

Yup, look on your distributor cap, the reverse order will be on there in smaller script below the standard #s. Glad you thought of it.

 

[jo8330]

Yeah, I was curious what the hell the bottom set of numbers was. Now I know. I still have to replace the ign sensor because after we pulled it out the engine lost all signs of spark, but tuats no big deal. Wow, what a weight off my mind. Thabks for the ideas everyone, always remember to check the lil stuff. I check the firing order twice, but for a LH rotating motor. Definitely gotta remember that one