140 Mercruiser 2 barrel Rochester Wont start, has spark.

[Steve8686]

Replaced fuel pump, filters, thought it may be a carb issue so i took carb off my running 120 merc and put it on there and still nothing. Runs for about one second then dies. Really weird. Has gas, has spark, wont run. Never seen anything like it, maybe someone else has, HELP!!!

 

[fishrdan]

Re: 140 Mercruiser 2 barrel Rochester Wont start, has spark.

Runs for about one second then dies.

Sounds like you are not getting power to the ignition when the key is in the run position. When you are starting the engine, the ignition gets full battery power from the starter's coil, then when you let off the key, power goes through the ignition wiring, resistor wire and to the coil. Check to see if you are getting voltage to the coil then the key is in the run position and let us know what the voltage is.

 

[Steve8686]

Re: 140 Mercruiser 2 barrel Rochester Wont start, has spark.

Thanks for the help. I bypassed the fuel system and just connected a pump bulb from my fuel tank to my carb. It runs fine as long as I keep pumping the bulb. It does not have a anti siphon valve on it if that makes a difference. Should i put one on? Should i replace the water seperator filter, would that make it die intermittently? Its a year old. Thanks again.

 

[GA_Boater]

Re: 140 Mercruiser 2 barrel Rochester Wont start, has spark.

Welcome to iboats Steve.

First, how was it running before you replaced the pump and filters? You do have a fuel problem if it runs while pumping the bulb. I'm guessing you connected the bulb between the line to the fuel pump from the tank and the carb. Is this correct? If so, you bypassed the fuel pump but the rest of the fuel system is intact.

 

[Steve8686]

Re: 140 Mercruiser 2 barrel Rochester Wont start, has spark.

Initial symptoms for the past few months it would die at 1/4 throttle but then start right back up and run fine. It would always run fine for 30 seconds or so at 1/4 throttle then die. Ran fine at every other throttle setting so I just lived with it. Then just got harder and harder to start after it would die and now it wont run at all. Since last post it now wont even run with primer bulb which is bypassing the entire fuel system. It wants to run for a second then dies. Since my throttle linkages were different on my 120 merc carb I just pulled the top off of it and put it on my bottom half of my 140 carb to see if it was a float needle and seat or pump issue. No change. I guess my question is what in the lower half of the carb could make it have this issue. Main jets are not plugged, What does the strainer do? It had some rust down it it could it being blocked cause an issue. All but one plug is dry as a bone. Thanks for the replies.

 

[Steve8686]

Re: 140 Mercruiser 2 barrel Rochester Wont start, has spark.

Sounds like you are not getting power to the ignition when the key is in the run position. When you are starting the engine, the ignition gets full battery power from the starter's coil, then when you let off the key, power goes through the ignition wiring, resistor wire and to the coil. Check to see if you are getting voltage to the coil then the key is in the run position and let us know what the voltage is.

The voltage is zero when the key is on with leads on + and - on the coil. Grounding out somewhere? good call.

 

[Steve8686]

Re: 140 Mercruiser 2 barrel Rochester Wont start, has spark.

Fishrdan,

I want to personally thank you my friend for your insight. Probably not the best way of doing things but i ran a jumper from my battery to my coil and she fired off right away and has been running every since. Send me your mailing address because I am putting 50 bucks in your mailbox. Steak dinner and beer is on me. Send it to sjhalldc@earthlink.net Now, what to do about finding where its grounded out, this is going to be a chore, this boat is 35 years old and already has wiring from bad grounds all over the place. Is there an easier way I can get power to the coil and still be able to shut it off with the key. I had to choke it to kill the engine. thanks again so much.

 

[frank246]

Re: 140 Mercruiser 2 barrel Rochester Wont start, has spark.

What about the Landyard-kill switch..?

 

[fishrdan]

Re: 140 Mercruiser 2 barrel Rochester Wont start, has spark.

Thanks for the $ offer Steve, but I'll let you save it to fix the ignition. I've received a lot of priceless info off the forums so far, so I'm paying it forward

What year is your 140HP? Post up your serial number and one of the guys might stop by and post a link for the repair manual. I have a couple that show the wiring diagrams.

I might suspect the ignition switch, but you'll have to troubleshoot with a meter to find out where you are loosing voltage to the ignition. Remove the 2 wires from from the coils + post, one goes to the starter's coil and the other (purple?) to the resistance wire. See what voltage you have when the ignition is on and the wire removed from the coil. If the shift interrupt switch is engaged, or permanently shorted to ground, that could cause your problem too. The shift interrupt switch should have bullet connectors on it, so you can temporarily disconnect it to see if that's your problem.

BTW, don't run the engine too long with the coil jumpered to 12V, not good for the coil and points.

 

[fishrdan]

Re: 140 Mercruiser 2 barrel Rochester Wont start, has spark.

What about the Landyard-kill switch..?

Possible, but I don't know if they had those on the ol' 140's. Good suggestion though.

 

[Steve8686]

Re: 140 Mercruiser 2 barrel Rochester Wont start, has spark.

Well thanks Dan. Could it be as easy as my coil ground. Seems like the distributor isnt a very good ground, I am going to try a good engine ground. I will try all those things, I have a manual so Ill look at the wiring diagrams but sometimes looking at those is like chinese arathmatic to me. Ya, no lanyard on mine.

 

[dubs283]

Re: 140 Mercruiser 2 barrel Rochester Wont start, has spark.

Could it be as easy as my coil ground. Seems like the distributor isnt a very good ground

the (-) side of the coil MUST run to the distributor, this is the path to ground for the primary side, the points are what control that path to ground, when they are open the field inside the coil collapses and the path to ground is then out the coil tower through the rotor and thus to whichever plug wire post the rotor is pointing to

 

[Steve8686]

Re: 140 Mercruiser 2 barrel Rochester Wont start, has spark.

Thanks again Dan, What should the voltage be to the wire that goes on the positive side of the coil with the key on? the shift interrupter switch brown wire never did have a wire running from it to the coil like the wiring schematic shows. Seems kinda weird those 2 wires running to the shift interupter just ground on 2 screws. no other wires running 2 them?

 

[fishrdan]

Re: 140 Mercruiser 2 barrel Rochester Wont start, has spark.

The coil's + voltage should be 9-10v, the resistor wire cuts the voltage down. The shift interrupt switch's wiring to the coil might be terminated in the harness. My 140 wiring diagram shows a gray wire from the coil's - terminal to the the harness, then a gray/white wire from the harness to the shift interrupt switch. The other side of the shift interrupt switch has a black wire to ground. When the shift interrupt switch is tripped, it shorts the - side of the coil to ground and keeps the coil from firing.

 

[Steve8686]

Re: 140 Mercruiser 2 barrel Rochester Wont start, has spark.

Thanks again Dan, much appriciated my friend.