Merc 120 jet cold start problem (1999 yr)

[6x]

At first cold start up a aerosal hot shot is needed. After engine is warm, it starts up fine. While fishing etc for 2.0 hrs or so. extended crank and or more either is needed. Previos owner had removed the wall mounted electric pump primer from boat. ??? No problms w/ starting untill after 1 year after pump was removed. I recently installed a bulb primer in main line thinking that this may help . No luck. Any thoughts??

 

[Silvertip]

Re: Merc 120 jet cold start problem (1999 yr)

My only thought is that continued use of ether will destroy the engine. There is no lubricant in ether. Cold fuel delivery problem indicates choke/primer system needs attention.

 

[6x]

Re: Merc 120 jet cold start problem (1999 yr)

Thanks, i use WD-40 thought that it may confuse the question.. Ok how does the choke system work? Electric or mechanical. I am really going in this blind. Any way to check the choke system?

 

[funpilot]

Re: Merc 120 jet cold start problem (1999 yr)

You should buy a manual. I don't know what changes were made from 1995 to 1999 on the Sport Jet engines.<br /><br />However, since you basically have an inboard engine with an L-drive jet pump, the squeeze bulb is a fire hazzard. A bulb primer doesn't prime, it only fills the carburater bowls, something your fuel pump does pretty quickly with the small bowls on the 120.<br /><br />fp

 

[Zamboni]

Re: Merc 120 jet cold start problem (1999 yr)

I'm not familiar with 99's either-if they still used auto enricher valve I'd look at it.<br />Why did the owner take off the electric pump primer-I see posts of guys adding them and solving cold start prob on sportjets.

 

[6x]

Re: Merc 120 jet cold start problem (1999 yr)

Thanks guys for all youre time. I am trying to locate a manual,This past week end I took a closer look into the problem. The motor has a auto enricher or a primer mounted on the left top side of the carb area. Two yellow wires feed it. I ran a continuty test to it. It is open. I then tested for power while cranking the engine, No power to it. Then checking the feed to it. I found that the yellow wires off of the stator was burnt at there connectors. So I assume something shorted and took out the stator and pump. But the engine still runs fine. I have no clue why the previous owner removed the electric pump. My question is how does the primer know when to pump @ start up. Would it get power from the key swith w/ it pushed in. But why is it wired to the stator? Thanks

 

[Zamboni]

Re: Merc 120 jet cold start problem (1999 yr)

Hopefully someone else chimes in. I recall reading there is a replacable wax pellet in the auto enricher that melts. Auto enricher is known to be trouble prone...if you want pdf zip of 95-97 merc manual I can email, biggerhammer site took dl manuals off.

 

[6x]

Re: Merc 120 jet cold start problem (1999 yr)

Thanks Zamboni.. I will look into the pellet.

 

[funpilot]

Re: Merc 120 jet cold start problem (1999 yr)

I never thought the pellet was replaceable. But I could be mistaken. The pellet, I believe melts and causes the auto enrichner to close. Current is applied at start, and once the pellet is melted, the engine runs normally. Current continues to keep the pellet liquid. When the pellet cools and solidifies, the engine is cold enough to once again need auto enrichning.<br /><br />Advancing the throttle disables the auto enrichner. It only works with the throttle plates closed.<br /><br />The Clymer manual is terrible on information. Zamboni, I would love to see the pdf zip.<br /><br />funpilot15 at hotmail dot com<br /><br />thanks,<br />fp

 

[6x]

Re: Merc 120 jet cold start problem (1999 yr)

Funpilot youre are correct on the way the enricher works. I had obtained a copy of the test and infomation on the enricher yesterday. I was testing the valve incorrectly. I just ran battery voltage to the valve thinking that I would hear the pump cycle. See this is the incompatence you have w/ out a manual. Any way the valve gets power off of stator current which is different then 12v. I now need to obtain info on a stator check. I have not had a chance to test the valve yet. 18-20 ohms is resitance spec @ cold. for any one making mental notes. My gut is that the stator and valve are both fried, because of the burnt wire connectors. A boat tech said this most likely came from a bad ground ???

 

[funpilot]

Re: Merc 120 jet cold start problem (1999 yr)

Kenimpzoom is a member at iboats. He has a cool site for troubleshooting your system.<br /><br />I know he won't mind if I share it with you.<br /><br /> http://www.geocities.com/kenimpzoom/KensSeaRayder.html <br /><br />good luck<br />fp

 

[Zamboni]

Re: Merc 120 jet cold start problem (1999 yr)

Sent the manual funpilot, you should take it also 6x until you get one for your engine year...has electrical test info-should be the same.<br />Stator can't be fried or you wouldn't be running.

 

[6x]

Re: Merc 120 jet cold start problem (1999 yr)

Zamboni> please mail me a copy. Yeah thought about the running issue, didnt know if the stator leads supplied anything else. Tired of throwing darts.<br /><br />Thanks.

 

[6x]

Re: Merc 120 jet cold start problem (1999 yr)

 

[kenimpzoom]

Re: Merc 120 jet cold start problem (1999 yr)

6x, these guys know a heck of a lot more about these newer engines than I do. My knoledge stops at 1995. I am not even sure the test procedures on my website apply to a 1999.<br /><br />The yellow leads from the stator are for charging the battery. They leat to the rectifier/voltage regulator, which then leads to the battery.<br /><br />If your worried about a blackness under the bullet connectors, mine is black too, but runs fine and charges the battery fine.<br /><br />Ken

 

[6x]

Re: Merc 120 jet cold start problem (1999 yr)

Thanks everyone. I will read the manual. And if I cant fix it. I will have to sub it out. <br />First time on forums. Lots of great info and people... Take care..

 

[funpilot]

Re: Merc 120 jet cold start problem (1999 yr)

Wow Zamboni... That manual is going to be a huge help to me. I really appreciate your kindness.<br /><br />6x, keep us posted. The trouble shooting in the manual is very similar to what Ken recommends. I didn't know that they changed the crank and rod journels, and the piston trueness after '95. The crank, rods and pistons are definitely not interchangeable.<br /><br />Ken, good seeing you again!<br /><br />fp

 

[6x]

Re: Merc 120 jet cold start problem (1999 yr)

Zamboni thanks for sharing the manual. Last evening I ran a ohms check on the enrichment or primer valve the specs are 18-20 I am @ 22 <br />So I expect that to be bad. I need to check the supply voltage to the primer. This is the two yellow wires from the stator.Again my engine does run. There is none servicable wax pellot in the primer. The primer is nothing more then a heater w/ needle valve,spring that opens and closes as the wax pellot melts. This allows gas to be injected into the air box @ start up. I will keep you guys updated to my fix. But the primer cost is$175.00 so I am going to bargin shop due to I am not positive this will be the fix.

 

[kenimpzoom]

Re: Merc 120 jet cold start problem (1999 yr)

6x, I can tell you my SPort Jet 90 is a pain to start. Usually easier when cold.<br /><br />WHen hot, it takes a lot of choke and throttle manipulating. It is in perfect shape, carbs spotless, etc, etc.<br /><br />I guess this is the reason Mercury put the fuel enrichment on the later models.<br /><br />To get mine to start when hot, I advance the throttle about 1/3, start cranking, and work with the choke. It can take 10 seconds sometimes.<br /><br /><br />Ken

 

[funpilot]

Re: Merc 120 jet cold start problem (1999 yr)

6x, My Sport Jet 120 with the Autoenrichner is a breeze to start. I just crank it until the bowls fill, and then bingo. It does run with a miss of sorts until the autoenrichner 'comes off'.<br /><br />If you have the Morse control box at your cockpit, you can pull the knob out, advance the throttle plates and start it at a higher idle. This does disable the autoenrichner.<br /><br />Let us know.<br />fp