1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

I got the A/C Marine Spark plugs in today, getting ready to take the carb apart and check the float and fuel pump. I have 3 lines on the fuel pump. 1 Line is suction from the fuel//water seperator/tank, one if pressure going to the carb, and the third line (Sight Line) goes to the carb? Should i see anything in this line? What is the purpose of this line? Can i tell if the fuel pump diaphram is bad without disassembling the pump by this line?

 

[Don S]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

and the third line (Sight Line) goes to the carb? Should i see anything in this line? What is the purpose of this line? Can i tell if the fuel pump diaphram is bad without disassembling the pump by this line?

The clear hose is there to carry the fuel to the carb instead of the bilge in case the diaphram fails in the pump. On automotive pumps, there was just a hole and the gas went to the ground. No ground under a boat

 

[ktbarrentine]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

I got the A/C Marine Spark plugs in today, getting ready to take the carb apart and check the float and fuel pump. I have 3 lines on the fuel pump. 1 Line is suction from the fuel//water seperator/tank, one if pressure going to the carb, and the third line (Sight Line) goes to the carb? Should i see anything in this line? What is the purpose of this line? Can i tell if the fuel pump diaphram is bad without disassembling the pump by this line?

The "sight tube" is how I diagnosed my prob with my fuel pump, and hence the problems with hard starting when warm (due to flooding). Trace the line to the carb and see it enter the top of the air horn (on the aft side of the carb). With the engine running, you should see no gas in that line or entering the air horn from it. The fuel pump is non serviceable (cant replace the diaphram). I just took mine apart (and snapped the photo in my previous post) to see how bad the diaphram was. Since my sight tube was 22 years old and very discolored and hardened, I replaced it, too. More expensive than I thought it would be....oh well!

 

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Okay, That makes sense when Don and you explain what it is. On this boat, it has evidently been replaced as it appears to be a vacuum line. It is black instead of clear. I will try and obtain a new line locally since it is supposed to be clear, and will post an update when i have it. Thanks

 

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Okay, I started the engine tonight, ran it to operating temp on muffs. The sight tube is clean and dry. I am in the process of pulling the carb so i can verify everything. Any other suggestions until i get the carb verified?

 

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Carb has been gone through, everything set at factory specs. The float was slightly off, not sure if that would make a difference, however it is now perfect. Book calls for 3/8", it was measuring at 5/16". Replaced plugs with marine version, new fuel/water seperator filter, new style fuel pump bowl filter, had the old rock, now has paper, some debri from the old filter in carb bowl. Runs good on muffs, weather is not conducive to launch today, hopefully will try to launch tomorrow and finish setting carb in water and give it an optest. Many thanks to Don and everyone else who provided troubleshooting tips.

 

[Jmunk]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

With the float being 1/8" higher then where it was supposed to be I would think the fuel would have been leaking after the boat was turned off and flooding it?

 

[dollarten]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Here is another thing to check , plus another theory that might apply . After you hive it a hard run and the engine is shut off , take off the flame arrester and look down in to the carb and see if fuel is dripping on the throttle plates . This could be due to a leaky needle and seat or an internal leak inside the carb essentially flooding the engine . Then when you put the throttle all the way open you are getting some air in the engine to evaporate the fuel I had a similar hot start situation happen to me with a 120 some time ago I took off the silencer and there was fuel shooting from the accelerator pump and no internal fuel leaking on to the throttle plates . After about a 10 minute cool down , the engine started up fine .. The fuel I was using was a ethanol blend . I later fueled up at a marina that had non ethanol fuel and did not have any more hot start problems . My thinking is that the ethanol blended fuel was the cause of the problem . I am no scientist but, I think the ethanol blended fuel is has a different ignition or flash point and is an unstable fuel for carburated engines Especially when they are hot

 

[achris]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Carb has been gone through, everything set at factory specs. The float was slightly off, not sure if that would make a difference, however it is now perfect. Book calls for 3/8", it was measuring at 5/16". Replaced plugs with marine version, new fuel/water seperator filter, new style fuel pump bowl filter, had the old rock, now has paper, some debri from the old filter in carb bowl. Runs good on muffs, weather is not conducive to launch today, hopefully will try to launch tomorrow and finish setting carb in water and give it an optest. Many thanks to Don and everyone else who provided troubleshooting tips.

The only place you'll find 'Marine' plugs is in the price book. There is no such thing as a 'marine' spark plug. Alternators, starter motors, carburettors, fuel pumps... definitely, but not spark plugs.

On my old 4bbl Weber (I know yours in a 2bbl MerCarb) I would set the float level down about 3-5 mm LOWER than the book spec. It runs the engine a tad leaner, yes; but it made the starting a LOT easier.

Chris.........

 

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Put in the water today, Run WOT for about 30 minutes, pulled back into the marina and shut down. After a 5 minute cooldown, engine would not start until you began to open the throttle past the half way point. Marine Mech friend suggests installing a spacer between the carb and the manifold. Could not locate one. Any further suggestions? Comments?

 

[Jmunk]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Have you verified that you have a good spark when it will not start ? If it's not dripping fuel after shutdown, then I would learn towards an ignition issue that occurs when the distributor gets heat soaked.

 

[jimbo_jwc]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Hook up wire on choke , set as spec in manual with drill size as measure , It will come open soon enough , sounds to me as if its to lean to start if you have it wired open , you didn't say you were pumping throttle to get more fuel with accelarator pump. I couldn't get mine right
till I got choke set adjusted and a good connection on the female quick connector . Plus ending up using old accelarator pump as the kit had 90 deg rod and the old one's set screw to the linkage in the carb loosened and was comming out .Plus you will be readjusting other carb settings once its back in circuit and varring air flow with fuel .

 

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Choke was hooked up and set according to factory spec sheet during latest rebuild. Wire is on. When the engine is cold, You advance the throttle one time and pull back to idle, the engine will fire before you can get off the starter. After the engine has been run and got some heat on it, When you try to do an immediate restart, the only way it will fire is to advance the throttle while cranking. This is like when pulling skiiers, or tubers, and you shut down for them to get into the boat at the boarding ladder. If you have run the engine and pull into a restaraunt or something, shut down and let it sit while you are eating (30 minutes or more), it will fire like a cold engine. Spark is hot (Blue/White) when the engine is cold or hot. Plugs are tan colored and new. I am almost positive that it is a fuel issue, either vapor lock or in the old auto days, the carbs would percolate and boil the fuel creating a flooded condition.

 

[dubs283]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

you have something definitely going on inside your carb leaking fuel into the manifold

check for corrosion, faulty/incorrectly installed parts, etc...

you are absolutely sure you don't see any fuel leaking down the throats immediately upon shutdown?? - this may require a helper

if not it is most likely happening on the bottom end of the carb so i would check there first- broken/missing/misadjusted/installed parts, corrosion, cracks, etc...

 

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

We launched again today, run hard for 30 minutes, Pulled up to a local eatery and shut down. After 30 minutes, Did not want to restart until you opened the throttle. Fired it off, ran at 4000 rpm (30 Mph) for about 30 minutes, until we got to our home pier, shut down for fuel, did not want to restart. Got it on the trailer, pulled up to the flushing dock, pulled the air breather/flame arrester, and the throat was wet. While craanking the engine, if you give it no gas it will fire but is a flooded condition. The line from the fuel pump weep hole to the carb is dry. The fuel line is warm to hot to the touch. I am leaning towards the carb percolating and causing a flooded condition. Unsure what the next step is. Any more advice, tips, etc? I am thinking maybe a spacer between the carb and the manifold. Not sure.

 

[dubs283]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

I am leaning towards the carb percolating and causing a flooded condition. Unsure what the next step is. Any more advice, tips, etc? I am thinking maybe a spacer between the carb and the manifold. Not sure.

you would see that upon shut down, if you spent some time investigating it

you stated earlier that you saw no fuel going down the carb upon shutdown but if it was percolating you would see it, maybe not immediately but it would happen

 

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Correct, I see no fuel coming into the carb after shutdown. The line from the pump weep hole is dry, when you look into the top of the carb, you see no fuel, however it is extremely wet. This carb has been rebuilt three times in the last year by two different mechanics. Everything in the carb is set to factory specs.

 

[dollarten]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Years ago , (25-30 ) The AC spark plug company did make a marine type spark plug . There might have been some substance to it, but I remember the spark plug body was either painted silver for corrosion resistance and the porcelain had blue rings located on the ridges . It was a modified number of the regular plug number . An AC plug for marine use would be MR45S. Broke down it would be M , marine , R resistor , 45 , heat range and S meaning it had a shorter porcelain tip. I'm sure this was a big marketing gimmick , bit it worked back then . True , there are no marine plugs any more but, marketing gimmicks last quite awhile

 

[Harritwo]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Years ago , (25-30 ) The AC spark plug company did make a marine type spark plug . There might have been some substance to it, but I remember the spark plug body was either painted silver for corrosion resistance and the porcelain had blue rings located on the ridges . It was a modified number of the regular plug number . An AC plug for marine use would be MR45S. Broke down it would be M , marine , R resistor , 45 , heat range and S meaning it had a shorter porcelain tip. I'm sure this was a big marketing gimmick , bit it worked back then . True , there are no marine plugs any more but, marketing gimmicks last quite awhile

The plugs called for are a MR43S which is a "marine" plug center fire, the "auto" equivilent is AC 10. My local merc dealer would not or could not provide the MR43S unless i bought a case lot, i could not see where i needed that many plugs so i had been running the AC 10 until another board member told me i could order from crowleymarine. It seems to make a little difference on fuel consumption and idle quality, but hard to tell since i have had the carb off three times now.

In my other life (Outboard) all i would run is the centerfire since they would not foul as easy as a regular plug with the premix.

Thanks for all the info and help, now i just need to know where to go to the next step?

 

[Don S]

Re: 1994 Mercruiser 3.0L Alpha 1 Gen II Hard Start when Hot

Your engine does NOT call for an MR43S, it calls for an MR43T, the non marine version is R43T This assuming you have a 3.0L engine and not a 3.0LX model. Do you have your engine serial number handy?

If you get the right plugs, it might start easier. Did that MR43S info come from that clymers manual you have?