Problem with startup on '97 mercruiser 454

cschauerj

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I'll start with a little history. I generally start the motor per the manuel with one pump of the throttle to prime the engine and then crank with a quarter throttle. It generally fires right away. Once it does I slow the motor down to a 1000 rpms. Once the operating temp. starts to rise and the rpms start to climb I can idle it all the way down and depart. This has been standard operating procedure since I bought the boat several weeks ago. I've been using the boat once a week since purchase so it wasn't through inactivity that I had a problem this past weekend. After starting the motor and letting it warm up at a high idle, the rpms never increased as they usually would have. It didn't pay much attention to that but when I tryed to idle the boat all the way down it stalled. I was able to start it a couple more times using the same procedure but was unable to get the boat to idle without stalling. A couple attemps later I could not get boat to fire at all. At this point I went through the normal checks. Plently of fuel pressure. Plenty of spark. Consequently the plugs were not wet with fuel when I checked. I finally got the engine to run by having someone manually hold the choke plate open on the carb. long enough for the motor to fire and clean itself out. It then took about 15minutes of operation to clear the excess fuel and fouling out of the carb and engine. It ran and started fine for the rest of the day. Could I have simply flooded the engine? If so why weren't the plugs wet with fuel? I used the same starting procedure as always. I'm new to carburation. Is there some kind of float mechanism that would allow fuel to pool up in the carb and not flow into the cylinder heads? Could the choke be faulty? Any suggestions would be greatly appreciated.
 

cschauerj

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Re: Problem with startup on '97 mercruiser 454

I'm not that familiar with it other than it's a 4-barrel. I'll find out the model and write back.
 

petryshyn

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Re: Problem with startup on '97 mercruiser 454

If this is a one time thing, I guess you could have flooded it..but it also mimics a leaking choke break diaphram (choke pull-off). But Before we speculate, lets find what carb. manufacturer...... :confused:
 

cschauerj

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Re: Problem with startup on '97 mercruiser 454

Schematic, the only # I could find on the carb is 9780S. Does Mercruiser make carbs? Today I started the boat up and it ran good, not great though. Although not as bad, it had some hesitation where the motor did not what to speed up. In this senario you could either give it more gas and it would work it's way through or I could manually hold the choke plate open and the motor would accelerate normally. So it seems to me that the solenoid or choke or whatever isn't functioning properly. How does the choke operate? Any thoughts.
 

petryshyn

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Re: Problem with startup on '97 mercruiser 454

I'm guessing, but I think you have a rochester 4bbl carb. (someone please correct me if I'm wrong) The carb has a black choke housing mounted on the side. That is what closes the choke valve. A second or two after the engine starts, a vacuum diaphram should open the choke valve a small precise amount. If this diaphram is bad, the choke valve will remain closed after start-up causing a rich mixture (slow rough idle). Thats what I suspect is happening. After a few minutes of operation, the choke mechanism (bimetal spring inside the black plastic choke assembly)will become warmed by an electrical element and will open the choke and allow normal idle speed and normal engine operation. Not sure on your application, but on some engines, the electric choke will not function properly if the charging system fails, and the result is .....hard to keep running when cold, but when engine fully warmed up...runs OK. Is this whats happening?
 

cschauerj

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Re: Problem with startup on '97 mercruiser 454

You described the carb. exactly. As far as your assesment of the engine running poorly when cold but ok when warm, that is what is happening. The choke is opening that small amout as you described, maybe the problem lies after the motor has started to warm up it doesn't continue to open as it should. As a matter of fact you mention the charging system.... I didn't notice today when I was playing with it, but the past weekend when the problem first showed up, I noticed the battery gauge was a couple volts lower than it usually runs. About 11 instead of 13. Sounds like you're onto something.
 

petryshyn

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Re: Problem with startup on '97 mercruiser 454

Automatic chokes are quit complex. If you wish, I can help you with the long drawn out process of testing and adjusting the choke mechanism. Also need to clarify the charging system issue. Do you want to give it a go??<br /> :confused:
 

petryshyn

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Re: Problem with startup on '97 mercruiser 454

Too much water has passed under the bridge since you started your posts. Lets start from scratch. You must start with a good battery which is fully charged, or you'll end up giving us corrupt information. Then see if the starting problem (just clicks) goes away. Then see if it starts everytime.(igniton problem go away??). Then take note of battery voltage while running(you mentioned 11v before). This will clarify you alleged charging system problem. After all this is rectified, we'll continue on the choke issue.<br />A 'weak' battery can give all of your symtoms. 'Weak' can mean bad, or in need of recharging. So lets get the basics covered first!! Remember to always wear safety glasses when working with or near batteries!! One mistake or even a battery defect can cause a lethal explosion.... :(
 

cschauerj

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Re: Problem with startup on '97 mercruiser 454

Your absolutely right about this site. It's great! I'll go ahead and take care of the battery situation. I went today and charged one. I'll top the other one off tommorrow. I did some poking around today and traced some wiring. You're right. There is a power wire that goes from the alternator to the automatic choke. Coincedentally, the connection was loose and had a little corrosion. I took care of that and the boat seemed to run good out of the water. I hope that was the culprit, but I won't know for sure until I get out on the water hopefully Mon. or Tues. By then I'll have both batteries in good shape so they can be ruled out. The battery gauge is still reading erratically however. Around 11 volts. It drops when I rev the engine. As far as the questionable starter solenoid, it hasn't given me any trouble since you explained to me how to diagnose. Anyways, like I said, I'll know more after I take it out. Thanks again for the advice! I'll give you an update in a couple days.
 

petryshyn

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Re: Problem with startup on '97 mercruiser 454

Instead of relying on a dash-mount voltmeter(not always accurate) check the voltage at the batteries using a hand held voltmeter. Do this while engine running around 2000rpm. I need this value to continue our trouble-shooting..... ;)
 

cschauerj

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Re: Problem with startup on '97 mercruiser 454

OK. <br />Forgot to mention that the voltage to the choke from the alternator read approx. .75 volts. Didn't know if that was important in diagnosing anything. I'll check voltage at the batteries tommorrow.
 

petryshyn

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Re: Problem with startup on '97 mercruiser 454

The voltage at the choke terminal should be approximetaly 6 - 8 volts AC while the engine is running. Thats AC voltage not DC, so you must set your voltmeter appropriately. If the charging system is malfunctioning, you might not see any voltage at this terminal. Don't forget, this voltage must be measured while engine running. :) Buy the way....where is St.Pete??
 

cschauerj

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Re: Problem with startup on '97 mercruiser 454

Please don't complicate matters anymore with your ballpark guesses Schematic. Shame on you..JK I for one am finding your advice invaluable. <br /><br />The voltage at the choke terminal read approx. 1 volt AC with the engine running. I hope the alternator is not bad... The voltage at each battery at the terminals with the engine running 2000-3000 rpms was about 12.5volts(which is about what they read when the engine is not running.) It ran pretty decently again today out of the water. Weather permitting I'll get it on the water tommorrow. Hopefully I won't be writing you to tell you of my experience being towed in. St. Pete is on the West coast of Florida. If you've heard of Tampa, we are across the bay from them. Pretty nice area if you ask me. Take care.
 

petryshyn

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Re: Problem with startup on '97 mercruiser 454

Where were we...Oh yes.... Your charging system is bad. You should have between 13.8 to 15 volts while running. Before we get started, check the belt(engine off). Can you turn the alternator pulley by hand with the belt in place? If you can, its either loose or oil soaked. Replace or tighten before we continue. Wouldn't that be an easy fix!!<br />We have to repair the charging system before we continue with the choke adjustments. We have to determine which alternator is hung on this puppy. I'd guess its a delco 10DN with an external regulator. But again ....thats a guess. Get a number off it. Then I'll know how to guide you in trouble-shooting. See if you can spot a little black box about 3" square hanging around. Might be easy to just follow the wires from the alt to see where they take you. I hope you realize that this is known as trouble shooting, not a shot in the dark. There will be an end to our means! If you want the shot-gun approach, replace the alternator, regulator, batteries, belt and all supportive wiring and she'll go!! Sorry but thats not my style. <br />Don't think I'd take her out on the water till the system is up!!
 

cschauerj

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Re: Problem with startup on '97 mercruiser 454

Well against your advice I took the boat out today. My mom and stepfather were in town from England and I had my heart set on showing them my new toy. Same problems. The starter was hesitant to turn the motor over when cold. But again the problem didn't last long enough for me to get the voltmeter out and test. The belt is not slipping on the alternator pulley. Although if I used alot of force the belt actually slipped a little on the crank pulley. I've checked with Mercury and the belt deflection measures fine so it shouldn't be excessive. As far as I can tell there is no external regulator. All I could find for identification was Mondo J1171. Almost looks as if the regulator could be molded onto the back of the alternator caseing but I'm not sure. So we took it out for a spin and the motor was flooded to hell. Took about two minutes of coughing to get on a plane. It slowly but surely ran better throughout the day. Once the engine for the most part had cleaned itself out and was still warm, starting was not a problem. So the same syptoms exist. Should I just pull the alternator and take it to a shop or can it just as easily be tested with a voltmeter for operation?
 

petryshyn

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Re: Problem with startup on '97 mercruiser 454

Hello again....man its cold up here. Snowed like crazy today. <br />So she's a mando alternator with a built-in regulator. Never seen a mando before. The odds are its just a bad alternator and most would say replace it!!! Sorry,,, I don't work that way. Before I recommend a replacement, you have to prove its bad. How deep are you willing to go? Do you want to take a shot in the dark and replace the alt., or work through it with me, save a few bucks and possibly learn something along the way? You make the call....<br />Either way, I recommend getting a charger on those batteries or they will become permanently sulphated(unuseable). Do you know how to charge the batteries properly? Please stop running the engine! Due to the rich condition the choke is providing, your crankcase oil is probably diluted with fuel and getting more so each time, so the engine may require an oil-change once the problems are solved. We'll talk more on how to determine that later.<br />Make the decision, then let me know...<br /> :rolleyes:
 

cschauerj

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Re: Problem with startup on '97 mercruiser 454

How's the snow shoveling going these days Schematic? I have a confession. The boat is under warrantee, although there are some complications with that(long story, I'll spare you). Not to mention I've had trouble finding a place close that I can drive the boat to and I don't have a trailer. I'm pretty mechanically inclined and would prefer to learn and fix something myself if it's a cheap fix rather that waiting two weeks for a Merc. mechanic to look at it. Anyways, to make a long story short, it's in the shop and it's somebody else's problem for the time being. I knew in the next couple of weeks I would not have time to work on it myself and I found a place that could get in in quickly. I hope you don't feel slighted or that you've wasted time on my cause. Your advice has been great! I'll be printing the entire post for future reference(warrantees don't last forever). Anyway's, if you're interested I'll let you know what the pro's diagnosis is. I'm sure we'll be posting again. Take care.
 

petryshyn

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Re: Problem with startup on '97 mercruiser 454

Thanks for replying and not leaving me hang. Next step would have been to check supportive wiring to the alternator. If that checked ok, I'd guide you through the diagnose and overhaul of that alternator. I've done so many, I don't care what name is hung on it!! If this ends in you purchasing a new alt., go with a delco-remi. Once the charging system is up, be sure there's power to the choke cover. One last thing.....change the oil, unless you feel qualified to determine fuel dilution...<br />Its been fun.....<br /> :D
 
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