Intermittant starting issue

[rad1026]

1989 Chaparral, 5.7L merc with Thunderbolt ignition, 4bbl Rochester.

I had my carb rebuilt last year and just had the carb adjusted again by my local mechanic at the lake. The boat runs great but I'm still having times where it takes a long time to start. Sometimes it will start with just a bump of the key and sometimes I have to crank and put the throttle all the way forward, then it lugs and black smoke comes out of the exhaust until the engine smooths out. It sure seems choke related but the mechanic says the choke is perfect and don't touch it. I know my timing is good. How long does a coil last? It is probably the original coil. I haven't changed plugs in a couple seasons, but only put maybe 50 hours on my boat last year. I probably could do a complete tune up, plugs, wires, rotor, cap but should I think about replacing the coil also or is it one of those things that if its working its working and don't replace it unless it goes out. Sure would like to be able to just bump the key every time. Thanks for the responses!

 

[Maclin]

Re: Intermittant starting issue

The carb could be leaking from the fuel bowl into the intake manifold, or be over-filling and fuel running over into the carb throat and on thru the butterflies and into the intake. If this has happened a lot then check the odor of the oil on the dipstick. A chronic carb leak like that will end up with fuel in the oil as it works it's way past the rings when the engine is not running.

You can replace the coil but you will have the same problem in my estimation.

 

[Bondo]

Re: Intermittant starting issue

The carb could be leaking from the fuel bowl into the intake manifold, or be over-filling and fuel running over into the carb throat and on thru the butterflies and into the intake. If this has happened a lot then check the odor of the oil on the dipstick. A chronic carb leak like that will end up with fuel in the oil as it works it's way past the rings when the engine is not running.

You can replace the coil but you will have the same problem in my estimation.

Ayuh,.... Agreed, changin' the coil won't fix a leakin' carb issue....

I too, think yer carb is leakin', internally.... The color of the spark plugs oughta verify it...
I suspect they're Black...

 

[rad1026]

Re: Intermittant starting issue

I will take a look at the spark plugs next time I'm down at the boat. That won't be for a few weeks yet. So tell me gentlemen, can I see the fuel over filling? Is it a float issue? Leaking from the metering well plugs? How do I determine it is a over filling problem and what would you do if you determined the carb was leaking internally? Get it rebuilt again by someone who does a better job, buy a new carb? I really hesitate to dig in to a Rochester quadrjet, I just have too many projects going on, there is no way I could devote the time to it. Thanks for the help!

 

[rad1026]

Re: Intermittant starting issue

I just got off the phone with the people who rebuilt my carb. They guy is animate that he tests all throttle lever tolerances, epoxys all metering plugs, etc. Says nothing goes out of his shop with internal leaks. So I kind of have to go back to the choke. I guess I really need to see what the electric choke is doing. I just can't see how shutting off the engine so a skier can get in the boat and then going to start the boat up and having to clear the rich symptoms has anything to do with the choke shutting back down. How could it happen that quick? Should I go back to the old remote mount spring choke that I replaced with the electric choke?

 

[NHGuy]

Re: Intermittant starting issue

No, electric chokes stay open from the residual heat during the brief time you shut down to pick up a skier. When your motor is warm it should start with a short crank on the starter with little to no throttle. If it does not it's ok to pump it a little while cranking. It's then OK to rev it to 1500 or 1800 to clear it out and smooth up the idle. While operating this way keep the bilge blower running, it not only keeps fuel vapors down, it also brings cooling air to the engine compartment. This can help it start too.
If you end up starting with a lot of throttle and get the rough running and black smoke just stay where you are in neutral and run the motor for a half a minute or whatever it takes to clear out the extra fuel that's in there inefficiently burning. It will go, but it's easier to get rid of in neutral. In gear under load it won't run as well and might stall.
When cold starting, pump the lever almost wide open a couple or three times before you crank. Set the throttle a little above idle. Then while cranking if it does not catch you can pump lightly between 10 and 30% throttle, til it starts. Then run it at 12 or 1500 rpm til it warms and gets smooth.
If you want to check the choke, take a look at it. When the motor is warm the choke should be wide open. When cold it should be closed. If it's not come back and tell us.
I'm thinking that since your guy says it is working right that you might just not be familiar with carburetors, they aren't like fuel injection. They mix the fuel and air on top of the motor, which then gets pulled into the combustion chambers to be burned. When cold (choked) the mixture is rich, and when cold a carb motor won't be as smooth. That's one reason you are better off getting it up to temp before moving off. When warm and the choke is off the mixture is normal, and you can operate normally.
Fuel injection in your car does a precisely measured dose of gas right at the entry to the combustion chamber. That motor doesn't need to be managed like your carbureted boat motor. You just start it when you want to go.
Hope I am not being too preachy, but maybe it's that.

 

[NHGuy]

Re: Intermittant starting issue

You live in Alberquerque? Prety high elevation there right? Did the carb builder jet it for high elevation? Did guy who checked it on the boat take it out for a quick ride?

 

[Maclin]

Re: Intermittant starting issue

The elevation can definitely affect this, although it has to be in the extreme, say 4000+ feet. One time on vacation I was up pretty high in New Mexico (Glorieta), and that 2bbl car would "choke" so rich that if it did not start on the first crank it flooded so bad I had to get out and prop the choke open and start with throttle wide open before it could clear out. This was because the carb was jetted for the higher atmo pressure at almost sea level,and the non-electric automatic choke may have been set a little rich. Up in the mountains not as much air and thus too much fuel for the air mix and choking it caused immediate "flooding", carb was jetted for way too much fuel for the amount of air. It acted like that even warm until I got back down below 3000 feet or so.

 

[rad1026]

Re: Intermittant starting issue

NH Guy, I appreciate the time you put in to helping me. I have owned this boat for 9 years now and I very familiar with how the carb works. Believe me I have a 1987 jeep wrangler that is carbureted and I know what the choke does. My issue with the boat is new, since I got the carb rebuilt. It never acted that way before. I will be down at the boat this weekend and I will take a look at the plugs and the choke and report back. I spoke with the rebuilder about the altitude before he worked on my carb. He did not recommend re-jetting for my altitude. My normal boating is done at about 3500 feet. Its not like a high mountain lake. My normal air temp is above 75 degrees when our boating season starts, so in reality the choke should open fairly quickly and stay open all day.

 

[ktbarrentine]

Re: Intermittant starting issue

1989 Chaparral, 5.7L merc with Thunderbolt ignition, 4bbl Rochester.

I had my carb rebuilt last year and just had the carb adjusted again by my local mechanic at the lake. The boat runs great but I'm still having times where it takes a long time to start. Sometimes it will start with just a bump of the key and sometimes I have to crank and put the throttle all the way forward, then it lugs and black smoke comes out of the exhaust until the engine smooths out. It sure seems choke related but the mechanic says the choke is perfect and don't touch it. I know my timing is good. How long does a coil last? It is probably the original coil. I haven't changed plugs in a couple seasons, but only put maybe 50 hours on my boat last year. I probably could do a complete tune up, plugs, wires, rotor, cap but should I think about replacing the coil also or is it one of those things that if its working its working and don't replace it unless it goes out. Sure would like to be able to just bump the key every time. Thanks for the responses!

Had similar symptoms on a 1990 5.0L. Ended up being a cracked diaphram on the mechanical fuel pump that was putting excess gas in the carb airhorn. Didnt really affect things until I turned the engine off for short period, then tried to restart, and had to treat it as if it was flooded. Not saying this is your problem, but the sight flow tube is an easy thing to rule out of the equation.

 

[rad1026]

Re: Intermittant starting issue

oh, okay, see if there is fuel coming up the flow tube in to the carb? Is that what you mean?

 

[ktbarrentine]

Re: Intermittant starting issue

oh, okay, see if there is fuel coming up the flow tube in to the carb? Is that what you mean?

Exactly!! If the fuel pump diaphram is bad you will see fuel coming into the airhorn where the sight flow tube hooks onto the airhorn (of course, requires removal of flash arrestor while the engine is running).

KB

 

[Robert D]

Re: Intermittant starting issue

Check the wires to the coil, closely. In fact, inspect all the ignition related wires, by removing whatever wrap is over them so you can see them. Had similar issues, traced it to the 12v+ wire taking power to the coil. Sometimes it would run great for hours, then start acting up. Sometimes starting would be an issue, sometimes it wouldn't idle. Totally intermittent, wouldn't do it when I wanted it to! (For test purposes of course.) Apparently a combination of heat, humidity and whatever else would affect whether or not this wire would carry power. The wire itself was still connected, but burned by what appeared to be an overheated coil. Backside of the coil had what looked like oil leaking out of the top of it at one time.

 

[NHGuy]

Re: Intermittant starting issue

Sorry about the preaching then. So when you had the rebuild done was it maintenance? Or was it for solving a problem? And if it was for a problem, is that the same problem you are getting now?
Maybe RobertD has a good point. It's worth a look.

 

[rad1026]

Re: Intermittant starting issue

NH Guy, the rebuild took care of a bad accelerator pump diaphragm. I do not have the sputtering, hesitation on acceleration any more, but then this problem started. I think both RobertD and KTbarrantine have interesting scenarios. I will keep all these in mind when I get back to the boat this weekend. I would sure like to get this figured out! Thanks for the shared experiences everyone.

 

[rad1026]

Re: Intermittant starting issue

Okay, here is an update from my weekend. Put the boat in the water Saturday morning and started up fine, as usual. Ran the boat around for a good couple hours wakeboarding etc. Basically had the same problems. Runs great when its getting throttle, but as soon as it drops down to the idle circuit it idles inconsistent, seems to flood. Restarting requires throttle feathering with lots of smoke and about 15-30 seconds of clearing out the system so it will idle again. I verified my choke is open. So when the wind picked up and we headed back to the beach I decided to put a new fuel pump on. I brought this down to the lake with me, Carter m61073 NAPA AUTO PARTS

I spent a few minutes putting the new fuel pump on. Everything went fine. Got the push rod back in the block and the pump on fine. Got the boat back in the water and fired right up. Then she just died. Very difficult to restart. Seemed flooded again. Verified the choke plate was still open. Held the throttle down and it finally started again but would not idle at all. Could not back off of the throttle or it would die, had to keep the rpm's at 1000 or more to keep it running. I played with the needle valves for an hour, but could not keep it running. What the heck? What would have changed so much from the new pump? I took the old pump apart and the main diaphragm was quite cracked. I could not see and visible holes in the diaphragm but it was definitely cracked all the way around. I'm very frustrated. Did I use the wrong pump? The only thing I can think of now is maybe the new pump is putting out more pressure and possibly my float needle is not seating all the way and the pressure just enhanced the flooding problem. Any ideas?

 

[Bondo]

Re: Intermittant starting issue

Okay, here is an update from my weekend. Put the boat in the water Saturday morning and started up fine, as usual. Ran the boat around for a good couple hours wakeboarding etc. Basically had the same problems. Runs great when its getting throttle, but as soon as it drops down to the idle circuit it idles inconsistent, seems to flood. Restarting requires throttle feathering with lots of smoke and about 15-30 seconds of clearing out the system so it will idle again. I verified my choke is open. So when the wind picked up and we headed back to the beach I decided to put a new fuel pump on. I brought this down to the lake with me, Carter m61073 NAPA AUTO PARTS

I spent a few minutes putting the new fuel pump on. Everything went fine. Got the push rod back in the block and the pump on fine. Got the boat back in the water and fired right up. Then she just died. Very difficult to restart. Seemed flooded again. Verified the choke plate was still open. Held the throttle down and it finally started again but would not idle at all. Could not back off of the throttle or it would die, had to keep the rpm's at 1000 or more to keep it running. I played with the needle valves for an hour, but could not keep it running. What the heck? What would have changed so much from the new pump? I took the old pump apart and the main diaphragm was quite cracked. I could not see and visible holes in the diaphragm but it was definitely cracked all the way around. I'm very frustrated. Did I use the wrong pump? The only thing I can think of now is maybe the new pump is putting out more pressure and possibly my float needle is not seating all the way and the pressure just enhanced the flooding problem. Any ideas?

Ayuh,.... Even though ya rebuilt the carb, last year,.... Ya Still got a Carb Problem....

I'd either rebuild it again, 'n look for the problem, or replace it...

 

[rad1026]

Re: Intermittant starting issue

Yeah, I'm with you Bondo. Wish I had the boat home so I could spend some time with her. I really think it has been a combination of things. I bet the old fuel pump was weak and I bet my float needle valve is not seating all the way. The new pump just made it worse. I really had no choice this time but to leave it with the mechanic at the lake. I hate to be so pickey about the way the boat runs. Some people might just chalk it up to running a carbureted system, but I know how it is supposed to run and I know it is not right. I will report back in a couple weeks when I hear from the boat shop. Thanks for all the help!

 

[rad1026]

Re: Intermittant starting issue

update, I just got off the phone with the boat shop at the lake. Both my suspicions were correct. The fuel pump was putting out 12 lbs which is way too high. They shimmed to get it down to about 7 lbs. They also said who ever rebuilt my carb put the old brass float back in. Said they should have used the newer style float. I don't know why a brass float wouldn't be as good, but hey, if it works then it works. Just wish I had the boat at home, those are problems I could have taken care of. Oh well if it works and fixes my problems and I have more fun at the lake because I'm not mess'in with the boat then I'm happy to pay the professional. This time. Any comments about their diagnosis?

 

[rad1026]

Re: Intermittant starting issue

Final update on the intermittent starting issue. Got the boat back from the shop Saturday and took it out to the lake. Wow! The boat runs better then it has in the 8 years I have owned it. In addition to getting the fuel pressure corrected and the new float in the carb they also replaced some gaskets in the carb they said were automotive gaskets and they also replaced the distributor sensor. The sensor was completely rusted and was the original 1989 part. They said they had never seen one last that long. I should have taken a picture of it, I don't really know how the boat even ran. Sometimes you just have to call in a professional. I rarely do, but this time I needed help and they did a great job. I picked up another 3 mph at WOT and am hoping my fuel economy improves. Its time to change the plugs now since they have probably been fowled from flooding for two seasons now.