trouble with 4.3L burping

[Philom]

I have a 2006 Bayliner 195 with 4.3 L MPI engine. A couple of times this year when I start it up it idles poorly, when I try to give it throttle, it won't engage & engine gurgles, burps & won't rev up. Kind of sounds like it is flooding. I push the centre button on control to try to rev up & it does the same. Sometimes it stalls out. After starting it up a few different times it seems to clear itself out & away it goes. I changed the fuel filter, ( normally do every year) plus spark plugs, wires, rotor & cap as I have never changed them. Still acts same way. Any ideas?

 

[Fun Times]

What did the spark plugs look like? Fuel fouled at all?

Did the inside of the distributor cap look like there may have been any moisture on the contacts. Is the humidity high in your area?

Need your engine serial number to confirm this following idea but you might want to inspect/clean the flame arrestor cover, the inside of throttle body, both sides of the throttle plate and replace your IAC muffler to see if it helps clear it up. See IAC muffler item number 6 and maybe #11, http://www.mercruiserparts.com/Show...82.png&inbr=13808&bnbr=80&bdesc=Throttle+Body

Once it's running you can get to full RPM?

It's always good to take a fuel pressure reading before and after the starting/running event.

 

[Bondo]

I changed the fuel filter,

Ayuh,..... Did ya examine the Contents of the old filter for Water, 'n Crud,..??

If Not,..... Ya threw away a very Important diagnostic tool,...... even more so with electronic controlled motors,....

 

[Philom]

Ayuh,..... Did ya examine the Contents of the old filter for Water, 'n Crud,..??



If Not,..... Ya threw away a very Important diagnostic tool,...... even more so with electronic controlled motors,....

I did inspect the filter. There was no crud & no water in it.

 

[Philom]

No Title

What did the spark plugs look like? Fuel fouled at all?

Did the inside of the distributor cap look like there may have been any moisture on the contacts. Is the humidity high in your area?

Need your engine serial number to confirm this following idea but you might want to inspect/clean the flame arrestor cover, the inside of throttle body, both sides of the throttle plate and replace your IAC muffler to see if it helps clear it up. See IAC muffler item number 6 and maybe #11, http://www.mercruiserparts.com/Show...82.png&inbr=13808&bnbr=80&bdesc=Throttle+Body

Once it's running you can get to full RPM?

It's always good to take a fuel pressure reading before and after the starting/running event.

Plugs looked fine to me. Light brown, no fuel smell. I had little fuel in it before the season & put in premium fuel plus a can of Seafoam. Plus have ran about 2 tanks of premium fuel through it. The cap had some minor corrosion but didn't seem too bad. Humidity has been high but not normally a problem. When it ruins, it runs fine, WOT seems normal, no bogging or hesitating, doesn't miss, runs good. It did it again today on the lake. Took about 10 minutes of intermittent winding & all of a sudden the way it went. Every time it has done it we have been driving the boat than we sat for an hour + before we tried to start it again. Coincidence? I'm confused.

 

[Bonus Check]

Have you pulled a sample of fuel from the bottom of your tank? thats something simple to check and cheap to do. Rule out the simple things first.

 

[Fun Times]

Plus have ran about 2 tanks of premium fuel through it.

If you are filling up on land then there really isn't a need to use 91+ premium as your engine model was designed more for regular 87...Volvo says 89 which personally I agree with as I've noticed a difference in both boats and GM vehicles vs running 87 & 91.

The cap had some minor corrosion but didn't seem too bad. Humidity has been high but not normally a problem.

Just thinking out loud that had you noticed this starting issue on either really high humidity days or possibly after going swimming that could give the water a path that drips off of the swimmers clothing and eventually drip onto the distributor cap or into the throttle body. It happens more than one would think.

When it ruins, it runs fine, WOT seems normal, no bogging or hesitating, doesn't miss, runs good. It did it again today on the lake. Took about 10 minutes of intermittent winding & all of a sudden the way it went. Every time it has done it we have been driving the boat than we sat for an hour + before we tried to start it again. Coincidence? I'm confused.

Possibly not. Until now I was thinking cold start issues so it may be symptoms of heat soak or vapor locking fuel is a high possibly. Next time you're boating and you get ready to shut the engine down for awhile, first let the engine idle for a few minutes and if possible try lifting the engine cover a little to allow some of the hotter air to escape. Turning on the bilge blower may help as well. Then after your normal routine, see if the engine exhibits the same symptoms. Here's some info about vapor lock for you to catch up on, Gasoline Engine Vapor Locking

You're going to want to figure out what cooling system your engine model has, Standard Cooling System, Seven Point Drain ... Or Standard Cooling System, Single and Three Point Drain

On some occasions the check valve on the 7 point drain system closest to the thermostat housing has become stuck open allowing hot water to flow back down to the cool fuel pump letting the fuel get hot to vapor lock. See item number 13 in the first diagram. Having an infrared thermometer gun on board may help with your testing's. Try to see how hot that valve/water hose is getting heading down to the fuel pump mounted on the port side under the front motor mount next to the oil pan.

Sometimes with a rag in hand, you can push in on the fuel schrader valve located on the fuel rail to help remove the vapor out of the system quicker.

Crank Position Sensors can become heat sensitive as well. http://www.buyautoparts.com/howto/sy...aft-sensor.htm

Please bear in mind that these are only just some possibilities of your described situation.

 

[NHGuy]

That's a Schraeder valve. Looks like an oversize tire air valve.

 

[Fun Times]

That's a Schraeder valve. Looks like an oversize tire air valve.

Spell checker must be out of adjustment today since we both posted Schrader valve spelling incorrectly. That's what we get for relying on spell checker to spell it correctly for us....:lol:

 

[Philom]

I

Possibly not. Until now I was thinking cold start issues so it may be symptoms of heat soak or vapor locking fuel is a high possibly. Next time you're boating and you get ready to shut the engine down for awhile, first let the engine idle for a few minutes and if possible try lifting the engine cover a little to allow some of the hotter air to escape. Turning on the bilge blower may help as well. Then after your normal routine, see if the engine exhibits the same symptoms. Here's some info about vapor lock for you to catch up on, Gasoline Engine Vapor Locking

This could be part of the problem but not sure. On 2 of the 4 occasions that it has done this I have been on land and started it up at home with the muffs on it. So it hadn't run for over a week, so heat inside the engine wasn't an issue those times.

You're going to want to figure out what cooling system your engine model has, Standard Cooling System, Seven Point Drain ... Or Standard Cooling System, Single and Three Point Drain

I have the 3 point drain system

On some occasions the check valve on the 7 point drain system closest to the thermostat housing has become stuck open allowing hot water to flow back down to the cool fuel pump letting the fuel get hot to vapor lock. See item number 13 in the first diagram. Having an infrared thermometer gun on board may help with your testing's. Try to see how hot that valve/water hose is getting heading down to the fuel pump mounted on the port side under the front motor mount next to the oil pan.

Sometimes with a rag in hand, you can push in on the fuel schrader valve located on the fuel rail to help remove the vapor out of the system quicker.

Does the 3 point system have the Schrader valve?

Crank Position Sensors can become heat sensitive as well. http://www.buyautoparts.com/howto/sy...aft-sensor.htm

Please bear in mind that these are only just some possibilities of your described situation.

I really appreciate your thoughts so far and hope you conitune to send. I am going to try to find a fuel pressure gauge and see what the results are.

 

[Philom]

Found a fuel pressure guage, where & how do I test it, and what results do I want?

 

[duttymaxx]

So I've been having a similar issue with my 4.3 mercruiser 2005 model. I changed out the distributer and rotor, still had the same problem. After sitting for 1+ hr it does burping thing, I can open up the engine compartment take off the distributor cap look at it yep it's clean, put it back on and crank the engine a couple of times and it will fire up and run like a scalded dog.

 

[Philom]

It looks like the fuel pump is on the bottom of the engine which impossible to get at. How do I test fuel pressure? Are there any relays or sensors that I could check.

 

[Fun Times]

It looks like the fuel pump is on the bottom of the engine which impossible to get at. How do I test fuel pressure? Are there any relays or sensors that I could check.

To test fuel pressure look on top of the engine fuel rail, you should see a black cap that resembles a tire cap to add air to a car tire. The proper name is called a Schrader Valve: http://www.bing.com/images/search?q...orm=QBIR&pq=schrader valve &sc=8-15&sp=-1&sk=

Connect your gauge to the Schrader Valve which is item numbers 13 & 14 in the following link,http://www.mercruiserparts.com/Show...5&bnbr=90&bdesc=Intake+Manifold+and+Fuel+Rail

You should be seeing around 40- 43 psi.

To check sensors while the event is happening, you'd need to connect a marine scan tool which may or may not help depending on what is really wrong.

Typically a relay would keep the engine from running/starting vs running rough, etc..

 

[Philom]

Just figured it out.fuel pressure peaks at 44 than sits at 39 psi when pump is off.

 

[Fun Times]

Just figured it out.fuel pressure peaks at 44 than sits at 39 psi when pump is off.

On your next trip out, you'll want to do all the tests mentioned above, leave the fuel gauge connected to read the pressure during the event also have a container that is fuel suitable so you can push the button on the test gauge to air out any possible vapor to see if it will run better quicker.