Engine stalling seconds after starting

[maicoman]

Thank you members in advance for any suggestions.I own a 1998 20 foot Sea Ray with a 305 TBI motor and a alpha outdrive.This past week my boat overheated due to the exhaust manifolds being in bad shape.I replaced my manifolds and elbows and tried to start the boat.It would only start on the muffs with a little throttle.Once warm it would idle but not right away.I have since replaced the TPS,IAC,and the IAT.I have checked the ECM for error codes and there are none.This season I noticied that the alternator would not look like it was charging until the tach read about 1500 RPM.I was wondering if this is normal.The voltmeter would jump from around 12 to 14.7 volts right at 1500 RPM.I'm wondering, if the alternator is bad would the motor start for an instant then not have enough voltage to keep the ECM powered up.Thanks again for any help.The dealer listed the price of a new ECM at 2600 dollars OOUuCH

 

[mpdive]

Re: Engine stalling seconds after starting

Is the TPS adjustable? I'm just wondering if you have the right voltage value at idle being sent back to the ecm.

 

[maicoman]

Re: Engine stalling seconds after starting

I do not think that the TPS is adjustable,I have not tried reading the values of the computer while the engine starts for the few seconds.My fuel pump is just shutting down my injectors right away.

 

[mpdive]

Re: Engine stalling seconds after starting

With the key on engine off, it should have a value of around .045-.055 volts at closed throttle. It should have an adjustment on it such as the mounting hole being oblong. Might not be the problem your having but just want to make sure the ecm is not reading WOT. As far as the ecm being powered, if it's cranking fine power to the ecm is not an issue. The ecm usually runs on a 10 amp fuse so there is plenty of power to it. When you say overheat, how bad was it?

 

[maicoman]

Re: Engine stalling seconds after starting

My brother in law burned the boot off the starboard elbow.Is there a sensor that iniates a buzzer than shuts the power to the fuel pump.I'm thinking that the battery voltage is a little low and with the alternator not working the Ecm iniatially works at start up then drops off when no crank revolution is detected.Where does the ECM gather info regarding crank revolution and position.My experiance is with motorcycles and not boats but battery voltage seems to be the problem more often than not.Help !

 

[maicoman]

Re: Engine stalling seconds after starting

Is there a sensor that will iniate the buzzer than shut the injectors off.Where does the ECM receive signals that the engine is turning,Alternator? Maybe my battery is too low to hold power to the ECM after start up,assuming that the alternator is not helping and possibly shorting something.Help

 

[achris]

Re: Engine stalling seconds after starting

ECM get the temperature signal from the engine temperature sensor. Based on the engine temperature it will adjust the fuel delivery and, if necessary, fire the buzzer. The ECM gets 'engine timing' signals from the distributor. As MPDIVE said, if the battery is turning the engine, there is enough juice for the ECM...

You need to determine if it's dying because of a lack of fuel or a lack of spark. Connect up a timing light...

 

[RandyJ]

Re: Engine stalling seconds after starting

I would investigate what caused the boot to burn off the elbow. Water blockage, cracked exhaust manifold cooling jacket? I'm not familiar with these engines but it seems that error codes would indicate if there were low compression or misfire. Not at all a bad idea to look at compression after an engine runs hot.

 

[achris]

Re: Engine stalling seconds after starting

My brother in law burned the boot off the starboard elbow.....

When I was very young my father took me aside and gave me a small, but valuable, piece of advise...

"Never lend out your wife or your boat... They will both come back in the same condition..." (I'll let you figure that out.)

OP... Why isn't the brother-in-law paying for this to be repaired????

 

[Technorunner]

Re: Engine stalling seconds after starting

If it has gone that warm, I would look more to the Cyl.head. Blown gasket or cracked head.
Water leakage into the cylinder could give you that symtom. it dosent have to be a big leak.
Do a compression reading and remove the plugs and look down for water drops on the pistons.

With the Alternator. If you rev the engine to 1500 and then back down to idle does it still give around 14V or does it stop to charge again?
If it still charge after backing down i would just see if the (coal?) isent worn to much and that the collectors for those coals isent worn to unevenly. Hope you can make sence of this despite my English.

 

[achris]

Re: Engine stalling seconds after starting

...If it still charge after backing down i would just see if the (coal?) isent worn to much and that the collectors for those coals isent worn to unevenly. Hope you can make sence of this despite my English.

Coals = brushes?
Collectors = slip-rings?

 

[Technorunner]

Re: Engine stalling seconds after starting

thx thats what i was thinking of i did direct translation. Sometimes it works

 

[mpdive]

Re: Engine stalling seconds after starting

My brother in law burned the boot off the starboard elbow.Is there a sensor that iniates a buzzer than shuts the power to the fuel pump.I'm thinking that the battery voltage is a little low and with the alternator not working the Ecm iniatially works at start up then drops off when no crank revolution is detected.Where does the ECM gather info regarding crank revolution and position.My experiance is with motorcycles and not boats but battery voltage seems to be the problem more often than not.Help !

Keep in mind, the ECM will only set a fault light when it receives a "hard code" Your charging system is not monitored by the ECM. The ECM is purely a fuel management system.

 

[achris]

Re: Engine stalling seconds after starting

Keep in mind, the ECM will only set a fault light when it receives a "hard code" Your charging system is not monitored by the ECM. The ECM is purely a fuel management system.

and ignition timing....

 

[mpdive]

Re: Engine stalling seconds after starting

and ignition timing....

Yes. I meant that as part of the management team I wan't to live in the southern hemishere too!

 

[maicoman]

Re: Engine stalling seconds after starting

Thanks everyone for your help.Brother in law will pay but if he tries to fix I'll have more problems.Why do you think the boat will keep running if past the idle position within the brief start-up.In other words I can make the boat rev at 1500 all day smooth as silk just not at idle.I'm planning on doing cap and rotor and alternator soon.Will tell everyone what I find.Boat is in water 100 miles away and bro in law also busted the trailer axle so I can't get it home.He will pay for that also.By the end I'll have a new boat and I'll tell him to borrow the boat at the end of each season.Thanks again everyone.

 

[maicoman]

Re: Engine stalling seconds after starting

Technorunner and achris I forgot to mention that it seems that it stays at 15 Volts after it has been up there once.At what RPM does the alternator start to charge,it seems to be dead at idle.When the motor dies the injectors stop blasting and the fuel pump is not heard after initial,turn of the key part way,pressure build.I'm guessing that it is purely electrical as opposed to fuel issue.I also dont want to think about water in head but may have to investigate.After he pays for all new parts.Ha, so you like the boat do ya!

 

[Don S]

Re: Engine stalling seconds after starting

Do you have a Merc serial number for your engine handy?

 

[maicoman]

Re: Engine stalling seconds after starting

Don The Serial number is OL351438. Throttle Body 305 with Alpha outdrive

 

[mpdive]

Re: Engine stalling seconds after starting

Technorunner and achris I forgot to mention that it seems that it stays at 15 Volts after it has been up there once.At what RPM does the alternator start to charge,it seems to be dead at idle.When the motor dies the injectors stop blasting and the fuel pump is not heard after initial,turn of the key part way,pressure build.I'm guessing that it is purely electrical as opposed to fuel issue.I also dont want to think about water in head but may have to investigate.After he pays for all new parts.Ha, so you like the boat do ya!

Your alternator is technically charging or ready to charge at all times. The charging demand is based off the current state of the battery. If you are at a lower rpm and the battery is discharged, the alternator is still charging the battery at a lower rate. As rpm's increase the alternator output also increases if the battery demand is there. However, the alternator has a voltage regulator that limit's the charge rate, so as not to overcharge the battery. If you say it's stuck at 15 volts, I would probably pull it and have it tested but this is not causing the problem your currently having.