I have a 2005 Mercury 40hp 4 stroke efi outboard. On initial start up (after days of sitting) it will crank and run fine. After running several miles, I can stop, fish for a hour or so, but when I attempt to start again it will start then die. After attempting to start repeatedly, it will just turn over, no fire. The only thing I can do to resolve it is to remove the in-line filter, blow it out, replace it, pump the bulb and it will start missing a little at first but eventually running well at speed. Will idle once warmed up again. I have replaced: fuel tank, fuel hose, in-line filter (arrow pointing the correct way), Spark plugs. Added: sea foam to fuel, stabil for ethanol to fuel. I was thinking a fuel pump but have been told that there could be 2 on this motor and would really appreciate some advice from an expert. Thanks in advance.
Make (of engine): Mercury
Model (of engine): 40 hp
Replaced fuel tank, fuel hose, fuel in-line filter, replaced spark plugs. Added sea foam to fuel, added stabil for ethanol to fuel.
My name is XXXXX XXXXX X will be helping you today. Most questions will involve troubleshooting, and usually take many posts back and forth. Post back with questions as needed.
Mercury makes 2 different 40 EFI engines. Do you have your serial number handy so I can ID it.
If not, do you have the 3 cylinder 40, or the 4 cylinder 40?
The specs are different between the 2, so I do need to know which one you have.
Also, another question for you here. When it will not restart, have you tried doing a "clear flood" start?
This is a 3 cylinder 40. I am not sure what a "clear flood" start is... but I have tried to pump the bulb while starting. Tried to simple disconnect/reconnect the fuel line. The only thing that seems to work is to remove the in-line filter, blow it out, then reconnect, pump the bulb, then start it.
The issue here is your either flooding out or the engines computer does not know what the temperature of the engine is.
Flooding out means you turn off the engine and your still getting fuel to the engine. If the injectors are leaking on you this will do it every time.
To test for leaking injectors you need to hook up a fuel pressure gauge to the engine, cycle the key a few times so the fuel pump primes to peak pressure. Then watch the fuel pressure gauge and see if it starts to slowly drop on you or not. Your allowed a little bit of a drop, 2 to 3 psi every couple of minutes. But if it starts dropping quickly, then the injectors are not holding the fuel in, and they are leaking down when you shut the engine off, flooding the engine.
To "clear the flood" on a hot start what you would do is put the throttle in neutral, open it all the way up, and crank it. The engine will likely start after a few revolutions so make sure your ready to pull back on the throttle.
Option B here is if the engine has a bad temperature sensor, and the computoer (ECM for short) does not know how hot the engine is. When it comes to all of the various sensors on the engine, you only get a code and an alarm if a sensor goes out of range or is not seen by the ECM. But if a sensor gives a reading that is good, even if not correct, you do not get codes.
For example, if the temperature sensor is always reading 32F, that is a valid temperature. But the problem arises if the sensor is telling the ECM that the block is 32F, and the block is really 120F. The ECM will not calculate the correct fuel to air ratios, and the engine will be hard to impossible to start. Really the best way to test for this is to hook it up to the scan tool and read the temperature through that.
Feel free to post back with questions
Degree in Marine Technology. Gas and diesel marine mechanic.
,I have now replaced 2 temp sensors (one on the block and the other on the intake) and all 3 of my fuel injectors. This did not fix my problem. Did not change my problem. The only thing I have found through all of this is in order to get the motor running once the issue starts, I push a nail in the tire valve like valve on the side of the fuel pump while starting and do it a few times once its running in order to get going. Otherwise it just constantly floods out.
I have now replaced 2 temp sensors (one on the block and the other on the intake) and all 3 of my fuel injectors. This did not fix my problem. Did not change my problem. The only thing I have found through all of this is in order to get the motor running once the issue starts, I push a nail in the tire valve like valve on the side of the fuel pump while starting and do it a few times once its running in order to get going. Otherwise it just constantly floods out.,I have now replaced 2 temp sensors (one on the block and the other on the intake) and all 3 of my fuel injectors. This did not fix my problem. Did not change my problem. The only thing I have found through all of this is in order to get the motor running once the issue starts, I push a nail in the tire valve like valve on the side of the fuel pump while starting and do it a few times once its running in order to get going. Otherwise it just constantly floods out.
Whats the fuel pressure, key on engine off, and key on engine on?
Cold engine: Key on: 42lbsRunning: 42lbsWarmed engine for about :30 minutes (ran on hose):running: 44lbskey on: 43lbslet sit for 1 hour:key on: 42lbsrunning: 42lbsside note: when checking to see if motor was warmed up, I noticed that the voltage regulator was very hot. Much hotter than the block, much quicker. ,
Hmmm. Your fuel pressure is good. The voltage regulators do get hot, but not that hot. The problem with the voltage regulator heating up is it can be a bad regulator, or a bad stator.
You can measure the stator with a basic ohm meter. What you want to do is take 2 readings, on when cold, and one when hot after the problem has happened. You want to disconnect the stators wires from the regulator. And measure the resistance between the 2 yellow wires. Spec is .2 to .3 of an ohm. You also want to go between each yellow wire individually to engine ground. (Yellow to ground). You should not have any conitinuity at all.
Have you checked the charging voltage at the battery when running yet?
Stator: Cold engine- 0.4 ohms. Ran engine for 30 minutes, Hot engine- 0.0 to 0.2 (I measured it several times, as the connector/wire was very hot too). After engine cooled 1 1/2 hour- 0.4 again.Battery Voltage: key off- 12.52 vdc. Running idle- 13.38vdc. Running about 1/4 rev- 13.60
Take 1 more measurment for me. Put your voltmeter on the battery and set it to AC Millivolts. Let me know what you get for a reading.
Also, what kind of shape are the battery cables in? Are the cable ends nice and clean and tight, or do they look like they have seen better days?
Key off: 0.0 vac
Key on: 0.0 vac
running idle: 0.048 vac
running 1/4 rev: 0.077 vac
The battery cables dont look very bad; light surface corrosion. But, they have been on the boat since bought new.
Your charging good then here. And as you should be. Fuel pressure is also good. The only thing left to check here before putting the engine on a scan tool is compression, just to make sure your not fighting a low compression issue. Have you done a compression test yet? If so what were your numbers. If not, check it and see what you get.