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2015 merCruiser 3.0 MPI hard to start

D

Digidon

Member
I have a 2015 MerCruiser 3.0 multiport injection engine that is hard to crank I’ve changed spark plugs, spark, plug wires, cap and rotor, drained fuel and added fresh fuel, cleaned flame arrestor, and changed water fuel separator and I literally have to crank this thing 20 times before it starts, but once it starts, it runs fine What could be the problem?
 
Anti syphon valve stuck open contributng to fuel pump loosing prime is first thought...
A fuel pressure gauge can verify the rail has pressure...the engine won't start until fuel rail has adequate pressure...
 
Do you hear one beep when key is turned ON?
Check the fuel pressure, it should be 43 psi when key is turned ON before cranking and should stay that way
 
No, I do not hear the beep but upon inspection today, I was looking for a Schrader valve on the fuel rail and I noticed there is a clear tube that was disconnected from the intake manifold and looks like it goes around to the fuel pump so I connected it to see what happens. It was still hard to start, but once it started and ran once I turned it off, it started right back up before it would not do that. It would be hard to start even if I let it run for five or 10 minutes then turn it off. It would take a long time to crank. Can you tell me what that hose is I know it’s a vacuum hose of some sort and probably works with the diaphragm on the fuel pump. Thanks for taking time to help me.
 
That most likely the vacuum line going to the fuel pressure regulator. It was hard to start maybe because of the vacuum leak
 
OK, thank you very much but it still doesn’t start like it used to but a little better. I’m going to check the fuel pressure if fuel pressure is low. What do you recommend? Thanks again.
 
makomark said:
Anti syphon valve stuck open contributng to fuel pump loosing prime is first thought...
A fuel pressure gauge can verify the rail has pressure...the engine won't start until fuel rail has adequate pressure...
Click to expand...
OK, thank you do you know where the anti-siphon valve will be located possibly on the fuel pump? My boat has two fuel pumps and mechanical and a electrical thanks again.
 
Digidon said:
OK, thank you do you know where the anti-siphon valve will be located possibly on the fuel pump? My boat has two fuel pumps and mechanical and a electrical thanks again.
Click to expand...
usually, its the first fitting off the top of the fuel tank...most look just like a hose barb adapter but there is a spring loaded check ball on the inside...
 
makomark said:
usually, its the first fitting off the top of the fuel tank...most look just like a hose barb adapter but there is a spring loaded check ball on the inside...
Click to expand...
OK, thank you I will check into that fuel pressure seems to be OK at 40 psi and a rest pressure of 39 psi which has held for about 30 minutes so far
 
Digidon said:
OK, thank you I will check into that fuel pressure seems to be OK at 40 psi and a rest pressure of 39 psi which has held for about 30 minutes so far
Click to expand...
Digidon said:
OK, thank you I will check into that fuel pressure seems to be OK at 40 psi and a rest pressure of 39 psi which has held for about 30 minutes so far
Click to expand...
Digidon said:
OK, thank you very much. I checked fuel pressure today. It was at 40 psi and then when I turned it off, it had a rest pressure of 39 psi with so far has held for 30 minutes. I don’t know if rest pressure is important with these engines but thank you for all your help.
Click to expand...

AllDodge said:
The valve is item 5 in link below. Pressure should be 43 psi
https://www.mercruiserparts.com/bam/subassemblydetail/42593739/28167871
Click to expand...
OK, I see that item 5. Should I just replace that for kicks and grins being that it’s only $20 and can I purchase that from you?
 
Digidon said:
OK, I see that item 5. Should I just replace that for kicks and grins being that it’s only $20 and can I purchase that from you?
Click to expand...
NO, sounds like you need a parts cannon

Replacing parts just to replace parts
cat no.gif
 
Not really replacing them just to replace them some things do we’re out overtime boat is 10 years old but anyway that’s why I’m consulting you thanks
 
makomark said:
Anti syphon valve stuck open contributng to fuel pump loosing prime is first thought...
A fuel pressure gauge can verify the rail has pressure...the engine won't start until fuel rail has adequate pressure...
Click to expand...
I have a question I hooked up a pressure gauge to the fuel rail and I had 40 psi of pressure after I ran the engine and turned it off. I had a rest pressure of about 39 psi which held for over 30 minutes, but when I went out the next day, the rest pressure was down to 10 psi does this mean the antisiphon valve is not working I don’t know how long it is supposed to hold the rest pressure although the boat did start up in about five cranks but I was wondering, do you think I need to replace this antisiphon valve
 
you are measuring the 'product' side of the fuel pump...the anti syphon valve is on the suction side - i wouldn't change it...
 
Digidon said:
I have a question I hooked up a pressure gauge to the fuel rail and I had 40 psi of pressure after I ran the engine and turned it off. I had a rest pressure of about 39 psi which held for over 30 minutes, but when I went out the next day, the rest pressure was down to 10 psi does this mean the antisiphon valve is not working I don’t know how long it is supposed to hold the rest pressure although the boat did start up in about five cranks but I was wondering, do you think I need to replace this antisiphon valve
Click to expand...
Holding pressure for 30 minutes to an hour is good so don't change anything
The antisiphon valve is not an issue here
 
AllDodge said:
Do you hear one beep when key is turned ON?
Check the fuel pressure, it should be 43 psi when key is turned ON before cranking and should stay that way
Click to expand...
Good morning I just wanted to ask you because I just noticed I do hear one beep when I turned the ignition key to the start position. Does that mean there is a problem with something?
 
Digidon said:
Good morning I just wanted to ask you because I just noticed I do hear one beep when I turned the ignition key to the start position. Does that mean there is a problem with something?
Click to expand...
No, it should make one beep indicating ECM check completed ok and can start.
 
OK, thank you is there anything else you can recommend because I tried to start it up this morning and literally had to crank five or six times stop and then five or six times more before it started is there a certain starting procedure when starting fuel injected marine engines I bought this boat brand new and it used to start just like a car engine with just two cranks.
 
We're all guessing because we need some input from a scan of the motor. With a scanner we could look at what is taking place in real time

If every time you crank the motor the FP stays close to 43 psi then it's not Fuel, that leaves spark

Your motor has the EST distributor which the module controls the spark. Could put a spark gap TESTER installed on the coil or one of the plug wires. Crank the motor and see if you see spark

If it is no spark, then most likely it's the module, but not guaranteed
 
AllDodge said:
We're all guessing because we need some input from a scan of the motor. With a scanner we could look at what is taking place in real time

If every time you crank the motor the FP stays close to 43 psi then it's not Fuel, that leaves spark

Your motor has the EST distributor which the module controls the spark. Could put a spark gap TESTER installed on the coil or one of the plug wires. Crank the motor and see if you see spark

If it is no spark, then most likely it's the module, but not guaranteed
Click to expand...
OK, thank you maybe it is a weak spark because I know it’s getting some spark because it does start eventually
I have a spark tester. I will check it out later and let you know. Thanks again for your time.
 
hello OK I got a chance to connect a spark detector to spark plug wire number one and I cranked it over and now I’m not
Getting any spark at all and engine will not start so apparently I had some kind of intermittent problem. Do you recommend replacing the ignition module first or the coil thank you.
 
It's hardly ever the coil, in most cases it's the module. The good thing is can get it from any auto parts store, but if you get it from a GM dealer it's guaranteed
 
OK, thank you when I’m trying to purchase this part from the dealer. What engine do I reference when I tell them I need the part or do I just tell them I have a Mercruiser marine engine
 
AC Delco EST distributor ignition module.
GM D1943A
GM 19179578
Merc 8M6008208

Suggest call and ask if they have in stock and their warranty
 
OK, I called the dealership in my area and they did not have any of those part numbers listed. They gave me a part number of 19435461. Do you think that might be the same? Also, is it possible to know what car engines these go on so at least maybe I can tell them I need it for that model to make sure I get the right one thank you.
 
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