MCM 5.0L EFI 305 Will not Start.. Fuel Starvation? Cool Fuel Gen II? (FIXED ISSUE!!!) Fuel Pump replacement

[Challenger84]

MCM 5.0L EFI 305 Will not Start.. Fuel Starvation? Cool Fuel Gen II? (FIXED ISSUE!!!) Fuel Pump replacement

Hello guys and gals,

I'm having a little issue with my motor.
engine
Mercruiser MCM 5.0L efi (305) model year 2000.. engine serial # 0L606892
Hull:
Regal 2100 LSR

Back story:
Took boat out tubing/wakeboarding. I go to pick some people up at the docks and boat starts to bogg down a little bit. I give it a little throttle and the engine revs up and stays running.
Get to the docks and load up passengers and shut the motor off.
As i get everyone aboard i go and start the engine and starts up.
As i idle away from the docks the motor sputters and dies and will NOT restart..

Take the boat home and first thing i check is fuel..
I go through the check list that i've found searching the site..
Fuel/water seperator--replaced --No water in tank but there is a bit of black crude.. (i have a plastic tank under the floor)
filled up the seperator filter with fresh gas and tighten it back up..
As i turn the key to the ON position i can hear the fuel pump whinning..everytime.
I go to start the engine with ZERO luck..
Went back onto the forums and someone suggested to use a inline primer bulb ( I go and installed between the fuel pick up and the fuel/water seperator ) to pump the fuel up and BINGO !!! She fires up like normal.
Engine runs for about 10 min and starts bogging again like what happened the first time at the lake..
I squeeze the primer bulb again til its hard and go start her up again..
BAM she starts again.. this time i keep the engine running till i hear it bogg a bit and i start squeezing the bulb and the engine stays running..
as long as i keep squeezing the bulb the engine stays running..

I'm thinking that i have a bad fuel pump?
Once i get the fuel flowing with the bulb she runs just fine.

Any and all comments appreciated

 

[Bondo]

Ayuh,.... Sure sounds like there might be a problem in the cool fuel module,.....

Probably really easy to get to, too,....

 

[Challenger84]

Ayuh,.... Sure sounds like there might be a problem in the cool fuel module,.....

Probably really easy to get to, too,....

lol
First thing i looked at when purchasing a boat was how easy it would be to wrench on the engine..
It is fairly easy to get to..
After the removal of the back bench seat and side panels..
It's secured with wing nuts so the removal is very easy and gives me plenty of space to reach it..
I jsut need to be laying down on my belly.
I'll be removing it tonight after work..
I'll keep you guys posted.

Has anyone had an issue with this "cool fuel gen II" pump before?

 

[alldodge]

It could be the fuel pump but this statement gives me concern

as long as i keep squeezing the bulb the engine stays running..

You have a TBI system which if the cool fuel has an issue then having a fuel bulb is one issue and the other I'm having trouble with is the fuel pump produces high pressure. So if the pump is not getting fuel to the pump then the engine bogs down, but not having fuel to pump causes more issues.

So my first thought is to remove the bulb and the next is there is an issue with getting the fuel and not the pump. You might just have a restriction and the pump is fine. Start with the lines, pick up tube, and connections including filter (which you did check)

 

[Challenger84]

It could be the fuel pump but this statement gives me concern


You have a TBI system which if the cool fuel has an issue then having a fuel bulb is one issue and the other I'm having trouble with is the fuel pump produces high pressure. So if the pump is not getting fuel to the pump then the engine bogs down, but not having fuel to pump causes more issues.

So my first thought is to remove the bulb and the next is there is an issue with getting the fuel and not the pump. You might just have a restriction and the pump is fine. Start with the lines, pick up tube, and connections including filter (which you did check)

The only reason i have the bulb in between the lines is to "TEST" the fuel pick up.. It was never there to begin with..
I can pump the fuel through the line with the bulb..the fuel can get to the pump by pumping it but once it gets to the pump and beyond..
doesn't look like it continues to "pump/push" the fuel to the Carb. one the fuel is there.

AllDodge

Does this info change your thoughts on what might be wrong?
I'll try priming the system back and remove the bulb and start it again and see if that works.. Maybe the bulb is restricting the flow?
i ordered the fuel pump already. it's 15 years old so might as well for peace of mind

 

[alldodge]

It probably is the pump, the way to verify is to attach a gauge. Since you already bought the gauge won't hurt to swap it out. Could be the pressure is low but not so low to keep the motor from running

 

[Challenger84]

It probably is the pump, the way to verify is to attach a gauge. Since you already bought the gauge won't hurt to swap it out. Could be the pressure is low but not so low to keep the motor from running

I think that when I "prime" the fuel system, the fuel gets to the carb bowl and the engine will run until the carb bowl get empty...

The pumps not moving any fuel along to the carb when the engine is running but i can still hear it whine.

It's gotta be the pump right? lol

Well i wasn't able to get to wrenching on the boat last night. Worked a little later than expected.

I should be able to get to it today and report back on the results.

Wish me luck!

 

[alldodge]

Good luck, but your serial number listed says you have TBI. Your fuel pressure will be 30 psi at 1800 rpm.

 

[Challenger84]

Good luck, but your serial number listed says you have TBI. Your fuel pressure will be 30 psi at 1800 rpm.

Don't you hate how working gets in the way of your hobbies? Lol
So didn't get a chance to swap out the fuel pump today..
TBI.. Throttle body injectors?
So what does that mean to me?
My engine doesn't have a carb or a carb bowl?
can you please elaborate?

 

[alldodge]

You don't have a carb with a float bowl, you have a Throttle body with two injectors installed on top of it. Should look something like this


Here is how the system fuel flow works

 

[Challenger84]

You don't have a carb with a float bowl, you have a Throttle body with two injectors installed on top of it. Should look something like this


Here is how the system fuel flow works

Wow!
AllDodge i really appreciate the detailed info..

Yes.. i do have the TBI..
I have a better idea of the system now.
Once i change out the FP I'm hoping that will fix the issue.
Thinking that the FP is not moving the fuel.
When i use the primer bulb to get the fuel up through the sytem th engine runs fine..

I'll keep you guys posted.
Thanks for all the info so far!

 

[Bondo]

Compression, Spark, and Fuel is all you need!

Ayuh,..... Yer missin' the 4th component,..... All at the right Time,.....

 

[Challenger84]

Update..

So i had a little bit of time to play around with the engine today..
pumped the primer bulb and started the engine..
She starts right up..
runs and idels just fine..
I forgot to mention in my previous post the that the alarm starts to BEEP a few times before the engine starts to shut off..

I hear the beeps and start squeezing the bulb and the beeping goes away..
didnt have enouh time to get the old FP out and replaced yet..
Just wanted to add some additional info..

I should have the FP replaced tonight.. and get back here to update..
Bought a sweet LED work light so i can work on her in the late hours of the night.

 

[Fun Times]

I forgot to mention in my previous post the that the alarm starts to BEEP a few times before the engine starts to shut off..
I hear the beeps and start squeezing the bulb and the beeping goes away...

Though it's rare on most Mercruiser engine models, your engine model utilizes a fuel pressure sensor located at the throttle body unit. See item # 16...Merc part number 807399T,

 

[Challenger84]

Though it's rare on most Mercruiser engine models, your engine model utilizes a fuel pressure sensor located at the throttle body unit. See item # 16...Merc part number 807399T,

Fun Times
Would the sensor prevent the fuel from being pumped?
Does it help control how much fuel gets pumped from the TBI?
Or is it just a warning sign?

 

[alldodge]

The beep should do it 5 times then stop for low fuel pressure. My guess is you have the issue, just need to find out what part is keeping the pressure low, pump, regulator, injectors or something else

 

[Fun Times]

It just a warning it's low. It won't affect the PSI's.

 

[Challenger84]

Yes, there are about 5 beeps and engine dies..
Sometimes less because theres not enough fuel for the system to beep that long


Well the FUEL PUMP was a pain in the arse to get to. (not as easy as it looks)
It's installed with the cover facing the hull so I cannot open up the cover .. Genius!
I was not able to remove it last night.
I will need to remove all the hoses and clamps and fuel lines before i can get cool fuel system out and still might not be able to remove the fuel pump.

Question: your thoughts please?

What if i install the fuel pump in a different location?
Example: Right after the fuel/water separator and I tap into the wiring from the old pump to run it?
It will ONLY run when the engine has oil pressure because it's powered by the original wiring and that's already hooked up the oil pressure sensor.
so it would be "safe" to do?
So I took the boat to the launch last night and tried to start the engine. The engine starts up and idles for about 10 mins..(this is after i "prime" the fuel system with the bulb.
I looked at the TBI to see if fuel is coming out and i see a nice cone shaped spray while it runs..
The BEEPS come and engine dies..

JUST A THOUGHT..
While I am on the trailer under muffs the water pressure of the hose pushes water through the engine and through the cool fuel system, which cools down the fuel.
While in the water, if the impeller is not moving and the fuel gets heated will this cause Vapor lock?



What are your thoughts on this?


I've been reading too many different threads on here trying to determine what the cause is and my minds going crazy lol.

Sorry for the crazy questions.


Thanks again everyone for the advice and help!
I just want to get on the water already.

 

[Fun Times]

If you move the fuel pump then you will lose the benefits of cooling the fuel which you would need. Yes on some models like yours, it's possible that hot water can/has been known to flow back down to the fuel pump from the thermostat housing after shutting down the engine. Water flow helps keeps fuel cool and Mercruiser did come out with a one-way check valve to help prevent hot water from flowing back down to the pump after shutdown.

Typically to help get the cover off of the pump assembly, it sometimes helps to un-bolt the pump assembly bracket from the two top nuts of the motor mount and let the pump assembly drop-down and back as far in the bilge area as the lines will safely allow in order to start removing the parts needed. The black cover should just pull off as there isn't any clips holding it on....Thankfully.

Good luck.

 

[alldodge]

Agree, I wouldn't move it.

The cover does slide right off, once off there are two nuts (item 14) holding a plate (item 13) to gain access to the pump.
http://www.mercruiserparts.com/Show...=4856&bnbr=90&bdesc=Fuel+Pump+And+Fuel+Cooler

Since it only take a very short time before you cannot start again I don't think its vapor lock. This happens when given time to soak up the heat like a couple hours.