Smarty pants, I really could use your help! 350 Mag trouble SOLVED?? MAJOR UPDATE

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  • Black_DiamondBlack_Diamond Member Posts: 5,439 ✭✭✭✭✭
    Al: what does that orange wire do?  Mine was disconnected from a recall if I remember right. 

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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  • WildboatingWildboating Member Posts: 957 ✭✭✭
    Alswagg said:
    The fuel pressure should not drop at all when rpm drops.  This should be constant       Verify clean ground.  Reconnect orange wire at alternator.  Upcoming new cool fuel module assembly with regulator 


    I msy have have some time later today.  Where is this orange wire, where does it connect?   Also you mentioned a upcoming new cool fuel  module with regulator.  These are new ones coming out? Or are you saying I need to be looking there next. 
    2003 Rinker 342 Fiesta Vee, 350 Mag MPI, Bravo 3 2.20:1 w/ 22p 4 x4 props

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  • Black_DiamondBlack_Diamond Member Posts: 5,439 ✭✭✭✭✭
    Orange wire on mine is on the harness going to the alternator.  Mine is disconnected. 

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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  • WildboatingWildboating Member Posts: 957 ✭✭✭
    edited August 2017
    @Alswagg
    Is this the kit I need or is there another one with a regulator?   PN 861156A03

    I have OM6 and Up serial number

    2003 Rinker 342 Fiesta Vee, 350 Mag MPI, Bravo 3 2.20:1 w/ 22p 4 x4 props

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  • WildboatingWildboating Member Posts: 957 ✭✭✭
    If you watch in my video the fuel pressure rises as engine speeds up and falls off as the rpms decresase.  This tells me the vaccum regulator is working properly.  Im thinking there is a fault in this cool fuel pump.   
    2003 Rinker 342 Fiesta Vee, 350 Mag MPI, Bravo 3 2.20:1 w/ 22p 4 x4 props

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  • WildboatingWildboating Member Posts: 957 ✭✭✭
    No I have not BD, that is a great idea.

    2003 Rinker 342 Fiesta Vee, 350 Mag MPI, Bravo 3 2.20:1 w/ 22p 4 x4 props

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  • WildboatingWildboating Member Posts: 957 ✭✭✭
    Thought I would share this as well. This is the replacment motor.   

    https://www.perfprotech.com/new-gm-350-longblock-57l-vortec-for-years-1996-current-models-carb-tbi-mpi-w-crank-position-sensor-2541-s1/product/260508
    2003 Rinker 342 Fiesta Vee, 350 Mag MPI, Bravo 3 2.20:1 w/ 22p 4 x4 props

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  • Robs_232Robs_232 Member Posts: 212 ✭✭✭

    I have the same engine in my 2004 232BR. Have you replaced the fuel filter ahead of the fuel/water filter. Mine is between the tank and the fuel module and is shown as #27 in link. I have been following this from problem from the beginning and just thought about it today. I don't think many people even know about this pre-filter. Just thought I'd throw it out there.

    http://www.mercruiserparts.com/bam/subassembly/31761/8093/80

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  • WildboatingWildboating Member Posts: 957 ✭✭✭
    Thanks Rob.  It has been replaced.   We have almost 0 backpressure from water separator back which eliminates boat side issues. 
    2003 Rinker 342 Fiesta Vee, 350 Mag MPI, Bravo 3 2.20:1 w/ 22p 4 x4 props

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  • Robs_232Robs_232 Member Posts: 212 ✭✭✭
    Figured you did but couldn't remember.
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  • CaptianDanCaptianDan Member Posts: 94 ✭✭
    Man, I'm gutted thought it was the pump.  Some great suggestions above so far though.  I would reduce components in order to isolate as a first step, this would include:
    1. (as Al and Drew mentioned) remove reduce electrical components by removing isolator and charging system.
      Remove one battery from charging system and use that as test start battery, ensure the positive and more importantly ground are clean back to engine connections.
      Connect orange alternator cable direct to alternator out put and starter connection to positive battery.
    2. Add external fuel tank and remove filters (inline/external)
      Connect hose direct from Gen II module to external tank.  Making sure the external tank is clean and no contaminants are present, you don't want to ruin those new injectors.
    Now comes the troubleshooting, start at the fuel ingress and make sure you have constant fuel pressure.  I would have thought, and I haven't tested this, that only vacuum (regulator) or electric issues would cause the pump to reduce pressure when increasing RPM.  Someone may be able to confirm...?

    "Pipe Dream"
    2002 Rinker 342 Fiesta Vee
    2 x 350 MAG MPI Horizon Petrol

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  • dalekdalek Member Posts: 259 ✭✭✭
    Just to try and clarify the situation, this is the system you have, and the 43 PSI on the rail is inconsistent?
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  • Handymans342Handymans342 Member Posts: 10,375 ✭✭✭✭✭
    Where is the lift pump in this picture?
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  • Black_DiamondBlack_Diamond Member Posts: 5,439 ✭✭✭✭✭
    @Handymans342 :separate diagram. 

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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  • CaptianDanCaptianDan Member Posts: 94 ✭✭
    This diagram is for the earlier 350 MPI, there should be a later one which includes a boost pump.

    "Pipe Dream"
    2002 Rinker 342 Fiesta Vee
    2 x 350 MAG MPI Horizon Petrol

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  • dalekdalek Member Posts: 259 ✭✭✭
    Does anyone have a better diagram, or point me to it?
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  • Black_DiamondBlack_Diamond Member Posts: 5,439 ✭✭✭✭✭
    Go to: http://mercruiserparts.com/
    enter your engine S/N
    search for fuel pumps

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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  • WildboatingWildboating Member Posts: 957 ✭✭✭
    Alswagg said:
    The fuel pressure drop concerns me    If the fuel pressure would be stable with an ignition problem.  I would look at fuel/power to the fuel pump 
    Al,   
    Did you watch the video i posted?  The fuel pressure doesnt drop and stay down it has blips.   I ordered some clear fuel line to see if we are getting air into the system.   Would air bubbles cause the gauge to drop like that?  
    2003 Rinker 342 Fiesta Vee, 350 Mag MPI, Bravo 3 2.20:1 w/ 22p 4 x4 props

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  • JasonAJasonA Member Posts: 40 ✭✭
    Did you do a compression test on the new motor? Found out today that #6 in my motor was only making 90psi, the rest were 150psi.
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  • WildboatingWildboating Member Posts: 957 ✭✭✭
    Jason, we did last week. All cylinders are the same. 
    2003 Rinker 342 Fiesta Vee, 350 Mag MPI, Bravo 3 2.20:1 w/ 22p 4 x4 props

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  • dalekdalek Member Posts: 259 ✭✭✭
    I'm going to nail my colors to the mast here. It can only be one of three things.
    An air leak between the gas and the lift pump.
    A failure of the lift pump or power to the lift pump.
    An obstruction between the lift pump and the high pressure pump.
    I am no expert on this particular engine so feel free to call me out on it.
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  • WildboatingWildboating Member Posts: 957 ✭✭✭
    Dalek......


    You must be paying attention!

    I have also concluded it must be one of these things.

    1. Air leak in fuel supply

    2. Faulty high pressure pump

    3. Restriction on boat side fuel system.  (This was formerly checked via 5 gallon fuel cell and determined not at fault.  However now I discovered boost pump was faulty I'm rechecking this again. 

    I have ordered some test gear and will be back after it next weekend.  Currently having both transoms rebuilt.  

    2003 Rinker 342 Fiesta Vee, 350 Mag MPI, Bravo 3 2.20:1 w/ 22p 4 x4 props

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  • Black_DiamondBlack_Diamond Member Posts: 5,439 ✭✭✭✭✭
    Are you getting the 8psi with the new lift/boost pump now?  

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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  • dalekdalek Member Posts: 259 ✭✭✭
    I would be amazed if a faulty high pressure pump produced these symptoms. As you mention that you did the fuel isolation test with a defective boost pump, I agree the fault could also be boatside fuel restriction, so add that to my list. Indeed, fuel restriction or air may have led to the early failure of the pump.
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  • WildboatingWildboating Member Posts: 957 ✭✭✭
    Black_Diamond said:
    Are you getting the 8psi with the new lift/boost pump now?  
    I verified that I am getting 8 psi now. 
    2003 Rinker 342 Fiesta Vee, 350 Mag MPI, Bravo 3 2.20:1 w/ 22p 4 x4 props

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  • WildboatingWildboating Member Posts: 957 ✭✭✭
    edited August 2017
    Dalek,   I have the same thoughts.   Before ordering a new hp pump I have a few more test. I'm going to measure the restriction on boat side fuel system at wot, then I ordered some clear fuel line to verify no air is in the fuel line.  I have a 5 gallon tank and a primer bulb to assist the fuel pressure with.   I'm also pulling the cool fuel system to verify regulator screen is clear.  If all looks well my last thought is a big one....

    Mercruiser stopped selling the high pressure pump by itself and now it only comes as a kit with the fuel cooler.  Why did they do this??  After inquiring I have learned that the cooler was notoriously leaking and people were only replacing the pump.   Is it possible that I have a fracture where the fuel is being cooled and at higher pressure I'm ingesting water???   I don't know, but the plugs do have a rusty color to them. 


    These test will eliminate boat side fuel system, high pressure pump, regulator, fuel cooler and air in the lines.      If non of these then I'll probably lose a few more hairs.   
    2003 Rinker 342 Fiesta Vee, 350 Mag MPI, Bravo 3 2.20:1 w/ 22p 4 x4 props

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  • dalekdalek Member Posts: 259 ✭✭✭
    If the regulator screen was blocked the rail pressure would go up, not down. In your video, as the manifold pressure decreases, the injection pressure increase, which is correct, so I believe the regulator and the manifold pick-up are OK. Surely, if the fuel cooler was leaking it would inject fuel into the water, not water into the fuel?
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  • WildboatingWildboating Member Posts: 957 ✭✭✭
    Is the regulator on the return side?
    2003 Rinker 342 Fiesta Vee, 350 Mag MPI, Bravo 3 2.20:1 w/ 22p 4 x4 props

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  • dalekdalek Member Posts: 259 ✭✭✭
    I believe so, the pump outputs about 90-100 psi and the regulator bleeds the excess back to the filter.
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  • WildboatingWildboating Member Posts: 957 ✭✭✭
    edited August 2017
    Thanks DaleK!!   I have a number of test to perform.  I will hold off on the cool fuel removal until after my test.  

    I understand the vent line for fuel tank is in the fuel filler.  With the cap on tight, how does the line vent?
    2003 Rinker 342 Fiesta Vee, 350 Mag MPI, Bravo 3 2.20:1 w/ 22p 4 x4 props

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