350 Mag Fuel pressure

Discussion in 'Gas Engines/Drives/Transmissions/Props' started by Ted sikes, Jun 30, 2020.

  1. Ted sikes

    Ted sikes New Member

    9
    Jun 30, 2020
    2007 230 Sea Ray and 1997 210 Sea Ray
    350 Mag and 5.7 MCM
    I have an 2007 350 Mag in a 230 Sea Ray. Bogs with throttle increase unless it is slowly increased. I have read several threads here and on other sites and am now rather confused. Checked fuel rail pressure non running o psi. Switched on pump comes on and psi goes up to 43-45, pump shuts off and pressure falls back to 36-38 and will slowly fall to 30 over a minute or 2. Idles at 34-38 with heavy needle vibration. Pull vacuum line at regulator (or pressure damper as some have suggested on other threads) on rail with no change. Funny thing is if I remove my finger from disconnected vacuum line causing an engine vacuum leak the fuel pressure rises to about 40-41(that seems strange to me). Serial number 1A041805. Was going to do a injector balance test but first I have to get some sort of constant reliable pressure. Confused from other threads because some have said that this regulator at rail is a damper and the other fuel pressure regulator is port side below manifold with fuel pump. Thanks for any advice, appreciated.
     
    Last edited: Jun 30, 2020
  2. Espos4

    Espos4 Well-Known Member

    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    Correct on your last sentence. The Real regulator is on your cool fuel 3 module.
     
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  3. Ted sikes

    Ted sikes New Member

    9
    Jun 30, 2020
    2007 230 Sea Ray and 1997 210 Sea Ray
    350 Mag and 5.7 MCM
    Thanks for the info, but it really still doesn't make sense to me. I think this is going to be one of those pay for your education through trial and error trips lol. What doesn't calculate to me is the need for two regulators. If the one up at fuel rail is a damper designed to limited spikes in psi and not really a regulator then with the erratic readings at idle (needle fluctuation/vibration) of 5 psi then it is not doing its job either. Gonna go with the lower cost one at the cooler module first $165 vs $304. I've researched it quite a bit and I'm not really the parts changer kind of guy, but with the lack of info out there, I haven't been able to find a distinctive process to check to rule out one or the other. Thanks again
     
    Last edited: Jun 30, 2020
  4. Espos4

    Espos4 Well-Known Member

    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    Look for black paint debris when you remove that regulator on the cool fuel module. You may have an issue with the paint inside the module flaking off and clogging your system.

    Regulator on the rail is there because this engine is adapted from an automotive application.
     
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  5. Ted sikes

    Ted sikes New Member

    9
    Jun 30, 2020
    2007 230 Sea Ray and 1997 210 Sea Ray
    350 Mag and 5.7 MCM
    Ok will do. Thanks
     
  6. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    The 1 on the rail dampens the pulse, but don't think it would be in the 5lb.range. I'd go with the module 1 first.
     
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  7. Ted sikes

    Ted sikes New Member

    9
    Jun 30, 2020
    2007 230 Sea Ray and 1997 210 Sea Ray
    350 Mag and 5.7 MCM
    Thanks, gonna see how it goes lol
     
  8. stephenm27

    stephenm27 Active Member

    439
    Nov 3, 2009
    Milton, GA
    Boatless. ISO 2010+ 330 Sundancer w Axius
    I’m fresh off a fuel rail disassembly on a 350 MAG and can confirm absolutely that the regulator on the rail is entirely benign. I was told the same info prior to disassembly but verified it while it cleaning the rail.

    If your fuel coolers are original, I’d bet on paint contamination. Relieve the pressure, remove the regulator and I think you’ll find it impeded with paint flakes.
     
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  9. Ted sikes

    Ted sikes New Member

    9
    Jun 30, 2020
    2007 230 Sea Ray and 1997 210 Sea Ray
    350 Mag and 5.7 MCM
    Thanks for the info. Have been doing a lot of research today and analysis and have come up with some possibilities and theories. Paint flakes are a possibility for low pressure by blocking flow, but would they also be contributing to pressure lost over time......and yes I can see that if flakes are within seat area of the regulators diaphragm. Maintaining a constant fuel pressure is critical for fuel injection systems....this one is slowly losing pressure over a 5 minute time period. I've been pondering today what possibilities could also attribute to pressure loss. 1. Defective regulator valve sealing...letting a small amount bleed back to tank. 2. Sealing of fittings, hoses, filter/filter o-ring etc. 3. Cooler assembly heat exchanger....pin hole leaking fuel/pressure into water due to contamination of mineral deposits corroding inside of flow chamber. 4. fuel pump losing/backflow pressure after shutting off, also returning fuel back to tank. (Does fuel pump have backflow valve or built in check valve to maintain pressure once turned off)? These are my possibilities and as I said in an earlier post I'm not a guy who likes to just chunks parts and hopes one makes a base hit. I like to know for sure (if that's possible and I do realize it's not always and sometimes we do have to just chunk parts). I will go and pull regulator and look for the flakes. From experience have you found them in the reg itself or more so in fuel lines and filter? Thanks Guys for all your help and I will keep you up to date on the status and progress as to hopefully help someone down the line with these similar problems.
     
    Last edited: Jul 1, 2020
  10. stephenm27

    stephenm27 Active Member

    439
    Nov 3, 2009
    Milton, GA
    Boatless. ISO 2010+ 330 Sundancer w Axius
    I think I recall reading in Merc literature that an "eventual return to 0 PSI" is expected, though I can't remember the timeframe. I'll see if I can find that reference to substantiate my statement.

    Regarding the flakes, the source of them is the CF3 lid that the regulator is mounted to (and holds the lo + hi pressure fuel pumps in the cooler housing). If you have evidence there (under the regulator), there is the potential for the flakes to have migrated to the fuel rail and injectors since the regulator is post-fuel filters. I found evidence of some flakes in the rail. I also replaced the injectors as a result.

    If you find paint delamination under the regulator, you can purchase the new anodized CF3 lid including o-ring, regulator, screws as a simple kit from Mercruiser ($200 approx). Assuming you have the current CF3 lower housing, this is all you need to stop the problem. However, fuel rail and injector exploration might be required to clean-up what's already occurred.

    I've had several threads in the last 24 months that documented my experience with this...they include the part # for the CF3 cover as well.

    Some related thread references:
    http://www.clubsearay.com/index.php...l-rail-injector-removal-and-inspection.97847/
    http://www.clubsearay.com/index.php?threads/gen-3-cool-fuel-module-issue.51399/

    CF3 replacement cover kit: (includes regulator)
    8M0130861 (drop in google.com)
     
    Last edited: Jul 1, 2020
    Ted sikes likes this.
  11. Ted sikes

    Ted sikes New Member

    9
    Jun 30, 2020
    2007 230 Sea Ray and 1997 210 Sea Ray
    350 Mag and 5.7 MCM
    Thanks Bud, fabulous info there.
     

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