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Mercruiser hot start issue

T

tpin

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Mercruiser 6.2 mpi. After running the engine for awhile, when I stop and shut down for 30min plus I have issues when going to start up again. I will lose all fuel pressure (schrader valve pressure drops to zero) . I did install some shut off valves to keep hot water flowing back into the fuel cooler so that's not the issue (ie vaour lock). Eventually fuel pressure will return, however the boat has to sit for 6plus hours before this will happen, need help.
 
Hi, what year is the engine? Serial number handy?
By chance, does the fuel pressure seem to fluctuate rapidly when it returns back to normal.
If 2005 and under, Do you have an inline fuel pump booster installed? If not, that may be your next step needed to help compensate for lost fuel pressure while hot. http://forums.iboats.com/forum/engi...i-fuel-pressure-issue?p=10194180#post10194180

What does the fuel pressure rise up to when running normal?

Sounds like you've probably already read Mercruiser's Service Bulletin 99-07 "Gasoline Engine Vapor ... http://www.bing.com/search?q=mercruiser+fuel+vapor+service+bulletin&FORM=AWRE

Is the engine compartment well vented?
 
boat_tech said:
Hi, what year is the engine? Serial number handy?
By chance, does the fuel pressure seem to fluctuate rapidly when it returns back to normal.
If 2005 and under, Do you have an inline fuel pump booster installed? If not, that may be your next step needed to help compensate for lost fuel pressure while hot. http://forums.iboats.com/forum/engi...i-fuel-pressure-issue?p=10194180#post10194180

What does the fuel pressure rise up to when running normal?

Sounds like you've probably already read Mercruiser's Service Bulletin 99-07 "Gasoline Engine Vapor ... http://www.bing.com/search?q=mercruiser+fuel+vapor+service+bulletin&FORM=AWRE

Is the engine compartment well vented?
Click to expand...

Everything returns to normal after restart, havnt checked the actual pressure when running after restart, but since I usually need to wait many hours its the next day that it will run and run perfectly. I could understand vapor lock if the engine was still hot, however letting the boat sit for just a few hours should be enough??, problem is even after 5 hours of waiting and a cooled off engine I still get zero-no pressure (fuel pump does run and sounds normal over this period of time). The engine is a 2007 serial 0W663045, I have installed check values to keep hot engine water from back flowing into the fuel cooler.

My big question is what could cause total fuel pressure loss over a long period of time, then having everything return to "normal", could a faulty fuel pressure regulator cause this?
 
Being that you have a 2007 Bravo stern drive engine model that utilizes the Gen 3 cool fuel module tank/system, the hot water flow back check valves typically installed either as a kit or from factory depending on year and stern drive model that uses the Gen 2 cool fuel system are typically the only ones that would need the check valve devise....The Gen 3 cool fuel system I believe shouldn't be in need of a check valve as the hot water shouldn't be reaching the Gen 3 cool fuel water system portion. Plus its rare to hear of the Gen 3' to be vapor locking these days but it seems to have been excessively hot this year throughout the US. What general area do you live in?

Depending on drain system model/design you have, Item number 10 or 14 is part of the Gen 3 cool fuel module water system,
https://www.perfprotech.com/mercury...-7-point-drain/assembly/12840/215?umodel=1169
https://www.perfprotech.com/mercury...-3-point-drain/assembly/12840/205?umodel=1169
https://www.perfprotech.com/mercury-marine-parts-catalog/umodel/1169

While it sure seems like vapor lock issues from your description, I kind of suspect that you may have an internal fuel module failure of possibly the more common problems with paint peeling off the inside of the Gen 3 fuel tank module starting to clog up the fuel system which has been know to reach all the way up to the injectors eventually.

Typically the fuel regulator system of the top cover gets affected first by clogging both the top and bottom sides of the top tank cover. You'll want to pull the top cover, remove the regulator, and also inspect the inside bottom of the cover as well for possible paint debris...Also look inside the tank too.

Have you been keeping up with your two fuel filters found within the fuel module tank? Item numbers 21 and 26, https://www.perfprotech.com/mercury...ly-module-bravo/assembly/12840/70?umodel=1169

Be sure to search online, mercruiser gen 3 cool fuel paint issue. http://www.bing.com/search?q=mercru...5BA780A914D0EA5E6EF46B7D55466&FORM=QBRE&ghc=1
 
Fuel Filters and the actual fuel cooler are only a year old. I'm up in Canada, we did however have a warm day yesterday 34 Celsius which is about 95 F(we do get hot up here) with lake temp at 21 c which is about 70 F. There was no check valve installed thanks to SeaRay on my model year, so I installed one last year. Just picked up a compression tester, tested fuel pressure, on start up the pump is at around 42 psi, when running the pressure jumps rapidly between 25 to 42 psi, is this jumping normal?
 
tpin said:
Fuel Filters and the actual fuel cooler are only a year old. I'm up in Canada, we did however have a warm day yesterday 34 Celsius which is about 95 F(we do get hot up here) with lake temp at 21 c which is about 70 F. There was no check valve installed thanks to SeaRay on my model year, so I installed one last year. Just picked up a compression tester, tested fuel pressure, on start up the pump is at around 42 psi, when running the pressure jumps rapidly between 25 to 42 psi, is this jumping normal?
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Maybe you should manually Put power to the fuel pumps when the engine will not start and check the fuel pump operation.

And No, the fuel pressure should not fluctuate. 42lbs is also high.
 
I don't want to worry you as fuel pressure fluctuating could be a number of things wrong from low 12v power at the pump, bad fuel pumps, partially restricted fuel system anywhere along the line, or restricted fuel regulator at the fuel module, damaged fuel damper up on the fuel rail or possibly fuel a injector problem...Plus one other issue that always seemed to intrigue me if true or not was this guys issue on his Mecruiser 6.2L engine regarding his fuel pressure bouncing,,
FTomazinis;n3673129 said:
Re: Fuel pressure bouncing????
The reason the fuel pressure was bouncing was because of two burned up intake valves. The compression was leaking back into the intake and making the fuel pressure go up and down.
Click to expand...
http://forums.iboats.com/forum/engi...gines-outdrives/322189-fuel-pressure-bouncing

With this Gen 3 cool fuel system, 42 psi is within the specifications as seen below from a Merc service book.
Fuel Pressure Regulator Identification (Revised Aug. 6, 2004) • ECM and PCM 555 Fuel Regulator Identification Engine Color System Regulator Model Code psi (kPa) P/N Comments :
V8 5.0L, 5.7L, 6.2L, ECM 555, (MPI, Gen 3 Cool Fuel, GM MPI intake, GMEFI system). 5.0L MPI, 350 Mag, MX6.2 Models. None = No Color Code for regulator, 42.5 psi (288 kpa) 892681 Regulator in top of Gen 3 Cool Fuel Module.
V8 8.1L, PCM 555, (MPI, Gen 3 Cool Fuel, GM intake, plenum, injectors). V8 496 Mag, 8.1S Models. (None = No Color Code), 42.5 psi (288 kpa) 892681 Regulator in top of Gen 3 Cool Fuel Module.
Gen III Cool Fuel System Overview:
Water Separating Filter Element  2 pumps – Lift & Pressure - Lift pump - Gerotor - Pressure pump – Turbine  Fuel Pressure Regulator - New 288 kpa (~42 psi) regulator - O-rings seal between OD on regulator and ID in cover, rather than a face seal and return hose - Regulator dumps excess fuel to inlet side of pressure pump - Fuel pressure vs. flow characteristics differ slightly from Gen II, requires minor calibration changes  Internal Low Pressure Relief Valve - Limits pressure across lift pump to 10 psi +/- 5 psi - Dumps fuel to inlet side of filter.
System Module Features:  Dual Pump Configuration - Improved Vapor Lock resistance compared to engines equipped with current boost pumps which it is not recommended to install a boost pump in front of/inline of the Gen 3 fuel module.

Side Note: Just noticed that the aftermarket Sierra Marine brand regulator part number 18-33211 seems to say on the side of the regulator that it's rating is 300 kilopascals which = 43.5113213 psi. http://www.marineengine.com/newparts/part_details.php?pnum=MER892681

Even if peeling paint isn't the issue, at this point you might still want to consider opening up the top cover or at the very least remove the regulator and see if you see anything out of the ordinary just in case. http://forums.iboats.com/forum/engi...ives/417428-mercruiser-5-0l-mpi-fuel-pressure.

The proper way to test fuel pressure on this designed fuel system is to use both a fuel psi gauge along with a vacuum gauge which is outlined within Merc service bulletin number 2004-06 available with a search online. The majority of the testing procedures are quoted below for you though.

Checking Fuel Pressure:
1. Connect a fuel pressure gauge to the shrader valve on the fuel rail. 2. Cycle key switch 2-3 times (OFF to RUN position) at 3 second intervals to reach maximum pressure. 3. Verify that the pressure is within specification. 4. If pressure exceeds 44 psi (303 kPa): a. Replace the Cool Fuel Module. 5. If pressure is equal to or less than 40 psi (276 kPa): a. Use a tee fitting and connect a vacuum gauge to the fuel inlet side of the Cool Fuel Module. Do not remove the fuel inlet fitting adapter. b. Relieve the fuel pressure in the fuel rail. Refer to section 2A for fuel pressure relief procedure. c. Cycle the key switch 2-3 times (OFF to RUN position) at 3 second intervals to reach maximum pressure. d. Verify that the vacuum from the fuel source is within specification. If the vacuum exceeds 2 in. Hg (7 kPa) , excessive fuel restriction exists. Correct the fuel restriction before proceeding. e. With the vessel secured to the dock and the engine running in neutral, restrict the fuel supply and verify that the Cool Fuel Module has the ability to cause a vacuum reading of 11 in. Hg (37 kPa) or greater. If the vacuum reading is less than 11 in. Hg (37 kPa) with the fuel supply restricted, replace the Cool Fuel Module. In-Water Test 1. With a vacuum gauge and a fuel pressure gauge in place, operate the boat throughout the RPM range and record the pressure and vacuum readings. 2. If the fuel the supply vacuum reading is greater than 2 in. Hg (7 kPa) , find and correct the fuel supply restriction. 3. If the fuel supply vacuum is within specification and the fuel pressure is less than 40 psi (276 kPa), replace the Cool Fuel Module. IMPORTANT: It will be necessary to sea-trial the boat following repairs to be sure that the pressure and the fuel system vacuum remain within specification throughout the RPM range.
Click to expand...

Hope you find it to be something easy, please let us know what you find and good luck with it.
 
If a Gen 3 Cool fuel is showing 42lbs of fuel pressure at idle there is a problem. The regulator is packed with paint fprm the lid or the vacuum line if off the regulator.
 
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