2001 31 Formula dual, 6.2 L MPI, Bravo 3s. Engines started this Spring but not used since. Now starboard will mostly crank or occasionally catches but dies immediately. No backfires. I eliminated electrical. Don't have fitting to test rail pressure but when shrader valve is depressed after the engine cranked a few times pressure released is minimal not close to 30 lbs. I suspect either the electric fuel pump or the fuel pressure regulator. How often does the regulator go bad. Which is more likely the pump or the regulator (regulator is $140 the fuel pump is $90). Any way to test either one to see if it is working. Thanks for any suggestions.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
6.2 L MPI merc fuel pump
- Thread starter jnova1111
- Start date
Are you sure the pump is only $90? The parts list I just checked shows a Sierra brand pump for $269.71, but you didn't state your engine's serial # so that may not be for your engine..
It only showed 1 pump , not separate LP & HP pumps as on my Crusader MPIs.
Does the pump activate when you just turn the ign. sw. to ON, not Start? You should be able to hear and feel it.
If yes , you could try temporarily plumbing-in a clean portable O/B with fresh new gas to the pump inlet to see if it continues to run OK. That would point to an upstream issue back towards the on-engine or remote fuel filter/separators , shut-off and anti-siphon valves, tank pickup and tank vent. Any crossover valve is closed, yes?
If the portable tank makes no difference, check for a fuel pump fuse and relay on the engine.
Make sure the power connections on the pump are corrosion-free and tight.
And wiggle the wiring harness near those especially, with the key just to On to see if the pump suddenly primes. That would be a clue.
You could always jump 12 vdc + & - to the pump momentarily to test if it won't activate/prime otherwise.
Some pumps and regulators have a screen or denser filter at the inlet. Mine do ( screen in the regulator and small real filter at LP pump inlet,.... in addition to on-engine filter/separator and remote filter separator and tank pickup sock.)
https://www.homedepot.com/p/Innova-Professional-Fuel-Injection-Pressure-Tester-epi3640/206888866?cm_mmc=Shopping%7CG%7CHC%7CD25T%7C25-31_GARAGE%2FAUTOMOTIVE%7CNA%7CNA%7c71700000037147756%7c58700004141485310%7c92700035285887579&gclid=EAIaIQobChMItb3S1_KJ3QIVUrnACh36HApLEAQYAiABEgJUFvD_BwE&gclsrc="aw.ds&dclid=CMDukOTyid0CFYVgwQodAcgNVw"
That would connect to the Schrader valve on the rail.
It only showed 1 pump , not separate LP & HP pumps as on my Crusader MPIs.
Does the pump activate when you just turn the ign. sw. to ON, not Start? You should be able to hear and feel it.
If yes , you could try temporarily plumbing-in a clean portable O/B with fresh new gas to the pump inlet to see if it continues to run OK. That would point to an upstream issue back towards the on-engine or remote fuel filter/separators , shut-off and anti-siphon valves, tank pickup and tank vent. Any crossover valve is closed, yes?
If the portable tank makes no difference, check for a fuel pump fuse and relay on the engine.
Make sure the power connections on the pump are corrosion-free and tight.
And wiggle the wiring harness near those especially, with the key just to On to see if the pump suddenly primes. That would be a clue.
You could always jump 12 vdc + & - to the pump momentarily to test if it won't activate/prime otherwise.
Some pumps and regulators have a screen or denser filter at the inlet. Mine do ( screen in the regulator and small real filter at LP pump inlet,.... in addition to on-engine filter/separator and remote filter separator and tank pickup sock.)
https://www.homedepot.com/p/Innova-Professional-Fuel-Injection-Pressure-Tester-epi3640/206888866?cm_mmc=Shopping%7CG%7CHC%7CD25T%7C25-31_GARAGE%2FAUTOMOTIVE%7CNA%7CNA%7c71700000037147756%7c58700004141485310%7c92700035285887579&gclid=EAIaIQobChMItb3S1_KJ3QIVUrnACh36HApLEAQYAiABEgJUFvD_BwE&gclsrc="aw.ds&dclid=CMDukOTyid0CFYVgwQodAcgNVw"
That would connect to the Schrader valve on the rail.
I bypassed the anti-siphon valve by connecting a fuel source to the fitting on the fuel/water separator filter housing but the engine did not run. Ignition key turned on causes fuel pump housing to vibrate and from the noise the pump housing seems to energize, but does that mean that the pump is actually pumping???. Only after I poured about 2 table spoons of gas into the throttle body and turned the ignition to run did the engine start and run for about 4 seconds. So back to square one - is it the fuel pump, the fuel pressure regulator, fuel injectors or something else. Port engine is OM060271, fuel pump is off brand label not sierra or merc.
Does the pump keep vibratiing with ignition sw. to just On or does it turn off after a couple few seconds?
On my MPI's it is easy to remove the pressure regulator and check the screen inside.
Could your filter /separator be clogged or have suction air leak at the gasket or a fitting? Do you have more than one filter separator like mine?
If they are good , I would try to either remove the pump outlet and see if I could momentarily run the pump into a suitable container, or as above, plumb in the portable fuel to the pump inlet.
You could also try connecting an O/B primer bulb or little manual fluid transfer pump to the fuel line disconnected at the pump inlet to see if gas will suck freely or find there is an upstream blockage.
https://www.homedepot.com/p/Steel-Core-Self-Priming-Siphon-Transfer-Pump-39205/301122310?cm_mmc=Shopping%7CG%7CHC%7CD25T%7C25-31_GARAGE%2FAUTOMOTIVE%7CNA%7CNA%7c71700000037147756%7c58700004141485310%7c92700034088528867&gclid=EAIaIQobChMI6MuMv6uL3QIVwoqzCh0rtQkbEAQYBCABEgIZivD_BwE&gclsrc="aw.ds&dclid=CKb6xsWri90CFc1-wQod9wcFFw
On my MPI's it is easy to remove the pressure regulator and check the screen inside.
Could your filter /separator be clogged or have suction air leak at the gasket or a fitting? Do you have more than one filter separator like mine?
If they are good , I would try to either remove the pump outlet and see if I could momentarily run the pump into a suitable container, or as above, plumb in the portable fuel to the pump inlet.
You could also try connecting an O/B primer bulb or little manual fluid transfer pump to the fuel line disconnected at the pump inlet to see if gas will suck freely or find there is an upstream blockage.
https://www.homedepot.com/p/Steel-Core-Self-Priming-Siphon-Transfer-Pump-39205/301122310?cm_mmc=Shopping%7CG%7CHC%7CD25T%7C25-31_GARAGE%2FAUTOMOTIVE%7CNA%7CNA%7c71700000037147756%7c58700004141485310%7c92700034088528867&gclid=EAIaIQobChMI6MuMv6uL3QIVwoqzCh0rtQkbEAQYBCABEgIZivD_BwE&gclsrc="aw.ds&dclid=CKb6xsWri90CFc1-wQod9wcFFw
EzParts5://24554328031233/24554328245464/24554328139626/24554328245492/24554328188319/24554328188320/24554334461708:24558623322171|[Mercury Marine [Updated: Aug. 25, 2018]]/[Sterndrive]/[Engines - Gas]/[6.2L (377 CU IN) V8 GM]/[MX 6.2L MPI BRAVO]/[ [0L680003 THRU 0M299999] - Cat.# 90-88178200]/[Fuel Pump And Fuel Cooler]:[Fuel Pump And Fuel Cooler]
This will show the schematic for my fuel pump. It's compartmentalized and located under the forward belly of the engine. In reference to your first question the vibration and noise stops after a few seconds. 2nd question I change the fuel/filter first thing. I only have one filter that I know of. I assume that the fuel pressure regulator regulates the return flow of fuel based upon the vacuum in the intake manifold. So if it is non functioning the engine should run but engine RPM would be limited. Is that a correct assumption??
This will show the schematic for my fuel pump. It's compartmentalized and located under the forward belly of the engine. In reference to your first question the vibration and noise stops after a few seconds. 2nd question I change the fuel/filter first thing. I only have one filter that I know of. I assume that the fuel pressure regulator regulates the return flow of fuel based upon the vacuum in the intake manifold. So if it is non functioning the engine should run but engine RPM would be limited. Is that a correct assumption??
Sorry, I'm not really clear on exactly how the regulator in my blue MPI engines works on my non-return fuel system using 2 pumps, so I can't advise on yours other than that I have read that some Mercruiser pumps are in. manifold vac pressure influenced. Mine are not.
Sandy,
Thanks for all your posts. I appreciate your help. Depending on how involved it becomes, I may replace the starboard fuel pump and with the port fuel pump. I'll post the results for general info in case someone else develops the same problem. Again thanks.
Thanks for all your posts. I appreciate your help. Depending on how involved it becomes, I may replace the starboard fuel pump and with the port fuel pump. I'll post the results for general info in case someone else develops the same problem. Again thanks.
Sandy,
Thanks for all your posts. I appreciate your help. Depending on how involved it becomes, I may replace the starboard fuel pump and with the port fuel pump. I'll post the results for general info in case someone else develops the same problem. Again thanks.
Thanks for all your posts. I appreciate your help. Depending on how involved it becomes, I may replace the starboard fuel pump and with the port fuel pump. I'll post the results for general info in case someone else develops the same problem. Again thanks.
Sandy,
Thanks for all your posts. I appreciate your help. Depending on how involved it becomes, I may replace the starboard fuel pump and with the port fuel pump. I'll post the results for general info in case someone else develops the same problem. Again thanks.
Thanks for all your posts. I appreciate your help. Depending on how involved it becomes, I may replace the starboard fuel pump and with the port fuel pump. I'll post the results for general info in case someone else develops the same problem. Again thanks.
Problem solved - The vessel had been started only once (early spring) after it was decommissioned early Fall 2017. So after I blew out the line upstream of the filter/separator and properly primed the entire system the motor started right away with no problems.