2011 Mercury 90 Multiple Run Problems

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
bobct1
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2011 Mercury 90 Multiple Run Problems

Postby bobct1 » Wed Jul 01, 2020 1:25 pm

For the past two days I've had multiple symptoms [of poor engine running in a 2001 Mercury 90-HP engine of unspecified power cycle], but I am unsure if these symptoms are a result of a single cause. I'll try to explain. I hope someone can point me in the direction or a remedy.

[The 2011 Mercury 90-HP engine of unspecified power-cycle arrangement] started and initially idled fine. After starting to increase throttle then engine began to shake as if not all cylinders were working, and then the engine stalled.

On a re-start the engine would not run at idle and stalled.

Eventually, I got the engine started and was able to get the boat back to shore.

A day later, the [the 2011 Mercury 90-HP engine of unspecified power-cycle arrangement] started fine, and it ran fine for a portion of the day. That night the engine stalled out.

I thought [the cause of the engine stalling and having trouble running at idle speed might have been due to] water in the gasoline fuel, but later I decided that was not the cause because I had only just recently purchased the fuel.

connector_.jpg
Fig. 1. [Moderator's caption: fuel connector at red plastic fuel tank with one long crack clearly visible.]
connector_.jpg (7.5 KiB) Viewed 5704 times


I found [multiple] small cracks on the connectors on the fuel tanks. I then suspected air was getting in the [fuel supply hose] line. Possibly the [FUEL SUPPLY MODULE] was starved for fuel.

When the engine ignition key is moved to ON from OFF, I see bubbles entering the low pressure fuel filter from the supply side.

I replaced the connectors. I have not seen the air enter the fuel filter, even though the low pressure fuel filter is not completely full of fuel.

The high pressure [perhaps means some other portion of the fuel system] appears that to be full of fuel;

[The boat has not been run] on the water to test the stalling problem.


A float switch malfunction would cause fuel starvation in the [FUEL SUPPLY MODULE] for fuel.

[Discussion of a second problem has been moved to its own thread because the problem was not related to the Fuel Supply Module or to the leaking fuel hose connector--jimh]

bobct1
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Re: 2011 Mercury 90 Multiple Run Problems

Postby bobct1 » Wed Jul 01, 2020 3:10 pm

The low pressure fuel filter [in Figure 2 below] is on the left. The low pressure side pulls [fuel] from the fuel tank and into the [FUEL SUPPLY MODULE]. The low pressure filter [is filled with] approximately 65-percent air, and the fuel is in the bottom half of the filter.

Is [the low pressure filter to be filled with 65-percent air] normal?

[How can air in the low pressure filter be] purged?

The high pressure filter appears to be completely full of fuel.

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Phil T
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Re:2011 Mercury 90 Multiple Run Problems

Postby Phil T » Wed Jul 01, 2020 3:26 pm

Your description of the low and high pressure fuel pumps and filters is accurate and appear to be operating as designed.

Troubleshooting is best a series of eliminating possibilities one by one. Test. Substitute, test. repeat.

I would start by eliminating the fuel tank, fittings and fuel line to the engine by borrowing a separate portable tank and fuel line.

Test and report back.
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jimh
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Re: 2011 Mercury 90 Multiple Run Problems

Postby jimh » Wed Jul 01, 2020 5:39 pm

What sort of engine is being discussed? Is this a FOURSTROKE model?

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Re: 2011 Mercury 90 Multiple Run Problems

Postby jimh » Wed Jul 01, 2020 5:47 pm

bobct1 wrote:When the engine ignition key is moved to ON from OFF, I see bubbles entering the low pressure fuel filter from the supply side.


It is possible that air can be in the fuel system in the segment of the fuel system from the fuel tank to the engine, but eventually that air should be purged by the action of the fuel system. However, if there is a leak in the fuel supply hoses from the fuel tank to the engine, air could be continually drawn into the fuel system. Generally the LIFT PUMP pulls fuel out of the fuel tank by creating a negative pressure in the fuel supply hose. If the fuel supply hose and any other connections or filters are not air-tight, the negative pressure will draw in air into the fuel, producing the bubbles you report observing.

If the engine uses fuel injection there may be a fuel circulation system with a vapor separator module that works to remove air from the fuel. This may account for the observation that fuel at another point in the fuel system downstream from the location you call "the low pressure filter" may no longer contain air. The air is vented into the atmosphere in the fuel-vapor separator assembly.

In engines with carburetors, the air in the fuel is vented to the atmosphere in the carburetor or carburetors, and is eventually purged that way.

Air in the fuel will cause poor engine run performance. As a general rule, there should be no air in the fuel system coming from the fuel tank in the fuel supply hose.

What type of engine is being discussed?

Is this a four-stroke-power-cycle engine or a two-stroke-power-cycle engine?

Does this engine have carburetors?

Or, does this engine have a fuel-injection system?

If fuel-injection, are there individual fuel injectors for each cylinder?

Or is there just one fuel injector associated with a single throttle body?

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Re: 2011 Mercury 90 Multiple Run Problems

Postby jimh » Wed Jul 01, 2020 5:49 pm

bobct1 wrote:In Figure 2 below the high pressure filter is shown in the middle...


It would be more useful to illustrate the fuel system in a diagram. Knowing that from a particular point of view one filter is to the left of another filter really does not provide a great deal of insight into how the filters are located in the fuel system.

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Re: 2011 Mercury 90 Multiple Run Problems

Postby bobct1 » Wed Jul 01, 2020 6:13 pm

FSM [is an acronym used by Mercury to mean] fuel supply module [OK--I will replace all instance of FSM in prior posts with "Fuel Supply Module"--jimh]

This is a 2011 [Mercury] 90-HP EFI [FOURSTROKE] fuel injected.

image_178564.jpg
Fig. 2. Fuel Supply Module internals
image_178564.jpg (11.99 KiB) Viewed 5771 times
Last edited by bobct1 on Wed Jul 01, 2020 11:38 pm, edited 2 times in total.

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Re: 2011 Mercury 90 Multiple Run Problems

Postby jimh » Wed Jul 01, 2020 6:30 pm

The FUEL SUPPLY MODULE (also known by the acronym FSM) is discussed in a prior posting (on the old forum) and is believed to be the cause of similar engine running problems. See

http://continuouswave.com/ubb/Forum3/HTML/017515.html

A corollary for onset of problems with the FUEL SUPPLY MODULE is use of gasoline fuels blended with ethanol.

Has the engine that is under discussion in this the TOPIC been running on gasoline fuels diluted 9:1 with ethanol?

Since the engine had a production epoch (not a model year) of c.2011, the engine has probably been in use for nine or ten seasons. To have a fuel system component from c.2011 fail in c.2020 when the engine has been run on gasoline fuels with ethanol blending would not be unusual. Mercury fuel system components have something of a history of problems and failures when the gasoline fuel used with them was blended with ethanol. It can occur that gasoline fuels blended with ethanol and intended to only be in a ratio of 9:1 gasoline:ethanol can be sold at retail fuel stations with much higher concentrations of ethanol. Or that due to ingress of water into the fuel, blended gasoline fuels with ethanol can become modified in the fuel tank by the process of water bonding with the ethanol. The result is a highly corrosive mixture of ethanol and water, along with a remaining gasoline now deprived of its primary octane additive ethanol. Running on fuel with ethanol separation from gasoline will cause many problems.

bobct1 wrote:I thought [the cause of the engine stalling and having trouble running at idle speed might have been due to] water in the gasoline fuel, but later I decided that was not the cause because I had only just recently purchased the fuel.


The elapse of time between the purchase of the fuel and the onset of the problems does not have to be particularly long. If you buy poor grade gasoline that is improperly mixed with ethanol, or if you buy gasoline that contains high concentrations of water, the fuel you just purchased immediately mixes with the fuel already in the fuel tank, and the new blend of fuel is the fuel the engine will consume. It does not take a month for bad fuel to cause problems.

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Re: 2011 Mercury 90 Multiple Run Problems

Postby jimh » Wed Jul 01, 2020 7:28 pm

Regarding the FUEL SUPPLY MODULE:

What is the purpose of the Fuel Supply Module?

What function or functions does it perform?

I don't think that all readers will be able to intuit the purpose of the fuel supply module and to infer the functions performed by the fuel supply module without further explanation.

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Phil T
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Re: 2011 Mercury 90 Multiple Run Problems

Postby Phil T » Wed Jul 01, 2020 9:28 pm

I believe the item Mercury refers to as the FUEL SUPPLY MODULE is called the VAPOR SEPARATOR TANK (VST) by Yamaha and other manufacturers.
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bobct1
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Re: 2011 Mercury 90 Multiple Run Problems

Postby bobct1 » Wed Jul 01, 2020 11:14 pm

cowlingRemoved.jpg
Fig. 3. [Moderator's caption: the engine cowling has been removed. The blue arrow points to the Fuel Supply Module.]
cowlingRemoved.jpg (23.84 KiB) Viewed 5696 times

[The fuel supply module functions are:]

  • a low-pressure pump located inside that module fills the space inside that module;
  • a high-pressure pump pumps the fuel at a high pressure to the fuel rail and injectors;
  • a float switch controls operation of low pressure pump to run only at startup if the fuel supply module is not filled with fuel
  • if the fuel supply module is filled with fuel, then all is fine
  • after engine start, the ECM controls the both the low and high pressure pumps
  • a pressure regulator [limits fuel pressure in the fuel rail[/list]
The float switch is a common item to fail and caused by ethanol-gasoline blended fuels.

[I now believe the cause of the problem was not related at all to the Fuel Supply module illustrated several times above and the actual cause] was air being introduced at the connector on the fuel tank. If the fuel supply module was starved for fuel, that may have caused the engine to stall.

I replaced the connector [suspected of having an air leak at the fuel tank]. I ran the engine in the driveway for 30-minute. The engine seemed to to run fine.

To know for sure if the problem has been solved I will go for a test run.
Last edited by bobct1 on Wed Jul 01, 2020 11:41 pm, edited 1 time in total.

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Re: 2011 Mercury 90 Multiple Run Problems

Postby jimh » Thu Jul 02, 2020 9:35 am

Thanks for the several illustrations of the Fuel Supply Module and the detailed explanation of its operation.

You appear to have remedied the problem of the engine stalling by replacement of the defective fuel connector at the red plastic fuel tank. If this proves to have cured the engine running problems, then it appears there was no involvement of the Fuel Supply Module (or FSM) in causing those problems.

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Re: 2011 Mercury 90 Multiple Run Problems

Postby jimh » Thu Jul 02, 2020 10:15 am

I do not believe you replied to my question about the type of fuel that has been used with the 2011 Mercury 90-HP FOURSTROKE EFI engine. Let me try again:

Has the 2011 Mercury 90-HP FOURSTROKE EFI engine been running on blended 9:1 gasoline-ethanol fuel?

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Re: 2011 Mercury 90 Multiple Run Problems

Postby bobct1 » Mon Sep 07, 2020 10:54 pm

Sorry Jim—I must have missed your question. Yes, I have been running standard fuel that contains 10% ethanol.

Looks like I am having to re-visit the running problems that began this thread. I haven't really had a chance to use the boat until now. I started the [Mercury 90 FOURSTROKE EFI engine] in the driveway and it idled fine for about 15 minutes.

Then the rough idle started and the engine stalled. The [Mercury 90 FOURSTROKE EFI engine] appears to be starved for fuel. The fuel filter leading to the FSM is only about one-third full of fuel leading me to believe that [these running problems are due to insufficient] fuel getting to the FSM.

From reading on other forums, it seems that the float module [float switch] is very frequently the [the cause of running problems like these].

A suggestion on one forum was, "if [the Float Module] doesn't have the red wires, replace it".

[The Float Module on my Mercury 90 FOURSTROKE EFI engine] must have been an earlier revision and did not have red wires.

I also notice a high-pitch whine from the lift or low-pressure fuel pump that seems abnormal.

I'll be replacing both the float switch and the low pressure fuel pump.

I'll update once I get the parts installed and test the engine further.

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Re: 2011 Mercury 90 Multiple Run Problems

Postby jimh » Tue Sep 08, 2020 9:39 am

A float switch malfunction could certainly cause a lack of fuel.

Is the “float module” or “float switch” ( you use both terms) a separate component from the Fuel Supply Module?

Please clarify the nomenclature and which part you are replacing. To have consistent use of nomenclature in this thread will be important to being able to understand what components are being described and discussed.

In the illustration above at Figure 2, the float switch appears to be internal in the Fuel Supply Module.

Also in illustration at Figure 3 above, I see what looks like a red wire coming out of the Fuel Supply Module.

ASIDE: I had an old 1976 Mercury 500 (50-HP) engine with carburetors. The float valves in the carburetor bowls had a tendency to stick in the closed position, particularly if the boat had just landed hard in big waves. A minute or two later the engine would stall. I would remove the cowling and give the carburetor bowls a rap with the wood handle of a screwdriver. That would unstick the float valve, and the engine would return to normal running. I think gummy deposits from the pre-mixed fuel that would remain after the gasoline evaporated contributed to the little needle-type float valves sticking.

On that basis, a stuck float valve could easily be the cause of your troubles.

I look forward to hearing the resolution of the problem.

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Re: 2011 Mercury 90 Multiple Run Problems

Postby Tom Hemphill » Tue Sep 08, 2020 6:15 pm

jimh wrote:...I would remove the cowling and give the carburetor bowls a rap with the wood handle of a screwdriver.

In the 1970s this was a routine fix by those of us "in the know." The same method was also effective for sticking starter solenoids. Bystanders were always impressed by this little bit of magic!

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Re: 2011 Mercury 90 Multiple Run Problems

Postby Don SSDD » Wed Sep 09, 2020 6:50 am

I suggest you change or clean out, as appropriate, any filters or fuel separators on the Mercury.

Do you have a factory service manual?

Check the maintenance section for the service needed on these items.
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