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500 EFI Fuel/or Fuel injector issue?

Old 01-22-2012, 04:28 PM
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Default 500 EFI Fuel/or Fuel injector issue?

First, thanks in advance to all the "old salts" who contribute to this forum. I learn for you almost everyday.


Engines 500EFI Blue Merc Racing
Bravo I's 28" 4 Blade props
1987 Scarab 38 KV --Babied and loved, driven like Gandma on a Sunday afternoon.

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After about 2 months of not running my favorite toy I went out to run my Scarab today and both engines were slow to start--what I mean they needed a few seconds more cranking that usual and once they did start one seemed to be a little rough (barely noticeable but I have a pretty good ear for this stuff-esp flying airplanes for a long time) I let them warm up and as I was pulling out of the slip--the starboard engine quit. I restarted that engine and let her idle without putting a load on her. I returned to the slip and shut everything off.

I changed the Fuel Filters as I did an oil change in Nov (the last time I ran her) and forgot to change the fuel filters so I did that really quick.

Had a friend who is an ex-marine tech at a local Marine Max and had him give a listen. Both engines started easily this time (about 1 hour later) and were at idle with no issues--they sounded great!) we went out for a quick spin and now the port engine didn't like being in gear....exactly like the starboard engine....a slight roughness to her at idle as if a cyl was not firing...we ran for about 10 minutes and nothing changed except both engines were fine in gear at idle with the port engine a tad rough.

My friend seems to think that it is a fuel related problem (I agree) and have since learned we got a "higher then normal shipment of ethanol based fuel" at all the local marinas. Not sure if that is a clue or not......but I think I might have a clogged injector?

I just had put in 100 gallons of gas the last time out. This is the only thing that has changed since the last time they ran, and ran really good.

I am debating having the injectors cleaned--or what ever you all recommend. I do appreciate the vast amount of information on this site!

I look forward to your suggestions!
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Old 01-22-2012, 05:41 PM
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Wink

Sounds like fueling could be an issue and it also could be something as simple as sparkplug issues. I would recommend looking at the plugs to see if one or so cylinders look like the plug is firing or not, pretty simple check and if plugs have some serious hours on them, a new set wouldn't hurt.
Have the engines alarmed or set any trouble codes on a scanner?
Have you measured fuel pressure on both engines at the fuel rail?
Getting at the injectors on a 500efi is not easy as the intake top plenum has to be taken off to get at the fuel rails and injectors, so it's a bit of a job.
Ethanol additives tend to be solvent so unless there was phase seperation and you saw evidence of that in the fuel water seperator (cut it open if you have not yet), the fuel rails are aluminum and the fuel lines are stainless and neoprene so rusting in the system is unlikely after the fuel water seperator. Injectors sometimes gum-up with stale fuel and that could be a problem that with a little system pressure flush you may be able to clear them without a tear down.
Maybe some other 500efi owners will chime in here with similar issues and fixes to help.

Best Regards,
Ray @ Raylar

Last edited by Raylar; 01-22-2012 at 05:43 PM.
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Old 01-22-2012, 07:04 PM
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Originally Posted by Raylar
Sounds like fueling could be an issue and it also could be something as simple as sparkplug issues. I would recommend looking at the plugs to see if one or so cylinders look like the plug is firing or not, pretty simple check and if plugs have some serious hours on them, a new set wouldn't hurt.
Have the engines alarmed or set any trouble codes on a scanner?
Have you measured fuel pressure on both engines at the fuel rail?
Getting at the injectors on a 500efi is not easy as the intake top plenum has to be taken off to get at the fuel rails and injectors, so it's a bit of a job.
Ethanol additives tend to be solvent so unless there was phase seperation and you saw evidence of that in the fuel water seperator (cut it open if you have not yet), the fuel rails are aluminum and the fuel lines are stainless and neoprene so rusting in the system is unlikely after the fuel water seperator. Injectors sometimes gum-up with stale fuel and that could be a problem that with a little system pressure flush you may be able to clear them without a tear down.
Maybe some other 500efi owners will chime in here with similar issues and fixes to help.

Best Regards,
Ray @ Raylar
Good stuff....and thank you!

I did not have any Engine Alarms/warnings. Since it was one engine, then the other what ever it is...it is happening to both engines. I like the plug idea first, then on to harder stuff.
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