Classic AquaSport

Aquasport Mechanicals - things that need a wrench, screwdriver or multimeter => Fuel tanks and anything about fuel systems => Topic started by: jdupree on July 17, 2006, 05:00:27 PM

Title: fuel pump symtoms
Post by: jdupree on July 17, 2006, 05:00:27 PM: I have already been to the TMD site and have not gotten much of an answer. Just wanted to see if any of you have replaced fuel pumps in the past and what were your symtoms :?: I have a 1988 Johnson 90hp vro. This motor has just been re-built and has about 20 hrs on it.

It started when I had run about 20 minutes at around 3800 rpms. All of the sudden it bogged down and cut off. Once I got it restarted ran back to the boat ramp and it did the same thing again after about 20 minutes. Just had it in the water last week and struggled to get on plane - seemed like it would not open up. When I finally got it up it ran for a couple of minutes and bogged down and shut off again. This time when it bogged down I noticed that I had gas going to the water/fuel sep. but none going to the motor. I also have a brand new fuel tank, so I have ruled out venting, etc.

I was just curious if any of you guys have had similar symptoms and what it turned out to be :?: Any input would be appreciated. TMD is a great guy but will never get into alot of detail. Thanks alot :!:
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Post by: JimCt on July 17, 2006, 07:42:51 PM: Symptoms you are describing fit perfectly with the problems a lot of guys are having with the reformulated gas containing ethanol. Likely your filter/separator is plugged up. Try thoroughly cleaning out the filter unit and putting on a new filter.

Been a LOT of discussion on this on thehulltruth.com.
For example:
www.thehulltruth.com/forums/thread-view ... 2&posts=12 (http://www.thehulltruth.com/forums/thread-view.asp?tid=110182&posts=12)
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Post by: jdupree on July 17, 2006, 08:45:36 PM: Hey Jim,

Thanks for the reply. I have not replaced the water/fuel sep. since I have had this boat so I do not know the history. Can the water/fuel sep. stop up and cause a "no fuel" situation :?: I thought that if anything that it would send water into the carbs :?: I am sure that it needs to be replaced. I am just trying to rule out a fuel pump because the whole vro pump has to be replaced$$$$. I just found it odd that when the motor bogged down and quit I had gas going to the water/fuel sep. but none to the motor. Either the water/fuel sep. is plugged as you say, or the fuel pump is not pulling enough into the motor.

Once I replace the filter, do I need to pull the carbs or just go give it a shot :?: Thanks as always for your valued input. Just let me know what you think. Thanks alot.
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Post by: RickK on July 18, 2006, 05:25:42 AM: If the motor only has 20hrs since the rebuild, I'd take it back to the mechanic that rebuilt it. Surely he'll have some idea and it would be a lot quicker.
My $.02
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Post by: JimCt on July 18, 2006, 08:01:36 AM: Replace the fuel filters. That should solve the problem. If it does, your carbs are fine.
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Post by: jdupree on July 18, 2006, 08:31:15 AM: Thanks for the suggestion. My water/fuel sep. is made by omc. Do I just unscrew the filter and take it off :?: Do I need to clean anything while the filter is off :?: Lastly, where can I find a Racor filter :?: Thanks,
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Post by: ddd222 on July 19, 2006, 12:48:02 AM: i forget whether someone else suggested, and take into account the ethanol issue which shortens the life of pumps and filters, but what i did w/ my old envinrude looper motor which is very common, and may be also a cheaper solution is disconnecting the vro system all together and mix the gas yourself. That bogging i would still suggest water separator changing, and keeping a spare on board at all times, but any system from omc labeled "vro", has been notorious for mixing way too rich, or way too lean, frying many a powerhead. Disconnecting the system is easy and ensures the precise blend those motors call for, but tends to be inconveniant
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Post by: JimCt on July 19, 2006, 08:42:42 AM: Racors are available on eBay and likely at your local Marine store. Not familiar with the OMC separator but if it has a disposable screw-on filter, which looks like a car oil filter, replace it. That should do it.

As ddd222 said, its a good idea to keep two or three spare filters in your on-board spares kit. Sooner or later you will need them.
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Post by: jdupree on July 24, 2006, 12:20:29 PM: Well, replaced water/fuel sep., re-built carbs, checked for air in fuel system and could not find a problem. Motor is still acting up :x It is hard to start as if starving for fuel. It will idle ok, but will not accelerate much at all. Did notice that the bulb will not stay tight. It has to be the fuel pump :?

Unless you guys can offer up a suggestion, I guess it is time to take it to the shop :( If any of you have had these same symptoms and have solved the problem please let me know. Thanks :!:
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Post by: Anonymous on July 25, 2006, 07:46:00 AM: When you say it boggs down and quits is it locked up or does it spin over freely with the starter but just not start for a few minutes?

What spark plugs are you using?
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Post by: jdupree on July 25, 2006, 08:33:17 AM: I did have champions in there. Switched to ngk and motor does idle better. When it bogged down it would not start for several minutes but would spin over fine. Motor never got hot - I have a good temp guage.

Now, I cant even get up on plane. Bulb will not stay tight, it will idle but when you give it gas it won't open up.
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Post by: Anonymous on July 25, 2006, 08:55:43 AM: OK, so when it dies it's not locked up. It sounds like there's some sort of fuel restriction. I'd suggest getting the NGK's out ASAP and go back with whatever Champion the rebuilder had in it. We use (Q)L77JC4's in that motor.

Obviously a compression check is the place to start. If the rebuild came with any sort of warranty I'd suggest that you let the rebuilder look at it before you run it anymore.

If it's locking up when it dies, that's a whole other deal. Even if it spins over after a couple of minutes. As long as it always spins free, there shouldn't be any internal damage.
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Post by: jdupree on July 25, 2006, 11:58:42 AM: Dhadley,

Thanks for the info. I told my guy who re-built it to start with a comp. and spark test. I did test the fuel pump per instructions from TMD. Hooked the gauge to the discharge outlet at the top of the vro pump. I pumped the bulb and the gauge went up to around 10psi. Let it settle down to around 1psi and then turned it over. The gauge didn't even move! The bulb will not stay firm but it will idle. Have you ever had a primer bulb go bad? Something is causing the bulb not to stay tight, so that tells me it should be a fuel issue.

If you have any more suggestions please let me know. It will be several days before my mechanic can look at it so I was trying to figure out what I could try in the meantime. Thanks,
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Post by: Anonymous on July 25, 2006, 12:53:45 PM: If the bulb goes empty as the motor runs then the fuel isny being pulled by the motor's fuel pump or there is an air leak after the bulb. We assume there is no leak or you'd see it as you squeeze the bulb most likely. If the bulb gets sucked flat then there is a restriction forward of the bulb (anti-siphon valve, clogged pick up etc).

If you run the motor again try squeezing the bulb as the motor starts to run out of fuel. If that cures the problem and the motor runs OK then the pump needs attention or replacing.
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Post by: jdupree on July 25, 2006, 01:16:11 PM: Dhadley,

Thanks again :!: I did notice when I was getting ready to stall that I pumped the bulb and the engine picked back up. The bulb is not being sucked flat but will not stay firm. Based on what you have said, I will concentrate on the fuel pump.

Thanks again for the help :!: Once the problem is determined I will post the results in an effort to help others if they have the same symptoms.
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Post by: Anonymous on July 25, 2006, 01:38:00 PM: OK, when you pumped the bulb you became the fuel pump. I'd say you got it nailed!

Just for kicks, check the pulse line real close. If it's not tight or is cracked / broken that means a weak operating pulse. Or if the pulse limiter is plugged. That will do the same thing.
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Post by: jdupree on July 25, 2006, 02:27:24 PM: Is the pulse limiter on the VRO/fuel pump? I don't know alot about these VRO pumps. Should I remove the VRO pump and take it apart to see what I have? Thanks,
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Post by: Anonymous on July 25, 2006, 02:42:02 PM: The pulse limiter is actually more of a flame arrestor than anything. There should be a round fitting screwed into the block or in-line in the pulse line. The fuel / oil pump works on crancase pressure and vacuume or "pulses". However, there can be fire in the crankcase and if there is no flame arrestor the pump diaphram can be damaged. If the fitting is clogged, the hose loose or the diaphram bad the pump will not work as designed. That usually results in a "weak" pump that cannot supply enough fuel to run the motor properly.

Now, depending on which pump you actually have (VRO, VRO II, OMS etc) you may be able to get parts for it. If you aren't sure which pump you have, I'd suggest looking into a new pump. In many cases a new pump is supplied as a part of the rebuild. Personally I like the idea of the oil injection. As long as it's maintained the newer systems work well.
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Post by: jdupree on July 25, 2006, 03:14:33 PM: If I am not mistaken, that hose plugs in to the first fitting on the vro pump at the front of the pump? I know the middle plug in is for the gas in and then the oil line plugs into the rear? If that is the case I will check it out. I noticed that hose when I had the carbs off. I assume that is supposed to be an air tight fit? I noticed that fitting was in the block and the hose would rotate freely on that fitting :?
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Post by: Anonymous on July 25, 2006, 03:24:44 PM: AH! You're getting warmer. Lets hope its just sucking air and losing the pulse.

I believe you are correct on the hose locations.
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Post by: jdupree on July 25, 2006, 04:17:20 PM: Dhadley,

Thanks again for the help. You hve taught me a couple of things today. I will let you know what I find.
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Post by: RickK on July 26, 2006, 05:48:04 AM: Geez, even I learned a few things that probably pertain to my 115 and I wasn't even trying 8)
Thanks Dhadley