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2005 Johnson 90hp J90plso Fuel pump # 5

leadhead

New member
not very optimistic but here goes --- started having fuel pump problems with 9 month old 90 HP Johnson --- last carbureted 2 stroke they made --- coincident with first use of E10 fuel in NJ --- fuel pump will not pump sufficient gas to motor and dies at normal operating speed (I rarely exceed 4,000 rpm) --- have to hand pump fuel to the motor to keep engine running --- have replaced original pump which lasted 9 mo with 3 additional pumps - 1 used 2 brand new - each pumps works for a while (varies from a coupe of hours for the used pump to a couple of months for the new pumps) --- but then fails in the same manner --- I have a new pump (pump #5) but I'm afraid to install it since I have not identified the problem --- I have a friend who is a retired Johnson/Evenrude dealer/mechanic who can not figure the problem out --- his assessment is that the pumps are definably failing but he doesn't know why --- I have changed the fuel line components between the fuel tank and the motor --- the tank is polyethylene (the boat is an 18' 2000 Sea Pro) --- I have changed all of the fuel filters / water separators several times including the water separator housing --- my friend has recommended I switch to an electric fuel pump --- but I can't stop wondering what is causing the problem --- it would be much cheaper to go electric than keep doing what I'm doing now --- I do a lot of fishing where I power drift (i.e. slow troll) with the motor in and out of gear and it is difficult to hand pump fuel and work the throttle at the same time all day --- I have a 2 ft length of tygon tubing (inert clear plastic tubing) installed in the fuel line by my friend to check for air in the line and have observed air bubbles in the line which increase over time --- I have run with the gas cap open and the squeeze ball never collapses from negative pump pressure --- the problem is more prevalent in hot weather then in cold with the frequency of stalling less likely in the colder weather --- ANY IDEAS regarding the cause of the problem or similar experience would be very help full --- Thanks ! ! ! leadhead
 
Re: 2005 Johnson J90plso Fuel pump # 5

The engine calls for a 5007420 OMS pump, which is completely ethanol-proof, in that ethanol will not damage the pump.

You must disassemble one of the bad pumps and do an autopsy on it. There are two "sides" to the pump, a fuel side and an air side. The air side is the motor that operates the diaphragms internally, and the fuel side is what delivers pulses of fuel to the carbs.

As you disassemble, check each Torx head screw for tightness. An air leak there will cause the pump to fail.

My bet is that you will find that the air side has failed. Disassemble and look at the diaphragms very very carefully examining them for pinholes. Some sort of failure in the pulse limiter could be blowing a hole in the air side diaphragm. Have you been replacing the pulse limiter (comes with pump) or just the pump?

You can take one of the old pumps and hook a small vacuum/air pump (MightyVac) to the pulse line connection, and pump it manually, looking for the diaphragms to operate. Setting the pump for pressure output, you should be able to pump it a couple of times, then hear a click...then pump it a couple more times...hear a click...etc. Also, if you put a vacuum on the pulse line input it should hold a vacuum. All this on the bench of course. It should hold pressure, also. One pump with the pressure pump, and it should hold. Cannot tell you how long, but it should not instantly bleed off. If it bleeds off fast, the air side is bad.

Sounds like an air side failure, but you have to determine exactly.
 
Re: 2005 Johnson J90plso Fuel pump # 5

Daselbee
Thanks for quick your response --- I gave the first (original) pump back to the dealer who was going to send it to Johnson for an autopsy but I never heard anything back from either one --- I have changed the pulse limitor on the 2 new pumps that were installed but those pumps came with a straight pulse limitor connector and the pulse limitor hose is kinked when attached --- also I did not the recommended sealant on the threads --- I have remove the pulse limitor hose and checked the hose to see if there is vacuum in the approx position of the kink and there is vacuum so it is not completely closed --- I checked an exploded view of the fuel system on line and it shows a 90 degree fitting instead of a straight fitting at the pulse limitor so I have ordered one --- may have to trim hose to make it fit though --- don't know if that will make a difference --- I will discuss this issue with my mechanic friend --- he will be much better able to do bench tests you recommend --- thanks very much --- I really do appreciate your time and know how ! ! !
leadhead
 
Re: 2005 Johnson J90plso Fuel pump # 5

If you would like, PM me with your number, and we can make arrangements to get one of those bad pumps to me to look at. I of course will do it for free.

Are you ready to pre-mix oil and gas in the tank? If so, you can probably use an older pump, since this is a 4 cyl, and the huge expense of a OMS pump can be avoided.

If you want to go that way, we can discuss exactly how to do that in later posts.
 
Re: 2005 Johnson J90plso Fuel pump # 5

daselbee
sorry for the delay --- I didn't expect another response --- I got very busy with work (thankfully) and at home ---

I have been pre-mixing oil and gas from day one with this motor J90plso --- my last motor was a SPL 90 Evinrude and I got great perfromance from it --- I'm trying to remember what happened to the old pumps I think I gave the two new pumps back to the dealer to offset the cost of the replacement pumps and I returned the used pump to my friend ---

I didn't get a report regarding the cause of failure for either one --- I might be able to get the used pump back again if that is worth while --- that leaves only the current pump if not --- also I don't know what PM stands for ? ? ? sorry --- I'm not too hip when it comes to our new world of electronic communications --- thanks again for your continued interest and your offer to look at one of the old pumps ---

ps --- I used the boat over the weekend and had the same problem --- sometimes the motor runs longer without hand pumping fuel than others --- I ran a while at higher rpm (3,000 to 3,500) without as much need to pump fuel in the morning --- but by afternoon it seemed as though it had to be pumped almost continuously

Thanks Again
leadhead
 
Re: 2005 Johnson J90plso Fuel pump # 5

I cannot get this website to send PMs. I am receiving them, and your phone number is bad. Maybe you transposed a digit. Re-send your number.
 
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