1985 Johnson 90 VRO Won't stay running...

Matty3614

Cadet
Joined
May 22, 2011
Messages
16
I have a 1985 Johnson 90 hp VRO V4. I pump the primer bulb until it is hard, engage the idle throttle 3/4 and choke. It usually starts pretty easily. For the winter, I replaced plugs, changed lower unit oil and oil from tank, and fogged through the air intake right into the carbs. I took the boat out twice so far. First time, no problems. Yesterday, began stalling about 5 minutes into running. If i pump the primer bulb when it starts to shutter it will stay running. Seems like it uses the fuel that I pump in by hand through the bulb then runs out, and will not draw it's own fuel through the line. Should I use engine tuner spray? Change VRO pump? Where do I start to diagnose?
 

Monte1961

Lieutenant Junior Grade
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May 8, 2011
Messages
1,180
Re: 1985 Johnson 90 VRO Won't stay running...

I have a 1985 Johnson 90 hp VRO V4. I pump the primer bulb until it is hard, engage the idle throttle 3/4 and choke. It usually starts pretty easily. For the winter, I replaced plugs, changed lower unit oil and oil from tank, and fogged through the air intake right into the carbs. I took the boat out twice so far. First time, no problems. Yesterday, began stalling about 5 minutes into running. If i pump the primer bulb when it starts to shutter it will stay running. Seems like it uses the fuel that I pump in by hand through the bulb then runs out, and will not draw it's own fuel through the line. Should I use engine tuner spray? Change VRO pump? Where do I start to diagnose?

Is the fuel tank vented? Fuel pump have 3 to five lbs. pressure? Go back and check these and get back to us and let us know what you find!
 

Matty3614

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Joined
May 22, 2011
Messages
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Re: 1985 Johnson 90 VRO Won't stay running...

Tank is under the deck and has a dedicated vent line to the starboard side which is not obstructed. I'm not sure how to check the pump pressure. Doubt I have the tools to do it either. I also traced the line from tank to external filter assembly and found no kinks or leaks. The inside of the filter canister looks clean, nothing floating, and the O-ring is good in the filter. Also, the primer bulb takes a few seconds to re-inflate with fuel after I squeeze it.
 

Monte1961

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May 8, 2011
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1,180
Re: 1985 Johnson 90 VRO Won't stay running...

Ok I have a few questions for you. 1st how do you know for sure its vent is not obstructed? Wasp and other critters can get up there a plug stuff up. 2nd. you should find away to check the pressure. At least you will know! Post back and let us know!
 

Matty3614

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May 22, 2011
Messages
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Re: 1985 Johnson 90 VRO Won't stay running...

When I filled it up two weeks ago, I could see vapors coming from the vent outlet port on the hull. I will be up there Saturday morning and I'll remove the deck panel to expose the tank, remove the rubber vent hose from the tank, clean out the nipple with a pipe cleaner, and try to run without the hose on. If it doesnt die, then I'll remove the hose and clean it out if needed. It runs up the gunwale right next to the fuel fill hose and it's a real pain to remove and replace it. There's a screen inside the vent outlet on the hull which may be restricting air flow. Ill let you guys know Saturday afternoon. Thanks!
 

Fed

Commander
Joined
Apr 1, 2010
Messages
2,457
Re: 1985 Johnson 90 VRO Won't stay running...

When you're there on Sat just crack open your fuel cap which will bypass your vent, if it runs ok then look for a vent restriction.
Also, the primer bulb takes a few seconds to re-inflate with fuel after I squeeze it.
Gas tank could be fitted with an anti syphon valve (gummed up) or you could have junk in your gas tank too. Do you have a filter/separator between the tank & the primer bulb, could be blocking.
Don't expect the primer bulb to expand instantly but it should be fairly quick.
 

Matty3614

Cadet
Joined
May 22, 2011
Messages
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Re: 1985 Johnson 90 VRO Won't stay running...

I worked on the boat today. Pumped the ball til hard and fired right up. Ran for about 3 minutes and shut down. Checked all the hose connections, the air intake, the fuel line, and vent line, and all looked fine. Used a pipe cleaner in all of the fuel line fittings. Removed vent line from fuel tank and blew through it with my mouth and it was clear. Also used some OMC Engine tuner in the schrader valve and tried to blow it out. Both filters look new. When it began to stall I pumped the primer bulb and was able to keep it running. Any way to check the VRO/Fuel unit without a gauge? A few salty old dogs in the marina helped me and said it seems like the VRO/Fuel unit went.
 

j_k_bisson

Lieutenant Junior Grade
Joined
Oct 6, 2010
Messages
1,082
Re: 1985 Johnson 90 VRO Won't stay running...

YOu can rebuild most VRO pumps. But only the fuel side. You will have to premix from here on out.

You mentioned a external fuel filter. And it takes a while for the bulb to reinflate. That would indicate a restriction in front of the vro.

Quick check, take a big coffee can or mason jar and put it on the ground on the fuel connection side of the boat. Dissconnect the fuel line from the motor and put the end of the line in the can on the ground. Try pump the bulb and see what kind of flow you get out of the hose. If is is just a trickle then look before the bulb. If is come fairly quickly then its after the connection. The flow should be without pumping. Just pump it until it start to flow. The flow should be constant after the pumping.

Justa thought.
 
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