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1984 40 hp problems

goldenjoe

New member
Hello Group, I am having an issue with my 1985 40 Johnson. It will start great, idle for a few minutes, then start acting like it is running out of fuel, starting with the top cylinder. It will caugh, then quit and run on the lower cylinder, then the lower cylinder runs out of fuel. I have replaced the diaphragms in the VRO pump, of which I have plugged the oil line and run mixed fuel. I have replaced fuel lines, pulse line, and have checked for crankcase pulse, and pulled the fuel lines, and fuel comes out when motor is cranked. I replaced needle and seats in both carbs, and set float, but not float drop. New fuel line and connectors. .Visually checked for any leakage at all connections, all ok. Primer bulb pumps and gets hard as it should. Any ideas on what I could check next?
 
I have tried that, it seems to make the engine run longer, but it still will eventually stall out. I am wondering about adjusting the float drop, as the new needle and seats seem to be a little different in size, although they were the part number that was listed. I am thinking that it may not open the needle enough to replenish the fuel in the bowl. Going to try that tomorrow. The diaphragms were bought on amazon, and not omc or sierra. Maybe it pumps fuel, but not enough. I don't have a fuel pressure gauge and the manual says you have to run it about 2000 rpm.
 
The starvation at idle is when your fuel requirement is very low, of course, so its not likely float drop.....besides it did the starvation symptoms before all the work you mentioned, right? When DID the problem start, after a storage period? What did the VRO parts look like? There could be a restriction at your fuel tank pickup screen. Is the squeeze bulb acting different than normal? Maybe the ethanol has something to do with it. I know that the motor was exposed to ethanol at some time in its life or there might not have been a problem with the VRO. Maybe the problem is in the supply line or the squeeze bulb. I have seen many of these newer type "laminated" type fuel lines come delaminated and create their own obstruction. Check out this one, right at the coupling.fuel hose_resized.jpg
 
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You are correct, it was after winter storage. Also correct about the ethonol, the diaphragms and also the bottom part of the housing had showed damage. It was very minor pitting in the housing, I smoothed that out but it still may be an issue. I have had problems with the valves in the primer bulb before, but this one seems to be working fine. I had thought about the venting of the tank so I loosened the cap, but no change. The tank is a 9 gallon plastic, which I emptied and dried out before storage, and the fuel line is new from NAPA. Good idea about the pick up tube, will check that today. The past ethanol may have affected the tube. I make sure I get supposedly ethanol free premium, but obviously, there has been a problem. I am at a point of buying just a fuel pump to mount on block and remove the VRO.
 
Ethanol has been a hard pill to swallow for me. I love the older technology and the often "bulletproof" engineering. Ethanol has destroyed so many things over the years that it almost makes me cry. The personal outboards and other equipment that we use at home as well as in the Canadian resorts that we own (brother Steven, wife Raquel, son Timmy , and myself), get only non-oxy fuel. I have NEVER EVER had to dismantle a carb or change a fuel pump on ANYTHING that I manage. Ethanol is illegal to use in airplanes and should be illegal....in any concentration....on the water. Yamaha engineers have told us that any concentration over 10 percent ethanol is now illegal to use in boats. The engineering and chemistry behind ethanol is disgusting and the power it produces is discouraging. We all pay for it in the "long run". It has no place in seasonal equipment. The shelf life is less than 6 months before phase separation begins. Since ethanol is a huge source of the effective octane, once it collects its moisture and sinks to the bottom of the fuel tank, it cannot be remixed with the original petrol and there goes your octane. When your motor sucks in this crap, then you now have a concentrated compound. Thats when the real troubles begin.
 
OK, I think I have identified the issue. I used a different tank, new primer bulb, all new hoses, connectors, and it boils down to the fuel pump. The motor still dies, and after some tinkering, I pulled the pulse hose and fuel came out of the chamber on the pump. I do believe that fuel leaking past the diaphragm is the issue. The kit I bought on Amazon did not have a lot of parts, and I should have bought a more OEM kit. The ethanol damage to the housing probably contributes to the fuel leakage. There is a seal for the shaft that connects both diaphragms that did not come with my kit that appeared to have some damage. So, I am ordering a new pump that mounts to the side of the block and will eliminate the VRO pump.
 
Good you have found the problem, it wasn't too technical. The VRO was too far gone to get it rebuilt effectively enough to pump fuel again....besides that, you had a kit that was very insufficient for the job.
 
What is your model #. I don't remember a 1984 model having a VRO pump. If you are going to replace the pump get the.one for the 48 hp motor. It will mount right to the block on the #1 cylinder.
 
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What is your model #. I don't remember a 1984 model having a VRO pump. If you are going to replace the pump get the.one for the 48 hp motor. It will mount right to the block on the #1 cylinder.

1984 was a typo, it is an 85. I think I mentioned that in my original paragraph asking for advice. It is a J40ELCO.
 
Happy to report that with a new non-vro fuel pump, engine runs like new. Should have done that when I saw the damage to the inside of pump.
 
Right NON Oxy, ethanol free. Note, some premium still has ethanol. The non-ethanol premium is marked on the pump it is required by law.
 
True, if the distributor is complying. I am staying with Tier 1 stations, as they have a higher standard of compliance. I did get gas at a non Tier 1 once because the usual station was backed up and busy. Not doing that again.
 
Hmmm 35 yr old VRO pump failed. So your pump probably ran most of its life on e-10. I guess you could blame ethanol for it. It really makes you think if ethanol did not exist your motor would never break down. And now we have found out there are free floating ethanol atoms flying around. To be safe I would make sure that I did not boat next to anybody else just in case. You may also not want to trailer your boat on the rd. Just to make sure those ethanol atoms cant get to your boat. I would also wash and wax the engine block to protect from those ethanol molecules. You could come.out some morning and your block would look like wormwood.

That is the problem with guys like tim who were born after 1985. They dont remember the problems with the real fuel from the 70s. The varnish that built up overtime, The rubber fuel lines rotting out under the hood. Most cars in those days had fuel filters held onto the steel lines by little rubber hoses. I lost count of how many of those rotted out. Or having the fuel filter being eaten away by the gas and ending up in the carb. Every 3-5 yrs you had to rebuild your carb because seals that were in contact with fuel would start leaking. Ethanol is an easy excuse to use when actually it just failed cause it was old. That old fuel was good for sticking floats to the float bowls. It did not matter if you ran the carb empty there was always enough to glue the float down. So its really not worth crying over because it is not a new problem.
 
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I was born in 1956. Thanks Mr. Scott for the compliment. Ethanol cannot be blamed for everything, but I have been around the block. There is way more fuel problems now than ever before and when Yamaha techs come right out there and blast ethanol for its damaging effects as well as its extremely short lifespan.......its hard to not side with them based on what I know from experience of well over 50 years in the marine/automotive/aviation/heavy equipment/small engine repair industries.
 
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