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1986 evenrude vro power pulse at full throttle

A

armyvalues01

New member
I have a 86 vro 40hp . The vro delete has been done by the previous owner. I noticed that the file pump that was used to replace it did not allow for the second pulse tube . The tube was off behind the starter and not plugged so I had a rough idol. My question would be should I have a fuel pump that allows for that second pulse line and could this be starving the engine of fuel needed during that cycle?
 
Second pulse??? (A contact to other techs... F_R, Bullet, Scott, etc..... Am I missing something here?)

Armyvalues01... Frankly, in my 30+ years which included 1986, I never came across any second pulse equipped fuel pump. The original V6 of 1976 was equipped with dual fuel pumps which of course had their pulse delivered from separate cylinders... but other than that, I never encountered such a setup.

If what you're saying is that you have a open threaded hole leading directly to the interior of the crankcase... you must have one hellava noisy running engine. Yeah, that'd give you one rough idle alright. If it were me, as long as you have a pulse to your present fuel pump, I'd plug that hole and move on.
 
If the replacement pump was properly mounted it would be mounted directly over the pulse port.-----Only needs fuel in and fuel out nipples.-----Pulse port for VRO would be plugged.----Very simple conversion but many folks are creative in doing this.----The pulse port on the side of the upper cylinder had a plug in it when it left the factory.----That plug is removed to mount the proper pump !
 
Ok that sounds correct. The pulse port for the vro is plugged now but I may need to revisit it to make sure it isn't leaking air . Any suggestions on the power pulse besides that?
 
My terminology may have been miss used . It was the vro pulse port not second pulse. The fuel pump I was referring to was a 438559 that had two other ports besides the fuel supply and where it mounts to the cylinder . From what I seen in some other installation videos one was used for the vro pulse port and the other for the fuel out.
 
Fuel pumps only need 1 pulse port.----That supplies plenty of PRESSURE pulses to run the pump.------The correct pump for your motor has one nipple ( filter cover ) for fuel in.-----And one nipple for fuel out.----The pump mounts directly over the pressure pulse port.-----There is much confusion about fuel pumps and many are replaced as a wild guess / last resort to fix motors.----What is your motor doing / not doing ?-----What do you mean by----" any suggestions on the power pulse besides that "-----Why that statement ?
 
racerone said:
Fuel pumps only need 1 pulse port.----That supplies plenty of PRESSURE pulses to run the pump.------The correct pump for your motor has one nipple ( filter cover ) for fuel in.-----And one nipple for fuel out.----The pump mounts directly over the pressure pulse port.-----There is much confusion about fuel pumps and many are replaced as a wild guess / last resort to fix motors.----What is your motor doing / not doing ?-----What do you mean by----" any suggestions on the power pulse besides that "-----Why that statement ?
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The motor at full throttle will run great for a few seconds then losses power then picks up power then losses power again ,so on and so on . If I back it off it runs fine and at idol it runs fine . It seams the pump installed now is the correct pump as you explained. The primer bulb stays tight with no loss in presure.
 
The fuel primer bulb, under normal conditions, would be laying horizontal on the deck or motor well somewhere. In laying horizontal, the fuel level would normally drop to the halfway mark and it would feel soft.

Only if the fuel bulb is in a vertical position would it stay full of fuel (hard).

Now, if your fuel bulb is laying horizontal and it stays hard (tight)... something is not right there... check it.

If your statement is in error, and the bulb fuel does drop down to the halfway mark... does pumping the fuel primer bulb constantly, acting as a manual fuel pump make a difference... causing the problem to cease?
 
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