1987 formerly-VRO 90HP idle issue

[powrguy]

I have a 1987 Evinrude 90HP, which I capped off the oil supply port, removed the oil lines, removed the wiring, and now use pre-mix (50:1). It runs like a top now, and reaches WOT without hesitation. However, after running at cruise speed and/or full throttle for awhile, and then backing down and idling, it will stall out.

To re-start, it ONLY can restart if the fuel bulb is being squeezed and keep squeezing to keep it running for awhile, then, you can go back and run, throttling up in gear, and continue to where you're going.

My question basically is whether the fuel pump is a "pulse pump", using crankcase pulses to pump the fuel, or a "vacuum-actuated pump", where engine VACUUM is what moves the diaphragm? The reason being, my thought is that vacuum is HIGHEST at idle, and LOWEST at WOT. If it's a pulse pump, then it makes sense that the fuel pump is weak.

I also have an in-line fuel filter, and suspected it might have some restriction, but at higher fuel flow, it allows fuel to flow enough to not have issues at other-than-idle.

Any thoughts on what to do?



thanks

 

[Daviet]

Re: 1987 formerly-VRO 90HP idle issue

I would start by checking the fuel pump pressure and flow at an idle. By the way you describe it, it sounds like you might have a fuel pump on the way out.

 

[powrguy]

Re: 1987 formerly-VRO 90HP idle issue

I would start by checking the fuel pump pressure and flow at an idle. By the way you describe it, it sounds like you might have a fuel pump on the way out.

I am thinking of removing the oil pump/fuel pump (the VRO pump), and installing a new fuel pump that's made for non-VRO motors. I'm not sure of how to mount it, but that's my question, too: is it a pulse-pump, or a vacuum-operated pump? If it's a pulse pump, then it's a weak pump for sure.


thanks

 

[Daviet]

Re: 1987 formerly-VRO 90HP idle issue

It is a pulse type pump. Sometimes when you convert to a standard type pump, you have to make your own mounting bracket.

 

[emdsapmgr]

Re: 1987 formerly-VRO 90HP idle issue

You have a pulse type pump. It alternates between vacuum and pressure-provided by the intake side of the crankcase. The alternating of the two provides movement to the diaphragm, which alternately sucks fuel from the tank, then pressurizes/flows it to the fuel manifold. As the rpm's increase, so do the pulses and thus the fuel flow. Same for either the cheap (early pumps) or the later VRO-type. Agree that the current pump may be weak. Take a friend with you next time out. Throttle up to WOT. When you think you have fuel issues, have the friend constantly prime the fuel hose bulb. If the engine runs WOT as long as you prime the bulb, the pump is probably weak. (The pump won't provide enough fuel to sustain the fuel level in the carb bowls.)

 

[powrguy]

Re: 1987 formerly-VRO 90HP idle issue

The boat does fine at WOT; it only needs the bulb-assist at idle. That's why I think the pulses at idle are insufficient to maintain it running, yet pumping the bulb makes it idle fine.

thanks

 

[kenmyfam]

Re: 1987 formerly-VRO 90HP idle issue

Take a look at this thread. It may help you.

http://forums.iboats.com/showthread.php?t=265363&highlight=pre-mixer

 

[powrguy]

Re: 1987 formerly-VRO 90HP idle issue

Okay. That's a good thread for info. I'll have the same setup with my 90HP, just like the one he modified. I believe the pulse-port and mounting bosses are there, but have to look to be sure. I'll work on it, and when done, I should be rid of the VRO pump and hoses and wiring, and have a standard fuel pump, then. The ONLY reason I initially converted, was because I have a 2-stroke kicker, and can run either motor of the main tank of pre-mix fuel. Otherwise, I would have left the VRO in service.

thanks

 

[powrguy]

Re: 1987 formerly-VRO 90HP idle issue

Okay. That's a good thread for info. I'll have the same setup with my 90HP, just like the one he modified. I believe the pulse-port and mounting bosses are there, but have to look to be sure. I'll work on it, and when done, I should be rid of the VRO pump and hoses and wiring, and have a standard fuel pump, then. The ONLY reason I initially converted, was because I have a 2-stroke kicker, and can run either motor of the main tank of pre-mix fuel. Otherwise, I would have left the VRO in service.

thanks

Okay. Today I took the boat out, and now it not only is starving for fuel at idle after a short time (you can keep it running by pumping the fuel hose bulb), it also is starving after a period of time at mid-throttle and even full-throttle (you can keep it running by pumping the fuel hose bulb at speed, too).

I'm thinking fuel pump, and I don't know the part number for an installation of a pre-mix pump, removing the VRO unit, on the 90HP V4 crossflow motor.

Anyone?

 

[gibletts]

Re: 1987 formerly-VRO 90HP idle issue

Any chance you have an air leak somewhere along the fuel line assembly on the tank side of the fuel pump? maybe around that in line filter?

 

[powrguy]

Re: 1987 formerly-VRO 90HP idle issue

Any chance you have an air leak somewhere along the fuel line assembly on the tank side of the fuel pump? maybe around that in line filter?

I'm gonna go over it all tomorrow. I am going to first try using a portable fuel tank, and see if the issue is upstream of that input connector. If that doesn't cure the problem (meaning an issue in the water separtor filter, or the tank pickup), then I'll go over the in-line fuel filter, the connections all the way to the fuel pump, and see what I can find, if anything. If all that doesn't cure it, I think it narrows it down to that fuel pump on the VRO. If that's the case, I'm now already trying to find a part number for a pre-mix (non-VRO) fuel pump for this motor.

thanks

 

[Daviet]

Re: 1987 formerly-VRO 90HP idle issue

All you need is a 3 line pump, like this one.
http://www.ishopmarine.com/ishop/js...CatFilter=BRP&eCatSupFldr=supplier-100-005-EJ

 

[powrguy]

Re: 1987 formerly-VRO 90HP idle issue

Okay. I believe there is a port and the two mounting bosses for that pump on my motor, right?

thanks

 

[Daviet]

Re: 1987 formerly-VRO 90HP idle issue

I am not sure on your engine if it had the optional fuel pump set up. All you have to do is use a 3 port fuel pump, make a bracket and mount the pump and run the fuel lines.

 

[powrguy]

Re: 1987 formerly-VRO 90HP idle issue

OK. I'm sure there's a pulse line to the existing VRO pump, and I'll see how that is set up. That hose would be the source for the pulseline to the non-VRO fuel pump, I think.

 

[emdsapmgr]

Re: 1987 formerly-VRO 90HP idle issue

Check out this 3-port pump from your Bombardier dealer: 438559

 

[Daviet]

Re: 1987 formerly-VRO 90HP idle issue

Yes, you might have to install a longer pulse hose to reach your new pump.

 

[powrguy]

Re: 1987 formerly-VRO 90HP idle issue

I removed the VRO pump, and there WAS a mounting location with another capped pulse port. I un-capped the pulse port and mounted a pre-mix fuel pump, and removed and capped the old pulse fitting. The routing of the fuel hoses have more bends in it to reach the fuel manifold, but it's working okay now. I had to make a pretty sharp u-bend in the bottom of the fuel pump hose route, then up and over in a large loop to reach the top of the fuel manifold that was original. I am running and not stalling so far.

thanks

 

[emdsapmgr]

Re: 1987 formerly-VRO 90HP idle issue

You need to be careful using normal bulk fuel hose, then bending it around corners. It could present a fuel starvation problems (fuel starvation)-at high fuel flow rates: ie: high rpm's. OMC specially heat-treated hoses when they had to bend around sharp corners, then issued actual part numbers for them. Normal bulk fuel hose tends to kink when bent in a sharp radius. You may be able to overcome this problem by making large loops in the bulk hose to prevent kinking.

 

[powrguy]

Re: 1987 formerly-VRO 90HP idle issue

Since this is a "home-brewed" modification, I don't know what part numbers to seek for "pre-shaped" fuel hose. Using the best grade vinyl-coated fuel hoses, which are less prone to kinking, is the alternative, I guess.

In the off-season, I may re-engineer the routing/fittings, and maybe go to a brass elbow to make the turn at the bottom of the fuel pump, and then would only need to have a large loop to the top of the manifold.

thanks