Fuel problem

[sailfish-steve]

The culprit is a 89 Evinrude 200. At WOT it runs for about 30 seconds then starts struggling. If I have a buddy pump the primer bulb it picks back up but after a while even the primer bulb wont keep up. It's almost like the bulb is being pulled flat. I pulled the fuel lines all the way back to the tank and they all flow well. There is no obstruction in the fuel pickup tube. Fuel/water separator has been replaced and is flowing freely. Any idea what to check next?

Steve

 

[Joe Reeves]

Re: Fuel problem

The culprit is a 89 Evinrude 200. At WOT it runs for about 30 seconds then starts struggling. It's almost like the bulb is being pulled flat. Steve

It's almost like the bulb is being pulled flat? If that's the case, you have a fuel restriction.

(Fuel Anti Siphon Valve)
(J. Reeves)

Many of the later OMC V/6 engines incorporate a fuel restriction warning via a vacuum device attached to the powerhead. If the engine overheats, or if you have a fuel restriction, the warning is the same.... a steady constant beep.

NOTE... Only the V/6 & V/8 engines have the above "Fuel Restriction Warning". The warning horn will not sound on the other models.

The fact that a engine is not overheating, but the warning horn sounds off with a constant steady beep, and that the rpms drop drastically would indicate that the engine is starving for fuel due to a fuel restriction. Check the built in fuel tank where the rubber fuel line attaches to the tank fitting. That fitting is in all probability a "Anti Siphon" valve which is notorious for sticking in a semi closed position. It will be aluminum, about 2" long, and the insides of it will consist of a spring, a ball, and a ball seat. If this valve exists, remove it, knock out those inner components which will convert it to a straight through fitting, then re-install it. Hopefully that cures the problem.

The above procedure will cure a restriction problem with the anti siphon valve as stated. BUT, it may also allow fuel to drain backwards to the fuel tank when the engine is not running (siphoning backwards) due to the fact that the carburetors/fuel pump etc are higher than the fuel tank. This condition is not an absolute as the valves in the fuel primer bulb usually prevent this backwards siphoning problem. However.... if this does take place, the cure would be to install a new anti siphon valve.

NOTE: There has been cases when the output valve in the fuel primer bulb would come apart, and the inner portion of the valve would actually reverse itself and be drawn back into the primer bulb's output valve body. This in effect would create a shut off valve and result in a fuel restriction. If this is the case, you should be able to feel something laying in the bottom of the primer bulb when held horizontally.

 

[Chris1956]

Re: Fuel problem

Steve, Check for an antisiphon valve, somewhere in the fuel pickup tube at the fuel tank. Remove it and retest. if that is not it, check fuel tank vent. Loosen fuel filler cap and see if that fixes it.

 

[dodgeboy1979]

Re: Fuel problem

had the same problem, i changed the bulb itself. I think over time the rubber breaks down and the bulb looses its rigidity.

 

[sailfish-steve]

Re: Fuel problem

I replaced the bulb last week because it had some cracking in the surface. Ill check the anti-siphon valve and report back. May take it out tomorrow evening.

 

[Tim Frank]

Re: Fuel problem

Any chance the bulb is in the line backwards?

 

[sailfish-steve]

Re: Fuel problem

Thanks for all the replies.

I went through the entire fuel system from gas cab to carb. Checked flow at each hose at each connection for restrictions to see if they may have broke down internally. checked flow at the fuel water separator, fuel pumps, as well. I did a siphon test at each connection as well. The bulb is connected correctly and when I pump it I get a full stream of gas into a cup. I checked each fuel pump by sucking/blowing into the pulse tube and they both checked out(is there a better way of doing a fuel pump flow test?). I'm using 2 older style fuel pumps rigged in series (438559) since VRO has been removed along with the pump itself by PO. I am going to try and take it out to the lake this evening after work to see if any of that work could have fixed my problem. I will post my results.

Is there any chance my Attwood 3/8 primer bulb just cant keep up? Doesn't make sense to me that this could happen. After all it is the right size and brand new.

Thanks,
Steve

 

[Tim Frank]

Re: Fuel problem

I checked each fuel pump by sucking/blowing into the pulse tube and they both checked out(is there a better way of doing a fuel pump flow test?). I'm using 2 older style fuel pumps rigged in series (438559) since VRO has been removed along with the pump itself by PO.

Yes, you can use a fuel pressure gauge.
The OEM manuals usually show the hook-up for a fuel pressure gauge and the range of values for your particular motor at several RPM levels.
e.g. the only manual that I have in town is for my 8 HP E/rude. Output pressure from fuel pump at 600 RPM should be 1 PSI, at 2500 RPM = 1.5 PSI and at 5000 RPM = 2.5 PSI.

I have no idea what effect your non-OEM setup might have on any readings, but presumably you'd need whatever the original fuel delivery spec was as a final output.

Do you have a manual?

 

[sailfish-steve]

Re: Fuel problem

I do have a factory manual. Ill look up the fuel pressure testing procedure. I wouldn't think the pressure from the VRO pump would be that much different from the pulse pumps added to replace it.

 

[Tim Frank]

Re: Fuel problem

I would think that if you can match the spec'd pressure in the manual as a final output from your tandem pumps that the motor should not notice the difference.
With pressures this low, you probably want a gauge with a 0-5 PSI range s that you are operating in the middle of the range.

 

[Fed]

Re: Fuel problem

It's almost like the bulb is being pulled flat.

It won't be the fuel pump.
You have to have a restriction between the tank and the fuel pump or the breather vent is restricted.

It may flow fuel when you siphon to test but that's not much compared to 200HP at WOT.
Think partial restriction, did you also check the tank breather & line?