Fuel vacuum alarms

[RetNav]

I have a pair of 1990 200 HP Evinrudes on a 256 WAC Dusky that run real good.

The problem I have is when the rpms is up around 5000 after a short time I will get a steady alarm. The VRO has been long ago removed so it is not that. The temp and water pressure is normal so that is not it. I have decided that it is fuel related and that leads me to the following question.

Is it possible to install two electric fuel pumps at the tanks to ensure continuous flow to the motors without any adverse effects?

 

[ob]

Re: Fuel vacuum alarms

If the VRO harness and oil reservoir wires are disconnected,I'm not aware of any other sensor that can trip a constant alarm except the overheat sensor.Have you determined which engine is initiating the alarm?Have you disconnected the overheat sensors and water tested to verify whether the constant alarm still sounds at speed?

 

[RetNav]

Re: Fuel vacuum alarms


On page 457 of the Clymer shop manual there is mention of a vacuum switch on models prior to 86 that is used to set off an alarm if the vacuum pressure reaches 7 in Hg. According to the tag both of my engines are 90 models, but both have the vacuum switch, located by the VRO pump, and both are alarming at various times.

All the above brings me back to the original question, can electric fuel pumps be effectively used at the tanks to increase the supply to the engine mounted pumps?

 

[ob]

Re: Fuel vacuum alarms

Sure electric fuel pumps can be added as long as you regulate the pressure around 3 or so lbs.Not sure how safe or legal that is.Since you mention that the engines are running real good and you seem sure that the engine overheat sensors are not initiating the alarm you are getting,it seems a bit extereme to install electric fuel pumps to appease an alarm instead of a performance issue.But then ,that's just my opinion.Then there's the potential of vacuum switch reliability etc..

 

[RetNav]

Re: Fuel vacuum alarms

ob,

I appreciate the reply.

I very seldom run the motors at WOT due to the voracious appetite of those monsters. I don't know if they are starving for fuel at the higher rpms and if it would cause damage if I continued to run them there.
The reason I ruled the switches out is there is one on each engine. I guess both could be bad. I wonder if putting 1/2 inch lines instead of 3/8 would lower the vacuum and supply enough gas without alarm.

Maybe I should just quit going offshore and concentrate on fishing the flats and streams as the Carolina Skiff runs extremely well and with no issues. It also uses a lot less gas..

 

[ob]

Re: Fuel vacuum alarms

First thing I would try if it were my rig is to perform a water test with the vacuum switch leads disconnected and see if the alarm sounds.Next I would disconnect each temp sensor lead one at a time and water test.Reason being is to rule out the possibility of chasing a phantom alarm that could even be due to a faulty alarm itself .It wouldn't be the first.

Oh and I totally agree on the gas consumption factor.At 3 bills a gallon those two bangers can pull a vacuum on the wallet.I wonder if there is an alarm for that.d

 

[RetNav]

Re: Fuel vacuum alarms



Yes there is, it is called WIFE.

 

[Dhadley]

Re: Fuel vacuum alarms

The fuel horn indicates a fuel restriction. Even when running below the rpm that the alarm sounds you're probably still getting a restricted fuel flow. That's not good news for the life of the motor. Find and fix the restriction. Electric pumps will work but are not necessary. And your insurance company won't think much of them either.

 

[RetNav]

Re: Fuel vacuum alarms

Thanks Dhadley,

I was thinking along those lines when I mentioned the 1/2 inch lines. Before I take it out again there will be changes made. I believe the alarms are working correctly and that there is indeed a restriction somewhere. That is the other reason I don't run WOT.