Fuel Pump Mystery

Maine Sail · Dec 20, 2011

The Carter rotary vane pump below has about 1400 hours of polishing on it. It can move 70+ GPH through our Racor 900 and other than being a little noisy, and drawing more current than the Walbro, it has proven to be very reliable and also inexpensive, got it at NAPA. These were originally designed for the US Military. We have started our motor hundreds of times, with it running, and suffered no issues. Of course I have not been able to measure any spikes on our system even with an o-scope, so this should not be an issue.

I know the Walbro pumps are very often used in these applications, many of the mega yachts use them, so perhaps Roger just bought the wrong one for his application. I know Rich H. also uses a Walbro. A call to the manufacturers tech department may be a good move as they could advise on possible reasons for failure and the best pump to use for the application..

kloudie1 · Dec 20, 2011

Interesting page here too:
http://carterfueldelivery.com/fuelpumps/_pdfs/training/CarterFTS3bw.pdf
Roger it sounds like you've suffered an early failure (infant mortality) of the electronic switch.. Sounds like you are on the way to a good fix.. Good luck ..

Maine Sail · Dec 20, 2011

Roger Long said:
Fellow on the next boat saw me working on my engine and we got to talking. He just lost his fuel pump, the regular fuel supply lift pump, and bought the same Facet pump I did at NAPA to keep him going until he could get a heavy duty unit.

His pump worked for 20 minutes so he thinks I did well to get a day for my 60 bucks. His was working as intended, design wise. These pumps are junk.

You have to be careful which Facet pump you buy. I've never used the plastic one sold out front at NAPA. We have the Facet cube style pump, Pro-42 model, and she's got 3300+ engine hours on her. I have a spare one that is collecting dust.. The older cylindrical style Facets also lasts a good long time. Most every Universal or Westerbeke out there has a Facet pump on them and while they can fail they are quite reliable. Was working on a mid eighties Ericson today that still has the original Facet pump...

JoeWhite · Dec 26, 2011

Being in electronics I have seen how a spike can kill electronics circuits. Assuming this is what kills the electronics of the pump - the solution is very inexpensive. Simply add a 1 AMP diode just where the +VE and the -VE leads of the pump is at. The diode must be connected in parallel to the pump leads. The cathode goes to the +Ve side and the Anode goes to the -VE side. When the circuit is turned off the spike will forward bias the diode and the reverse voltage will not exceed 0.5V. For those who are not familliar with a diode and its designation - It looks like a large resistor and has line on one side. The line is the cathode side.

Bill Roosa · Dec 27, 2011

the pump in question is just a coil of wire and a machanical switch. I seriously doubt that a spike could kill it. It would have to be a pretty high amp spike IMHO.

Don12364 · Dec 27, 2011

Joe,
Your solution only works for spikes caused by switching off the pump's own coil or any other negative spikes. i.e. to handle positive ones as well one needs the varistor.

JoeWhite · Dec 27, 2011

Donalex - there are no spikes created when first turned on. Like you said it is only when turned off. The collapsing magnet field creates a very high voltage across the points where it is cutting off the current. Diodes are very commonly used across relay coils to kill the spikes.

Bill Roosa · Dec 27, 2011

I think that you will find that the spikes in question to be on the order of 50 volts max for this device. A simple capacitor across the power and ground fixes this. As Roger suggested this has probably been incorporated into the design already.
The spikes are not what is causing this pump to fail. It is how it is being used. They are designed for continuous operation as a fuel supply pump not a fuel polishing pump. completely different application

Waybad · Jan 22, 2012

From waybad, My best guess is your alternator took out your pump. If somthing goes wrong even for a split second it can take out any number of electrical Items. electrons move very fast. Coils can show resistance and still not function. Use a fuel transfer vane type pump for moving fuel threw a filter and the walbro for small engine or stove use. Short of using a megar on your winding or coil, their is know of knowing if it is good.
I use a Jabsco spo-60-n for moving fuel. It is fast and efficent. If you needed it as a emrgency engine pump you would need to add a presure switch to run it. good luck, I see lot of advice is available.