Mechanical or electric

[Tar34]

I'm afraid I'm in for a mechanical fuel pump rebuild. What is the current thinking on fuel pumps. Rebuild or go electric? Why are the Catalina 30 electric pumps higher pressure? Distance to fuel tank? Also, if I choose to go electric,
is there a downside to leaving the mechanical pump in place? What I experienced. Just prior to winterizing in the fall, I noticed a sudden symptom where the engine seemed to sputter on startup and rpm fade when the throttle was increased. Having been carefree for two years this was a bit of a jolt. My Racor fuel filter was spotless as was my fuel tank owing to a very recent cleaning. I put the symptom out of my mind for the winter. Yesterday, I fired her up for the spring. Prior to ignition, I sprayed some carb/gunk cleaner in the carb just for in case it might help. Just a spritz or two. In the cockpit I turned the key and the engine instantly fired up. I had change the oil prior to layup so I had great pressure on startup 50lbs+ I did notice a clicking sound when I got down to the cabin and chocked it up for a sticky lifter and after a few minutes all seemed back to normal. Too normal. Flawless without a hiccup. After running for about 45 minutes, sometimes under load, I shut her down feeling we were off to a good start. This morning, first thing I go to start her up. She starts right up. As I back off the the choke she starts the symptomatic sputter. She's is starving for fuel. I can keep rpms with a little choke. If I increase throttle rpms fade. I work it choke and throttle but she's a little rough so I shut down. I drain the the Racor. Pure fuel but smells a little old even with treatment. But she ran great the first day so I dismiss fuel. With the empty Racor I go to prime with the mechanical pump. I notice there is little to no throw in the primer. I have primed the Racor with the mechanical primer in the past but no joy this time. I can tell the diaphragm is just not pulling. Which brings me back to the clicking sound I spoke of earlier. I think it may have been the fuel pump making the clicking sound. Anyway, I may try the prime with a bulb just for laughs but I think it's the fuel pump. Comment welcome.

[ndutton]

Try two things first

Try bumping the starter and see if the priming bail travel returns to normal. There's a chance the eccentric that drives the pushrod is at it's peak.

Secondly, check the oil level (looking for too high) and give it a sniff. The mechanical pump is designed so that a diaphragm failure dumps fuel into the crankcase.

[Tar34]

Try bumping the starter and see if the priming bail travel returns to normal. There's a chance the eccentric that drives the pushrod is at it's peak.

Secondly, check the oil level (looking for too high) and give it a sniff. The mechanical pump is designed so that a diaphragm failure dumps fuel into the crankcase.

Yes, checked the oil, no problem there, thankfully. I will bump the starter first thing. Thanks for that heads up!

[CalebD]

Rebuild kit?

Moyer sells a rebuild kit for mechanical fuel pump.
They also sell refurbished and new pumps.

The problem with the electric fuel pumps, as I see it, is that they violate the "KISS" principle. You are behooved and required to install an oil pressure shutoff switch (OPSS) with the electric pump set up. Besides the extra wiring into the ignition circuit you are now dependent on this OPSS to allow the pump to operate. The OPSS is designed to shutoff the fuel pump at something like < 10 psi oil pressure. That is all well and good but I know an A4 owner that searched for a month to figure out why their engine would just stall out. It turned out that the new OPSS they had installed had failed and was shutting off the fuel pump. Because of this, many owners who have the electric fuel pumps also install a way to bypass the OPSS which kind of negates the safety factor the OPSS was designed to add, IMHO. While the electric Facet fuel pumps are cheaper than the mechanical pump, many who use the electric fuel pump keep a spare (or two) electric fuel pump on board to swap in when the one that is hooked up fails (and it will fail, eventually).

I like the simplicity of the mechanical fuel pump; when the engine is turning, the fuel pump is pumping. When the engine stops spinning the fuel pump stops. I hadn't given our mechanical fuel pump much thought during 10 years of A4 ownership until last season when we discovered a slow fuel leak from the neglected pump. A new rebuilt pump and I'm guessing it is ready to go for another 20+ years as long as I spend some energy maintaining and cleaning it now and then.

[Skywalker]

Hmm.

I've had the electric pump on both my Tartan and C&C and did not have the OPSS on either. Guess I have work to do.

Chris
T27 249

[TomG]

Tar34,

Can you get the engine to run "off-idle"? A clogged idle jet can give the same symptoms. If the engine will run normally above 1,100-1,200 rpm (the rpm where the high-speed jet kicks in) you might consider a blocked idle jet.

Definitely check the fuel pump after turning the engine as Neil suggests. If the pump is centered on the high lobe of the cam currently and then starts to behave normally once the engine is turned (i.e. the fuel pump isn't the likely culprit), the winter layup could've offered enough time for the fuel to dissolve a little varnish this side of the Racor and it found its way to the idle jet.

Good luck and let us know what you find.

[tenders]

Hmm.

I've had the electric pump on both my Tartan and C&C and did not have the OPSS on either. Guess I have work to do.

Chris
T27 249

I don't have an OPSS on my E32, and I don't think my dad's '76 Pearson 28 used one either. I'm fully aware of what it does but have never wanted to add the complexity. When the engine shuts off, I turn the switch off, every single time.

[JOHN COOKSON]

Quote: &quot;She's Starving For Fuel&quot;

After you get the fuel pump and filters squared away if there are still problems try running from an auxiliary tank. Also think about an air leak or blockage in the carb.

TRUE GRIT

[Tar34]

Try bumping the starter and see if the priming bail travel returns to normal. There's a chance the eccentric that drives the pushrod is at it's peak.

Secondly, check the oil level (looking for too high) and give it a sniff. The mechanical pump is designed so that a diaphragm failure dumps fuel into the crankcase.

Your advice worked. Ticked the engine starter and the throw on the pump was enough to prime the racor and start the engine. Thanks. Not the fuel pump after all, seems to run fine and smooth. Will clean carb shortly. Thanks again,

[Administrator]

You are something else, Neil! Way to go!

Bill

[lat 64]

Get the opss installed

Sometime you will forget to turn off the key, or sometimes the engine will quit while you are distracted.
Here's a excerpt form one of my rebuild posts back in '10:

"...Now the cautionary tale: We were reefing the sails to get home in a gusty blow that went from 0 to 25 knots of wind. Very fickle and challenging.
I kept the motor idling for safety during the sail changes. It was idling too low and just died. We finished the reefing and forgot to turn off the ignition key until ten minutes later.
I started to smell gas. lots of scratching heads and lifting bilge boards to find the leak. Then I realized the fuel pump was on during the time the key was left on.
I checked the air horn and sure enough, gas was dripping out at the bottom. The pump was strong enough to overcome the float valve and flooded the carb.
I got out the fire extingusher and cranked the engine as you would with a flooded carb—full trottle, no choke. She coughed and gagged and started to run fine.

The PO had bypassed the oil pressure shutoff switch on the fuel pump because there was not enough oil pressure to keep it closed. Now I have oil pressure! I will reinstall the switch and be much safer for it.
I might have the wrong fuel pump. It is a facet, but I think it just something from a NAPA store and it probably makes too much pressure. Time to upgrade...."

[dvd]

Tar

The mechanical fuel pump rebuild is a no brainer. Even if it turns out not to be the problem it is really easy with the moyer rebuld kit. I rebuilt mine in just a few minutes and at the very least you can cross it off the list.

I prefer the mechanical because there is no way for it to pump gas unless the engine is turning over. How simple is that.

dvd

[ndutton]

You are something else, Neil! Way to go!

Bill

Yeah, how 'bout dat? Somedays chicken, somedays feathers. Glad it worked.

[roadnsky]

...Somedays chicken, somedays feathers. Glad it worked.

Or...
Sometimes you're the windshield
Sometimes you're the bug

[lat 64]

Tar

The mechanical fuel pump rebuild is a no brainer. Even if it turns out not to be the problem it is really easy with the moyer rebuld kit. I rebuilt mine in just a few minutes and at the very least you can cross it off the list.

I prefer the mechanical because there is no way for it to pump gas unless the engine is turning over. How simple is that.

dvd

Yea, +1 on that. I should have clarified in my post above that Tar34 ought to just stick with the mechanical pump for all the reasons stated.