Mechanical Pump not Pumping

[Bigeye]

Bought a 1974 Sabre 28 last season - my first cruiser with an inboard. Have been reading this excellent forum since then. Time for Spring start up. I had taken apart the fuel pump over the winter and put it back together with old parts and flexing the handle produce a vacuum. Installed it and it didn't pump the gas. Engine did not fire. I could see no gas was getting through the clear finish filter. The lever was limp. Turned over the engine in case the position of the pin was causing the limp lever. No change. Opened the drain plug in the carb and no gas was being pumped. Tried some starter fluid and the engine fired but no gas got to the carb.

Bought the MM fuel pump repair kit, re-installed the pump and same thing. Yes, the one way valves in the pump are oriented correctly. The lever works when the pump is not attached to the engine but when I install it, I get one pump on the lever and it goes limp. I could suck gas from the tank which is higher than the engine. (Tasty)!

Took the lower body apart and reset the springs. Rocker arm appears to be working correctly, I understand the throw of the engine pin is shorter than the stroke of the lever handle. Re-installed the pump and same thing. (Getting good at doing this)!

Bought a siphon pump and installed it in line before the Racor filter. Pressurized the fuel system and no leaks found. Finish filter had gas in it. Lever still limp. Engine ran well until the fuel ran out. Could not see any gas in the finish filter. Not sure it's relevant but reviewed Don's list of potential causes of the pump losing pressure but they checked out.

When the engine starts to falter for lack of gas I pump the siphon pump and the engine recovers.

Any thoughts would be very appreciated.

Thanks

[domenic]

Check for air in the line between the tank, and the pump. Pump will not work if air is in the fuel line. Chech for air leakes in the line, and filter.

Take off fuel lines, and mouth blow to make sure they are clear of dirt, etc.
A rebuilt pump should work fine. Did you put the two round in, and out parts in the pump in the right position?

My pump will not work unless I have gas in the tank about 1" above the fuel tube in the bottom of the tank.

[gary gerber]

Sounds like you have become an expert at disassembly and reassembly, is it possible there is an air leak around the diaphragm flange or an air leak at the fuel pump metal bowl? I read in the forum that the metal pump housing can warp.

We have all experienced mechanical pump problems at some time or other, good luck.

[Dave Neptune]

Pump!

Bigeye, if it will not pump with the "bail" the first thing to check is the seal on the attached filter. It can be problimatic to get a good seall on an old housing. If that checks out good look for something leaking air behind the pump.
Did the push rod possibly fall out?

Dave Neptune

[Bigeye]

Mechanical Pump Not Pumping

Thanks to all of you and to address your points:

I am pretty sure the lines are clear. When I used the siphon pump to drain through the main carb plug there were a few flecks of black (rubber)? but the gas cleared. Might be something lodged against the "in" valve in the pump but I can pump fluid well when the pump is not installed. If all else fails, I'll take it apart again.

I had tightened the top housing of the pump to the bottom housing a couple of times, compressing the seal a bit more each time and I had cleaned and sanded the top and bottom flange before re assembly so it should be tight. All the screws feel tight in their threaded openings. I'll check for leaks again.

I had checked the flatness of the setlement bowl rim and the cup did rock a bit so I sanded down the flange with the sandpaper provided in the rebuild kit (much appreciated)! The rocking is gone and the seal is new. No drips at the bottom of the bail.

The fuel lines are new as are the clamps but I'll check the barb fittings for cleanliness and unevenness. I do tighten them all the way down. I should note the PO installed a new gas tank just before I bought the boat.

The push rod is visible and resists pushing on it. I haven't been able to crank the engine and see the rod work (can't stretch that far) but I'll try to film it. It worked last season. Can I, should I pull it out and check the bearing end?

I guess what I'll do is take the Racor and finishing filter off line and go directly from the tank line through the siphon pump to the fuel pump and pressurize the system again and see what happens. Can I assume that if I pressurize the system and I get no gas leaks that there would be no air leaks that could cause this problem?

I am sure you can appreciate my frustration. I have been successful at flushing the engine, replacing the thermostat, rebuilding the water pump and carb, replacing the sealing washer at the oil pressure control shaft, replacing the points, rotor and condenser, replacing the internal brass fitting on the water jacket side plate, patching the side plate and even sanded down the brushes and armature in the starter motor when a dead spot developed and because of this forum, I had fun, too!

When she runs she appears to be running better than ever. I just hope this is the last hurdle (for this year, anyway)!

Thanks, again.

Bigeye

[Baltimore Sailor]

You need to get rid of the clear finish filter. USCG regs say only metal filters below deck with an inboard. If it would crack, you would end up with a lot of gas in the bilge.

[Bigeye]

Understood! Thanks.

[Al Schober]

Bigeye,
Sounds like you've done one part of the diagnostics - you've checked that the pump will indeed pump when it's not on the engine.
Two to go. Check that the pump will pump when connected to the fuel tank but pumping into a coffee can. If it doesn't, you have a problem on the suction side.
Next, see if it will pump from a coffee can into the carb. If not, you have a blockage between the pump and the float bowl. Perhaps a piece of your mystery rubber in the float valve?

Al

[Bigeye]

Fool Pump Finally Working

That's right FOOL pump. No air leaks, no blockages. I reinstalled the pump tonight and it turns out I did not quite have the springs positioned correctly. (Slightly red face, here). It was good enough to pump some gas but was not actuated properly by the engine rod. She started right up and ran smoothly out of a bucket for 15 minutes. Now I just need to adjust the oil pressure and the idle mix and check the timing again.

I did have one little scare, though. The temperature gauge spiked hard to the pin after she warmed up. Turns out the wire to the temperature sensor was loose!

I wrote last year that the #1 and #4 plugs fouled badly after short runs but now, after changing out the points, rotor and cap and with better timing, all of the plugs look to be running hotter and cleaner.

Thanks for the advice.

[sastanley]

BIGeye, great report. I still love my mechanical fuel pump..I just rebuilt a spare this spring in case I need it.

Stainless Allen head screws make the installation and removal a lot easier if you haven't already done so....Extensions & universal joints to your ratchet drive to get around the pump parts are a pain!