When is it primed?

[Mattlurzo]

I tried looking for this answer, but I didn't really find anything definitive -- just bits and pieces. I am trying to get the A4 in my 1975 Sabre 28 to start and I don't really understand the hand primer (the manual primer). I've read that "up" is priming it and that it might need some pressure to get it primed. I've also read that I should hear or feel the swoosh when it is priming.

My problem, besides being very new to this and ignorant, is that it doesn't seem to me like the primer is doing anything. It just hangs there and doesn't seem to do anything when I move it up and down (and it barely moves -- maybe a few inches).

So, any advice would be appreciated! How do you prime this? Should I put extra pressure on it going upwards? How much priming does it usually take, and how do I know it is primed (does the lever feel different when it's primed?)?

Thank you so much!
Matt

[ndutton]

It's primed when the carburetor bowl is full and should do so on its own with the starter cranking. Do you suspect the carb is not full?

Be sure to leave the raw water intake thru-hull closed until she fires, then open it immediately. No prolonged starter cranking with that valve open.

[sdemore]

The wire hanging from the bottom of the fuel pump moves from front to back, like a lever. If it is loose and flopping around, something is wrong. If it is very tight, the float bowl is probably full. If you want to check the bowl, there is a drain plug (bolt) on the bottom of the float bowl that you can loosen or remove to drain the bowl. Make sure you have something to catch the draining gasoline. Presuming it is full, you should feel a definite difference in the fuel pump after draining the bowl.

[Al Schober]

The mechanical fuel pump is driven off the camshaft by a short push rod, which pushes the diaphragm up and a spring returns it. The priming lever does the same. If the engine stopped in the position where the diaphragm was up, the priming lever won't do anything. Give the starter a kick and try it again.

[Mattlurzo]

Thank you!

I appreciate all the advice! It gives me some things to go on and makes it much more clear. I'll get out and check it and will get it going!

Matt

[capnward]

The bail on my pump is usually mostly loose and flopping around, except I get resistance at the outboard or port side of its motion. The 'up' side, as you describe it. The bail pumps more or less gas per stroke, according to what position the engine stopped in. As I pump against the resistance, which doesn't need much force, I hear gas flowing through the filters and into the carb. It usually takes about ten pulls, less if fuel is already in the bowl, more if you are drawing gas all the way from the tank through empty hoses and filters. As the fuel fills the bowl, elevates the float valve in the carb and closes it, the fuel line becomes pressurized, the resistance in the bail goes away, and the bail is loose and floppy all the way across its arc. Nothing is wrong. Then it is primed. Your fuel pressure gauge, if you have one, will register the pressure. If it loses pressure quickly, look for leaks. Manual priming is a good thing to be able to do if you want the engine to start quicker and not use much electricity to crank the engine more than a few seconds. You get fuel pressure before you crank. Cranking with the starter will eventually prime the fuel line. Or you can use the bail and start the engine with immediate fuel pressure. You shouldn't need to use the bail if there is fuel in the bowl.

[Mattlurzo]

Perfect!

The bail on my pump is usually mostly loose and flopping around, except I get resistance at the outboard or port side of its motion. The 'up' side, as you describe it. The bail pumps more or less gas per stroke, according to what position the engine stopped in. As I pump against the resistance, which doesn't need much force, I hear gas flowing through the filters and into the carb. It usually takes about ten pulls, less if fuel is already in the bowl, more if you are drawing gas all the way from the tank through empty hoses and filters. As the fuel fills the bowl, elevates the float valve in the carb and closes it, the fuel line becomes pressurized, the resistance in the bail goes away, and the bail is loose and floppy all the way across its arc. Nothing is wrong. Then it is primed. Your fuel pressure gauge, if you have one, will register the pressure. If it loses pressure quickly, look for leaks. Manual priming is a good thing to be able to do if you want the engine to start quicker and not use much electricity to crank the engine more than a few seconds. You get fuel pressure before you crank. Cranking with the starter will eventually prime the fuel line. Or you can use the bail and start the engine with immediate fuel pressure. You shouldn't need to use the bail if there is fuel in the bowl.

That was perfect information. Thank you! When I had a mechanic look at it, he got it started but said it took him a long time to get fuel to the engine. I'm wondering if he didn't prime it and was just cranking (I wasn't there when he was doing it). It has been starting and I totally understand the bail now.

Thanks so much for the excellent information!
Matt

[capnward]

Matt,
I'm glad you saw my post. The mechanical pump used to be a big mystery to me, too. Now I am an advocate for them. I think people assume electric ones are an upgrade, and they are easier to replace, but mechanical ones have advantages, IMO. They have better suction, and don't require electrical connections, or an OPSS that needs to be bypassed when you want to prime the carburetor. My mechanical pump has worked perfectly for 2500 hours. Good luck with yours. Make sure to use MMO in the fuel to keep the rubber parts from drying out. And, dare I say it, non-ethanol gas doesn't degrade the rubber. IMO.

[GregH]

Last spring getting the new fuel system primed for the first time, I only had to pump the bail maybe a dozen strokes before I felt resistance and the system was ready to go.

Didn't think such a short throw would work so well and quickly.

[joe_db]

Matt,
I'm glad you saw my post. The mechanical pump used to be a big mystery to me, too. Now I am an advocate for them. I think people assume electric ones are an upgrade, and they are easier to replace, but mechanical ones have advantages, IMO. They have better suction, and don't require electrical connections, or an OPSS that needs to be bypassed when you want to prime the carburetor. My mechanical pump has worked perfectly for 2500 hours. Good luck with yours. Make sure to use MMO in the fuel to keep the rubber parts from drying out. And, dare I say it, non-ethanol gas doesn't degrade the rubber. IMO.

My engine never had and has no way to put on a mechanical pump. I would probably do it if I could, the electric ones can be a large PITA.

[ndutton]

I would probably do it if I could, the electric [pumps] can be a large PITA.

????

Not my experience at all. I've always run with an electric pump and it has never, read: N-E-V-E-R failed me. When I bought my boat I replaced the pump with a new one on principle (14 years ago) and I once had an OPSS failure that was my own fault and diagnosed in seconds. The electric pump has also afforded me system priming and filter purging at the flip of a switch, fuel polishing and transfer from one tank to the other with the same switch.

No PITA here.

[Al Schober]

Hey folks, let's not get silly here.
Both pumps move fuel the same way - a moving diaphragm moves fuel past check valves. With the mechanical pump, the diaphragm and the valves are bigger and the diaphragm is moved by lump on the camshaft. With the electrical pump, the diaphragm is moved by an electric solenoid, and requires an OPSS.
Basically not liking unneeded electrical stuff, I feel the mechanical pump is better. No electrical contacts to work/not work, no solenoid to burn out, no OPSS, primer lever right there, etc. My big issue with the original mechanical pump is leakage from the sediment bowl. The Moyer pump is improved in this area (vs the original pump), but why have the sediment bowl at all??? I went so far as to modify an original pump to eliminate the sediment bowl, but was never happy the resulting fuel inlet connection - not enough metal around the nipple.
</rant>

[ndutton]

I understand that some prefer a mechanical pump over electric for various reasons the same as the other way around but trying to sell it with electrics can be a large PITA sounds unjustifiably dramatic especially to someone who has enjoyed trouble free electric performance for many years.

I dunno, I must have a very special engine. My electric fuel pump has not been a PITA in the least, my five batteries charge fine without an ACR or a fancy 3 stage external regulator, I have never blown out my alternator diodes, my electric FWC (now dialed in) works perfectly, I don't need to use the R terminal to run the electric fuel pump when starting and my cabin isn't filled with smoke even though I don't have a PCV, all things that at one time or another I have read are chronic problems. I'm on such a roll I should buy a lottery ticket.

[Dave Neptune]

Al, re the mechanical pump and the fuel strainer. I have seen a few mech-pumps modified by cutting away the bowl portion and tapping the housing, then the bowl and it's leaking are eliminated. And with the filters today inline it is not a necessary part.

Don't remember who posted that info on this site though.

Dave Neptune

[capnward]

The sediment bowl seems to be unnecessary; every time I have opened it up, which is hardly ever, there is nothing in it. I usually leave it alone, it doesn't leak. I replace the inline filter upstream of the pump every spring. I also have another inline filter between the pump and the carb.