So we're doing a 73 restoration project

[Captain Obvious]

11 hours ago, Michaelwk said:

Anybody have other thoughts on what might cause it to not pump?  It was bone dry when I opened it

Diaphragm pumps like that require two check valves. One on the input, and one on the output. If either of those check valves aren't working properly, the pump won't.

I gotta believe the answer would be in this thread somewhere:
https://www.classiczcars.com/forums/topic/50679-rebuilding-the-nikki-fuel-pump/

[duffymahoney]

Message me, I have a new check valves and diaphragm for your fuel pump. 

[Patcon]

Yes, look at the check valves. They can stick closed or open and can get gunk in them, holding them open.

[Michaelwk]

22 hours ago, w3wilkes said:

Don't know if there were any differences between dealers on the installation of electric fuel pumps on the '73s, but my 73 240 electric pump ran when the ignition was turned on. When the car was cold I would let the pump run for a bit before starting the car, seemed to make it a little easier to start when cold. If you can't find a spacer and one is required for the mech pump, you can get a block off plate for the mech pump and use an electric pump.

I talked with my Father last night and he had the same recollection, that the pump would run with ignition on originally.  So that's good.  I do need to go troubleshoot it though, maybe the wiring is just bad. 

[Michaelwk]

12 hours ago, Captain Obvious said:

Diaphragm pumps like that require two check valves. One on the input, and one on the output. If either of those check valves aren't working properly, the pump won't.

I gotta believe the answer would be in this thread somewhere:
https://www.classiczcars.com/forums/topic/50679-rebuilding-the-nikki-fuel-pump/

 

3 hours ago, Patcon said:

Yes, look at the check valves. They can stick closed or open and can get gunk in them, holding them open.

Thanks for the advice guys, the check valves look clear and move easily.

Thanks for linking that thread as well, CO.  I may try to open up the replacement I bought and see if the diaphragms and seal would fit my original.

Second option is to 3D print a new spacer and just use the new assembly.  Will see if it comes to that.

Thanks for the help!

[Patcon]

If the check valves move and seal then the pump should work. They can have a difficult time pumping air to prime themselves though. I like to prime the engine to get it to fire over which helps prime the pump

[Michaelwk]

The world’s slowest project is moving along.  I’m also getting smarter as I sit in my garage and stare at the car, so that’s good!  I finally just did a hand pump test on the old fuel pump and it could barely get any fuel up from the can.  I tried the new pump and it did it quite easily.  So the original part is just worn out and needs to be rebuilt.  I also smartly cut the old spacer off with a razor blade, rather than try to pry off with a screw driver, which I may or may not have tried first and broke off a piece. 

So we got a working fuel pump.  Awesome.  But not so fast, I accidentally left the key on after the last time working on it (or rather my wife did, but I definitely won’t blame her because then I’d lose my most useful assistant).  I only have a trickle charger so it took a solid 4 days to recharge the battery.

Once we got that sorted, I gave it a crank but still no fire.  Sprayed a bit of starter fluid and that worked, so the problem is now the carbs.  I check the vacuum slides and they both move easily, although there’s no oil in the top… but I don’t think that would affect operation, right?

So next step is see if I can pull the carbs off this weekend and run through the checklist of float, jet, etc.  Maybe just pick up the rebuild kit and do it right the first time… but it is getting quite cold in Wisconsin and I need to get my daily back in the garage!

[Patcon]

The oil helps control fuel metering but the car should run oil or not.

Check the float needles and the inlet screens for trash. If you fill the float bowls manually (through the vent port) will the car run for a little while?

[Michaelwk]

On 10/20/2018 at 3:53 PM, Patcon said:

The oil helps control fuel metering but the car should run oil or not.

Check the float needles and the inlet screens for trash. If you fill the float bowls manually (through the vent port) will the car run for a little while?

Thanks for the advice.  I couldn't find anything in the FSM or Clymer about a vent port though, so I did not try that before removing the carbs today.  Didn't want to pour fuel down some place it shouldn't go.  Is the vent port the same place you access the inlet screen?

[Michaelwk]

Got the carbs off today… managed to only damage one hose, so I’m calling it a success.  Not looking forward to trying to get them back on and get all the hoses in the right place, but that’s a future-me problem.  .

Looking at the bowls, I appear to have 74 model carb I think.  Worst of the worst?  Haha. There’s 7 screws rather than 6 like the manual shows, and my float pin is only accessible from behind an external screw (the one that's half was out on the upper left of the carb in the pic below.  The only marking I could find was a number 2 stamped on both carbs.  From the Clymer, it says 73s had HMB46W-1 and 74s had HMB46W-4.  It also claims that only thing you can do with a 74 is open the float chamber cover, implying that you cannot take out the floats or needle valve.  Found another thread from a while back that talks about the same thing and it sounds like his was a 74.

I opened the float chamber and the floats look ok. 

The screens on the other hand are in rough shape.  Not clogged, but pretty smashed.  Seems like they could be reformed, so I’ll try to do that after cleaning them.

Next step is get some carb cleaner and see if I can clean out any gunk that might be hiding.  And maybe pick up tiny pliers to try and pull out that float pin.

Bonus picture of the garage assistant after a freak snow shower we had on Saturday morning.

 

Michael

 

[Patcon]

@Captain Obvious

This is your realm, the "Darkside" Teach away...

[Captain Obvious]

Actually, you have the better set of flat tops there. I wasn't there at the time, but from what I've heard, the earlier versions with the square float chamber covers were a problem and a lot of them were updated by Nissan to the newer version like you already have.

However, yes... One of the things that was easier on the earlier versions was getting the float pin out so you can pull the float and remove the needle valve. There isn't a lot of material to grip down in that hole, and my advice is to use carb cleaner and lube on the pin until you can finally pull it out. Narrow tipped pliers is the way to go. Don't mangle the tip of the pin to the point where you can't grab it anymore or you'll have to resort to more dramatic procedures to get it out.

Sometimes you can use a razor knife right beside the float hinge to wiggle the pin back and forth a tiny tiny bit, or walk it out a tiny bit at a time. Once they loosen up, they usually come out pretty easy. But if they are varnished in place, they can really be a bear to get started.