The Jensen Models 50 and 51 utilize the same eccentric driven feedwater pump, pulling intake water from a cup on the 50 or the water tower on the 51. While quite simple in design and very effective...such a system is a bit mysterious to the uninitiated.
Having acquired said pump with the Jensen 50 I converted to a replica 51, I was quite disappointed to turn things on for the first time and get ZERO water passing thru the pump. The tower stayed full and the boiler level went down quickly as the Jensen 50 motor is a hog for water consumption. With some help from other Jensen 50/51 owners and a lot of tweeking after the fact, the following should cure what ails your pump if you are facing similar zero pumping issues.
The following is a simple diagram of the pump's components as if viewed from it's right side with X-ray vision.
Servicing the pump:
1) To do this right...remove pump for a benchtop checkup
- drain boiler and close downtube valve from tower tank if you have one
- undo the Swagelok inline compression nut if so equipped on the water intake line from tower or cup (this is the only line connection you need to undo...leave rest of piping and fittings attached to pump and remove pump and piping as a whole)
- unscrew the two screws (long) holding the pump to the cast iron engine frame
- unscrew the two screws (short) holding the outlet block
- loosen outside feedwater tube fitting close to boiler by use of two 3/8" open end wrenches...one wrench held fast on fitting closest to the boiler side while turning outer fitting counterclockwise to loosen before pivoting the feedwater tube up and out of the way
- swing outlet block and feedwater tube that goes to boiler up and out of the way.
- loosen the pump compression nut (or screws on flange if so equipped instead) and slide the pump free of the piston. Let piston just dangle on engine while doing next few steps.
2) Working on the benchtop now...
- remove the intake plug (hex nut on mine pictured above...others have a knob)
- tip the assembly upside down to remove spring and checkvalve ball from the outlet well and the checkvalve ball alone from the inlet well
- if the checkvalve balls are stuck...mouth suction on a short piece of silicone tubing will lift them right out of the wells
- clean the balls and then clean the seats they sit in with Q-tips, alcohol etc. If seats are limed up put a bit of SimiChrome or Maas type polish on a shortened Q-tip and chuck it in a variable speed drill...ream holes with the Q-tip until shiny brass in appearance. If you do this polish step you will need to rinse pump out well in the kitchen sink to remove grit.
- Make sure the internal passages are clear by running water thru or blowing thru.
3) Replace TWO 5/32" (0.156") diameter chrome balls, one in each well
- measure existing balls to be sure someone didn't experiment with larger or smaller balls
- new balls are available from Jensen or ACE hardware sells same for 20 cents each. If you are going to all this trouble, it's worth a few cents to replace them.
4) NO spring is used on the intake side...just the one ball
- intake plug is meant to bleed air from system and must occasionally be cracked open a bit during startup to let air leak out. I put a homemade white teflon gasket under mine as the original was shredding and bits could get in the guts of the pump and stop things up. The teflon from 0.025" thick sheet is very durable and makes a good seal. eBay seller "Materialmaster5" sells this teflon sheet reasonably.
5) A short compression spring of the same diameter as ball goes in the outlet well above the ball
- Jensen sells replacement springs for the outlet well which work fine, but only after snipping off one turn of the coil...otherwise they put too much compression on the ball and prevent pump feeding the boiler. I also got good results using a piece of Wilesco pressure valve spring cut in length so it just barely stuck above the pump body before screwing down the outlet tube block over it.
- this spring actually serves as a checkvalve to prevent water from the tower siphoning into the boiler when the engine isn't running...without it the boiler can overflow
- the pump works with or without the outlet well spring in place. I have tried it both ways and concluded it works better overall WITH the spring and that also eliminates overflow risk if you later forgot to close the downtube water valve from the tank.
6) Clean out any gasket material inside the compression nut that surrounded the piston
- slide compression nut onto the piston
- take a 2 1/4" long piece of teflon (PFTE) 3/32" diameter valve/faucet packing and pre-wind it around a screwdriver...this makes it easier to slip on the piston...use NO oil at any time, it degrades PFTE...water itself will be adequate lubrication
-Here is the stuff I found works very well...bought for $2.50 a package at Lowes Home Improvement store. (you can use plumbers teflon tape alternatively, but I found it shreds fairly fast)
- Slip the empty pump compression nut on the piston, then slip the pre-coiled piece of teflon onto the piston and work it into the compression nut with fingernails and/or a blunt instrument...goal is to get teflon coil a couple of threads below the opening with the piston just protruding.
- Before threading the compression nut onto the pump body, I add one additional piece of assurance, a 1/4" wide strip of plumbers teflon tape wrapped around the threads where the compression nut tightens. THEN thread the compression nut onto the threaded body of the pump, first with fingers, then snug it up with a wrench...tighten only after pump is operating so as to stem 99% of the drips and confirm it's working.
- I have found that you can tighten the compression nut several turns with a wrench to the point of stopping the engine, then back off 1/4-1/2 turn and piston will again cycle freely. It is a balancing act...too tight and it slows or stops engine, too loose and it leaks too much. Expect to make several wrench tightenings/loosenings after installing the new teflon packing as it has to compress around the piston within the compression nut. Goal should NOT be to totally eliminate drips, they help with keeping the packing lubricated. I use a shallow plastic drip tray under the compression nut to catch drips and I'm content to empty it every 30 minutes or so.
- IF the pump eventually loses pumping ability, try further tightening the compression nut, then backing if off 1/4-1/2 turn as done initially upon installing the teflon packing. The packing might not need replacing, just snugging up a bit. If that does not work, disassembly to clean checkvalve balls/seats and put new packing in is called for. I have achieved 30 hours run time on a fresh piece of teflon before pump volume began to decline...BUT since balls need to be cleaned about every 15 hours to avoid sticking problems, that makes a good interval to change the teflon too since you have it all apart anyway.
8) Screw the pump body back onto the cast iron engine mount with two screws
9) Screw the outlet block down with it's two screws after putting a new gasket under it
- I hand punched a new gasket from fiber based automotive gasket from Autozone and saturated it with a bit of oil to make it flexible and seal better. It takes a bit of dexterity to center the gasket on the top of outlet area and screw the block on with 2 screws, but with a bit of practice it's not that difficult. Just be sure this gasket is not blocking the flow of water thru the small center hole under the outlet block and be sure the spring is in place atop the ball before screwing down the outlet block.
10) Retighten the feedwater tube fitting near the boiler by using two 3/8" open end wrenches, one holding inner fitting closest to boiler fast while turning outer fitting clockwise to snug it up (check for leaks later and repeat tightening procedure if any drips).
11) Reconnect the intake water line's Swagelok compression nut (or slide on tubing from cup as the case may be)
Running the pump:
1) Be sure the tank/cup or whatever you use to hold water is filled with distilled water
2) Be sure the boiler itself is filled approx. to the center of the top porthole, again, distilled water only (if pump turns out to be an ambitious pumper that gains on the boiler like mine does now, be thankful and just fill boiler half way full instead...end run or drain off excess boiler water when water level nears top of upper window).
Experience with your particular setup will guide how much water you should start with in the boiler. I like at least a one hour run, so gauge my water fill accordingly and drain off any extra at end of run.
3) Close whistle and screw in the pressure valve.
4) Open the valve from the water tank if one exists, to permit flow to the pump
5) NOW...Start your engine heaters, open the main steam valve to allow the engine to warm up gradually, bring pressure up to about 10-15 PSI on the guage, spin flywheel towards the rear by hand to work steam and water thru the engine, it should start running of it's own accord after a few spins.
6) Loosen the pump intake nut with a 3/8" nut driver or turn knurled knob (depending on which you have) until air and a little water seep out, then retighten...it is critical to get the air out of the line between the water tank and the pump. DON'T completely remove that nut or you will have a gusher...just crack it a half turn or so til you get water seepage...then retighten and clean up any dripped water.
7) Check fittings you loosened, removed and/or re-gasketed to be sure they are not leaking water...tighten as needed. Snug the compression nut on the piston only enough to minimize drips...a little water leakage is acceptable as it shows water is lubricating things...don't tighten nut so much it slows engine. NEVER put oil on the pump piston, tempting as that might be. The water is lubrication enough and oil just deteriorates the teflon packing material, gunks up the chrome balls causing them to stick and eventually gets into the boiler.
8) IF the pump is working as it should, you will soon see the water level drop in the tank or cup. I put a Sharpie Marker line on the inside of my tank, and fill to that point, then it's easy to see if it's gone down. Also, if the short feedwater line from pump to boiler stays cool during the run, that is another indication you are pumping just fine. If that line warms up, it means just the opposite...boiler water is backing up into the pump and something is wrong...I found this happens quickly if the water tank runs dry!!!
9) IF you have a Model 51 with a 0-30" inches of water guage, that guage will read a progressive drop in tank water level as inches on the meter...a way to keep track of the need to refill tower tank.
10) Watch the fill line in the boiler...if it drops you are not pumping, if it holds steady you have the perfect balance of input and condensate loss...congrats. If the water level starts rising in the boiler, DON'T cut back on inflow as it causes cavitation sounds in the water pump. I prefer to start my water level at 1/2 boiler full mark, ensure everything is pumping as desired and keep and eye on that line.
11) My specific pump actually gains on the steam loss and would eventually over fill the boiler, but from the 1/2 boiler full mark I can go in access of 60 min run time without overfilling (past middle of top porthole)...that is when I shut things down or bleed off extra water from the boiler to a catch jug by hooking silicone tube to boiler drain and opening drain a little while pressure is still 10 PSI or so...it drains off with vigor and takes less than 2 min. to get back to 1/2 mark on the boiler. DON'T open boiler drain valve more than 1/4 turn to the left while draining under pressure...otherwise the other end of hose can come whipping out of the jug and spray hot steamy water everywhere!
With a bit of fiddling you can find a pretty good equilibrium. Just check your tower periodically, water level in the boiler and keep an eye on the pump for any leaks (initially)...gauge for routine monitoring of pump function. My pump drips a tiny amount at the compression nut and I'm content to catch that in a small drip tray...it's lubricating things and I don't want to mess with something now that it is operating 99.99%.
Follow the above steps and in under an hour you should have a fully serviced pump that works as Mr. Jensen designed it...simple and very effective at moving water against boiler pressure.