RWP not drawing water

Last season the RWP stopped drawing water. Impeller had no visible issues. Tried replacing the impeller, O ring, and gasket with a brand new one. Still wouldn't pump. So we ordered a new RWP, replaced all the water lines with 1” clear braided tubing (definitely a nice addition so you can actually see the water moving) and removed the strainer. New pump worked perfectly. Did some research and thought long and hard, decided to add the strainer back in (before the trans cooler) and enjoyed the rest of the season without issue.

So, determined to figure out why the old RWP wasn't working, I decided to test all the different parts. Here is my “motor” for the tests.



I used a 2' section of the 1” line on the input side of the pump dropped into a 5 gallon bucket in the bathtub. the output was left open and pointed toward the drain. I also added an arrow on the back of the housing showing water flow as to not put the tubing on the wrong side with each test.



Test 1: New RWP, impeller from last season. Result: Pumped water.


Test 2: Old RWP, new impeller. Result: Did NOT pump water.

Test 3: Same as Test 1, but only swapped the Gasket plate from the old housing (it has some pitting on one side). Result: Pumped water. Rules out the gasket plate as being the issue.

Test 4: Same as Test 2, but only the Gasket plate from the new housing. Result: Did NOT pump water. Again confirms that the gasket plate is not the issue.

Test 5: New Water Pump Housing with same impeller, Old Gasket Plate, Old Crankshaft (shaft and belt wheel). Result: Pumped water. Rules out the crankshaft as being the vacuum leak.

Test 6: Old housing, new impeller, new gasket plate, new crankshaft. Result: Did NOT pump water. Starting to think the old housing is the problem. Possible the CAM or the CAM screw.

Test 7: New pump housing with same impeller, old gasket plate, old cam, new cam screw, old crankshaft. Result: Pumped Water. Rules out the CAM.

Test 8: Same as test 7, replaced with OLD CAM screw. Result: Pumped Water. Rules out the screw and washer.

Test 9: Old housing, new impeller, new gasket plate, new crankshaft, new cam, old cam screw. Result: Did NOT pump water. Another check in the bad housing column.

Test 10: Same as test 9 with new cam screw. Result: Did NOT pump water. Third check in the housing column.

Test 11: Back to original setup with New Pump (housing and crankshaft), used the new impeller from Test 2. Result: As expected pumped water.

Test 12: Back to original setup with Old Pump (housing and crankshaft), same test 2 impeller. Result: Did NOT pump water. At this stage I am convinced the housing is the problem...but how and where?






All impeller fins are bent inside the old housing making contact with the walls the entire time. One thing I will note is that with New RWP Test 1: there is definitely more resistance turning the crank by hand compared to Old RWP Test 2. There doesn't seem to be any visible cracks in the housing body at all.

Obviously, I don't NEED the old one to work, but if I could figure out the issue, it would be nice to have a second pump ready just in case.

Any other thoughts of things I could try?

That easy turning is probably the deal. I am betting water leaks by. It has probably been bored out by years of use.

The pump appears to be original with the motor (same paint color), it is from the 89 SpN and it had 1200 hours when we purchased it. I have no idea how often the impeller was changed, but we changed it immediately (the one in the pump appeared as expected with minimal bending of the fins and no apparent wearing abnormalities). The day after we bought it (late October '13), we put it in and drove it around for about an hour without issue, then it sat in a heated garage for the '13-14 winter. The block and exhaust were drained prior to being put in storage, but no other winterization steps were done since it was in heated storage. It wasn't until Memorial day 2014 that we started having issues with the old pump.

I'll try and get measurements tonight or tomorrow and report back.

Colin,
Certainly some extensive testing! This should go in the FAQ thread. You proved that the pump was sucking air someplace. I don't feel it was an impeller problem but rather a housing or the shaft seal.