Wash Cycle Pressure Loss

[MudMoney]

I am looking for some answers or insight to this problem that I am only experiencing in one bay.

Problem:
There is a drop in pressure on the high pressure cycles of soap and wax which are gravity feed. The drop is from 1200 PSI to 500 PSI over 2-3 minutes. On high pressure rinse from the incoming city water there is no drop in pressure.

I changed all the soap line hoses, the wax hoses, the soap line check valve, the soap and wax solenoid, the fittings and connectors. I replaced the hose from the gravity tank to the pump. I used a five gallon bucket with soap and a feed line and still got cavitations.

Finally, thinking that I had a washed out head, I replaced the CAT 310 Pump with a new one. The problem seemed to be fixed, but only for 2 days and the problem has returned.

Is it possible that this could be a downstream problem?

 

[Washmee]

What about the regulator/unloader?

 

[washnvac]

Check valve on the hot water gravity feed. Pump is starving for water; thus the pressure drop. The springs corrode, or something gets stuck in it.

You want to rule out everything else before a pump head change.

 

[waright]

being a 310, it must be belt driven, so maybe a slipping belt. maybe a check valve on the bay manifold is failing. this is where the presoak, spotfree, air assist, etc, all combine into the main line.

 

[bigleo48]

Swampdonkey,

First you need to properly identify the problem BEFORE you fix it. Just replacing parts is "shooting in the dark", costs more can can create other problems thus making the original problem more difficult to determine.

When I have a drop in pressure as you described and there is no excessive vibration, its either an unloader or bad belt. I can easily see the belt and disassembling the unloader and finding bad 'O' rings is very easy. In your case, I would think it's the belt because it takes a few minutes...so the belt needs to warm up and start slipping. Those are the easy checks I would do first.

However, to properly troubleshoot this you need to simplify and break it down. So input or output? Disconnect pump output and hookup a short hose and gun and run it for a few minutes. That will tell you if its the downstream equipment (solenoids, unloader) or pump & fluid input. Still happening, then switch inputs from a different bay or replace feed with a bucket of water or hose from city water. etc, etc.... When you eventually find the problem , then replace the part.

 

[2Biz]

Do you have gate valves on the "Gravity Feed" water supply to each individual pump? If so, I have had this type valve fail to where the gate will not open and close. The shaft breaks off from the gate. Sounds like you're starving the pump of gravity fed water. If the problem is only in one bay, I think I would start there to make sure you're getting adequate water supply.

 

[Jim L.]

I had the check valve break a couple of times as Wahsnvac described. It drove me crazy for a day or so till I figured it out.

 

[dbrown2911]

Ok i dont want to sound repetitive but i am having same issue..well kind of. One day I all of a sudden lost pressure on one of my self service bays. I removed head checked valves and seals etc. I then hooked up small hose with gun and I do have more pressure..it was pulsating quite a bit but I had way more pressure then when I hook original line back up. So where do I start. Would it be the entire length of the hose..the short piece that goes into the swivel boom arm or could it be the hose with the gun? Right now i will just eliminate one at a time..but if someone has better solution i would like to start there first. Thanks!

 

[bigleo48]

Dbrown,

If your pulsating a lot, its your valve(s)...

 

[dbrown2911]

ok but i have no pressure what so ever when i connect the hose that goes all the way out to the bay..but if i hook up short hose with gun I have pressure.

 

[MEP001]

Is there only no pressure in the bay, or are you reading no pressure on the gauge?

 

[dbrown2911]

Neither. No pressure at bay or on gage. Gage works..I take outlet hose off replace with short hose and have pressure.

 

[I.B. Washincars]

Plugged tip???

 

[cantbreak80]

Big leak in the downstream plumbing...probably a failed check valve on the weep system.

Turn the bay on soap for a few minutes. Check for soapy water in your rinse tank. If so, CV failed and the pump is dumping pressure (and water) back into the car wash's water supply.

Or, failed CV on the SFR system...resulting in soapy water in the RO storage tank.

 

[2Biz]

What CB80 said. If the line was plugged in any way, tip or hose, you would be running in by-pass and still have pressure showing on the gage. But since the gage is showing no pressure, there has to be a big leak or bad CV. I can't believe it hasn't blown a line off if its a failed weep CV or Pre-Soak CV...

 

[I.B. Washincars]

Also, check to see if water is coming out of all the other bays while problem bay is running.

 

[cantbreak80]

I can't believe it hasn't blown a line off if its a failed weep CV or Pre-Soak CV...

Unless the weep inlet supply is rigid or hi-pressure hose...

THAT'S why weep inlet plumbing should be no more than 200psi wp tubing or hose. A blown check valve will likely pop the tubing. Works like an "early warning" system...water spewing all over the equipment room instead of filling the water softener and boiler with soap/wax...or worse, getting past the backflow preventor and filling the city water lines with soap/wax! YIKES!

 

[dbrown2911]

This is what I tried so far. Removed each connection in Bay Area. At gun at bottom of boom at top of boom and still no change in pressure. I again remove main line that runs in attic to the bay... I remove it from pump and connect short hose with gun and have 800 psi when squeezing. The hose is rigid. There are only 2 other connections in attic where it tees in with all the soap wax functions. Could a check valve where these come on be bad?

 

[dbrown2911]

No soapy water in tank. All other bays are fine. I hooked water line to bay to air compressor and got plent of air out so don't seem like there is a blockage. If my valves were bad in pump why would I get pressure if I use shirt hose but not when I run the entire length to the bay. And there are no leaks anywhere? Help!!

 

[dbrown2911]

Went to attic took line off of manifold where all tubing ties in. Hooked gun up there before manifold and had pressure Took manifold down removed all 5 check valves and found one of them missing stop..replaced. Though for sure it was going to work... Nope still no pressure!!! Calling it a day.