Shureflo 4008 Pump Intermittent Cycle Fix

[SmokerBill]

I replaced my pump with a new one from Camping World (yes, I paid the big bucks for it), and from day one it would cycle every 10-20 minutes. I thought I had a leak in the plumbing and checked everywhere - several times - and never saw a drip.

A couple days ago I had a lightbulb moment, and realized that if the check valve on the fresh water inlet leaked, the pump would cycle. So... I checked it, saw some water and figured that was the problem. While I was at it I pushed the check valve piston inward and water blasted out. But it didn't quit when I let go. I ended up ruining the check valve- water pressure pushing outward pushed the O ring out of position, and I couldn't get it back in place.

After buying a new plumbing fitting and with a half-hour of work, I got the city fill line plugged up, so I could use my pump again.

I did a final test of the pump/water system. I pressurized the system and then shut off the intake valve going to the tank. The pump never cycled during the next hour, and the system remained pressurized. That verified that my plumbing is good, and there's leakback through the pump.

I called Shureflo customer service today, explained my problem, and got the fix. I will need to adjust a screw (5/64 allen) on the pressure switch. Clockwise, 1/4 turn at a time, and no more than 1 full turn. Haven't done it yet, but will when I feel up to removing the pump in order to access the screw. Hope it works, but at least I know that I don't have water dripping into a hidden spot in my trailer.

[Murphie]

Bill thanks for posting this. I've had a similar issue but it only started happening about 6 months ago. The line would lose pressure and I would hear the pump cycle for a second or two and than would happen again after about a hour or so.
Found no leaks and thought the spring on the water inlet was getting weak. I replaced the inlet fitting and all is fine now. Our trailers are the same age. Not sure I understand why you need to adjust your pump now if your line remains pressurized after you replaced the water inlet valve? So after you replaced the pump you found that you still had the same problem. Than replaced the inlet valve
and found that the line remained pressurized. Would this not mean the leak was from the inlet valve loosing pressure. By turning the screw on the pump, what does that do?

[SmokerBill]

So many questions! LOL

"Not sure I understand why you need to adjust your pump now if your line remains pressurized after you replaced the water inlet valve?"
It only remains pressurized when I shut the intake valve from the water tanks. Water leaking through the pump can't go anywhere with the valve closed, so plumbing keeps its pressure.

"So after you replaced the pump you found that you still had the same problem."
Started when I installed new pump.

"Not sure I understand why you need to adjust your pump now if your line remains pressurized after you replaced the water inlet valve?"
Shureflo pumps have a backflow feature that helps keep the flow from the faucets steady. Switch pressure has to be adjusted a certain amount higher than the backflow pressure to prevent leaking. I was told to adjust the switch pressure higher to fix the problem, and she knew right away what to say. Must be a common problem.

I didn't replace the inlet fitting that I broke. I just plugged the incoming line with a cheap pvc plumbing fitting. And the pump still leaked after I sealed the inlet fitting line.


"By turning the screw on the pump, what does that do?"
It raises the switching pressure. It's set, supposedly, at 55psi at the factory, which balances with the backflow adjustment. Raising the switching pressure stops the backfow.

[Murphie]

Sorry for all the questions. It makes sense now. Much appreciated.

[SmokerBill]

Originally Posted by Murphie

Sorry for all the questions. It makes sense now. Much appreciated.

No apology needed. I'm glad you asked. Helped clarify my first post. Here's more info about my Shurflo pump- I found the user's manual online.

http://www.shurflo.com/images/files/...s/911-1008.pdf

I might burrow under the sink today and remove the pump so I can try that switch adjustment recommended by Shurflo customer service. What I don't understand is why a brand new pump would need to be adjusted anyway. Seems that they would do it right before sending it out from the factory. Oh, I forgot! It's an RV part- that's the way the industry works- sell it and make the consumer responsible for making it right.