ShurFlo switch went out!


New Member
Jan 11, 2004
The pressure switch on the top of my shurflo pump just went out. I thought they could handle constant cycling. Has anybody else had this problem. I spoke with someone at shurflo and he said that the switches could handle 500,000 clicks. He suggested putting a valve before the pump to get the pressure that I needed (50 psi on an m15 nozzle). So i think its time to design a new setup.
Nope never heard of one going bad.

Actually there was a guy running lots of lube with his alcohol that had a pressure switch go bad.

I do things a little differently, I crank the pressure on the switch up and run less voltage to the pump, that way it never has to hit the switch. makes it reliable.

Shurflo will send you a switch assembly within the first year of purchase for free. You have to call them tho.

yeah i tried running an m10 but i could never bog the car, even with the screw cranked. This made me switch to the m15. I wasn't able to find a resistor or POT rated to handle the pump. I need to find something like a 3 ohm POT rated at about 100 watts, it won't be cheap.
Heres something for you to chew on,



This is Ohms Law. The pump acts like a giant resistor. As the current increases, becuase the pump is trying to deliver additional pressure, the voltage drop across your pot will increase thus applying less voltage to pump. In other words, your potentiometer will absorb more energy as the demand increases. Thus putting even less voltage across the pump terminal.

The only way to correctly drive a pump is using a regulated drive, or pulse width modulation. You can not correctly regulate voltage to a pump using a resistor of any kind. Even if its rated at 1KW, it will not regulate the voltage to the pump.

If your pump draws 10 amps at 12volts... its consuming 120watts.

I guess you now know why I do what I do ;) , and make those gizmos to drive pumps.

yea sounds familiar. So your saying as the demand on the pump increases the output decreases. thanks for the help. I have tried to avoid buying something like that because of the cost but it all keeps coming back to it. Now that the pump has died I may have to reconsider.

Thanks again!
How many pumps do you have to kill and how many hours messing with it will it take before it would have been cheaper to do it right to begin with?? What happens if the Alky doesn't come on during a WOT run because you were too cheap?? Get the point, don't halfass what is keeping your engine together, if you want to be cheap then turn down the boost so it will run on pump gas without a problem.
so, am i bieng cheap with the basic stevemon kit? I was under the impression it was pretty standard around here.
If you have it working correctly and don't have any problems, then good. If you are having problems and are attempting to "BandAid" it, then you are being cheap.
Out of 1000's of those pumps in service, this is a non-issue. If that were to be the case, believe me, there would be tons of posts relating to it.

Now while a great idea, and cheap, I doubt bicycle inner tube rubber is alcohol compatible. If you have a leaking switch, get with Shurflo for a new assembly, or if you want to do something like Twitch has recommended, get appropriate rubber. I only mention this becuase on this site, most use higher concentrations of alcohol. Against the grain of what Aquamist preaches.

Well I have seen a lot of post about this but most people dont know that it is the Pressure switch that is bad. Most people think it is the pump itself that is bad. The seal is weak from the factory and over time it losses its seal and the pump cavitates ( pulls in air) if you have not had this problem great. I have had two pumps and both pumps pressure seal has failed. Also if you run more of a concentration of alcky it might be wise to use a better kind of rubber :D I use 100% water in the summer and just a little alcky in the winter to keep my water from freezing.

Great, something else to worry about.

Do you think it has anything to do with us cranking down on that Allen screw to raise the pressure and reduce the pulsing? I've lost track of how many turns I've got on mine. Probably too many.

Julio, time to find us some gasket material to fix this!!



Those gas tank straps on Buicks break due to age, watch out for falling piano's out of the sky.. If my aunt had a mustache she'd be my uncle.

Where's Red Regal T :D

No worries mate, I bet it has to do where and how the pumps are mounted.
Curiousity killed the cat

well I got off the phone with my pump supplier. They sell an average of 3000-4000 8000 series pumps per year. They have been selling the 8000 now for 6 years.

I asked, whats the chance of a switch leaking?

Reply " we dont have any history of a leaking switch." maybe one or two couple years back.

I asked whats between the switch and housing? " a piece of teflon material for seal" .

Asked.. do you have any of these gaskets in stock, since they are the parts supplier for Shurflo in the country. Response "we only a few of those".

So if a leaking switch was a problem, wouldnt there be an overwhelming supply of them/parts? And if the pump builders dont even carry these parts that are claimed to fail.. wow.. guess that answers my question.

Twitch, Sorry you had a couple switches fail. maybe your pump was packed incorrectly from Northern and sustained damage, or is mounted somewhere wher vibration may be of issue? Dunno.. I dont get my pumps from nothern anymore due to packaging issues with them.

Peace guys.. no worries.
Mine failed before it got on the car, non adjustable now.

Gonna bypass that cheesy thing anyway. ;)

I don't need it. :)
RAZOR, RAZOR, HELP, HELP.............My sureflo has 4 years and 100,000 miles on it with no failures or misfires. :( I'm a lucky guy but I know this can't keep up. How long do you think I have before my $60 pump goes kapoot? :confused: I'm really worried. What should I do? Should I convert to water injection? :p
I'd bypass that cheesy switch on the front of it before you blow that motor up.

Better safe than sorry.