[Steve VXR]

I must apologise if this has been discussed before, or if it is a common trait of the Shurflo pump setup, but I have had a look around the forum and can't find anything relating to this setup.

My car has a Coolingmist system, based around a Shurflo pump, mounted in the boot (trunk) of the car. I took some advice from Coolingmist and have the pump setup to operate independently of demand at the solenoid, so that it is pressurises the feed to the front of the car and then shuts the pump off on its integral pressure switch.

In the engine bay the solenoid for water injection is controlled by a boost pressure switch, so the idea is that the engine comes onto boost, the solenoid opens and allows a pressure drop in the line, which then brings the pump in the boot back on and the WI operates.

Although when bench tested this worked fine, since fitting to the car I have noticed that the pump doesn't run constantly when the system is 'on'. Instead, it appears to be pumping intermittently (I have wired in an extra feed to a dash LED, which tells me that the pump pressure switch is electrically closed and this is flickering, rather than constant).

My question is this, is that a normal phenomena with a Shurflo pump when running such a setup, or do I need to increase the pressure at the pump pressure switch to overcome this? I did try adjusting this, but the screw does seem to be quite tight already and I was concerned about damage.

Also, my kit was supplied with rubber hose of approximately 4mm ID, but in order for a neater installation I used 6mm OD polyurethane tubing. Could this be a factor in the problem, as this is more rigid than the rubber tube? I have read about using pressure accumulators in line, but not really found any product information relating to this.

Thanks for any advice, I know I have gone on a fair bit!