View Full Version : Fuel Injection Pump Pre-Filter

27-05-10, 10:49 PM
I won't bore you with how I have got to this stage but I run a MkIII RV8 with fuel injection. Originally I used the standard flow & return pipes in the Pilgrim tank with the SD1 high pressure fuel pump mounted below the bottom level of the tank. Trouble was that the pump as it is with all of them is supposed to be gravity fed. Lots of air locks etc later I modified the tank and fitted an outlet on the bottom of the tank with a small standpipe inside the tank to avoid all the crap coming into the pump. For good measure I fitted a new pump at the same time. (Mainly because I picked it up for 15 at one of the shows last year!!) Anyway not having actually driven the car but started it a fair bit in the garage I was surprised to find out that the reason for it not starting last week was that the pump is knackered again. So I splashed out on a new Systec Motorsport pump which arrived today. In big bold text it tells me that these pumps are fatally sensitive to dirt and contaminated fuel and that they must have a pre filter fitted. What I have at the moment is a fine stainless steel mesh trapped inside the tank outlet fitting to act as a filter. Now I'm thinking maybe this isn't enough and this is why the second pump failed. So to my question - is a pre filter different from a post filter. The post filter is having fuel pushed through it at 45psi whereas the pre-filter has only gravity. I say this but I am not entirely sure if in fact the pump is pulling fuel through it at the same rate as it pushes it out - guess it must be.
To recap is a post filter different from a pre-filter or can I just use a standard fuel injection filter as a pre-filter?
Thoughts anyone?

28-05-10, 07:21 AM
You are right in thinking you need a pre pump filter. I've never seen the need for post pump filters to be honest as the pump won't make dirt so if you have clean fuel going in, it must be clean coming out.
When I converted to EFI they supplied a post pump filter with the pump and also said it must be pre filtered so I now have both.

Anyway, back to the point, I would check you fine steel gauze in the tank pickup isn't causing a restriction. A high pressure pump won't like sucking against a restricted supply so it could be this that caused the previous problems.
As a pre pump filter on my car I have a Fram cartridge type filter (http://www.speedflowshop.co.uk/fram-hgp1-fuel-filter-602-577-p.asp). As you can see from the spec it won't take the pressure from the pump but it is a perfect pre-pump filter. Loads of flow rate too so it won't cause a restriction all the time it is clean.

My filter and pump are mounted higher than the tank too, It seems to prime the fuel just fine.


01-06-10, 01:36 PM
Craig, You were somewhat correct in your reply. In the end I drained the tank and unbolted the outlet flange I had fitted to the bottom of the tank to get a gravity feed into the pump. Sure enough some blobs of gasket compound came out of the 25mm hole in the tank. The outlet pipe in the flange is only about 10mm. What looks to have been happening is that the blobs have been getting drawn into the outlet and blocking the fuel. The knock on effect being the pump is running dry and with no fuel to act as a coolant has packed in. On further investigation on the tube of gasket paste I had used there it was in tiny print. 'Not suitable for continuous immersion in fuel' So lesson learned.
I took the opportunity while the outlet pipe was out to fit a 25mm mesh sphere on the inside end of the pipe so that any future blobs or anything else for that matter cannot block the outlet. I also fitted a bog standard fuel injection filter as a pre-filter to the external pump and it seems fine.
Thanks for the reply.