Fuel pump and filter routing

[Jonny TR6]

Here's a pic of my current fuel pump set up. I think it may have been installed incorrectly initially, as the Bosch pre-filter is a pressure filter, so some re-plumbing needed. Can the filter be converted to a banjo outlet, or do I need a new one ? The big Fram filter should I think be a pre-filter, but given it's a few years old, any recommendations for a more discrete replacement ? Having fun and games with this - was initially going to be just changing a couple of hoses to R9/R14, but ended up knee deep in it ! All guidance very much appreciated - especially given it's a safety and performance critical area (will get to PRVs later)

Edited July 14, 2022 by Jonny TR6

[Jonny TR6]

Found out today that there should only be a pre filter to the pump and a post pump filter  just restricts the flow. On that basis, my setup is correct with the pre providing the filtration to the pump and I can use low pressure connectors in the form of double ear O clips ?

Waldi - you’re an expert in the field ?!

 

[Waldi]

Hi Jonny,

Some prefer a pre-and post-filter, I just use a pre-filter, simply because our cars originally did not have a discharge filter, but opinions on here vary, and there are different ways to skin a cat.

It is more the suction filter that can create issues.  So it should be very large, to achieve an as low as possible pressure drop. I have a Sytec SF2012 suction filter per Stuarts recommendation. An alternative is a smaller filter with a courser mesh, this will give a low dp too. But with a coarser suction filter I recommend a discharge filter to filter out the finer particles (we are talking microns here) to reduce wear of the PRV and MU.

Discharge filters should not be an issue in restricting flow, if properly sized for the rated flow of the pump.

Jubilee clips are sufficient for the low pressure side from tank to filter to pump and the return from PRV to tank.

There is a lot of info about filters, pumps etc. stored on this forum, best to use google for a search on this forum. You will find a lot of useful back-ground info there.

Waldi

[Jonny TR6]

Thanks Waldi - useful summary. Spent about 2hrs reading up on pumps, filters etc without a definitive consensus. 
 

[astontr6]

1 hour ago, Jonny TR6 said:

Found out today that there should only be a pre filter to the pump and a post pump filter  just restricts the flow. On that basis, my setup is correct with the pre providing the filtration to the pump and I can use low pressure connectors in the form of double ear O clips ?

Waldi - you’re an expert in the field ?!

 

If you look at the installation of FI on modern cars using a Bosch set up they only have a pre-filter. If you are using a Bosch Filter like F5021, which is a low resistance type and is capable of stopping the micro crud getting through. What is the point? I have used this type for over 40 years with no ill effects!

Bruce.

[Jonny TR6]

Thanks Bruce - I think that’s sealed it in my mind. Pre filter only, with appropriate connectors and hoses. I’ll dispense with a post filter.

Will make up some suitable brackets and post up pics in due course.

[Paulfc]

Hi, I have the same set up as you (pre filter only) and it has not presented any issues to date.

Paul 

[Mk2 Chopper]

Looks similar to mine, which was fitted so badly, fuel having to go 'uphill' to reach the pump, now put it in its correct orientation. This one uses banjo bolts to connect the filter to pump but at that stage its low pressure so other clips will work fine. 

Gareth

[PodOne]

1 hour ago, Mk2 Chopper said:

Looks similar to mine, which was fitted so badly, fuel having to go 'uphill' to reach the pump, now put it in its correct orientation. This one uses banjo bolts to connect the filter to pump but at that stage its low pressure so other clips will work fine. 

Gareth

LOL I bet it ran just fine for many years!

Andy

[Mk2 Chopper]

49 minutes ago, PodOne said:

LOL I bet it ran just fine for many years!

Andy

You know what, it never missed a beat, crusty burnt wiring, badly sited pump, kinked pipe, but it ran just fine like that, lovely smell of fuel coming from the kinked pipe too. 

Gareth

[PodOne]

Always the way!

[Steves_TR6]

I use disposable sytec fuel filters , pre pump, like this : 

despite only having 8mm inlet/outlet the car performs very well even down below 1/4 tank.

interestingly the last time i ordered one i accidentally bought the smaller size which i thought would restrict flow but was fine even at a track day!

steve

Edited July 16, 2022 by Steves_TR6

[Jonny TR6]

Spent what seems like weeks on this so far, so many different unions, connectors, banjos, things to do/not do etc.

Getting there though.

My Bosch F5021 pre filter has arrived and I've ordered an M14 x 1.5 to 8mm push on union, for the inlet. Going with M12  x 1.5 to  12mm for the filter outlet to the Bosch fuel pump.

The fuel pump has a 12mm push on connector for the low pressure side.

My options and current head scratch are as follows.

1.) Mount the pump in the wheel well, with a pre-formed 90 degree elbow from the pre-filter. I can make one out of R9 8mm id fuel hose using the copper pipe and hot water method to prevent kinking. The radius has to be tight due to space restrictions. Only issue I can think of with that, is that the radiused bend can cause cavitation, but it's gravity fed and low pressure, so hopefully ok ?

2.) Mount the pump in the wheel arch, but I then have the issue of a bend from pre-filter to pump to contend with anyway, but benefit from cooling.

Given a lot of the aftermarket kits I see have 2 banjo 90 degree bends between pump and filter I may be overthinking it ?

Grateful as ever for any comments !

[Waldi]

I do not like sharp bends in rubber pipe. The fabricator normally states a minimum bending radius too.

This is how I installed mine.

[Tim T]

This was my initial set up straight from the box.

It made hell of a racket. I felt that all the banjos and 90 degree turns could not be helping the flow, so changed it to the layout below,

the noise disappeared immediately.

Job done for me!

Tim

[PodOne]

Or same kit different location.

Andy

 

Edited July 22, 2022 by PodOne

[Jonny TR6]

Thanks all - really helpful pics.

My main issue is a stub inlet on the pump. Rob at TRGB is hopefully sorting me out with a set of unions and bits to enable me to connect the filter outlet and pump inlet without a 180 degree rubber hose connection.

The pump is a Czech made Bosch 009 so might also be time for a replacement.

Edited July 22, 2022 by Jonny TR6

[Mike C]

4 hours ago, Waldi said:

I do not like sharp bends in rubber pipe. The fabricator normally states a minimum bending radius too.

This is how I installed mine.

I agree, 5 diameters of straight pipe straight into the pump suction is good practice. It helps ensure even flow across the pump internal elements.

[Jonny TR6]

Here’s a pic of my pipe work 

Got brain fog on what pipe’s what..

2 & 3 go together  - MU return to tank via 4.7mm copper pipe into 8mm pipe to tank

5 is the feed to the MU ?

4 is the feed from the pump ?

1 I think is the return from the brass T to the tank ?

Where does the PRV come into it ? If 5 is effectively direct from the pump, how is the pressure controlled by the PRV ? Doesn’t the MU feed come from the PRV ?

 

 

[Waldi]

1 is return from prv to tank.

4 is from pump to prv.

5 is from prv to mu.

Not sure what your 2 and 3 are.

[Jonny TR6]

Thanks Waldi - so the fuel doesn’t flow from the T piece through the PRV, to the MU ? Although the PRV controls the pressure in the whole system, it’s done after the MU ?

So is the PRV return to tank, relatively low pressure compared to the MU side of things (105 psi ish) ?

2&3 are the 3/16 return from the MU. The 3/16 in my case goes into a 5/16 before going into the tank.

Edited July 24, 2022 by Jonny TR6

[Kenrow]

Your pump should be putting out more than 105 psi hence:

1. Fuel from tank to filter (low pressure)
2. Filter to pump (low pressure)
3. Pump to PRV (high pressure)
4. PRV to MU (105+/-psi), excess fuel returns to tank
5. MU to injectors (105+/-psi), excess fuel returns to tank (low pressure)

Edited July 24, 2022 by Kenrow
added info

[Mike C]

The PRV is a pressure relief valve that just dumps fuel from the pump back into the tank if the feed pressure to the MU exceeds the PRV's set pressure. This keeps  a constant feed pressure in the feed line to the MU regardless of the engine fuel consumption.

The fuel released from the PRV back to the tank is at a very low pressure.

[Waldi]

Hi Jonny,
to familiarize yourselve with the Lucas fuel injection I can recommend reading the Lucas service manual. It is available on-line from a fellow enthousiast who has made a library. It will help you understand the system, what is critical, and what are the connections. The WSM helps too.

http://vitessesteve.co.uk/

 

Cheers,

Waldi

[Jonny TR6]

Got it at last ! Many thanks all. 

I was getting the PRV’s function as a relief valve confused with that of a pressure control valve, i.e I thought the flow was through it and it controlled the pressure, a bit like a tap.