Diesel fuel filter for petrol?

[Gazzar]

Cool! I'll get one, and the mounting screws. I'll have to fabricate a mount for the tank, should be fun. 

[Snagger]

On 12/25/2018 at 12:34 AM, Gazzar said:

That's good thinking, except getting the fuel return back to the active tank then becomes complex. That's where the two pumps come in. The selector electrics choose the pump, and the return is via the mechanical valve.

I'm now thinking of an in tank pump, like the RRC per tank, but one per tank.

Then I could feed to a single sediment filter and on. 

 

Tee the return to the feed for the lift pump after the fuel tank tap and it'll prevent aeration of the fuel, reduce evaporation, reduce the load on the lift pump, ensure warm fuel for the filter in winter once running a short time and eliminate the need for a return line to either tank or a selector valve on that line.  It's what a lot of diesel vehicle owners do with a vegoil conversion to keep the heat in the fuel for viscosity reasons and to prevent accidental contamination of the diesel tank with vegoil.  The only snag is that if there are any air leaks in the system, then the self-purging nature of the system is lost and the air gradually builds up.  It's no problem and has many advantages if you build the system leak free and protect lines from chafing. 

There are breather fittings which allow air to escape the system but not fuel, which could guarantee the above system never poses a problem.

[Gazzar]

I'm not using the lift pump, I think. I'll blank that off.

The current plan is a RRC efi in-tank pump, then filtration, then megasquirt gubbins (as yet unexplored territory).

Then return the petrol using the original feed system, to the applicable tank.

My concern now is that the seals on the filters won't take the pressure from the RRC pump. But it should.

I have taken on board the comments of simplicity, and I think that this is a good compromise. Two pumps, one per tank, in the tank. One filtration chain to the engine bay.

Standard system repurposed as the return.

I just need to build the tanks now.

[Snagger]

You can still tee the return into the feed, which will reduce the electric pump demand and keep warm fuel going through the filter, handy in winter.  

[Bowie69]

No need at all for petrol to do that, in fact can cause serious running problems in warmer weather with boiling fuel.

Also, given the fuel pressure regulator is on the fuel rail, you'd essentially be dead-heading the system, meaning the regulator wouldn't be able to do its job, and the injectors would be getting 100PSI, instead of ~35.

Two pumps, two returns = happiness

[Gazzar]

Aye, I think, unusually, snagger isn't 100% on this. For diesel, sure, but petrol is better cooler. Evaporation, vapour locking and stuff.

Mr Bowie has it.

I'll design the tanks to have the pump in the centre, and put it in the anti surge sump. The return can be aimed at the side of the tank to de-bubble the hot fuel.

Nearly there on the thinking part of this stage, now the fun part!

[FridgeFreezer]

Disclaimer: I've only skimmed this but I'd be wary of using a filter designed for the low-pressure "lift" side of a fuel circuit on the high-pressure EFI side of the fuel circuit, a spray of atomised petrol into the engine bay is going to lead to a bad day.

You don't want to warm your fuel up either, evaporation can cause problems. Been there done that, actually used a LR sedimenter as a mini swirl-pot in the end but my fuel system is not what you're aiming for and isn't what I'd do if I was doing it again.

If you are tee-ing two HP pumps into one line do you know the "dead" pump isn't going to back-feed and let all the pressure out of the line? On Mouse we ended up with a very swanky dual-changeover solenoid valve for the pumps.

Oh and you can't just extend an in-tank fuel pump with regular fuel hose, as only the inside of fuel hose is actually fuel-proof - ask Steve200TDi how we know this you need fuel hose that is specifically rated for in-tank / permanent submersion in fuel and be sitting down when you ask how much per metre

The old RR 3.5 EFI inline filter NTC5958 is a fair bit chunkier than those little plastic inline jobbies but is a simple fit (hose barb both ends), it's what I've always run on my RR, the 109 and the 127 and they have handled Russian fuel no problem. I tend to stick a cheapy inline filter on the return so you can see the fuel flowing as an easy diagnostic.

The 127 was a factory V8 and has a factory petrol filter in a little bowl very much like the old diesel ones, that might be the right answer but only for low pressure.

[Gazzar]

Failure of the seals on the filter was a concern. 

 

Is the way forward a low pressure in tank pump, and high pressure pumps post filter?

Then I could use a pair of simple non-return valve to avoid back flow.

This is fun!

[Gazzar]

Is thick wall nylon pipe rated for emersion? I'll ask the supplier. 

Would one of these, attached to a standard series fuel pick up, work? 

How would I get the electricity in to it? I'm quite sure that sparks in the fuel tank are bad. Could I get the electricity in through the level sender somehow?

 

[Bowie69]

Wouldn't the lightweight changeover valve sort the problem with back feeding the tanks, as well as shutting off the other fuel pump?

[Gazzar]

I was thinking of using that system for the return, all low pressure and so can use the original pipes and valve.

But use the electrics to switch relays for the pumps.

 

I think I'm getting hung up on the series look of the filtration system. 

 

But I WOULD like it to look series, and I think the sexy race type in-line filters would not look right. 

I'm overthinking this again.

 

G.

 

[Gazzar]

Okay, 

Option 1) 

   High Pressure RRC EFI pump, and suitable spec filters and non-return valve (anyone got  a specification manual for Lucas CAV filters?).

Option 2) 

  Low Pressure RRC Carb pump, standard series filters, high pressure pump under bonnet.

G

 

 

 

 

 

[Snagger]

I didn't think the fuel would get hot enough to be a vapourisation issue, but I have never tried it with a petrol, so note the experience of those who have.  Scratch the looped return idea.  My MoD SIII diesel selector taps have a tab on the cradle to mount an extra valve for the return and a mechanical link from the return valve's arm to an added arm on the feed tap's shaft.  It means that the feed tank is automatically selected for the return line.  They're not common parts, but someone like Dunsfold or Blanchard should have them.

Still, I think you're introducing excessive complexity and cost with dedicated electric pumps where a single electric pump after the selector tap will do.

[Gazzar]

I just like the idea of redundancy. 

Example

https://forums.lr4x4.com/topic/104519-dodgy-petrol/

G.