More fuel system questions

I've read through the archived threads in this forum on fuel systems, but I still have some questions.

1) Is the manual correct when it shows the high-pressure filter downstream of the high-pressure pump? I would think there'd be a filter upstream of the pump instead, but I'm not sure.

2) I've decided not to use carbon canisters. How should I run my vent lines? Do they need to be a certain height above the tanks? Do they need a check valve?

3) The manual references EFI clamps but all I have are worm-drive hose clamps. I don't believe these are suitable for high-pressure systems. Should I use EFI clamps throughout the system? A web search suggests that my local BMW dealer might be a source for good EFI clamps.

4) Can I use teflon tape on the fittings?

Thanks.

Can't answer all of them, but on 3, I don't think it makes any difference. Or, if it does, large car manufactuer Mazda doesn't think so.

I've built 3 Spec Miatas now and all the high pressure (35-45 psi) fuel fittings are secured with spring clamps - the kind you squeeze with your pliers and slide down the hose to get off. They don't offer nearly the clamping force of a worm clamp and, Mazda never had a recall or fire problem. The hoses are EFI rubber hose as RF supplies too, so I think you'll be perfectly safe with about any decent clamp there.

O'Reilly auto parts here in Texas now sells efi clamps, so you may be able to buy them at any decent parts store. I just put in pipe plugs where the carbon canister lines come off the fuel tank, if I remember correctly, that was what I was told to do.As regards the h.p. fuel filter, I placed them as described in the manual.

Reagrding teflon tape, I am not an expert, but I used Permatex "High Tack" Gasket Sealant. The item number on the 4 ounce can I have is 80062. You should be able to buy it at any parts store. From the can, and I quote, "Excellent for threaded fittings..." and "Will not be dissolved by gasoline, kerosene, glycol, transmision fluid, brake fluid..." Stuff never hardens.

Unfortunately, I can not edit my earlier post but I was mistaken about the clamps that RF had provided with the kit - they are most definitely EFI clamps. My mistake - I was confused about the definition of an EFI clamp.

I also decided to use Permatex High-Performance Sealant on the fuel fitting threads, along with their cleaner/activator product.

Mark,

The fuel system has been updated since the manual was written. There is the addition of two shut off valves fitted prior to the two LP / transfer pumps and the addition of a pre HP pump filter.

The fuel shut off valves are to shut off the fuel tanks when the ignition is off (maybe an accident or inversion of the car) but it has also stopped the transfer of fuel from one tank to the other that we had SOMETIMES. The reason I say sometimes is because the LP pumps are not supposed to allow the transfer of fuel in the wrong dirrection and this sometimes happened. The HP filter was added when we had a HP pump get some crap in it and it is for safety of mond.

We always use HP fittings and in particular hose clamps as the injection system can be VERY dangerous if there is the slightest of leaks. Another safety issue for me, better safe than sorry.

I will include a HP pre filter with the stuff I packed on Friday for you.

Best wishes,

Robert

Thank you Robert.

I knew about the two shut-off solenoids, and have allowed space for them in the plumbing. The addition of a pre-HP-pump filter makes sense, as the fittings on the HP filter supplied are the same size as the outlet of the HP pump, and it didn't make sense to step down from 1/2" hose on the inlet side of the HP pump.

I assume the HP pump pre filter has 1/2" fittings? Is it simply installed in-line or do I mount it somewhere? If I'm supposed to mount it, do you think you could send me a photo showing how/where it's mounted? Things are getting cramped in there!

Thank you again for your help, Robert.

Mark,

You are correct, the filter has 1/2" fittiongs on both ends and is fitted in line.

It is fitted outboard of the LP fuel pump and has fuel hose either side.

Best wishes,

Robert

Further to Roberts last.

I had a problem with one of the CAV replicas (prior to current ownership) The car ran on FI and the high pressure pump would overcome the low pressure pumps, draw fuel from both tanks (even though it should only have been drawing from the active tank) but it could only return to the active tank as the other circuit was closed, resulting in an overfilling and overpressurisation of the active tank and a constant seepage from the filler cap. This was exacerbated by an extra fuel cap (under the Le Mans filler) and when this extra cap was removed, an enormous gout of petrol would emerge under pressure - on one memorable occasion all over the gucci loafers of a prospective customer!

Frank Catts solution was to install a swirlpot (cunningly fashioned from an aluminium sailing ships mast as i remember)which not only looked good mounted on the bulkhead, but also solved the problem. The RF of course has this swirlpot as a standard item to the rear of the right hand fuel tank.

Rick

BMW has excellent EFI fuel line and clamps that the bolt head twists off when they are properly torgued. The Mazda spring clamps are good but after my 93 RX 7 turbo flambaed itself for the second time I went the BMW route.

If the bolt head twists off then how do you get the things off?

Update - Robert has a care package coming my way. Turns out the HP filter I had has 5/16" barbs on either end, and I was stumped as to how to go from a 5/16" barb from the HP filter to a 1/2" barb at the sill panel fitting. Robert is sending me a new fuel filter with a 1/2" outlet. The elimination of the carbon canisters is easy - I'm just putting a plug in that fitting and allowing the tanks to vent through the vent near the fill port. McMaster Carr carries the requisite 1/4" BSPT plug.

The customer support from Robert and Hershal and the entire crew at RF is just awesome.