markw

Hi all, as ive mentioned i`m doing the 5.0 EFI swap into my 68 and just wondering on a couple of safety points.

firstly, what is the best kind of fuel line to use? stainless or nylon? my plan is, as previously discussed to run a small f150/bronco II surge tank/fuel filter up front filled from a standard mechanical pump, this means my high pressure lines will be pretty short only running from just outside the engine bay to the fuel rails, i want to minimise any worries i might have about accidents or fuel line failure.

ie - fuel spraying on hot exhaust in an accident or line failure.

and secondly with regards to the fuel pump cutoff, i will be using the fox`s inertia switch at the back, but it looks as though the fox also uses a centreline crash sensor up front? do i also need this?

cheers,

Mark

My427stang

I run a Ford inertia/rollover switch in the back, 1/2 inch alum hard line in the stock location for the feed, all mounted in rubber Adel clamps

I used A/N pass through bulkhead fittings on the inner fenders, right behind the shock tower, but not in line with the flywheel, then a short braided line to the fuel rail, then to the damper and regulator

Then another bulkhead fitting a mirror image hard line on the passenger side for the return.

I did mine to make it look original, but I will say, with a combination on the inertia switch, a strong line, and no place where a line passes through a sharp hole (like a stocker), the impact needed to break that line would have already torn the tank or the whole car to shreds.

Ultimately, do what you think is safe, but the crash protection of the car itself is 60's technology, if you can get the fuel to shut off if you crash, thats about as good as its going to get, and as good as it needs to be

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70 Sportsroof, 427 FE/489 cid, TKO-600, 31 spline 4.10, A/C. modified Mass-flo EFI/CnC ported Victor.

PSIG

+1. Your system only has a couple ounces of fuel under high pressure. With the impact switch to instantly stop the pump, that's as good as the factory cars get. I would use SS braid fuel line from the chassis to the engine for flexibility with the engine movement (and that's all you have under high pressure anyway), and either steel or nylon for the rest. Keep your lines protected from abrasion, impact or excessive heat as the factory does.

The factory schematic does not show two impact cutoff witches. What is the second you are referring to?

David

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markw

thats great, thanks.

i saw the centreline crash sensor in the fast ford magazine write up schematic, admittedly ive not seen it mentioned anywhere else..

cheers,

Mark

5.0 Chero

Mark
If you are using the reservoir (surge tank) I sent you I am not sure the return line will work correctly if the tank is pressurized by the mechanical fuel pump.

PSIG

The surge tank is not pressurized by the mech (low-pressure) pump if properly plumbed. It simply flows from the mech pump into the surge tank, and (if the surge is full) then back out the main tank return. Any air bubbles go back with the returned fuel.

Supply side:
main out > mech pump > surge > return to main
HP side:
surge > HP pump > rail/regulator > surge

Except for the HP pump line and rails, the system is non-pressurized.

David

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markw

why is this? too much pressure from the mech pump? surely the excess pressure will just beed back to the tank? as long as the surge tank is always full?

unless i`m missing something?

cheers,

Mark

markw

just saw this reply, thats what i was thinking.. i noticed in the bronco surge tank there is a difference in the inlets and outlets, two are large, to are smaller, one is not connected to any other inlets, ie, just the inlet to the surge tank, the other smaller one is connected to one of the higher ones and they join before the tank, if that makes sense.. and the two top ones are also connected

http://img.photobucket.com/albums/v2...z/P1014164.jpg

not sure how this affects the flow, id imagined the solitary one to be the inlet feed from the mechanical pump, the other lower one return to the tank , though this is actually plugged in my tank, so it is just a branch of the three linked hose connectors, its not open to the tank itself, and the smaller upper one being the return from the rails, and the larger upper is the high pressure pump?

**edit** just thinking about this... as the three branched ones are fed from/to the bottom of the tank, i suppose the individual one (the only one fed from the top of the tank) should be the tank return so as to return air too? **edit**

cheers,

Mark

markw

just found this

1983 Ford Bronco '84-89 Fuel Reservoirs picture | SuperMotors.net


it mentions a check valve, but mine doesnt have one... does this matter?

PSIG

No, you don't need any check valves. The check valve they mention in that version is to prevent the main tank feed line from draining back to the tank when not running. This was found to be unnecessary in later versions. The same is true of the fuel rail return, as fuel can't flow backwards to the regulator anyway.

The reason the Ford accumulator/surge tank has the rail return and main tank return 'joined' in a cavity internally, is to prioritize the hot rail fuel for return to the main tank for cooling. Notice that they are not actually joined, but share a large opening together, where the rail fuel will drop into the surge tank if it's not full, or be re-directed (pushed upward) into the main tank return if it is.

It is important to note that the BC Broncos fuel filter mod has a few photos of a poor line routing, where they tee the rail return to the tank return. This is a bad idea, as the rail return must go to the surge tank first (as in the Ford accumulator pic), or else a portion of the fuel will go back to the main tank, draining the surge tank. This isn't an issue as long as you have flow from the LP pump. But if you are low on fuel and the LP is momentarily pumping air, the surge tank will run dry quickly - exactly what it's supposed to prevent. Be sure to route lines to provide rail return to the surge tank first.

David

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My427stang

Why bother with the surge tank? I can certainly see it working to keep a constant supply of fuel, but is it really an issue?

I run an in tank pump (actually dual pumps), they stay cool and quiet, then I run a pressure dampner after the second fuel rail to minimize effects of the injectors firing.

I have not had any indications of fuel starvation although I have never done any kind of cylinder contribution test under load, its a very simple setup and works super, even with a 489 inch engine at full boogie

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70 Sportsroof, 427 FE/489 cid, TKO-600, 31 spline 4.10, A/C. modified Mass-flo EFI/CnC ported Victor.

PSIG

It's an issue in fuel tanks that do not have baffling or sumps. That's most tanks originally used with carburetors. Carbs don't have an issue because they have their own 'surge tanks' - the float bowls - that can separate air that is sucked into the tank pickup at low fuel levels in accelerations such as turns, forward acceleration and stopping. Also, mechanical diaphragm pumps for carbs pass air without damage, unlike most EFI HP pumps. Still, carbed race cars use sumps or accumulators to keep fuel to the carb during high-flow conditions to prevent lean-out. It's not just for EFI systems.

So, an EFI accumulator for fuel (a.k.a. - surge tank, swirl pot, header tank, etc.) is used to provide a mechanism to remove air and bubbles from the fuel flow, and to provide a constant, uninterrupted supply of fuel for the HP pump. If the EFI high-pressure pump ingests air, it stops producing some or all pressure (depending on how much air), and the engine runs poorly or quits. If bubbles enter a fuel injector, that cylinder will go lean while the bubble is passed instead of fuel.

Millions of cars from Alfa Romeos to Volvos (and many Fords) have used these accumulators to solve this issue. In the 1990's some continued with this system, and others moved to the fuel pump module alternative. Only a few have used sump systems or baffling to solve it.

David

__________________
-=≡ If it was easy everyone would do it ≡=-

My427stang

Makes sense, I just used a Tanks Inc baffle and tank fitting in a stock tank.

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70 Sportsroof, 427 FE/489 cid, TKO-600, 31 spline 4.10, A/C. modified Mass-flo EFI/CnC ported Victor.

markw

i`d certainly consiedr a baffled tank later on, but shipping a tank over here costs a fortune, if i pick up an old one at some point i`ll have a go at making one perhaps, but it depends if the noise of the efi pump annoys me or not, if not, i wont bother.

i dont like the idea of the EFI conversion tanks as they have the top loading fuel pump and fuel lines in the trunk, my car is used for all sorts and quite often ends up with a trunk full of crap..

cheers,

Mark

My427stang

Here is mine from the trunk, both of those hard lines connect to bulkhead fittings



and you can see the underhood here, needless to say it wasn't quite finished in this pic

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70 Sportsroof, 427 FE/489 cid, TKO-600, 31 spline 4.10, A/C. modified Mass-flo EFI/CnC ported Victor.