D Jetronic help for a new guy please Options

[JeffBowlsby]

That's a correct install, nothing else to comment on.

the following is how I installed the stainless steel lines (green) from tangerine...

when I posted this over a year ago, and asked for a critique, no one responded..

I still do not understand the "Y" and how that works. ????

blue is return line..



tks

randal

[Dave_Darling]

I still do not understand the "Y" and how that works. ????

Your fuel is supposed to go from the tank, to all of the injectors, and back to the tank again. The injectors use what they need, of course, but a whole lot more fuel is pumped than they could ever possibly use. So you need a line that goes from the fuel pressure regulator back to the tank.

The fuel pump is supposed to be able to dump excess pressure that it sees (a higher pressure than the FPR regulates to) in order to keep from blowing out seals or some such. It needs to be able to dump that excess back into the fuel tank as well.

The Y ties together the bleed-off line from the fuel pump (labeled "R") and the return from the FPR, and sends them back to the fuel tank.

Later, they figured out that they didn't really need the return from the pump if they changed the design a bit, so in the 75-76 914s the Y was eliminated. (And also if you convert over to a more modern pump.)

--DD

[r_towle]

From what I recall when shopping for a pump last time the stock inline pumps are rated at 65-70 psi.

[SirAndy]

I still do not understand the "Y" and how that works. ????

The Y is used to route the overflow fuel from both the pressure regulator and the fuel pump back into the tank.
(IMG:style_emoticons/default/smile.gif)

[Wyvern]

(IMG:style_emoticons/default/pray.gif)
THANKS !
I re-routed the new lines ( almost everywhere) and installed the "Y" as in the above pics (at the fuel pump) ....
29 lbs !
Wow ... Smooth . Idles . Got power .
Super happy . Thanks to all for information.
I hope to be able to return the favor here.
Now ... Very motivated to work on smaller stuff .

[jacksun]

never mind the below, as i missed the following "The Y is used to route the overflow fuel from both the pressure regulator and the fuel pump back into the tank."

thank you, i kind of understand now. something inside the pump allows for
fuel to be routed out into the return line under pressure so the return from the
fuel injector loop combined with the fuel pump pressures the fuel to move to
where there is no pressure, and back to the fuel tank the fuel goes.
tks


what i did not understand was how the Y worked in that

the fuel is under pressure returning from the fuel injector loop and then it

comes to a Y .... is the short piece also under pressure from the fuel pump ?

seems like they would be at odds with each other.. as where does the fuel

pump obtain a continued source of fuel to send down stream to the fuel tank?

obviously i do not understand how this works.

tks

randal

[SirAndy]

something inside the pump allows for fuel to be routed out into the return line under pressure so the return from the fuel injector loop combined with the fuel pump pressures the fuel to move to where there is no pressure, and back to the fuel tank the fuel goes.

That is correct ...

what i did not understand was how the Y worked in that
the fuel is under pressure returning from the fuel injector loop and then it
comes to a Y .... is the short piece also under pressure from the fuel pump ?
seems like they would be at odds with each other.. as where does the fuel
pump obtain a continued source of fuel to send down stream to the fuel tank?
obviously i do not understand how this works.

The pressure in the return line is much less than what is needed to open the valves and there is no resistance towards the tank return.
Since both the fuel pump return and the fuel regulator have a (pressure driven) valve they really aren't at odds.
Both bleed off excess fuel into the same return line.

(IMG:style_emoticons/default/smile.gif)

[Wyvern]

And off to Cars & Coffee today ... was fun to drive it .

[r_towle]

Confess,

What type of line did you run through the tunnel?
What was the situation at the tank with no line on it from the previous setup?

[914_teener]

He is attending the bbq aforementioned.

[Wyvern]

The PO or P - PO had been in there .
Lines at the tank through the tunnel were new (that triple layer FI hose).
The return line was there, it had just been routed to the return port on the pump only.
And the "upper part" of the system ad just been routed incorrectly.

[JeffBowlsby]

Danger Will Robinson...!

Rubber fuel lines through the tunnel are a problem waiting to happen. Advise replacing with the SS tubing for safety.

[Wyvern]

^^^
thanks & understand .

I just needed to know I didn't have a BIGGER issue.

Now that it runs and pressures are correct and i have been able to test other components .
My winter project(1 of them) will be to do SS lines

Thanks again to all for info !

[Chris H.]

I am running on 70 lbs pressure .

Ugh I started this one from post 1! Yikes. Good thing you noticed that! Wow that's a LOT of pressure to run through the stock system.

Hey like Jeff said, get yourself some stainless center tunnel lines. Call Chris at Tangerine Racing. He makes a nice set. Took me a matter of minutes to install mine once I pulled the tank and got the old stuff out. Never have to replace them.

Stainless Fuel Lines

Don't put it off too long!