MillenniumFalcon

What kind of fuel pressure do you think is in the fuel return line coming out of the warm up regulator? I am concerned because I found a simple vacuum hose installed on the brass barbs, instead of a plastic fuel line- any idea what is supposed to be there- a high pressure line?

Trying to avoid a fire!

1975 911 2.7

rusnak

I've seen some hideous substitutes on the WUR. A pic would help. Iceman is the go-to guy on your question. The stock hose is a pita to replace.

Oh, and love the username. I've thought about both my 911 and my work truck as MF-like from the standpoint of all the mods and occasional sad looking demeanor they get after a long road trip.

theiceman

I actually have not played much with the fuel system and to be honest I don't know cis systems had a return fuel line. I will have a look for you what I have as my car is stock and report back.

MillenniumFalcon

thanks!

On the diagrams, it is not clear exactly what kind of line(plastic/flexible/clamped/push-on) goes there- only that it is a very small diameter (1 to 1.5mm ID) return line that feeds into a "T" into the larger return line that goes back to the fuel tank....

rusnak

I think you're talking about the supply line from the fuel distributor to the WUR? Either that or you're calling the accumulator the WUR? Pics would certainly help.

theiceman

I read up on the theory .. the gas is fed to the distributor and some is routed through a small channel inside the FD to the top of the distributor as control pressure. Then as Russ points out it goes off to the WUR. If that is closed off the full pressure is on top of the FD. As the car warms up the WUR allows flow and relieves pressure on the top of the FD and the open gate in th WUR allows gas to "return to the Tank. Never really looked at it before now .. quite ingenious. I imagine it s a small line though .. and not the high pressure line as a lot is choked off in the FD.

MillenniumFalcon

Yes, it is a very small line- much smaller than the pressure feed line (it is about 1.5mm ID). If you look very carefully in the attached pictures (not from my engine), you can see the return line hose hanging there with the banjo fitting for the WUR (2nd photo), and you can see the other end going into the 4-way return line fitting (top photo- right in the center of the photo)... The line is the same composition as the injector lines- the hard dark plastic line material. I would guess that since it is a line flowing back to the tank, that it isn't high pressure because there should be very little resistance pushing fuel back to the tank...

Also- lots of shade tree mechanic work done on this engine.... the fuel pump safety switch on the CIS was disconnected and the wires taped together (which is why my pump comes on with the ign key!!! Hoping to sort this out, and guessing that it was done because the switch is bad- we'll see.

MillenniumFalcon

Thought I'd post these- found them on eBay- nice to see what the back of your CIS looks like, if you've never had the engine out...

pjrebordao

A rubber hose on the return line is ok, as the pressure after the WUR is much lower...
Probably the line that you'll be T-ing is also rubber...

MillenniumFalcon

pjrebordao,

I think you're right, because there was vacuum line that was used for a return fuel line from the WUR, and it had been in there for quite some time.... I haven't found a source for fuel line yet that is 1.5mm ID- nobody has anything even close!

theiceman

try a diesel shop

MillenniumFalcon

Good idea iceman.... thanks