Replacement fuel pressure regulator

(David Judd) #1

My 1975 XJ12C has D-Jetronic Fuel injection with a Bosch part number 0 280 160 001 which is an adjustable fuel pressure regulator. There does not appear to be a new one available anywhere in the US. Most listings show the replacement part number 0 280 160 200. This one is similar having two barbs for fuel hoses and a third barb for a vacuum hose. Does anyone know at what pressure this second part operates? Does anyone have experience replacing one for the other or know the operating pressure of the vacuum operated FPR?

(David Judd) #2

I received a reply from Bosch this morning. For those of you interested, the pressure for 0 280 160 001 is 2.2 Bar (31.9083 psi). The operating pressure for 0 280 160 200 is 2.5 Bar (36.2594 psi) to Zero at no vacuum, which would be off or at full throttle. Since the injectors cannot pass more fuel than their design capacity, I am hoping the added pressure will not negatively impact my drivability. My thought is to take the one original FPR I have that is working and move it to the return side and place the 2.5 Bar regulator on the fuel pump side. There have been other posts saying the fuel pump side FPR can be eliminated and the car will still run fine.

(Frank Andersen) #3

The amount of fuel passed through the injectors is proportional to fuel pressure, David - which is regulated by the pressure regulatorā€¦

According to the book; each regulator serves one bank - implying that there are two separate fuel rails. On later models, using one regulator, one fuel rail serves all injectors. If the former is the case; your solution is not directly viableā€¦

Secondly; the ECUs are programmed to deliver the correct amount of fuel based on the spec fuel pressure. For the V12 this is about 30 psi - while the xk use about 36 psi. Increased fuel pressure will overfuel the engines - and adjusting the ECU for different fuel pressures is likely impossibleā€¦

However, Iā€™m not sure if the later V12 single regulator uses 30 or 36 psi - my manuals are silent on that point? Nor am I all that certain that the early V12s had separate fuel rails for each bank - only that the manuals so impliesā€¦soā€¦?

If a single rail is used; there is indeed no need for two regulators - but the specs must be to the respective ECUsā€™ likingā€¦

Also; the pressure regulator opens to the return line when the pressure difference between rail and vent line (at atmospheric pressure, 15 psi) exceeds spec pressure. The fuel pump delivers, depending on its state, between 60 and 100+ psi. If regulator is placed between the pump and the rail - Iā€™m not convinced that the rail will have the spec pressure?

As an aside; the spec pressure is actually test pressure; assuming atmospheric pressure in the manifold. With the engine running, manifold pressure will drop (vacuum increases), and the regulator reduces rail pressure to maintain a ā€˜constantā€™ pressure difference between rail and manifoldā€¦

xj6 85 Sov Europe (UK/NZ)

(John Testrake) #4

I removed the inlet side, pressure regulator on my 87 HE. The regulator on the return side is sufficient. If you install two regulators with different values, I think youā€™re fuel pressure will still run at the lower of the two.

(John Testrake) #5

After reading the original post again I realize itā€™s a D-Jet system. Two separate fuel rails and you need both pressure regulators. Sorry for any confusion.

(DavetheLimey) #6

Does your car have one fuel rail, or two? Or, asking the same question- Does your car have two FPRā€™s with the SAME part no. This would help answer your problemā€¦

(sawyer10702) #7

Isnā€™t that regulator the same has series 3 xj6 ???

(David Judd) #8

to clarify, my car has the D-Jetronic fuel injection system. The fuel rail is a loop serving all 12 injectors. Both FPR are identical with the same part number and both have the adjustment screw. Since the fuel pressure was a solid 30 psi, the regulator was working except with the exception of the fuel leak. I wire-brushed the body and cleaned it with acetone then applied a nice bead of JB Weld to the seam where it was leaking. So far so good. Took the jag for a 40 mile run on the freeway and ran as well as it has ever run.

(Frank Andersen) #9

Fair enough, David - just keep an eye on itā€¦while you keep looking for a proper replacementā€¦:slight_smile:

xj6 85 Sov Europe (UK/NZ)

(Frank Andersen) #10

Negative, different pressures and configurationsā€¦

xj6 85 Sov Europe (UK/NZ)

(sawyer10702) #11

Frank. Thatā€™s a big 10\4. Thanks for saying.