Fuel Pressure Gauge for CIS pressure measurements

(Click here for WUR pressures)

This is the fuel pressure gauge setup needed to check the system pressure (set by the fuel distributor) and the control pressure of the Warm Up Regulator. The adapters in the center came with the guage and can be used to plumb into the the fuel lines in differing ways. There's nothing magic about this particular gauge. You can buy the fittings and build one of your own.

The device just under the gauge itself is a pressure relief. You can relieve the pressure and drain some of the fuel out of the hoses before you disconnect from the CIS after testing.

The female fittings on the hose ends are 12mm x 1.5mm.

The sizes of the adapters are (top row left to right, followed by bottom row left to right):

12mm x 1.5mm male : 8mm x 1.0mm male
8F : 12M
8M : 12M
8M : 12M
12M :10M
10F : 12M

All the 12mm diameter threads have a 1.5mm pitch,
All the 10mm diameter threads have a 1.0mm pitch
All the 8mm diameter threads have a 1.0mm pitch

The gauge hooked up to the fuel distributor and the Warm Up Regulator. Note that the on/off valve is on the side of the warmup regulator. This is important. If it's hooked up the other way you cannot read system pressure.

The 12mm hose end mates with the fitting on the WUR.

This hookup completely replaces the FD to WUR hose. There are other options for accomplishing this same hookup like splicing in on the WUR end without disconnecting the hose on the FD. You just need to maintain the same fuel flow of the hookup shown.

A better view of the connection to the Fuel distributor. This end uses the long 12mm x 8mm adapter.

Directions for Use

Hook up the gauge with a cold engine and no pressure on the system (it's less messy this way).

With the gauge hooked up, and beginning with a cold engine, you can do the following tests:

  • WUR contol pressure cold engine
  • System pressure (cold or hot pressure is the same, but you can't *monitor* it with engine running)
  • WUR control pessure warm engine (engine either running or not)
  • Leakdown pressure versus time (after engine shutdown). Check for leaky components in this mode. (Check valve,
    accumulator, injectors, fuel distributor)

Switch on fuel pump with electrical connection to WUR unplugged. Read system pressure, valve closed.

Open valve, read and record WUR control pressure for cold engine.

With fuel pump running, plug in electrical connector on WUR. Watch for pressure to increase, valve still open. When pressure stops rising, note reading.

With valve still open, you can now run the engine. If you take care that all connections are tight, and the gauge is secured to prevent it from being damaged, you can drive the car in a normal fashion leaving the gauge in place. If you're having trouble with hot starts, drive the car until it's up to normal operating temperature, then stop and open the engine lid and watch the pressure. It should drop fairly quickly below the hot control pressure, then slow at maybe 2 Bar or so, and not fall below about 1 bar in 20 minutes. You can do the leakdown test without running the engine, but pressure leakdown could be more pronounced with more engine heat. This test will include the WUR. Stopping the engine and closing the valve will eleminate the WUR from the leak test, but still include the check valve, accumulator, injectors, and fuel distributor.


Warm up Regulator Specifications

System, cold and warm control pressures in Bar. Some information is conflicting for the early years, see info source and notes. (Euro Models are followed by asterisk). Entry in "Vacuum Connection" column is the control pressure specified with vacuum applied to the WUR.

Note: I have added Pressure Specs for the 930 Turbo below this table.

Year model System Pressure Cold pressure Warm pressure Vac conn Info Source Note
Bosch part number 
  @ temp (C) @ temp (C)      
73.5 .001 4.5 to 5.2 1.6 @ 10 2.7 @ 35 None
74 - 75 .001 4.5 to 5.2 1.6 @ 10 2.8 @ 35 None F.M.  
74 - 75 .008 4.5 to 5.2 1.3 @ 10 3.0 @ 40 None F.M.  
74 - 75 .009 4.5 to 5.2 1.2 @ 10 3.0 @ 40 3.6 @ 40 F.M. 1)
75* 911, 911S .017 4.5 to 5.2 1.3 @ 10 2.7 @ 35 None S.B.  
75 911S/C 4.5 to 5.2 0.6 @ 10 2.2 @ 35 3.6 @ 35 S.B.  
76 - 77 911, Carrera, 911S 4.5 to 5.2 0.8 @ 10 2.4 @ 35 not spcf'd S.B.  
76 - 77 .033 4.5 to 5.2 1.4 @ 10 3.2 @ 40 3.6 @ 40 F.M. 2)
78 -80 * .045 4.5 to 5.2 1.8 @ 10 3.0 @ 40 3.4 @ 40 F.M.  
78 - 80 after Jan 79 * .069 4.5 to 5.2 1.4 @ 10 3.2 @ 40 3.4 @ 40 F.M.  
'78 - '79 .045 4.5 to 5.2 1.8 @ 10 3.0 @ 40 3.4 @ 40 F.M.  
'80 .072 4.5 to 5.2 1.8 @ 10 3.5 @ 40 None F.M.  
'81 - 83* .089 4.5 to 5.2 1.2 @10 3.0 @ 40 3.6 @ 40 S.B.  
'81 - '83 .090 4.5 to 5.2 1.6 @10 3.4 @ 40 None F.M.  
* ROW            
There are some discrepancies between the T.S. (TroubleShooting) Guide, spec books, and the factory workshop manuals on the control pressures.        
1) T. S. guide says   0.6 @ 10 2.2 @ 35      
2) T. S. guide says   1.4 @ 10 2.4 @ 35      
Nominal values specified            
Not spcf'd = Not specified            
F. M. = Factory Manual            
S.B.=Spec Book            
T. S. Gd = Trouble shooting Guide            
Original '80 WUR had no external atmosph connection, replacements had one.            
An entry in the "Vac conn" column indicates a WUR connection to the intake manifold, the number is the contol pressure with vacuum applied.            

Notes for the table below:
This is temporary until I can type up a nicer one. The first notes, e.g., "same as 911" means that the procedure for testing the 930 WUR is the same as testing the 911 (normally aspirated) CIS unless otherwise noted. This info was copied from the Porsche Factory Manual for the Turbo. Note the Control Pressure Flow test - this is accomplished by removing the fuel line from the Fuel Distributor to the WUR at the WUR and measuring the fuel flow into a container with the fuel pump running. If the fuel flow is less than the spec this could indicate a blocked orfice in the Fuel Distributor. If it is greater than the spec limit, there is a possibility that the FD may have been rebuilt and an oversize orfice provided by the rebuilder if the internal diaphragm was replaced.

A number such as 438 140 016 on the right side of the table is the Bosch number of the WUR.

930 WUR and FD pressures

Last Updated on 8/20/09
By Jim