I just picked up a CIS-specific pressure tester. The photos in the benz manuals are poor and the instructions with the tester are unclear.

How do you hook this thing up? Basically, it's gauge with two ports. One port has a cut-off switch to isolate that port from the gauge.

This means with the cut-off swith open, fuel will flow through the gauge and the system will operate as normal, and the gauge will report the operational pressure.

With the switch closed, the gauge is still hooked to one port and you can read pressure, while the other port is cut-off.

The instructions for measuring control pressure that came with the gauge said to put the port with the swith "downstream". I take that to mean disconnect the fuel line from the center of the fuel distributor and connect the line to the port with the switch while connecting the other port to the distributor. That's presuming "downstream" means follow the fuel flow from the fuel distributor back to the fuel tank.

Something like this, where the "X" is the cut-off switch...

fuel distributor->>-Gauge-X->>-damper->>-warmup/enrichment-<<-tank

Thx -CTH

__________________
- cth350@gmail.com
http://www.111lakeside.com/

The gauge goes between the fuel distributor and the warm-up compensator on the earlier engines. You want the shut-off valve on the WUC side which I guess is what they mean by "downstream." You close the valve to measure System Pressure, which is what the pump-filter-accumulator-regulator assembly is delivering to the FD. Then you open it to measure Control Pressure, which is what the WUC is doing to change the pressure to adapt to different engine conditions.

The easiest place to attach the gauge is at the FD if the WUC is mounted on the block like on the M110's or at the WUC if that is mounted at the top of the engine, like on the 3.8's.

On the later engines, the gauge goes between the FD and the EHA.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe