Help needed CIS Fault finding
 

Hello
New to the group
I am trying to help a mate get his 1980 280E Running.
It's been stood for 2 years.
We can make it run with start gas so the engine is OK.
We seem to have a CIS problem.
It's had a new pump and filter.
I bought a quality gauge and have made some adapators to check pressures.

From the pump direct to the CIS is 5.8 Bar 85 Psi. I think this is ok ?

Checking on a feed to the injectors its 2.1 Bar 31 Psi. I think the injectors open at 40 something Psi so this is low I think ?

Where do I look next?
I know there is a pressure adjusting valve.
And some valves I don’t understand their use, like the Warm up Compensator and the Pressure Damper ?

This is a UK version and I think won’t have some of the features of the other versions.

Any help appreciated please.

Thanks

K:

1) Disconnect the return line at the Fuel Distributor (FD); attach a hose so that fuel can be discharged into a container. Return flow should be 1 liter in 30-45 seconds.

2) If insufficient flow, remove the inlet fitting at the FD, remove the screen & check it for clogging.

3) Yes, the injection nozzles do have ~40psi check valves, however, after sitting for a prolonged time they may be clogged. They can be cleaned.

Thanks for that.
I had read about that fuel flow test but didn’t realise it was on the return.
I shall have to test this and check the screen

I had the injectors out and gave a blast with high pressure air and as it moved the fuel inside all had a clear even spray.

Thank you

CIS Problems
 

Is it defiantly the return to check the flow as nothing comes out of it. ?

I attempted to check the supply but there is lots of air in the feed even though it eventually made the pressure. The owner says he put 3 gallons of fuel in the tank.

Is the tank pickup a pipe that could rust away?

Thanks you

Yes.

If there is actually three gallons in the tank, it would be enough.

When the pump/filter were changed how was tank draining handled?
It would appear that the reason that there is no return flow is that there is no supply flow!

Thank you for the reply. I didn’t realise it was there.

When I done the pressure test it soon got up to pressure 81 Psi but when I attempted a flow test I noticed the amount of air.

The cars owner said he put 3 gallons in. We may have lost a little but he has now put another 2 gallons in. I am awaiting a new union with the filter attached that I just realised was fitted before I try again.
The owner changed the pump himself and drained the tank. The filter he just fitted last week and he said there was not much fuel came out.
I will report back
Thanks

The owner drained the tank? Completely? I wonder if completely draining the tank loosened some crud, which in turn got stuck at the exit fitting. Draining the tank to change the filter or pump isn't necessary. Just put a pair of hose clamp pliers on the exit line.

Cis
 

He had drained the tank to fit new pump himself. I think only what came out with the pump pipe not fitted.

Thanks

Test the fuel pressure somehow at the pipe that goes to the cold start valve , with the fuel pump on , and you have at least 70 psi , push on the air flow plate , you should heat the injectors whistling . If so dont over do it so you dont hydrolock the engine . Remember on cis , if you loosen the injectors pipes , you wont have fuel coming out .