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View Full Version : Fuel system bleeding problem on a S3 2.25 diesel



jvsimmons
07-10-2022, 04:42 PM
My 1983 S3 diesel injection pump started leaking so I purchased a rebuilt pump from the UK I have installed the diesel injection pump. This morning I started to bleed the fuel system. Success with the fuel filter (squirts fuel fine - no air) but am having difficulty getting one of the two bleed ports on the injection pump ( the one under the fuel line connections to the front two cylinders - it is on the part of the pump where the throttle and shut off enter the pump) to even show fuel coming out. The other bleed port on the main body of the pump squirts fuel. Should both bleed ports squirt fuel when loosened? I loosened the fuel line to the injector of #1 cylinder and turned the engine over with the starter and fuel leaked from the line. Hand pumping doesn't seem to have an affect even though it is getting harder to move the lever. Not sure what to do now. Anyone have experience bleeding air from fuel system after replacing the pump or have advice on what to do next? Thanks
Jim

roverp480
07-11-2022, 09:44 AM
The fact the lift pump feels harder means the pressure is up in the feed line and any fuel movement is back through the bleed to the tank and not compressing much air . It may be the injector pump needs turning over to allow the internal ports to align to allow fuel through to the second bleed port , have you tried it again since turning over the engine? . The air is only expelled by leakage past the moving parts so it may take a time to get all the air out. . One source I looked at online suggest slackening off all the injector pipes and crank the engine over at the same time pumping the lift pump, but with the throttle pedal fully open. There are a number of comments on the web about air only bleeding from one port and not the other . Look up Lucas CAV DPA injector pump bleeding.

jvsimmons
07-11-2022, 04:37 PM
Thank you for the input. I did look at several of the sites found when I googled the CAV DPA bleeding. Afterwards I decided to just tighten all the fittings and try to start it. Well, after several seconds of cranking it started but ran roughly.....idle was real rough. I haven't sorted that out yet but seemed like the idle setting was too low. I also discovered a leak at the #2 injector - bolt was not tight....must have skipped that one nut when installing new injectors. Tomorrow I will try to sort the rough running.....another option is that I need to adjust the timing on the pump. Could there still be air somewhere leading to the rough running?