I had the same issues while trying to tune the Lucas pump in my Cit Xsara 1.9 td.
Eventually I got so frustrated that I went to a local metal machine workshop with the plastic cap. They made me a metal cap with the exact same dimensions and as an extra, they machined a 19 mm bolt head on it. Now I only need a 19 mm spanner to open it. So much easier.
Eventually I got so frustrated that I went to a local metal machine workshop with the plastic cap. They made me a metal cap with the exact same dimensions and as an extra, they machined a 19 mm bolt head on it. Now I only need a 19 mm spanner to open it. So much easier.