K-Jet fuel pressure test part 4

I’ve been trying to narrow down poor running on my 79 280SE when cold. Previously, I had two issues I was trying to narrow down, high control pressure when cold, and after a while both system and control pressure dropping and fluctuating. I had replaced the fuel pump, which made no difference to the fluctuation issue. I had also sent off my warm up regulator to be cleaned.

When my warm up regulator returned, I refitted it to the car. Even without running the engine, the control pressure was much better. Actually it was now too low. I still had […]

K-Jet fuel pressure test part 3

This is part three of a series where I am trying to diagnose poor cold starts on my 1979 280SE. Please click here for part 1 and here for part 2. In the last part, the fuel pressure tests had pointed to high control pressure. This would most likely be cause by the Warm Up Regulator (WUR). However, after a while the pump became very noisy, and since rebuilt WURs are expensive, I wanted to rule out a bad pump.

Luckily I had a 420SEL parts car on hand. The previous owner told me the fuel pumps were almost new. […]

K-Jet fuel pressure test part 2

Earlier in the week I attempted to run a fuel pressure test on my 1979 280SE. On further examination, I was pretty sure I had it connected up wrong. The instructions call for the pressure gauge to be attached to the larger fitting on the warm up regulator. The warm up regulator is hidden down to the side of the engine on the M110. The bigger fitting is actually a banjo bolt on this WUR, so this time I hooked it up (hopefully) correctly. My goal was to test cold control pressure.

The readings made more sense this time. System […]

K-Jet fuel pressure test part 1

I’ve been trying to get to the bottom of the running issues on my 1979 280SE. The last thing I tried was draining all the fuel and replacing the fuel filter and tank strainer. Once the car warmed up, it actually ran reasonably well. I took it for a drive for about 40 kilometers and it was running better and better. After this drive, I assumed that the running issues was due to bad fuel and that I had solved this part of the problem.

However, when I needed to start the car and move it out of the way […]