I have a Cummins 350 in my '86 Freightliner COE. It goes under 1K miles per year and has for 20 years now and with next to no problems.
Recently it was very hard to start, felt like it had a miss and seemed to improve with a short drive, but not to perfect level. We found water in the fuel and changed the filter, drained the bottom of the fuel tanks and made new fuel inlet hose and tank cross over hoses all to no real improvement.
Then I used a temp gun on the exhaust manifold and found that only the rear two cylinders were developing power. And there is a lot of loud rattling. It starts easily, no smoking issues. I checked the filter in the fuel pump & found it quite clogged. I ordered a new filter but I started it with no filter in the pump to test and didn't find any improvement.
How can I test the fuel pump itself? And what does anyone suggest I do next?
Jim in Arizona