With 3 out of 5 dead plugs, you will definitely notice an improvement when you replace them. It sounds like the relay and harness is correct, just need some new glow plugs.


Replace and enjoy.

SteveM

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'93 190E/D 2.5 Turbodiesel 5-speed (daily driver)
'87 190D 2.5 Turbo rustbucket - parts car
'84 Dodge Rampage diesel - Land Speed Record Holder
'13 Ram 2500 Diesel
'05 Toyota 4Runner