Swapped out old glow plugs for a Ford cylinder pressure test kit. Night and day difference.
Wasted 4 hours last Tuesday on a 6.0 that would barely start when cold. Did the whole dance, checked harnesses, tested relay, even ohmed the plugs. All passed. Then my buddy Dave said quit messing around and grab his cylinder contribution tester. One pass on each hole and I found #3 and #5 were weak as hell. The plugs looked fine but they were just done. Swapped in new ones and it fired up like it was summer. Anyone else got a go-to for diagnosing cold start issues that beats guessing at glow plugs?
Is something like that really worth grabbing for a truck that only acts up a few mornings a year? I get it when you are chasing a gremlin every week, but for the odd no-start I would just toss in a set of plugs and call it a day.