1983 300d - intermittent jolts on start up
 

Sometimes when I start it up, in the first 10 sec or so I might get these 'jolts'. The jolt lasts just a moment, and briefly shakes the entire car. Somewhat violent, you might say. Feels like it's coming from the engine compartment. Maybe a pump clogged and fighting through something?

I very often get 0 jolts upon start up. Sometimes I get 1 or 2 jolts. Today, I got 6 or 7 and the car idled very roughly; shut it down, started it back up and it smoothed out.

Fuel filter is old, and diesel purge has been pumping through its veins for a while (and is currently in right now too). Power steering is intermittent.

What worried me is the car idled so roughly today when I got 6 or 7 jolts... The most I've ever gotten. Any ideas?

I'd say to start with that fuel filter. Low hanging fruit, easy to pluck.

When was your last valve adjustment?

Any fuel leaks?

Also plan to check your glow plugs. That was what my mind went to when you described the symptoms - a failing glow plug.

Your problem is likely air in the fuel line. Try changing the hoses on the primary filter. Eyeball the whole fuel path. I had a similar problem due to a rusted fuel line. If it had gone much further, it would have been more than an air bubble.

You may even have a collapsed mount or two. This sort of sounds like a typical neglected car. I would go down the list.

Fuel filters 2
Air filter
Primer pump if old white one
valve adjustment
oil change
rack damper bolt
motor mounts 2
transmission mount 1
clogged alda
fuel pressure relief valve
glow plugs
Injection pump timing

check all glowplugs first, prolly have 1 or 2 bad plugs. The jolt is a cylinder misfire.

Come to think of it, the glow plug light didn't come on once, which if I recall correctly is often due to 2+ failing glow plugs.

Might as well replace the fuel filters too. Motor mounts look ok (though one is kinda caked in oil), haven't checked the tranny mount yet.

Not sure of the last valve job. Bought the car roughly 3k miles ago. On my to-do list.

I'll audit the fuel lines too. Miiiight have a slight fuel leak... Car can be a bit smelly at times, and I get about 24mpg, but I attribute that to unknown fuel filter state, unknown valve state, etc.

Thanks for the replies.

Yup, sounds like it's time to get it caught up on basic maintenance.

Glow plugs
Fuel filters
Valve adjustment (if you don't know when the previous owner did it, assume it was way too long ago)
Motor mounts (oil and diesel fuel degrades the rubber, usually on the driver's side)
Tranny mount while you're at it
Fuel return lines and any possibly leaking feed lines.

Check the iFixit link in my signature just below for how to guides on almost all of the things you need to do.

If you do it yourself, you can get all this done for under $200.