Ok guys, so the car is 1992 300D. Story is that I've been replacing what seems like everything on the dang car for a time now. One of those things was the starter. Then a couple weeks later a couple glow plugs went out. I dealt with it for probably a little too long. The rough starts weren't too bad and once the car warmed up it ran fine.
One day I went out and it just did not want to start period. I cranked and cranked and it seemed like it was running at just a very low/rough RPM but it wouldn't keep going, not even while pumping/pressing the accelerator. So I tried jumping it a few hours later and it fired up. Still rough, but it ran.

Next day same problem, I try cranking it, engine seems to fire a bit, just wont start and run. When I stop cranking I hear a soft clanking sound around the starter area and when I try to start the car again I can hear the starter spinning, but it's not turning the engine. So I decide to take the starter out, maybe the cranking was too hard on it. . . I dunno . . . Anyway, I just took it out and down to an auto store. The starter tested just fine. Solenoid popped out and it spun like a dream.
So I pop it back on and try again. Same results. I can hear it spinning, but it's spinning freely. It's not turning the engine at all. I did notice though that on the tach it read somewhere between 700-1000 RPM while I was cranking. Any idea what's going on here?

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1992 300D OM602

Ben

Curious - I've heard of the torque converter shearing off the drive plate but never the ring gear shearing off the drive plate or the drive plate shearing off the crank. Is there expected resistance when you turn the crank pulley by hand? Does the torque converter turn with the engine when you turn the crank pulley by hand?

Sixto
87 300D

I'll have to look into that. Right now I have to go to work. But just to make sure, is there a way to get to the crankshaft pulley without taking off the radiator fan? Or is there another way to turn the engine manually?
Lastly, I would turn the engine clockwise (standing at the front of the car looking back) right?

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1992 300D OM602

Ben

27mm socket to the center of the crank pulley. If you set a ratchet to 'tighten,' you won't spin the engine the wrong way. I can get a socket and ratchet into place in an '87 300D between fan blades so I imagine you can do it in a 2.5.

Sixto
87 300D

He is getting >700 RPM at the tach so starter is turning the engine over, isn't it? Sounds like lack of fuel or heat (GP's or compression).

Test your battery.

Then test your glow plugs (even though they are new) and test out your glow plug relay.

I suspect the GP relay. It might not be sending 12 volts to all the plugs. Making starting very difficult.

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87' 300DT (Grey w/ red leather)
87' 300TDT (silver w/ palamino tex) SOLD

2012 VW JSW TDI (on tdiclub.com all the time "btcost")

No way will a starter motor spin the engine at >700 rpm. Should be around 150 rpm

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

^X2 on checking the battery.

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[/SIGPIC]~cirrusman

1983 Mercedes Benz 300SD - Wife calls him "Chitty Chitty Bang Bang"
[SIGPIC]




1983 Toyota Tercel (Tommy, The little Toyota that could)
1965 Ford F100 (Grandma Ford)
2005 Toyota Sienna (Elsa, Wife's ride)


Gone:
1988 Toyota Pickup
2004 Subaru Outback

1987 Cadillac Fleetwood Brougham
1986 Volvo 740 GL Station Wagon - Piece of junk.
1981 Volvo 242 DL 2 Door - Hated to see it go. R.I.P.
1987 Pontiac Fiero GT

Well, I honestly can't tell you what's going on. I turned the engine by hand, there's expected resistance and the torque converter turns also. (At the time of writing the first post I had all the glowplugs out for replacement. I also charged the battery for good measure.)
After turning the engine a bit by hand I decided to give it another go with the key. Same results. I could hear the starter turning, and the tach read about 1000 rpm and it wasn't turning the engine.
Then I decide to film it so you guys can see what's going on. I set up my camera, go turn the key again and what do you know, the engine turns over!
I'm still confused as heck, but decide to put the glowplugs back in and try it out again.
After that I try the engine again aaaaaaaannnnndd back to square one. So I decide to set up the camera AGAIN and catch it on camera and wadda ya know! The car starts! Good news? Bad news? I dunno.

Well I jack the car down and one last time decide to try to get video of it. Just in case. And I caught it! It's from my phone camera, so it sounds pretty crappy, but you'll see on my first attempt the starter spins, tach at 1000 rpm, and on the second attempt it actually starts right up.


Starter - YouTube

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1992 300D OM602

Ben

Hmm... maybe the current to the starter is triggering the rpm sensor. Otherwise, my guess is a worn starter solenoid or Bendix gear, hopefully not a worn ring gear.

Sixto
87 300D

you have a flakey starter... change it. the Tach is just an electronic meter. my bet is there is something amiss with the starter, and it's causing the tach issue, as well as the odd start issues... Notice that when the starter engaged the engine, the tach did not spin up...

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

That's interesting, because I just replaced the starter. . . last week. . . With a new one

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1992 300D OM602

Ben

Problem is in your tach. It is picking up noise probably due to bad ground in the tach circuit.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Hi there!
The bendix is a one way clutch on the starter pinion. This lets the starter drive the engine but does not let the engine drive the starter if you keep the key in the start position after the engine has actually started. It will spin the Hell out of the starter pinion gear, but the starter itself is not being driven. These can go bad and start slipping. When this happens the starter motor will spin, but the shaft is just spinning in the bendix clutch and not driving the ring gear. It is very common to "test" a starter and proclaim it "good" because when it is off the car the pinion shoots out to engage and the motor spins. However, since no torque is being placed on the pinion, you can't tell the bendix clutch is bad. Typically, they work intermittantly until rather suddenly, they stop engaging altogether. I had one on an old Ranchero that was so shot that 9 times out of 10 it would just slip, but if I just kept keying it, it would eventually grab and start the engine! Ahhhh, good times!

I know you just replaced the starter, but most starters are remanufactured. The bendix clutch is often NOT replaced during the rebuilding process. I think this is what happend in your case.

I agree with the previous posters that the 1000 rpm tach reading is some sort of electrical noise from the starter "fooling" the tach.

Just change the starter and it should be fine. I hope this helps!
Cheers,
Chris

How did the previous starter fail? Do you still have it?

Sixto
87 300D