3.5v8 starter question

[thermidorthelobster]

Having burnt out the starter solenoid on my 3.5v8 I bought another starter from Brookwells (not much more expensive to get the whole thing than just the solenoid).  Somebody warned me that the alignment / teeth would be different on the SD1 engine I have, from the standard Range Rover / 101 V8, but it looked OK and fits fine.

However, when starting the engine, particularly when cold, the starter usually spins without engaging the pinion for a few times.  After a few goes it engages and everything starts OK.

If it spins freely and I try to turn it over again on the key before it's stopped, I get a grinding noise like it's attempting to engage.

I always thought that these starters worked by the rotation of the shaft pushing the pinion to engage with the engine, but the guy at Brookwells said that the pinion itself is actually engaged by the solenoid - ???  Which is correct?  If he's right then maybe there's enough juice at the solenoid to engage the motor contacts but not the pinion.  But I didn't think the motors worked in this way.

Cheers,
David

[thermidorthelobster]

Duh...  just remembered I still have the old starter, so took a look.

The solenoid does indeed cause the pinion to engage, but then, so does turning the shaft.  So maybe we were both right, assuming they both work the same way.

So it looks like lowish voltage to the solenoid could potentially cause the motor to turn but not be enough to engage the pinion.  Sound feasible?

[MuddyMike]

1.It should be a "pre engage" starter.

2. Check the engine earth, strap poor connections here can cause the starter to be slow to engage. A simple test is to use a decent jump lead from neg terminal of battery direct to a nice clean unpainted bit of engine to back up the earth strap. If this improves starting you have found the problem.

Mike

[Range Rover Blues]

OK if it's a pre-engager then it works like this

The solenoid is made 'live' by a starter relay (on my car at least) and the solenoid earths through the starter motor, so as the gear throws in the motor is turning but slowly and with little power.  This only ensures is engages fully.
As the solenoid hits full throw it then connects the starter to full battery power and starting occurs.  This has affectively shorted out the solenoid so the drive of the motor is all that's holding it in mesh until you release the key.
As the engine fire and over-runs the starter it should throw the starter gear clear of the ring gear, even if it is still running.

[thermidorthelobster]

Thanks for the info.  This seems to make sense.

So can you see how the motor would be getting full power without the solenoid engaging the pinion?  Could it be that the starter motor is wrong for the engine?  I was warned about this but assumed it'd either work or not work, not fall somewhere in between.

[Range Rover Blues]

The bit I forgot to mention, the starter is sticky, so it's spinning up but not throwing in.  Now I had a Cavalier starter go funny and what happened was the arm from the solenoif was plastic and the hook from the soelenoid was pressed steel, with a sharp edge that eventually cut into the arm and made it stick, ON :o

£175 exchange (no, I want a starter, not an new engine) so I stripped it and fettled it and it was fine (still is) for years.

[thermidorthelobster]

Right.  Done some more testing:
- Earthing the engine direct to the battery doesn't help.
- I've also earthed the starter direct to the engine, no difference.

- If I take the starter motor out and try it in the garage, it works fine, every time.  The pinion always engages.
- If I fit the starter to the car, it doesn't always engage.  It's worse when it's cold.
- With the starter in the car, if I jump the exciter lead directly from a separate 12v jump starter battery, it *still* doesn't work.  This leads me to think that it's not the starter wiring causing the problem.

The only pattern is:  if it's in the garage, it works fine.  If it's on the car, it doesn't, even if all other conditions are the same (ie if I use the same battery as in the garage, connected directly to the exciter terminal.

The only thing I can think of is that the starter motor is wrong for the engine.  How do I find out if the starter for the Range Rover 3.5V8 (which is the starter I have) is the same as the starter for the Rover SD1 V8 (which is the engine I have)?

Thanks!