'96 d1 300tdi intermittent not starting.

[dogman]

300tdi, manual, with alarm unit.

One morning recently my d1 wouldn't start.

The starter ran briefly then there was a continuous sort of screeching noise from the engine bay.
I disconnected the battery, noise stopped.

After that the starter wouldn't run at all although I think the solenoid was clicking.
Then the starter ran as normal, once, but never again after that.

After some tests I suspected the starter and took it for testing.
There was a problem with it. Put in a replacement.

Starting is normal for a couple of days then back to nothing happening at all,
which is the current situation. This time I don't think the solenoid is clicking.

As background the truck had existing electrical issues. Indicator intermittently
doing double time, battery not charging, alarm unit causing spontaneous hazard lights,
abs and airbag failing self-test.

I am working through the tests in the electrical troubleshooting manual (ETM)
but so far I'm none the wiser. Time to throw it open to the aulro crowd:
What has been known to cause this type of symptom in a 300tdi d1?

[AK83]

Only because you mentioned "a sort of screeching noise".

Not exactly sure what you describe as a screeching noise, but was it sort of gear not engaging type screech?

What can happen is that the teeth on either the flywheel or the starter can strip, and then cause the unmeshed noise, which is kind'a screeching, but distinctly gear like not engaged type noise.

I would call a slipping fan belt a 'screeching' noise, but worn and unmeshing flywheel/starter gears, to my ears, is more of a high pitched grinding noise.

More to the point: when you have this no start situation, does this screeching/grinding noise happen all the time, or no click from the solenoid at all?

[Tins]

Only because you mentioned "a sort of screeching noise".

Not exactly sure what you describe as a screeching noise, but was it sort of gear not engaging type screech?

What can happen is that the teeth on either the flywheel or the starter can strip, and then cause the unmeshed noise, which is kind'a screeching, but distinctly gear like not engaged type noise.

I would call a slipping fan belt a 'screeching' noise, but worn and unmeshing flywheel/starter gears, to my ears, is more of a high pitched grinding noise.

More to the point: when you have this no start situation, does this screeching/grinding noise happen all the time, or no click from the solenoid at all?

Could be wrong, but I took it as two seperate issues, firstly a failing starter which was replaced ( the screech ), and secondly a non related electrical issue, possibly conflated by the OP.

[loanrangie]

Check the earth straps for corrosion/ looseness.

[dogman]

Could be wrong, but I took it as two seperate issues, firstly a failing starter which was replaced ( the screech ), and secondly a non related electrical issue, possibly conflated by the OP.

Yes definitely two separate problems. When I took the starter in to the shop it was for elimination. When they said it had failed I still didn't assume that was necessary the whole problem but I need a working starter regardless, hence the replacement. The other problem seems to be intermittent - it just happened not to be manifesting when I replaced the starter, setting me up for a letdown later.

@ak83 Yes, using words to describe noises is pretty subjective. I probably wouldn't describe it as "gear not engaging". The auto sparky at the shop said the brush end of the starter was ok, but some other part of it had melted. I wonder if the melting and "screeching" were related.

In section B1 of the ETM (starting and charging), test A is all done on the starter solenoid relay. There are 5 parts to the test. My truck failed parts 2,4 and 5. In part 4 you connect pins 30 and 87 with a fused wire. It is supposed to run the starter but in my case it blew a 10 amp fuse and with a 30 amp fuse I just got sparks. The shop guy suggested this indicates a short between the relay and starter. He also said I could just bypass the relay completely. To run the starter only requires that current be applied to the spade connector on the solenoid. I made the bypass and it works perfectly so I'm back on the road while I continue to investigate, What is the relay even for?

[Tins]

In part 4 you connect pins 30 and 87 with a fused wire. It is supposed to run the starter but in my case it blew a 10 amp fuse and with a 30 amp fuse I just got sparks. The shop guy suggested this indicates a short between the relay and starter. He also said I could just bypass the relay completely.

Spot on. The wiring can, if it has been disturbed, run close to the turbo or manifold, or it could be pinched somewhere. What that test has done is eliminate the relay as the cause of the fault, but the short elsewhere could have damaged the relay anyway.


To run the starter only requires that current be applied to the spade connector on the solenoid. I made the bypass and it works perfectly so I'm back on the road while I continue to investigate, What is the relay even for?

The relay is to eliminate voltage drop to the solenoid coils, and more importantly to eliminate unnecessary current loads to the ignition switch. If you continue to use the car in its bypassed state the ignition switch contacts will likely fail at some point. I doubt that your "shop guy" would recommend the bypass as a permanent solution.