Intermittent no crank

[Justwatching]

I've got an intermittent no start-no crank situation. I say intermittent, but it's becoming regular. 

I turn the key, dash lights come on, "click" but no crank. Sometimes the fuel pump doesn't prime either. It starts after a few attempts, cycling on and off. Sometimes it will suddenly start if I just hold the key in the crank position and wait for several seconds. Not sure if it's a red herring, but the tachometer sometimes gives false readings for a while after start up. Only seems to happen following the no-crank situation. 


The battery is in a good state of charge and I gave the terminals a once over with wire wool, but no improvement. At this point my thinking is a switch/relay of some description, bad ground, or the starter itself (in that order). I'm still not very familiar with DeLoreans though, so inputs gratefully received.

[Rissy]

Have you tried swapping out the starter relay in the engine bay (on the bulkhead framework on the rear-left-hand-side)? Almost sounds like that's sticking.

The other potential culprit might be the actual start inhibit relay in the fuse box compartment. That's what feeds the starter motor. If it's not cranking at all, until after some time, then maybe that's sticking on supplying power to the starter motor?

Both are standard 87b 12V automotive relays.

Try those first and see if you get a different result. You may have to whip out the multimeter to determine volts through the circuits related to those too if it's not the relays themselves.

If you exhaust those and still have the problem, let us know and we'll suggest something else.

Good luck.

[Chris Williams]

All good suggestions above, have you checked the connections to your starter and main ground cables?

[Justwatching]

Update: I ended up ordering a set of relays and fuses - preventative maintenance for the relays and just to have spares on hand for the fuses. Found a slight mess in the fuse/relay area though. Let's start with the melted fuse box. The positions for fuses 1 and 7 are gone. By the look of it, they've been replaced by a fused wire arrangement, one of which has also melted. Deep joy!

   

   

Can anyone help with identification so I'm not guessing which fused wire corresponds to which position in the fuse box? Hopefully, the colour of the original wires will help. 

We've got brown wires going to the fuse that has melted.

   

One green and one white wire going to the other fuse. 

   

[Rissy]

Yeah.

Position 1: Green in one side and White out the other. Green is the slave side of the fuse. White is the Source. Green wire to the outside of the fuse box.
Position 7: Brown in one side and Brown out the other. Brown next to Position 1 is the slave side of the fuse. The source brown is next to Position 13.

For Position 7, you can determine which Brown is which by belling out with your multi meter between the fuse end and Terminal 30 on the RPM relay plug (as an example). If it Bells out, then its the slave. The source side should bell out direct to your Positive battery lead as its a permanently LIVE feed (with the battery connected of course).

[Justwatching]

(28 Jan 2022, 16:27)Rissy Wrote: Position 7: Brown in one side and Brown out the other.  

The two brown wires came from fuse No. 7? Right, they put the wrong fuse in it then as it had a melted 10 amp, not a 20 amp. They also put an incorrect fuse in No. 1 as well (15 amp instead of 10).

I've replaced the starter relay in the engine bay and the starter inhibit relay in the fuse box compartment. Also replaced the RPM/fuel pump relay for good measure. No cigar. Cleaned up the starter motor connections next (even though they looked fine). Again, no improvement. 

Any thoughts on where to go next? I can try tapping the starter with a hammer next time it refuses to start, see if that produces any results.

[acmetowers]

If you say the battery is good (keeps voltage above 11v when cranking) and all the contacts have been cleaned, I'd say it's the starter solenoid next. I've had the same issue in other cars where the contacts have become dirty so that when you start the car you hear the click of the solenoid pulling out the drive but it does not engage the electric motor. Some starters you can pull the solenoid apart and clean the contacts but not sure if the one on our cars capable of this.

[Justwatching]

I wired in a new fuse connector to fix melting damage. It seems to be starting first turn of the key, so tentatively case closed. I've noticed the fuel pump doesn't prime anymore though. Bit confused by that. It still starts and runs, so I'm not overly worried.

[Chris Williams]

Quote:Bit confused by that. It still starts and runs, so I'm not overly worried.

Sometimes they do, sometimes they dont.

[Justwatching]

Back to not cranking again. Gave the starter some love taps with large spanner and it turned over, so suspicion is on the starter now.

[Justwatching]

Just to conclude this thread, it was the starter motor at fault.