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Location of starter relay?

25K views 12 replies 6 participants last post by  c900 
#1 ·
Hi;

I have a 1990 Turbo 16 Aero Cab that has an intermittent problem in that when you turn the key, the starter solenoid doesn't fire up and spin the engine over. This happens more often when you've gone for a drive and get the engine hot, park it, then say want to start after 10 minutes or so. If you wait until the engine cools down, then the motor will fire.

There's nothing wrong with the starter motor or solenoid because it will quite readily fire up when you put a screwdriver blade across the terminals of the starter motor/solenoid (and it still won't work from the ignition switch). It's not the ignition switch as I've already replaced that. The battery is new.

I have noticed that on occasions (night), turning the headlights off whilst the key is on "start" will immediately fire up the engine, so it looks to me like the starter relay isn't contacting because the coil voltage is too low for it to pull in. So I'm thinking, replace the starter relay. Simple!

Problem is, there's no relay shown in any schematics I've seen, and I can't find any relay either in the engine bay, under the dash, or under the rear seat.

So... does this vehicle actually have a starter relay, and if it does, where is it???
 
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#4 ·
Starter problem

The contacts in your starter solenoid get burned over time and cause intermittent starting problems. When the solenoid closes, you get no current transfer from burned contacts. You can remove the starter and replace the solenoid for about $35. This is the most common type of starter failure on older cars.
 
#6 ·
The contacts in your starter solenoid get burned over time and cause intermittent starting problems. When the solenoid closes, you get no current transfer from burned contacts. You can remove the starter and replace the solenoid for about $35. This is the most common type of starter failure on older cars.
Or, the Commutator on the motor itself makes poor contact, with exactly the same results. There's no simple way to determine which one is causing an intermittent problem. If you want to do the job just once, after you determine that you're getting a proper signal at the yellow #50 terminal, replace the assembly.
 
#5 ·
I had the same problem on mine two years ago. Replaced the starter motor.

Slightly tricky on a 16V turbo with automatic transmission:
You have to "dremel" a cut in the plastic cover to get access to the starter motor nut. You need a slim, ratched? key to get it loose. Two front bolts and then the rear bracket bolt. When it is loose you have to think to manouver the starter down and out. Memorize your manouver for the refit :)

I removed some tubes in front for better access as I did a "hooter" valve replacement at the same time.

Knut
 
#7 ·
Thanks for the responses - I don't think that there's anything wrong with the starter itself because as I stated, you can reliably start the motor any time by shorting the terminals, so I'm thinking the juice to the solenoid is lacking. Problem is whenever it does it, I'm out on the road somewhere and without a meter to measure with!

So I take it that there is no starter solenoid relay in these things.
 
#10 ·
That's a smart move - I've carried one in my toolkit for a few years. I probably have much more tool-wise in my car than is required as I have three of the small steel army ammunition boxes loaded with tools at all times in the car - one with normal tools - one with spanners/sockets - and one with small tools and electrical gizmos. Where I live at present requires a good level of self-sufficiency as there's no mechanic anywhere around here.

Re the starter relay - they were never as far as I know a standard thing - the starter motor solenoid is wired up directly from the 'terminal 50' contact of the ignition switch between the seats. Lots of people do fit an auxilliary relay usually somewhere in the engine bay so it can connect directly between the positive terminal on the battery and the starter motor solenoid avoiding all the wiring joins and long run from the ignition switch to the solenoid.

Craig.
 
#11 ·
If your car is an automatic, a worn safety switch at the shifter can totally cause strangeness like this... you could also try supplying 12v to the yellow wire at your ignition switch in the center console--I think the supply wire to the ignition switch is grey, but it's been a while since I've been in there... it's the fat one...
 
#13 ·
It probably will be. I have a VDO voltmeter displaying the voltage fed up to the gear inside the dash and it displays just over 12 volts when the alternator is putting 13.5 out to the battery, so that's quite a bit of voltage drop. Also check that the crimped-on terminal connecting the yellow wire to the spade lug on the solenoid isn't loose - you might need to carefully squeeze the part that slides onto the solenoid lug with some pliers to make the metal-to-metal contact more reliable.

I've discussed re-working the battery and alternator wiring in my car here a little while back since the very early year cars have quite a different wiring setup for the battery positive cabling (with starter on exhaust manifold side) compared to the later year ones (with starter on intake manifold side), and one of the main things was that the voltage drop with the power to solenoid going from the battery via multiple wiring joins, ignition switch, etc. is going to have a fair bit of voltage drop.

Usually when I turn on the ignition to start the car, the voltmeter shows an internal voltage of well under 12 (generally about 11 - I get about 12.5 on the batt terminals). I know the battery is a good one (Odyssey PC925) so it's excellent for cranking. Just the power to the solenoid itself is quite sub-standard with all the 'hoops' it goes through esp. in the earlier cars such as mine. The issue with my car's starter is that the solenoid sticks (ie. can't start the car) if the engine block temp is above 95 C, and that's what led to the discussion about low voltage presented to the solenoid via the ignition switch. Basically needs an aux relay fitted along with pulling the starter to replace the solenoid or fit a different starter. I've got a working replacement starter (Aussie-made Bosch 9 000 063 054 actually salvaged from an 82 turbo 8V sedan) to go in if/when I have the inspiration. :cool:

Craig.
 
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