Car won't crank intermittently

[rcfanatic]

check the solenoid control signal with a meter to see that system voltage is being applied to the starter solenoid when it misbehaves.

The fact that the solenoid clicks implies that system voltage is getting there right?

I found the starting schematic in Bentley and it looks like the problem must be a faulty solenoid switch or if system power is getting to the starter via the field winding strap, then something internal to the starter is bad. Since they are sold as one unit, I must just need to replace it.

The only other thing is that I don't believe I have the load reduction relay hooked up. I just have alternator and battery cables on one post and the c101 black/yellow wire on the other post

My car is an 86 with motronic 1.3 conversion, and the late model (smaller) starter. Even though my fuse box has all of the relays populated, according to Bently only 1988+ came with load reduction.

Anyway, could load reduction play a role in this problem?

[jlevie]

The unloader relays in this car are engaged anytime the ignition is on (always loaded). They have nothing to do with operation of starter on early or late cars.

[rcfanatic]

They have nothing to do with operation of starter on early or late cars.

Why is there a wire leading from the starter to the load reduction relays in the Bentley schematic? Page 15-21

Still haven't had a chance to check voltage at solenoid/starter terminals, due to intermittent nature of the problem and requiring an extra person to hold key in start position

[jlevie]

On cars built from 9/87 on, the unloader relays are controlled by a switch in the starter solenoid. That switch grounds the relay coils to engage the relays when the starter isn't being used. When the starter is operating the switch is open, removing the loads controlled by the unloader coils.

[rcfanatic]

I'm starting to think the starter solenoid is the problem. 3 for 3 times now I've been able to get it to crank by tapping the solenoid with a breaker bar and dead blow hammer.

However, I recently noticed that my temp gauge shoots up when I turn the lights on and falls again with the lights off. Reading some posts it looks like this may be a ground issue or voltage regulator issue.

Is it possible that the two problems (starter and temp gauge) are linked to the same culprit?


Edit: Make that 3/4 times tapping has worked. Getting stranded all the time sucks!!

[jlevie]

I don't see how the temp gauge problem could be related to the starter problem. It sounds like you need to replace the starter. Then diagnose the temp gauge problem.

[Exodus_2pt0]

If your temp gauge is acting erratically, my bet is the ground strap from the oil pan to the body.

I had an intermittent no start as well as temp gauge acting odd. Replaced the ground strap and it's all good.

It will cost $5.

[rcfanatic]

I don't see how the temp gauge problem could be related to the starter problem. It sounds like you need to replace the starter. Then diagnose the temp gauge problem.

I was thinking more along the lines of a faulty ground causing both problems

[jlevie]

A bad engine to frame ground would cause starting problems, but tapping on the starter would be unlikely to affect that. You can remove and clean the ground strap and its attachment points. That part is from the forward left side of the engine to the frame.

There is a ground point for the cluster on the firewall just above the pedal box near where the steering column passes through the firewall into the engine bay.

One thing to check would be the see what the system voltage does when you turn on the headlights. Use a DMM. If the alternator is working properly you should see ~13.5v at idle, rising to about 14v at 2500rpm. Loading the system with the headlights should not appreciably affect those readings. but if the brushes in the alternator are worn you may see a significant drop. But that is easy & cheap to fix by replacing the regulator/brush assembly.

[Exodus_2pt0]

Also a good idea to do a voltage drop test across theground strap. Set your multimeter to dc volts, positive on the engine side of the ground and negative on the body side. Turn the key to start, the higherthe voltage reading you get the more resistance there is within the ground strap.

[paperplane94]

You can also do an easy test and connect a jumper cable from the engine hoist loop to the battery, just for giggles of course.

[rcfanatic]

A bad engine to frame ground would cause starting problems

I cleaned this ground strap really well with a file and haven't had any starting problems for a week. The coolant temp now runs a half tick below center at steady state.

First time I checked this ground I only felt to see that it was securely attached, but the second time I removed it and there was a fair amount of dirt and corrosion.

Problem solved! Thanks guys

[Nutzy]

Sorry to hijack a thread, but I have an intermittent no crank issue as well. I have only seen this rear up when the car is heat soaked. Such as the other day I was first in line waiting for the ferry at Berowra. I joked that it may not start due to extended idling in the heat, and I jinxed myself.

The solenoid makes no click, there is no attempt to do anything. Without doing anything else, a screwdriver shorted from the B+ on the solenoid to the solenoid engage pin produces an instant crank. So, the problem appears to be further up.

Looking at the wiring chart, the circuit seems simple enough. Do our ignition switches take a shit often??