No start due to heatsoak

[Arno]

A new no-start occurrence with my LJ70 TD2.4 this week, this time one that took a while to resolve.

Earlier this month I had a bad starter relay, See here;

Now a totally different No-Start situation.....

The engine was hot - it simply didn't start after 30 mins after turning it off.
This time manually pressing the starter relay or bridging the leads of the starter relay on the other end didn't help.

After several voltage drop tests, it seemed not enough voltage arrived at the starter lead of the startermotor.
A direct connection to the starter lead from the New battery didn't work as well.
It just sparked a little when connecting - the spark seemed way too small to get the solonoid going.

At some point during testing the starter motor started clicking, though sounded like the bendix hitting the tooth of the flywheel. (no turn) The clicking also sounded too weak.

It just couldn't be - the starter motor from Niparts is just 6 month old.
Burned plunger contacts so quickly seemed very unlikely!

At some point after 20 mins of testing, measuring the problem resolved itself......
Engine started normal, situation couldn't be reproduced.

With no-starts when the engine is hot got me on the trail of HeatSoak.
The engine always starts when cold, never ever one miss.

Heat has the effect of adding more resistance to already bad contacts or leads.
High amps, more resistance on bad contacts / leads causes voltage drop and even more (electrical) heat on already bad spots.

This got me thinking about the earth lead connecting the engine to the minus of the battery.

The cable looked OK upto the point where it was bolted to the engine.
Loosing the connection plate showed considerably corrosion on both sides of the plate including a bolt with rusted threads. The flat connection spot at the engine also was rusty.
Could this be it?

With the cleaned earth connection plate, the show goes on.....
When the situation occurs again, I'll measure the voltage drop over the earth lead

Cheers
Arno

 

[Ben]

It will be interesting to see if that was it and you've fixed it.

 

[Arno]

One things that's noticeable after a few days;

The starter motor sounds like there's more energy, turning the engine just a bit more faster.

Although it's a subtle difference in starting sound, it's especially noticeable during the first cold start.

Let's see!