DNS came back today

[mlipmd]

It's been 6 weeks since I did the extra relay mod to power my starter relay from a 12V hot wire coming directly from the battery instead of going through the CSS, energizing the new relay from the ignition starter switch as suggested, to eliminate the dreaded DNS issue.
This has worked flawlessly for 6 weeks but today after about an 18 mile 1/2 hr. ride into town, then coming back to the car 1/2 hr. later, it would not start, the ignition circuit totally dead. After waiting another 1/2 hr-45 min, apparently for all that's underhood to cool off a bit, it started up immediately and ran perfectly all the way home. When I got home and shut it off, it was immediately able to be restarted.
What causes this DNS, just the heat underneath the hood? Is my starter relay the problem? The starter does not make any funny noises and once energized, seems to work fine and starts the car in a second or two at the most.
Where so I look to solve this now?
Anyone else experience this even after doing that added relay mod to convert their car to the later starting circuitry?

[HAWAIIZR-1]

Sorry I do not have a solution other than recommend you send Marc Haibeck from zr1specialist.com your question and support him with some business. He will probably know the solution.


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[secondchance]

Condition you are describing is most likely caused by solenoid contacts and plunger.

[mlipmd]

By solenoid, you mean the regular starter solenoid? That would give an intermittent no crank?
What about the possibility of a bad or dirty ignition switch? Or VATS problem?

[secondchance]

Similar condition I had was caused by starter solenoid contacts.
http://www.zr1.net/forum/showthread.php?t=27965&highlight=Starter+rebuild

[ZR1North]

I had the same issue - DNS weeks after the relay mod. Starter replacement solved the problem. It has to be ten years problem free now. I bought a rebuilt starter from Marc Haibeck. The replacement starter uses components that address the original flaws.


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[secondchance]

The fact that, when cold, starter runs with no unusual noise leads me to believe the issue is with solenoid contacts.

[Paul Workman]

By solenoid, you mean the regular starter solenoid? That would give an intermittent no crank?
What about the possibility of a bad or dirty ignition switch? Or VATS problem?

secondchance is correct. there are a pair of contacts in the starter connected by a copper surfaced ring. The contacts (Denso kits) are cheap enough - about $10 for the kit w/ the contacts alone. And, with a piece of emery cloth you can polish up the bridge "ring" to remove all the pitting it collects over time.

Some Denso kits include a new armature/pin assembly as well as new contacts. More money of course, but there can be an issue if the plunger pin is shorter (or longer) that the stock pin. It is very important to be sure that pin is the same length as the stock plunger OR severe damage to the ring gear on the flywheel or the pinion on the starter (or both) might occur. So, a little piece of emery cloth to polish up that copper ring is A LOT cheaper than replacing the armature with one whose pin is short/long.

Your symptoms are exactly what I experienced too. Temperature seemed to affect the DNS issue UNTIL I cleaned up that "ring" and replaced the contacts. I bypassed the CSS too (as I learned on the farm when starting the Farmall tractor, CLUTCH IN ALWAYS before starter switch!)

Now, all this (above) is true, but it would be negligence on my part if I didn't mention one other check you need to run. And, that is, turn on the lights when experiencing the DNS and see when you hear the starter "CLICK" that the lights dim slightly. OR, you can hook a VOM to the battery POS terminal and see if the voltage dips (indicating significant current draw) when you turn the starter switch to START.

If you hear the starter "CLICK" and the lights dim slightly and the voltage drops slightly too, but the starter does not turn, then the starter itself may be bad.

So, since it doesn't cost you anything to try this, I would suggest your try this first. (The key is the lights dimming and the voltage dropping a tad = the solenoid in the starter is working, but the starter itself is not working.)

In the 13 years of monitoring this forum (and the other one) I'd have to say the vast majority of the DNS issues are the CSS in the 90-92s. And, almost equally common is those (high current) contacts in the starter itself. But, very few end up being a bad starter, or something else (comparatively speaking).

FWIW, I had to overhaul those starter contacts at the 40k? mile point.

[Young1]

Solenoid contacts get burnt. IMO it is a 40k mile ritual to shine them up. The solenoid itself is 30 bucks on Rock Auto if you wish to replace. Anytime the plenum is off, shine the contacts.