Hot Start Relay Problem...?
 

Back in October 2013 I installed one of the Pelican "hot start relay" kits on my '74 2L. Easy to install, worked great.

However, for the last couple months I've noticed a very-slight delay between when I move the key to the start position and when the starter turns over. It's almost imperceptible, maybe half a second? Wasn't getting worse, so it didn't bother.

However, tonight...the car would not turn over. Not a solenoid click I could hear, nothing. Only thing I notice when I put the key to the start position was the fuel pump coming on. I bumped the car with it in gear, tried it again, nothing. Lights are not dimming, not action from the starter. Voltage gauge shows "normal" 12-ish volts.

I got a couple guys in the parking lot to give me a quick push start and it started right away, drive home was normal with normal voltage, got it home in the driveway and tried the starter again...nothing. Battery voltage with my VOM is 12.75V.

So I'm going to get under it with a test light and check for operation of everything, but are there any known issues with either the hot start relay or the starter that fit these symptoms...?

Thanks,

GA

Bad ignition switch? I replaced mine about a year ago with one of the cheap replacements, and I currently have symptoms similar to yours - slight, but noticeable delay before it cranks. Or it may be that I just have to turn the key to the exact right position before the circuit is closed. Its' one or the other. I installed hot start relay a month or two ago, but it can't fix a crappy quality ignition switch.

Otherwise, it could be tranny ground strap or actual bad solenoid, but my guess is ignition switch.

Over the years I found that 75% of electrical gremlins can be traced to a bad ground connection.

So to rule these out, clean both ends of the battery ground and clean both ends of the engine ground strap.

Yeah, I'll check the wiring, but I don't think that's it. The car came with the battery flopped into the trunk - prior owner had the hellhole replaced and didn't re-install the battery tray - so I installed a tray and Miata battery in the rear trunk, and replaced all the big wires. New hot wires from battery to starter, new big ground wire from battery directly to the ground point on the chassis above the trans (both wires through grommets in the floor), new chassis-to-trans wire strap, and clean connections with wire grease all around. I'll re-check all that anyway, of course. And a screwdriver from underneath shorting the solenoid will give me a quick check if the starter is working.

The ignition switch...well, that's certainly suspect. The car uses a VW ignition key - and, I'm sure, a VW lock cylinder - but I've not pulled it apart to check the condition of the switch itself. I think karma may have bit me on this one, because I was thinking last night right before I got into the car that I'd like to replace the lock cylinder with a Porsche one so I could use the same key for the ignition and trunk lock...so as long as I'm going in there I may as well replace the switch, see what happens.

40-yr-old cars. Fun is.

GA

Just a warning: Some of the ignition switches that are currently available aren't the most robust. We've heard tales of them starting to fail after a few months. Not sure if they're the ones that we supply, or a cheaper brand... :(

--DD

Ugh.

And the answer is...blown fuse in the hot start relay kit. Replaced fuse, turns right over without noticeable delay.

Now to wonder why the starter (edit: solenoid) is pulling more than 15A...are the wires in this kit big enough for that starter?

I like this system and have used it before..however it can mask other issues in the system,starter ,connections/cables etc.
FYI your starter may just require a strip down and clean,generally very robust units.
Yes the ignition switches do go and have only just found that myself....working ,not working !!!!!!!!,really drives you nuts.

The majority of wear in an ignition switch is in the crank position. If there's a "hot-start" relay installed, energize it with a separate momentary ON switch. Use the ignition switch in the ON position to energize the ignition system and other ancillary circuits.

Starter motors require many amps of electrical current. Could be 100A or more depending on engine configuration, condition of starter, resistance in starter circuit, ground connections, etc.

Starter Motor. Amps? | Electronics Forum (Circuits, Projects and Microcontrollers)

Sherwood

Thanks, Sherwood. No need to mod for separate switch; spending a couple hours every 20 years to replace the stock switch for wear isn't that hateful.

And the fused circuit on the "hot start" relay isn't seeing the cranking amps; that's coming directly from the battery cable. That relayed circuit is just energizing the starter solenoid.

GA

Ignition switch is probably different from early 911s which are either NLA or $450+ to replace. In this case, extending service life via a separate "crank" switch is preferable.

Sherwood

Thanks Sherwood. Yeah, they're different parts: the 914 uses a $20 VW ignition switch.

Well the -4 does. No idea what the -6 uses.