Electrical System Question

[vonshavingcream]

Trying to help my dad get his delorean running again. He tried to start it the other day and no go.

Just clicks when you try to start it. We thought it was the starter at first,

but upon further testing we have discovered it is the start inhibit relay (105 on the wiring diagram)

We ended up jumping the starter to get the car running and pulled into the garage for working on it.

I was just wondering if anyone has any experience with this problem.

Thanks,
C

[Bitsyncmaster]

Whats your VIN? The early cars need a modification on the start inhibit relay.

[David T]

It is also important to know if the car in question is an automatic or a 5-speed. On the 5-speed the start inhibit relay is bypassed in the wiring harness. On the automatic the relay is used. If you do have an automatic, check the wiring to the shift computer under the car. If it is not secured properly the wiring gets burned on the hot exhaust pipes and can cause this problem.
David Teitelbaum

[stevedmc]

I was having starter problems myself. It used to fail about 10 percent of the time. I got a new starter (cross referenced to an eagle premier starter) and things were fine until about 4 months ago when it began having problems again but not nearly as frequent as before. I replaced the starter relay and continued to have the same problem.

The problem went away after upgrading my AC circuit breaker from 25A to 30A. I didn't expect this to fix my problem but while doing this I noticed a line running from this circuit breaker to the starter. Perhaps you have an old circuit breaker that needs to be replaced. They only cost $3 and are available at autozone.

[Bitsyncmaster]

The problem went away after upgrading my AC circuit breaker from 25A to 30A. I didn't expect this to fix my problem but while doing this I noticed a line running from this circuit breaker to the starter. Perhaps you have an old circuit breaker that needs to be replaced. They only cost $3 and are available at autozone.

That wire to the start inhibit (used as a starter relay on all cars) is part of the modification that is done on all cars. So a faulty breaker could cause the starter problem depending if it was on the output side of the breaker. My guess is that wire should be on the input side (not circuit protected).

Good find Steve. We will have to remember this start problem. I will have to check my wiring and see it that wire is on the correct pin of the breaker.

By the way, that breaker is for the blower fan speeds 3 and 4. So you probably only had the problem if you started the car with the fan on speed 3 or 4.

[DCUK Martin]

http://dmcnews.com/bulletins/ST-05-2.82.html

[Bitsyncmaster]

http://dmcnews.com/bulletins/ST-05-2.82.html

Yes it says connect to the battery side. But I bet those wires can be switched by someone not knowing they are not interchangeable. I think I may pull the battery wires and install a ring terminal so they won't accidentally be switched.

Edit:
I wonder if this was "JIMJAMs" (old forum member) problem that plagued him for so long. I always try to switch may AC and fans to off before I shut the engine down but I know a few times I have forgotten. Fan speed #4 draws 23 amps (from what I remember), add to the starter solenoid current and "BAM". You would have to wait till the circuit breaker resets.

[content22207]

How much amperage can a simple starter solenoid draw? Why run it through a relay in the first place? All of my vehicles (ie: all of my vintage vehicles) have solenoids attached directly to the start switch and they have started just fine for thirty years or more (solenoids themselves have died, usually from arcing eating away the high amperage contacts, but the starter switches themselves are all still original).

Bill Robertson
#5939

[Bitsyncmaster]

How much amperage can a simple starter solenoid draw? Why run it through a relay in the first place? All of my vehicles (ie: all of my vintage vehicles) have solenoids attached directly to the start switch and they have started just fine for thirty years or more (solenoids themselves have died, usually from arcing eating away the high amperage contacts, but the starter switches themselves are all still original).

Bill Robertson
#5939

I have not measured it but my guess would be 10 amps.

[DCUK Martin]

I had the problem in #1458 which had never been updated. Bill, your starter solenoids are usually much closer to the start switch than on the DeLorean and knowing you is probably connected with a 2" bus bar... :angry:

The original wiring has the solenoid drawing directly from the ignition switch. The presence of the start inhibit relay is for automatics and only on 5-speeds for the sake of manufacturing simplicity. Some early 5-speeds also have the gear surround illumination bulb holder present, FWIW.

However it made for a very simple modification when it was realised that the wiring, and probably the ignition switch itself, were causing enugh of a drop that with a moderately low battery, there wasn't enough current to properly fire the starter solenoid with the wiring running from battery to igniton switch and back to the engine bay. You just get a click.

The extra pin on the fan circuit breaker should be fed by a heavy gauge wire directly from the 12v stud underneath the coil.

[content22207]

Just to trigger a solenoid? Even though I've got 1,001 things to do today, I do believe this warrants attaching a meter to #5939 to find out....

Bill Robertson
#5939

[Bitsyncmaster]

Just to trigger a solenoid? Even though I've got 1,001 things to do today, I do believe this warrants attaching a meter to #5939 to find out....

Bill Robertson
#5939

It's not a "trigger" It has to magnetly pull the starter gear into the ring gear, overcome the return spring and make solid contact with the starter motor contacts.

[content22207]

Forgot that I had a trigger wire in my engine compartment. A Paris Rhone solenoid draws 5-6 amps (fluctuates).

Bill Robertson
#5939

[DCUK Martin]

Well that makes for a nice easy 2 ohm impedance then. Consider the wiring from battery to ignition switch and back again, it's not difficult to imagine a drop of similar magnitude, creating a potential divider and halving the available power at the solenoid..... Ohm's law innit :D (I miss the "mrgreen" smiley!)

[David T]

There is a relay between the start switch and the starter solenoid so you can't energize the starter unless the transmission is in Park or Neutral on the automatics. Has nothing to do with overloading the starter switch. The starter solenoid does draw a considerable amount of power though hence the need for the wiring service bulletin. When the starter is operating it reduces the battery voltage and you need all you can get for the solenoid while the starter is operating. The starter solenoid is more than just a relay. it moves the bendix of the starter into contact with the flywheel. While it does that it closes a set of contacts to allow electric to flow to the starter motor and it also energizes a wire to bypass 1/2 of the ballast resister in the ignition circuit to get more power into the ignition coil. Meanwhile the cold start circuit is giving an extra shot of fuel to the motor. A lot going on during the starting cycle if it is all working the way it should!
David Teitelbaum

[Ron]

FWIW:
The average amp draw for an automotive starter solenoid is ~25-35 Amps (for ~500 milliseconds) to engage and <12 Amps to hold. (These are values shown to be acceptable on a Crumbliss Tester for starter mounted solenoids.)
If you want to measure yours to know exactly what it is for a D, keep in mind many solenoids actually have two windings, with one grounded through the starter....

[Bitsyncmaster]

There is a relay between the start switch and the starter solenoid so you can't energize the starter unless the transmission is in Park or Neutral on the automatics. Has nothing to do with overloading the starter switch. The starter solenoid does draw a considerable amount of power though hence the need for the wiring service bulletin. When the starter is operating it reduces the battery voltage and you need all you can get for the solenoid while the starter is operating. The starter solenoid is more than just a relay. it moves the bendix of the starter into contact with the flywheel. While it does that it closes a set of contacts to allow electric to flow to the starter motor and it also energizes a wire to bypass 1/2 of the ballast resister in the ignition circuit to get more power into the ignition coil. Meanwhile the cold start circuit is giving an extra shot of fuel to the motor. A lot going on during the starting cycle if it is all working the way it should!
David Teitelbaum

I disagree unless your taking about the early cars not with the wiring modification.

The original wiring powered the starter solenoid directly from the key switch contacts. Now with the correct wiring, the key switch only power the relay called "start inhibit". But that relay now powers the solenoid on all cars, auto or 5 speed. Pull your start inhibit relay and see if your 5 speed will even turn over.

[content22207]

That relay is totally useless on a 5 speed (missing neutral safety switch is jumped at the bulkhead connectors). IMHO all it is is a failure point waiting to happen. You'd be just as well off jumping the relay too.

(Relays do go bad BTW: I lost my exterior light relay when leaving Justin's last soiree).

Bill Robertson
#5939

[DCUK Martin]

FFS Bill :angry:

The system as originally designed uses the start inhibit relay to inhibit the starter (fancy that) if an auto tranny isn't in park. On the 5-speeds it was indeed pointless.

However, with the update, it performs an extremely useful task on either transmission, that of off-loading the starter solenoid from the ignition switch, in addition to still inhibiting the starter if an auto tranny isn't in park.

[content22207]

Cheap starter switch.

(As already noted, vintage domestics are wired directly from the switch to the solenoid).

Bill Robertson
#5939

[JIMJAM]

Ok JIMJAM is back and I see some familiar names and the sos.

Ive been posting at dmctalk but just switched here seeing Ive always had this issue. However anyone wanna explain why mine, vin 1597 manual only has this issue when its really hot outside and the car is at normal temp?
Winter or cool I can drive for hours, starts right up. Come summer, like today, 95 and in the sun, turn the key and nothing. No starter,no turn over, nothing. As long as its in the sun, this issue remains and it takes 3-5 or so tries but it ALWAYS starts. I park the car in the shade and let it cool, turn the key and it fires right up.
So its a definite connection betreen the heat and the dead key. Something is getting hot and the outside temp aggrevates it. Add the sun and its maybe 50/50 or worse.

[DCUK Martin]

If you mean the ignition switch is of lower-than-ideal quality, I'd agree. This is true of a fair bit of the electrics. I don't think you'll find many modern cars whose starter solenoid is wired directly through the ignition switch though, for the previous reason already stated (ohm's law/large current).

[Farrar]

Jimjam, have you tried replacing that circuit breaker? Could be it's going bad and opening at a lower temp than it should. That's a shot in the dark, but I thought I'd try to help.

Farrar

[stevedmc]

Jimjam, have you tried replacing that circuit breaker? Could be it's going bad and opening at a lower temp than it should. That's a shot in the dark, but I thought I'd try to help.

Farrar

Not a bad idea. It will take less than 5 minutes to install a new one and it is only a $3 part at autozone. It definately wouldn't hurt to try and see if it will get your door unlocked. I'm still a big fan of not having power locks though.

[content22207]

If you mean the ignition switch is of lower-than-ideal quality, I'd agree. This is true of a fair bit of the electrics. I don't think you'll find many modern cars whose starter solenoid is wired directly through the ignition switch though, for the previous reason already stated (ohm's law/large current).

Too bad JZD never worked for Ford Motor Company (or maybe not...). It's a much simpler circuit:
778
(The "Relay" in this diagram is actually a large industrial solenoid with 5/16" ring studs, mounted to the inside of the fender -- if necessary you can start your vehicle with any piece of metal handy).

Bill Robertson
#5939

[Bitsyncmaster]

Too bad JZD never worked for Ford Motor Company (or maybe not...). It's a much simpler circuit:
778
(The "Relay" in this diagram is actually a large industrial solenoid with 5/16" ring studs, mounted to the inside of the fender -- if necessary you can start your vehicle with any piece of metal handy).

Bill Robertson
#5939

That's not really a solenoid but a relay. The solenoid on the D or any chevy has to do a lot of mechanical moving of parts and will draw much more power than those ford relays.

[content22207]

Whatever you want to call it, it is a much better design than what Hethel came up with.

They do arc like hell inside, eventually eating up the brass contacts, but you can drill out the pop rivets that hold the housing together and flip the contacts over to get another gazillion starting cycles.

Bill Robertson
#5939

[Bitsyncmaster]

Whatever you want to call it, it is a much better design than what Hethel came up with.

They do arc like hell inside, eventually eating up the brass contacts, but you can drill out the pop rivets that hold the housing together and flip the contacts over to get another gazillion starting cycles.

Bill Robertson
#5939

I've done that before (open and fix them). They get eaten up because those contacts drive the starter (150 amps). The Ford starters engage the gear with ring gear by the centrifugal force of the starter spinning. Those gears would sometimes not engage or not release when the grease got dirty.

[Bitsyncmaster]

Here are the before and after (ring terminals). Only bad thing about the ring terminal is you have exposed +12 volts if you remove the terminal. So be careful.

Also to note is my breaker had markings for "BATT" and "AUX". I think it's just to label them and don't think the breaker is polarity sensitive.