Car not starting randomly? READ THIS (30 Amp Starter Relay Mod)

Idealsupra

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Moderator edit: Please read the entire thread. The circuit already has a relay that is easy to diagnose and fix.-Poodles

INTRO TO PROBLEM:​

I figured I would post a little public service announcement to hopefully help some people and save them the aggravation of trying to replace a starter multiple times and not fixing the problem.

My car had been randomly "not cranking" over the past few weeks. It was getting worse and left me stranded numerous times. Although it is a manual so I was normally able to recruit some guys to give me a push for me to pop it and be on my way.

Of course the normal response around here is the starter contacts are worn/bad. Sure this MIGHT be the case, however I would bet more often its something a LOT simpler to deal with and correct.

There ARE random threads on this site and others that have this in them and they are great tool. I figured maybe one more isnt a bad thing as there are more "Help my car isnt starting randomly" threads then I could sift through.

Ok so enough rambling. Here you go. If you are having problems with your car not cranking (yet youre hearing a click at the starter relay, and a "thicker" click at the starter area), then try this. DO THE 30AMP RELAY MOD. SERIOUSLY.

WHY THIS IS A PROBLEM:​

Basically, the old wiring and the setup of the stock starting circuit causes the voltage getting to the starter simply not enough at times. (Thanks IJ) The stock wire from the IGN side to the starter energizes the bendix and it's copper contacts and ring complete the motor circuit.

What happens though is not enough current to hold these contacts causes arcing so it just gets worse and worse.

SHOPPING LIST:​

To correct this (and basically enhance your starting circuit along the way), simply go to Advance Auto Parts and get the following:

  • 30AMP Relay- 4 prong self enclosed and it has a spot for a screw for mounting.
  • Spool of 10 gauge wire. 12 gauge would be ok as well but I prefer to be safe then sorry.
  • Spade connectors for said gauge wire
  • Loop connectors for said gauge wire

DIRECTIONS TO MODIFY AND CORRECT THIS PROBLEM:​

DISCONNECT NEGATIVE BATTERY TERMINAL

Now find a place to mount the relay. I put mine down by the starter almost right off the framerail. I used one of the 10mm bolts that holds on one of the little shields.

Now take the wire and connectors and make:

  • 1(A)- loop end connector---> spade connector. Length is from wherever you mount the relay to the positive battery terminal.
  • 1(B)- spade end connector---> spade end connector. Length is from wherever you mount the relay to the terminal with the spade connector on the starter. Its encased by a brown "clip".
  • 1(C) spade end connector----> loop end connector. Length is from wherever you mount the relay to a body ground. Theres a lot of random 10mm bolt holes that you can use for this.

Connect (A) to the input side of the switch on the relay.

Connect (B) to the open side of the switch on the relay and the other side of (B) to the starter terminal (brown clip).

Connect (C) to either side of the coil on the relay and ground other side of (C) to the body.

Take the clip/wire (should be black with blue stripe) that normally goes to the starter and connect it to the other side of the coil on the relay.

Finally connect the other end of (A) to the positive terminal on the battery.

REATTACH NEGATIVE BATTERY TERMINAL

WIRING DIAGRAMS:

sm_photo_missing.jpg


Thats it. Ill bet doing this solves MOST of the starting problems out there. Its about a 30 minute job at most and only costs a total of about $15 if you need to buy everything.

I hope this helps. If someone does this and would like to take pictures from start to finish they can be added. Im going to be doing this to another Supra in a couple of weeks so if theres nothing by then I can do it myself.
 
Last edited:

Idealsupra

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tekdeus;1081735 said:
This mod solved my starting problem as well. There must be a way to get this message across to more people, since it is the #1 reason for our starting problems. Sticky?

Firstly... your car came out AWESOME. Nicely done.

Secondly, I would be glad to organize my post a bit more, add an actual wiring diagram and some pictures of everything as well if I knew the post wasnt going to just get buried in a day or two.

This info is seriously top 5as far as common problems with the supra that can be fixed easily.
 

IJ.

Grumpy Old Man
Mar 30, 2005
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Always thought it odd just how long the Black/blue stripe heavy line to the starter is.

Why did they bother putting the stock relay so far from the starter ;)
(add the NSS switch or bypass plug into the length + 20 year old wiring and it's a wonder any of these cars start)

Small correction Jay, this line doesn't provide the electricity to turn the starter at all it only energises the bendix and it's copper contacts and ring complete the motor circuit.

What happens though is not enough current to hold these contacts causes arcing so it just gets worse and worse.
 

Idealsupra

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IJ.;1081756 said:
Always thought it odd just how long the Black/blue stripe heavy line to the starter is.

Why did they bother putting the stock relay so far from the starter ;)
(add the NSS switch or bypass plug into the length + 20 year old wiring and it's a wonder any of these cars start)

Small correction Jay, this line doesn't provide the electricity to turn the starter at all it only energises the bendix and it's copper contacts and ring complete the motor circuit.

What happens though is not enough current to hold these contacts causes arcing so it just gets worse and worse.

Yep you are right (no surprise). I think I got caught up in my rambling lol. Good catch. Ill fix it.

CyFi6;1081757 said:
Feel free to use this picture if you would like.


Thanks I got motivated and went ahead and made one using the TEWD icons. We can use both though :D
 

Idealsupra

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IJ.;1081769 said:
I use a 30a icecube relay that has it's own blade fuse :)
(there's no protection in your circuit so if anything goes wrong you let the magic smoke out)

FusedRelay2.jpg

Hey thats pretty nifty. I actually threw an inline fuse in my personal one lol. I guess I should add that huh...bah! I have to go back into the POS wannabe paint program I have and fix the diagram lol.

Whered you get the fused one? Not that it would help considering you are across the big pond lol.
 

IJ.

Grumpy Old Man
Mar 30, 2005
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I come from a land down under
They're available from our local parts store Jay :)

Makes life so much easier.

I made a bracket that bolts under the brake pipe bracket by the starter and bolted a Relay Socket to it then if a relay dies it's a simple plugNplay change.
 

Idealsupra

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IJ.;1081771 said:
They're available from our local parts store Jay :)

Makes life so much easier.

I made a bracket that bolts under the brake pipe bracket by the starter and bolted a Relay Socket to it then if a relay dies it's a simple plugNplay change.

Must be nice :(. They only had regular relays at my place. And Im doing a quick google search and every fused relay Im finding is out of this country lol.

Grrrrr.

They way I have it it would only take a few seconds also (just remove the four spade connectors and 1 one bolt and put them on the new relay). But yeah the relay socket would be quick pull out and put in(thats what she said heh).

EDIT: Heres a good cheap relay socket: http://www.robotmarketplace.com/products/0-REL-H.html Only $3. Not bad. Ill pick one up. Now just need to find a fused relay like you posted thats available in the states lol. Otherwise Ill just stick with my inline fuse I guess.
 

CyFi6

Aliens.
Oct 11, 2007
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Hmm I have never seen a relay with a fuse on it like that before, thats pretty cool.

About the topic: A classic example of having this problem is the car starts fine when cold, but wont start and just clicks when the engine is still hot. As the wire gets hot its resistance increases and gives this same symptom
 

Poodles

I play with fire
Jul 22, 2006
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I don't remember if the starter wiring is part of the engine harness or not, but I haven't really had an issue with cranking/starting since replacing the harness (and fixing my crappy battery cables)
 

Idealsupra

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Poodles;1081792 said:
I don't remember if the starter wiring is part of the engine harness or not, but I haven't really had an issue with cranking/starting since replacing the harness (and fixing my crappy battery cables)

Yeah the wire that goes to the starter from the IGN side runs through the harness.
 

Angry7M

Formerly redmaro
Sep 6, 2007
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Yeah i had seen this mod on supraforums already.

I had the same problem sometimes the car wouldnt start when ever the engine was hot, sometimes it would be random. Finally saw the thread on supraforums and did this relay mod and my car has been starting fine, its been three weeks now.
 

Quin

Trans killer
Dec 5, 2006
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Sometimes have a somewhat similar problem but it's just due to a crappy connection. Upgrade time :)

Nice write up.