starter relay keeps blowing

starter relay keeps blowing

Postby jomo on Fri, 29 May 2020 2:08 +0000

2005 Hilux 2.7 Petrol (model TGN16)

For the past couple of days, the starter relay keeps blowing, so I cannot crank the engine. After it happened the first time, I replaced the starter relay with a secondhand one from the wreckers ($33 versus $103 for a new one from Toyota). That worked for a few starts, but now the starter relay has blown again. I know its the starter relay because if I remove the relay and jumper the relevant connections in the fuse box, I can start the car easily.

What could be causing the starter relay to keep blowing?

Thanks.
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Re: starter relay keeps blowing

Postby martynvella on Sat, 30 May 2020 5:55 +0000

Open the relay up and see what part it damaged, the contacts will be burned it it is a load fault. The fault could be on the primary side anywhere from and including the ign switch and you will still be able t o start it by bridging the relay socket.
Does the relay click when the key has turned to start? Make sure the click is coning from the start relay because accessory relays will drop out in the start position and make a similar click noise.
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Re: starter relay keeps blowing

Postby martynvella on Sat, 30 May 2020 7:50 +0000

By bridging the relay doesnt prove it is the fault, all it proves is that the starter is ok.
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Re: starter relay keeps blowing

Postby jomo on Wed, 03 Jun 2020 5:30 +0000

martynvella wrote:Open the relay up and see what part it damaged, the contacts will be burned it it is a load fault. The fault could be on the primary side anywhere from and including the ign switch and you will still be able t o start it by bridging the relay socket.
Does the relay click when the key has turned to start? Make sure the click is coning from the start relay because accessory relays will drop out in the start position and make a similar click noise.



OK, the relay is purple-coloured and is Toyota (Denso) part number 28300-0L010
I obtained the pinout diagram for this relay and bench-tested the replacement relay that I had obtained from the wreckers - there is absolutely nothing wrong with the relay itself. If I apply 12 volts to the signal terminals of the relay I hear the relay click on and I observe electrical continuity on a multimeter connected to the power terminals of the relay (i.e. the terminals that deliver power to the solenoid of the starter motor).

Furthermore, I removed the plastic case of the original relay (that I had assumed to be blown) and saw it to be in pristine condition internally, as if it had just come from the factory. No evidence of burning there.

So I can rule-out the starter relay as the cause of the problem - especially because I have now tried 2 different starter relays in the Hilux.

I then put the multimeter on the 2 connections in the Hilux's fuse box that correspond to the trigger from the ignition switch to the starter relay - I observed 12 volts when I turned the key as if to start the car. So it would seem that I do not have a faulty ignition switch (unless it's an intermittent fault).

So....where does this leave me? A faulty solenoid in the starter motor? An electrical short in the starter motor itself? If so, why does the starter motor crank when I shove coat hanger wire to jumper the power to the solenoid in the Hilux's fuse box?

Any suggestions would be most welcome.....
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Re: starter relay keeps blowing

Postby martynvella on Wed, 03 Jun 2020 7:07 +0000

Multimeters are too sensitive, one could read 12 volts but the circuit could still not be able to deliver any current when loaded. Does the relay click when the key is turned to start?
You are correct in saying the starter seems ok because it works when it is fed with power.
I f the relay clicks is there 12 volts getting to the starter solenoid?
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Re: starter relay keeps blowing

Postby martynvella on Wed, 03 Jun 2020 7:14 +0000

Is it an automatic, if so is the inhibitor switch on the positive side of the relay in series with the ign sw or is it on the negative side of the relay coil?

Biggest clue is... does the relay click when the key is turned to start and the engine fails to crank?
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Re: starter relay keeps blowing

Postby jomo on Thu, 04 Jun 2020 5:06 +0000

martynvella wrote:Is it an automatic, if so is the inhibitor switch.......

Biggest clue is... does the relay click when the key is turned to start



No, it's a manual, so inhibitor switch is not present.

This evening I will get an assistant to help me check if the relay is clicking when it is installed in the car and I turn the key.
Will advise.

Thanks.
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Re: starter relay keeps blowing

Postby jomo on Thu, 04 Jun 2020 12:41 +0000

Well, I'll be damned !

I reinstalled the relay back into the fusebox, turned the key and the starter motor cranked and the engine started !

It looks like I have an intermittent connection problem on the ignition switch side of the circuit (because I know that the relay itself is OK, and when the no-cranking problem occurs I can get the starter cranking by shoving coat hanger wire onto the relevant connections in the Hilux's fuse box).

The next time this problem occurs, I will verify that the relay is indeed not clicking when I turn the key to start the car - that will verify the cause is ignition switch/wires.

I hope the ignition switch is not hard to remove when I eventually get around to replacing it.
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Re: starter relay keeps blowing

Postby martynvella on Thu, 04 Jun 2020 1:06 +0000

Dont jump to conclusions, dont replace anything till you confirm it is faulty.
Have a very close look at the pins of the original relay and look for very light burn marks. As vehicles age the terminals in the relay base come loose with years of vibration....or someone jaming coathanger wire in them lol. If there are faint burn tracks on the terminals tighten the terminals in the socket with a small screw driver or test light till it takes a firm push to fit the relay. This is a very common intermittent fault in engine bay fuse/relay boxes.
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Re: starter relay keeps blowing

Postby jomo on Fri, 05 Jun 2020 4:49 +0000

martynvella wrote:Dont jump to conclusions, dont replace anything till you confirm it is faulty.
Have a very close look at the pins of the original relay and look for very light burn marks. As vehicles age the terminals in the relay base come loose with years of vibration....or someone jaming coathanger wire in them lol. If there are faint burn tracks on the terminals tighten the terminals in the socket with a small screw driver or test light till it takes a firm push to fit the relay. This is a very common intermittent fault in engine bay fuse/relay boxes.



I appreciate your sage advice. It does look like I am staring at an intermittent connection issue somewhere so, yes, I am going to have to get forensic.
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Re: starter relay keeps blowing

Postby jomo on Fri, 12 Jun 2020 2:35 +0000

CORRECTION:
I had previously reported that I could get the starter motor cranking if I shove coat hanger wire into the relevant fuse box connections to energise the solenoid of the starter motor.

Now I know that trick does not always work - when I try that now I just get sparking on the tips of the coat hanger wire jumper, and the starter motor does not crank.

HOWEVER, now I have found that, when the starter motor refuses to crank, if I whack the casing of the starter motor with a wooden stick, I can eventually get the damn thing to crank and start the engine !!!

Clearly, I have a faulty starter motor......
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Re: starter relay keeps blowing

Postby DeadlyBeast on Fri, 12 Jun 2020 5:40 +0000

Solenoid plunger sticking.
Given its age it may have water damage or just worn out
Pull it apart, have a look at electrical contacts/ terminals, signs of corrosion etc
There's a fairly good guide on wikihow to test the starter solenoid before removing it.
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Re: starter relay keeps blowing

Postby Gipsy on Sat, 13 Jun 2020 6:45 +0000

If the starter works after a hit with a hammer it's a good sign the solenoid is stuffed. If it is, the starter motor is in need of an overhaul also. Recon starters are not necessarily cheaper than a new one, I got a new one for my LandCruiser from Repco for $120 and a recon was $180. Go figure! I suppose a new one has less labour involved than a recon. (That was a few years ago so prices would be higher now)
Cheers Gipsy :D
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Re: starter relay keeps blowing

Postby martynvella on Sat, 13 Jun 2020 7:58 +0000

Banging it to make it crank is, as the others have indicated a sign of water ingression siezing things up, either sol plunger or brushes, or could be good old fassioned worn out brushes, but the brushes in these things are an extreemly hard compound so unlikley.
If the starter wasnt klunking when you bridged it then it wont be the reasonably common easily repairable worn solenoid contacts. If it is corrosion thats killed it then replace it, if it is a recent dunking in mud then it could be stripped and cleanec out if your handy with tools but can be very challenging if you have never done starter repairs before and dont know how to align solenoid contacts correctly.
Would be cheaper to buy a new one that pay someone to rebuild it for you. That is a major reason that I got out of the automotive side of the trade, starter and alternator rebuilds used to be our mainstream income but chinese built replacements took that away.
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Re: starter relay keeps blowing

Postby Gipsy on Sat, 13 Jun 2020 9:42 +0000

Just priced a new one on eBay, $139 so why would you bother? Just put a new one on! A new solenoid would cost almost that!
Cheers Gipsy :D
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Re: starter relay keeps blowing

Postby martynvella on Sat, 13 Jun 2020 11:27 +0000

Id be very cautious with a new starter at that price, I would at least stick with something like OEX from ashdowns or JAS brand.
Havent got a link by chance?
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Re: starter relay keeps blowing

Postby Gipsy on Sat, 13 Jun 2020 12:15 +0000

Cheers Gipsy :D
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Re: starter relay keeps blowing

Postby martynvella on Sat, 13 Jun 2020 12:57 +0000

Ahhh ok.
My bad, i forgot it was an earlier petrol model.
If thats the case forget the stuff i put about the hard brush compound and sol contact alignment, the standard starter on those were a 3 brush set up with only one negative brush and that wares out faster than the other two. Simple job to solder one new brush in, bit rough i know but I have done it a few times for people having cash flow problems, id rather do that for them to keep costs down than fit a second hand starter.
But as you say for the price of a new one these days it isnt worth stripping it down.
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Re: starter relay keeps blowing

Postby Gipsy on Sat, 13 Jun 2020 1:20 +0000

The kun26 version is still only$139 from same supplier
Cheers Gipsy :D
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Re: starter relay keeps blowing

Postby martynvella on Sun, 14 Jun 2020 8:39 +0000

Being an aviation engineer, would you consider using such a cheap starter on anything that goes to remote places?
I have dismantled cheap copies and once inside its easy to see why they are cheap.
Shake proof washers that have cracked, crimps that have missed their mark, bearings loose in housings and no seals,
Solenoid windings insecure on spools, brittle solenoid windings, solenoid contacts mis aligned.
The units failed for one fault but strip them down and see several other dodgy things.

Very little quality control, or more likley companies buying the ones that failed the QC and flog them off on ebay.
The really cheap ones will have no brand name attached on the unit, maybe on the box and some dont even come in a box.

One outstanding example I had was a chap bought a cheap starter for his 1HZ cruiser because the original one failed, as they do. He found it cranked slowly and only just managed to start so he replaced the battery then heavier battery cables a pilot solenoid all on advice from forums before calling me.
I removed the nice looking new starter and it just didnt sound right in the test bench, like it was turning slowly.
Stripped it down and everything looked really good but on closer inspection I realised the motor field coils were configured to 24 volt. All this while the customer was watching. I dug out a second hand case containing the fields and reassembled and fitted it to prove the theory. It worked very well with all the other improvements he had done I had never heard one crank so well.
Asked him if he wanted a written report to send the supplyer but he was so happy to hear it start he said no leave it as it is, happily paid me for my time and dropped back a box of beer.

The non reduction starters have a lot less things that can go wrong during assembly.

Sorry about ratteling on but i an in self isolation in a perth hotel room. So bored lol
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