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sc300 crank no start

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Old 10-01-22, 05:21 PM
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sc300leo
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Default sc300 crank no start

hey everyone, i bought a 1992 sc300 a few months ago and had a crank no start issue. I’ve replaced the ecu with a rebuilt ecu from @TaninAuto , replaced the ignition coil (was deemed bad), replaced all blown fuses, and it’s still having the same problem. The car was reverse jumped/terminals placed wrong by previous owner, so im thinking either distributor or igniter? Car is getting no spark. It gets fuel. No spark coming from the ignition coil still. Just wanted to get some insight on this problem. Can igniters and distributors go bad with a reverse jump? ecu got fried, hence the replacement. Really hoping it’s not a wiring harness, but will keep diagnosing using the alldata no spark diag chart. Car also has coilovers (i know some have that wire problem with coilovers). Car does not throw codes due to majority dash lights being out. Just wanted to see if anyone has had a similar issue and could help speed up the process. Thanks

Last edited by sc300leo; 10-01-22 at 05:27 PM.
Old 10-02-22, 02:29 PM
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Matteo
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I have had a comparable problem with my 1993 SC300, one not yet fully solved, I'm sorry to say. That noted, I would suggest replacing both the igniter (aka ignition control module) and the EFI relay. The aftermarket versions of each are inexpensive and can be found on Amazon, among other sources. Each can be installed very easily: the igniter is a matter of just two screws and the EFI relay (which is located in the fuse box in the engine compartment) simply gets pulled out/pushed into place.) Total cost will be about 50 bucks for the two parts. Certainly worth a try!
Old 10-02-22, 08:24 PM
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Originally Posted by Matteo
I have had a comparable problem with my 1993 SC300, one not yet fully solved, I'm sorry to say. That noted, I would suggest replacing both the igniter (aka ignition control module) and the EFI relay. The aftermarket versions of each are inexpensive and can be found on Amazon, among other sources. Each can be installed very easily: the igniter is a matter of just two screws and the EFI relay (which is located in the fuse box in the engine compartment) simply gets pulled out/pushed into place.) Total cost will be about 50 bucks for the two parts. Certainly worth a try!
I will try this, my next step was the igniter and distributor. I was a little iffy on the aftermarket igniters, seeing the large price difference between oem and aftermarket, but i suppose it should work the same, maybe at some point if it does solve the issue maybe replace it with an oem one. I’ll look for the EFI relay as well, not sure i’ve replaced that yet.
Old 10-02-22, 09:55 PM
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As it happens, I originally tried the OEM igniter (which is, as you note, quite expensive). Ironically, it was defective. The aftermarket one, which was maybe 30 bucks, worked perfectly. Same for the EFI relay (which I bought from Amazon). Given the low cost of entry on this, there's little to lose.

By the way, I also replaced the distributor (and the rotor and distributor cap, for good measure). I originally bought a cheaper aftermarket distributor. There are several out there. And it was a dud. Paid a bit more and got the Cardone brand from RockAuto. Works perfectly. Keep in mind that some of the sensors in the SC300 are built into the distributor.
Old 10-03-22, 12:08 AM
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KahnBB6
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Yes, the igniters CAN go bad... but it is very very rare even with the age and high mileages that these SC's are up to today. Extreme age can eventually be a factor affecting any igniter but it's not very common so long as everything else is working well. I never had my original OEM 2JZ-GE Non-VVT-i igniter go bad on me even up to around 250k+ miles, however due to an initial wiring problem after my engine swap I DID have several 1JZ-GTE/2JZ-GTE Non-VVT-i igniters go bad on me before I realized the failures were being caused by a missing ground wire on the back of my GTE cylinder head. Once corrected the problem hasn't reemerged.

In this type of failure condition, whether you have a 2JZ-GE igniter or a 1JZ/2JZ-GTE igniter the lack of adequate ground connection does not allow the power to flow correctly on the ignition circuit which will eventually burn out the igniter unit, cause CEL Code 14 for "Bad IGF Signal Or IGF Signal Not Present". The IGF signal, on both 2JZ-GE engines and all GTE engines through the igniter unit is what allows the ECU to monitor and verify each ignition firing cycle between the igniter unit and the engine ECU. If there is no consistent or present IGF signal between the two computers then the engine will shut down and eventually not start at all until a fresh igniter is installed.

Now I wish I could tell you that there is a simple and clear way to *test* your igniter but due to how it works, in a nutshell, you really can't in a practical way. There *is* a way to sort of test it but it's more complicated than it's worth getting into and it's still not as reliable as what Toyota suggests in their factory shop manuals for the SC300/400, Supra and any other vehicle which uses similar igniter designs of the era: replace it with a known working good or new igniter to test whether or not the old igniter is at fault.

That having been said, just to be safe, make sure all your major factory ground connections in the engine bay and between the engine block to chassis and cylinder head to chassis are in good order.

But generally it is a very rare thing for an OEM Toyota/Lexus igniter to fail if everything on that circuit is in good working order.

You can buy them brand new from Toyota/Lexus, go for a stated good working used OEM Toyota/Lexus igniter on eBay or go with one of the options from RockAuto. If choosing one from Rockauto I recommend the Standard Motor Products LX721 since SMP more or less has historically sold rebranded new old stock versions of the same OEM new parts that Toyota and Lexus dealers stock for the same applications.

.....

Regarding distributors... yes they can go bad but not for a very, very long time from being brand new. Usually it is the distributor shaft oil seal that leaks and which needs a new O-ring but the cam position sensor built into the distributor can eventually wear out which will require you to replace the distributor.

There are aftermarket remans of the OEM distributor or you can get an OEM new Toyota/Lexus unit (P/N 19100-46011). Normally I'd have suggested buying it new from Amayama Japan for a low price but they seem to not be able to order those for United States deliveries any longer (even though they are still in stock in Japan). This leaves McGeorge Toyota (toyotaparts-McGeorgeToyota-dot-com) as the cheapest place for a brand new one that I am aware of right now. Rockauto lists three "new" and one "remanufactured" option for these by AutoLine (listed as AutoLine "Nippon Denso Type"). If going with the Rockauto options I'd personally pick that one since Denso was the only manufacturer of these distributors and all the aftermarket ones should be remanufactured OEM units at this point.

Definitely test the distributor in accordance with the TSRM first before spending money on a new distributor. Instructions are in the SC300/400 factory TSRM and on Stu Hagen's 97supraturbo website as PDF scans of specific sections pertaining to the identical-to-SC300 93-97 Toyota Supra NA engines.

....

Overall your issue culprit will not be BOTH your distributor AND your igniter unit. Testing and process of elimination will determine which.

As for the wiring harness yourself there should not be an issue with that unless you notice any clearly burned or damaged areas. I don't think even the mistake the previous owner made could have physically affected the high quality wires throughout the engine and body harness.

....

Coilovers will not in and of themselves cause any strange issue such as yours, however if you are lowered a bit too much and have not yet done a driver's side fender-well body harness relocation job and the tire on that side has eaten through the plastic fender liner and started to rub away at your body harness wires that are right under it then that WOULD be a suspected area for your issue.

Have you jacked up the car and checked in your upper driver's side fenderwell area for any signs of having rubbed through the plastic and wire harness underneath? If that happens to be the case then it all can be repaired (and extended/relocated following DIYs and build threads covering how to do it) so that you can get things back to normal *and* safely enjoy your SC with an aggressively lowered suspension.

Last edited by KahnBB6; 10-03-22 at 12:15 AM.
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