Turns over but doesn't start and no CEL

mk3.anime

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#1
This problem has been baffling me for weeks. I'm trying to start my supra but all it does it crank with the tachometer moving. I've tried to start it up with starter fluid which brought it to ~550rpm before dropping back down to cranking. My timing is correct, TDC, CPS, and cam gear position should all be good. I've checked the spark plugs and they're okay. There's good gas in the tank and I can hear the gas pump running. Fuel sprayed out when I took off the cold injector tube. I've checked the EFI fuse and it's not blown. I tried different grounds with no luck still. Any advice would be greatly appreciated. I've tried to ask people on mk3 supra facebook for input and followed their advices and I'm still stuck. My car is a 92 7mgte 5spd supra.
 

3p141592654

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#2
Validate plugs are firing. Tach moving validates CPS. You need to check the ignitor/coil circuit is good.
Validate injectors are firing. At the very least confirm the injectors are getting electrically activated with a reasonable waveform.
 

zachm611

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#3
Check for spark. If you are not getting spark check the wires on the CPS for any broken or split wires sometimes they just loosen up in the connector due to the heat of the exhaust manifold this is a very common problem.
 

mk3.anime

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Validate plugs are firing. Tach moving validates CPS. You need to check the ignitor/coil circuit is good.
Validate injectors are firing. At the very least confirm the injectors are getting electrically activated with a reasonable waveform.
Injector connectors aren't getting any power. I also Don't have CEL.
 

hvyman

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#5
Do you have 12v at the efi fuse?

No cel when you turn the key to on?
 

hvyman

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#7
http://www.cygnusx1.net/supra/Library/TEWD/MK3/manual.aspx?S=Main&P=49

You need 12v at igsw which is the b1 connector by the ecu when ign is turned to on.

12v igsw signal at ecu
Ecu sends 12v to mrel
Mrel powers main relay
Main relay powers the ecu.

But if you don’t get 12v with key on at the black and orange wire for injectors then it’s likely you have a bad ignition switch. Which would be the common problem for both of those.
 
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supraguy@aol

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#8
Since nobody asked, and you didn’t mention;
What precipitated the engine issue? Did it just one day become an issue,
or did you do any sort of maintenance/ upgrade and the issues began?
 

jkendall86

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#9
I have spoke with him on this. Hvyman is closest to the issue....ignition switch. When he pulls the key out, the dash stays lit.
 

hvyman

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#13
Bad turbo timer harness or one that unplugged itself could cause that for sure.
 

DeadlyWrenches

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#14
I had the same problem about 8 years ago when my supra sat outside for years.

Listen to hvyman he explains the circuit perfectly.

Engine would crank, no start and no CEL when Key On Engine Off.

Was getting 0.88 volts at Main Relay activation circuit.

7.5A IGN fuse in driver foot well corroded so bad it widened the fuse box terminals for that fuse so even with a new fuse still no CEL.

There are 4 terminals at the Main Relay. 1 is ground, 1 is 12v switched through 7.5A IGN fuse to ECU then back out to power Main relay activation circuit, 1 is full time power from 15A EFI and the last one powers the engine harness with 12V coming from 15A EFI fuse when Main relay is activated.
 
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