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1997 Tacoma 2.4, No Spark, No Start, Can't Solve. Impossible Fix?

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10 Apr 2019 18:03 #28561 by brianzero
Hi All,

I've been working for months to fix this no start / no spark / no fuel pump situation on my 1997 Tacoma. This is what we know:

No ODBII Codes.
No Rodent Damage.
Distributor is rotating.
Body Grounds Good. Kick panel grounds good. Sanded contacts and body contact points.
Rebuilt Battery to Body Ground Wire.
Battery, 6 months old.
New Crankshaft sensor. Sensor is within Ohms range.
New Ignitor Coil. Tested 4 different coils. No change.
New Distributor (coil, condenser)
New Distributor Cap.
New Distributor Wiring.
Tested NGK coil, no change.
New and verified working EFI relay.
Fuses under hood verified intact and getting power.
Fuses driver side fuse box verified intact and getting power.
Donor wiring harness (Junkyard wiring harness).
Donor ECU swap. Didn't change no start condition.

Getting power to distributor.
Getting power to coil.

Cannot get spark with pull up / pull down test.
Cannot hear fuel pump activating. Seems to be sending fuel though system (strange).

If anyone has any more places to look, I would really appreciate any suggestions. I feel that having the truck towed off is the next step, I sure some of you are familiar with that 'I give up' feeling. The toyotanation forums even gave up on me!

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11 Apr 2019 07:21 #28564 by guafa
Hi brianzero,

Do you have power on sensors?

That is what we name 5v ref. This tell you PCM is energized and internal voltage regulation is working.

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11 Apr 2019 10:55 #28567 by brianzero
Yes, I have power on sensors at various places, like the ignitor coil.

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11 Apr 2019 11:59 #28568 by guafa
What diagnostic tools do you have?

Scope, wiring diagrams, amp clamp, secondary ignition test probe.

Assuming here engine is cranking, isn't it?

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11 Apr 2019 12:20 #28569 by brianzero
Ive got a multimeter, that's all. Yes, the engine is cranking over, no issues there.

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11 Apr 2019 13:05 #28571 by John Curtis
I would test for voltage drop and ground at the PCM.

Thinking out loud always helps me in the process.

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11 Apr 2019 13:29 #28573 by brianzero
I replaced the entire ECU side wiring harness, and all the grounds are clean (and updated).

The ECU is sending the ignitor coil a signal and Im getting the signal at the ignitor coil plug. This doesnt make any sense as to why the brand new ignitor coil wouldnt be firing.

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11 Apr 2019 13:45 - 11 Apr 2019 13:56 #28574 by guafa
Ecu could be sending firing signal, but at wrong time (not synchronized with mechanical TDC.

How do you know ecu is sending firing signal? Although we know you changed some parts, we need to assume you have tested nothing
Last edit: 11 Apr 2019 13:56 by guafa.

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11 Apr 2019 14:09 #28575 by brianzero
Im going to retest my ECU signal to the ignitor coil while cranking. Ill report back what it is.

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11 Apr 2019 14:27 #28576 by guafa
You can quickly check also for coil output, by unpluging one coil from its spark plug, insert a screwdriver in it, leave the screwdriver over the valve cover taking care that screwdriver shank is separated 1/2 inch (12mm) of ground and far from fuel lines, injectors or any fuel leakage.

While cranking, you can see spark jumping to ground.

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11 Apr 2019 14:32 #28577 by brianzero
I have 11.8v signal from the ECU to ignitor coil. This is with the ignition in the ON position. Acceptable range is 9 to 14v.

I need to test this while cranking. Ill let you know the voltage.

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11 Apr 2019 14:43 #28578 by guafa
Please post a pic of ignitor and point where you are getting 11.8v

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11 Apr 2019 14:45 #28579 by brianzero
I have a voltage drop from 11.8v to 10v while cranking. This value was taken from the IG+ ignitor coil plug.

Is this value significant?

And yes, i tested the spark test method with a spark plug touching the valve cover. No spark seen while cranking.

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11 Apr 2019 14:51 #28580 by guafa
I'm afraid that voltage drop, is due to starter current demand.

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11 Apr 2019 14:56 #28581 by brianzero
Check this out, photo where im getting the 11.8v from:
Attachments:

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11 Apr 2019 15:00 #28582 by brianzero
Heres the ignitor:
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11 Apr 2019 15:13 #28583 by brianzero
That makes sense.

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