2nd Generation Specific 1986-1992 Discussion

No Spark, No Fuel, No Tach

Old 05-24-2012, 11:16 AM
  #1  
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Join Date: May 2012
Location: Detroit, MI
Posts: 4
Default No Spark, No Fuel, No Tach

As the title says, fuel pump doesnt turn on, injectors dont fire, tach doesn't move, and there is no spark. I'm just about out of ideas on how to get this thing to work.

First, the background info:

'86 NA, MT, manual steering, no A/C
Engine blew an apex seal, replaced with an S5 keg and intake. All electronics are from the S4 motor except for the rear iron temp sensor. Vacuum rack, air pump, EGR, and cold start system were removed during the install according to the directions on Rotary Ressurection.

Short list of attempted fixes/diagnostics: (I may have forgot some)
Engine diagnostic light
Change CAS
Change coil packs
Change ECU
Check all fuses
Check ECU voltage
Check coil voltage
Check Main Relay
Check coil impeedance
Check CAS impeedance
Check all ground point impeedances
Scrub grounds
Replace battery cables
Check continuity between ECU and coils, ECU and CAS
Remove RPM Switch
Disconnect MAF
Check clutch switch continuity
Check neutral switch continuity

Now the story:

First Startup attempt:
The rear upper fuel injector began leaking profusely due to a pinched o-ring. Ring was replaced, and I tried it again.

Second startup attempt:
Engine has spark, unsure of fuel and tach. Engine does not start

Third attempt:No spark, no fuel, no tach. Diagnostics begin

Change CAS - No effect
Check all fuses - Good
Check coil voltage - 12V at the check bullet by the trailing coils
Check Main Relay - same as coil voltage
Check coil impeedance - within range
Check CAS impeedance - within range
Check all ground point impeedances - varried, 0.5-4.5 ohm
Check continuity between ECU and coils, ECU and CAS - 0.5 ohm all around
Check clutch switch continuity - 30-inf ohm depending on position
Check neutral switch continuity - .5 ohm

Changed the CAS, no effect. Went home.

Next day:
Hooked up engine diagnostic lights - Both lights flashed once quickly as the key was turned on, and remained off. Both flash quickly again when the key is turned off. Lights illuminate and stay lit while cranking. Doesnt match any of the diagnostic codes in the manual

Replaced ECU - No change

Replaced Coils - Spark! The plugs sparked, injectors worked, tach worked. Put the plugs back in, and everything reverted to where it was before changing the coils. no spark, no fuel, no tach. Tried some more, with jiggling wires, and the entire car shut down, as if the battery had been disconnected.

Replaced Battery Cables - Car turned on, but still no spark, no fuel, no tach

Cleaned all grounds - Scrubbed all the grounds with wire brush and carb cleaner. got battery grounds to chassis and engine, ECU brackets, coil brackets, wires going to chassis... checked all continuities, nothing more than 2 ohm. still no change

Removed RPM switch - I read that this worked for somebody. no effect for me

Disconnect MAF - same story as RPM switch


I'm running out of ideas, anybody know what causes this?

Thanks
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Old 05-25-2012, 11:17 AM
  #2  
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Join Date: May 2012
Location: Detroit, MI
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Default Re: No Spark, No Fuel, No Tach

ECU ground wire blends in with the main harness, and attached under the intake manifold. Reconnecting that fixed the problem. Do not confuse the strap from the back of the rear rotor to the firewall for the ECU ground.

http://www.aaroncake.net/RX-7/grounding.htm
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