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78 280Z flooding, weak spark, will not start


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#1 Zlost

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Posted 18 December 2016 - 06:21 PM

Hello all
About a month ago I cranked my car and when it started it was sputtering and was running very rich with a lot of black smoke. I also noticed much lower idle. I went for a 15 minute drive and laid into a bit. It cleared up and I went back home and the car sat for almost 2 weeks.
When started it again it had the same issue as before except it was worse. More black smoke (heavy smell of gas), the engine was sputtering and was barley staying on. The idle dropped to under 500. I went for spin as I did before but this time it did not help. As I was checking a few things under the hood it stalled and I could not get it started again. The car turns over just fine and you can smell the gas, plugs are wet.
I ran the recommended EFI and EE checks from the manual for the ECU and ignition.
The only thing I found was low spark at the plugs, spark at coil looked ok but it could be weak.

-I have 12 volts at the coil and fresh gas, fuel pressure is around 35.
-I have replaced with new or known good parts I had or borrowed:
The coil, coil wire, complete distributor with new cap and rotter, removed the condenser, swapped the transistor ignition box with a known good one, water sensor (and checked for corroded connector) checked vacuum hoses and grounds. Cleaned all relay sockets in the engine bay (in front of battery) cleaned ECU connector and checked the solder joints on the PC board.

I have a GM HEI module on order, should be here tomorrow but with a known good ignition box in there I don't think it will help.

I tried starter fluid and it did start for a few seconds but would not stay on
I took out all the plugs and wiped them off and blew out each cylinder with air to make sure the are not flooded. I also checked the fuel return from the regulator, fuel was coming out when I was cranking it and I blew out the line with an air compressor to make sure it is not clogged back to the tank.
 

I did read the post about the torn diaphragm on the APR, I will check that next.

 

Any help would be apreciated

 

Zlost



#2 JSM

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Posted 18 December 2016 - 07:19 PM

I would unplug your ECU and check to ensure there is no corrosion on the ECU or plugs.

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#3 Zlost

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Posted 19 December 2016 - 05:00 AM

Hi JSM

I cleaned the ECU connector and soldered some suspicious looking solder joints on the PC board.

 

Do you know if the car would start without the ECU connected?

 

Thanks

Zlost



#4 TimZ

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Posted 19 December 2016 - 08:31 AM

Hi JSM

I cleaned the ECU connector and soldered some suspicious looking solder joints on the PC board.

 

Do you know if the car would start without the ECU connected?

 

Thanks

Zlost

 

No, it won't.

 

You've likely fouled your plugs at this point - wiping them off or spraying with carb clearer won't help - you either need to burn the carbon deposits off with a propane torch or replace the plugs.

 

That's probably going to be necessary, but it will likely keep happeing if you still are running too rich.  Soulnds like you already checked the AFM and coolant temp sensors.  The FPR is a good thing to check too.  Basically any component that is used to determine the fuel mix.


Edited by TimZ, 19 December 2016 - 04:40 PM.

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#5 Zlost

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Posted 19 December 2016 - 10:08 AM

Thanks for the info,



#6 Zlost

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Posted 30 December 2016 - 08:02 AM

Hi there, thanks for those who responded.

My problem turned out to be the ECU, I'm not sure why but it looked like the ECU was keeping injectors on too long causing it to flood.

I don't think i had a weak spark after all.

I found a Bosh ECU online, so far it works great, I had to adjust the AFM because it was running lean with the new ECU. I plan to take in for a proper tuneup soon. Does anyone know a good Z mechanic in the Raleigh NC area area?

 

Thanks

Zlost






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