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superduner

L28et swap not starting/staying on

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Hey guys. So Ive previously done a L28et swap previously back in the day and car ran fine. Just did another 81 L28et swap into my series one 240z and got it all bolted up and cranking. Now, on the donor car the car started up and ran up and down the block before I took it apart( 2 years ago) so things seemed all functional at least back in the day. Issue I'm running into is the car won't come on. And when it does start briefly,  it dies within 3 seconds. 

 

I Bought a new fpr and verified that there is fuel and pressure (36psi) while car is off and in the ON position. There is verified spark in all 6 sparkplug wires. I've got two separate grounds on the engine so engine and car is well grounded. I also took the fuel rail off and verified that while cranking the Injectors are indeed spraying and there isn't infection leaks. Below is a YouTube video link I uploaded for your viewing pleasure haha. The ECU light  seems to come on then shut off after cranking  and sometimes intermittently the Injectors will stay on buzzing even if I stopped cranking. Anyway, any idea what's going on? 

 

https://youtu.be/p-DhNG0mq7E

 

Your help is Much appreciated! 

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The ECU light is normal.  It lights at IGN ON and goes off as soon as the ECU gets a CAS signal.  That's normally during cranking or engine start.  The buzzing, I've never seen before...  Is that buzz really coming from the injectors?  Check the injector wiring again.  (stock)They should have power through a fusable link and the ground is controlled by the ECU.  If there are no problems on the +12v side AND the wiring from the ECU is good with no continuity problems (shorts) than you likely have a problem with the ECU.  The 1981 ECU needs dropping resistors in the harness.  You've already been through the harness and connectors and cleaned the hell out of everything electrical connector related, right?

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18 minutes ago, cgsheen said:

The ECU light is normal.  It lights at IGN ON and goes off as soon as the ECU gets a CAS signal.  That's normally during cranking or engine start.  The buzzing, I've never seen before...  Is that buzz really coming from the injectors?  Check the injector wiring again.  (stock)They should have power through a fusable link and the ground is controlled by the ECU.  If there are no problems on the +12v side AND the wiring from the ECU is good with no continuity problems (shorts) than you likely have a problem with the ECU.  The 1981 ECU needs dropping resistors in the harness.  You've already been through the harness and connectors and cleaned the hell out of everything electrical connector related, right?

Yeah man,  mind bogged the heck out of me the first time I heard that. I pulled the rail with the Injectors when I was testing to see if the Injectors were spraying and or leaking  but when that noise comes on after cranking I noticed  the Injectors were all on and spraying at the same time. Never seen anything like that before. I Followed the same swap guide i did beforeon my last project so I definitely got blind sided on this one. Checked out the Efi harness wiring and made sure that the wires that needed to come on in the ON position did and the wires that needed all time power did and everything checked out ok. Didn't really clean connections and plugs so that's next. The dropping resistor that plugs in the harness I haven't even looked at I left it connected the whole time. How would I go about testing to see if it's good? 

On a side note. I'm running an 81ecu off an automatic now swapped BW t5. Can I plug in a manual 82 zxt ecu to test? I know the 82+ cas is in the distributor so not quite sure if I would need to change anything to run a 82/83 ecu 

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Oh...  You have a REAL '81 CAS?  Doesn't matter - input to the ECU is the same as with the '82-'83 optical CAS.  You can use an Auto ECU with a manual transmission and vice-versa.  The difference between the ECU's has little to do with the EFI and more to do with the transmission lock-out (safety feature on the 280ZX).  And yes, I've used an '82-'83 ECU on an '81 harness for testing purposes and it works.  If you leave the '82-'83 ECU on the '81 harness, you need to jumper out the dropping resistors.

 

If you're getting power to each injector, the dropping resistors are good.  There is one resistor for each injector.

 

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19 minutes ago, superduner said:

 when that noise comes on after cranking I noticed  the Injectors were all on and spraying at the same time. Never seen anything like that before. I Followed the same swap guide i did beforeon my last project so I definitely got blind sided on this one.

 

Even the ECCS system is not too complicated to follow the wiring diagram and figure out how the injectors get opened.  I always get in to trouble when I only follow instructions.  Are you sure that they're not just stuck open and the noise is the fuel pump, or FPR?  

 

The typical failure mode of the 280Z EFI ECU is to flood the engine, due to something in the ECU shorting the injector power to ground.  You might unplug your ECU and see if the injectors still spray.  If they don't the problem might be in the ECU.  If they do, you have a short to ground somewhere else.  That's the key to understanding injectors.  They open when the power is grounded.

 

You could also unplug all of the injectors, electrically, and see if the buzzing noise is still there.  If it is, it's not the injectors.  You could disconnect the dropping resistors to remove power and do the same.

 

Lots of ways to troubleshoot.  And your description of what's happening isn't super clear.  Were you holding the key to Start while the injectors were spraying, or did you let go and it was at On, or was it off?  Lots of "after cranking" possibilities.

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