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Discussion Starter #1
Hi guys, I just started having a problem with my Z, when I turn the ignitoin on, the fuel primes for like 5 seconds then turns off, I start the car runs for about 20-30 secs then dies.... I wire straight 12v to the fuel pump the car runs fine. any Ideas? Im looking at the FSM and from the limited tests I see everything is fine, I think it has something to do with a signal going to the ECU indicating if the car is running or not. ie. CAS, Ignition Switch, or Throttle valve switch.
Johnny
 

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the fuel pump is supposed to prime and then turn off after 5 seconds. However, it sounds as though you aren't getting much pressure....

First thing to check is the fuel filter. Might as well replace it, they only cost like $5.
Next, make sure the vacuum line that connects to the fuel pressure regulator is not hard or cracked.
The FPR itself might be going out..
If you're fuel pump is going bad, usually it will take longer than the normal 5-6 seconds to prime the system and it should sound like its struggling.

those are just somethings to look at.
 

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i had a similar problem but i didnt test the pump with constant 12volt , anyway my problem was the ecu , something went wrog with it so i changed it out for another and it went away , i have also heard of just cancelling the ecu controlling the fuel pump and just hooking it up to the ingition switch but i dontknow if its totally safe and parcticall as a daily driver mod.
 

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Looks like its my ECU, I replaced it with another with a "24" marking on it and it starts up and runs, the ECU I had in there was marked "26" do you think there would be a problem not using the exact same ECU?
 

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deopends on what car you got it off and what car you are putting it in , if you have a turbo you can only put a turbo ecu in and same case with n/a , if you have an auto , you can only put an auto ecu in , but if you have a 5speed you can put both the 5speed and auto ecus in without a problem.
 

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Discussion Starter #6
well seems to run just fine, booted around the block with this other computer.
I think its from a NA. I have a turbo.
 

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well since the injectors are different size you car might run a little rich because it makes the n/a injectors open more to give the same amount of fuel as the turbo do in a certain amount of time,if you have problems with it , go and get a turbo ecu from the junkyard or maybe even ebay.
 

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There is a fuel pump rely as domdogg mentioned. It is at the base of the back of the passenger seat and you'll have to remove the b-pillar to get to it.

My 85 N/A ECU had the number "24" on it but I don't know what range that number covers.

I would swap in a turbo ECU that is compatible with your set up as your fuel mixture isn't quite right if you are running with an N/A ECU.
 

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Discussion Starter #10
I opened up my turbo ECU today and found a semiconductor with a broken middle leg. Im guessing this is my problem, seems like the leg broke due to corrosion. Guess I`ll order a new semiconductor from mouser and see what happens.
john.
 

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I wired my pump to run at a full 12v right after I bought it (recommendation of the Service Manager at the local Nissan stealership) and it has given me no problems. The only draw back is that the pump runs constantly when in the ON position but not in the ACC position.

If your FPR is good there should be no problem with this, although I would check/replace that relay first off.
 

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You should probably just get a new ECU John....put up an ad on z31.com and you'll probably be able to get one for <$50 shipped. Just make sure it's an 86, because the o2 sensors won't match up otherwise.
 
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