Question about 1985 Nissan 300ZX

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  • Nissan Master
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On a 280 ZX, one side of the injector elecrtical feed is hot all the time.
Pull an injector lead off. Usially #6 is the easiest one to get to. Get a test light and touch one of the electrical connectors in the plug. One of them should light the test light. Or if you have a voltage meter, set it to 20 volts, ground the black lead and touch each terminal in the connector. You should have battery voltage on one of the connector pins.. The computer makes and breaks the grounds on all the injectors, pulsing them all each time a signal is sent to open and close them. The injectors pulse at the same time they are not sequential.The ground for the injectors is a black wire, most of the time it is just one larger diameter black wire which goes back into the engine harness.There are some harrnessess with a cluster of black wires akk joined together using 1 connector This connector(s)wire is bolted to the top of the intake manifold usually coming out of the same wire harness which carries the injector harness plugs, the coolant temp sensor for the engine gauge, from 1979 and later they used cylinder head temp sensors which do not get exposed to the coolant. (I mentioned that because had told someone with a 300Z about makeing sure of cleaning the coolant temp sensor terminals and plug for a good connection. I gave him the right connection, however if he diagnoses the sensor as bad, when he removes the old one, nothing will come out of the hole.) The 300Z's use dry sensors as well. The ZX'S sentsors are locaed near the back of the cylinder head, I think just below the #5 or #4 cylinder, just before it reaches the block. The 300Z's sensor is located at the front of the engine below the thermostat housing. You have to look closely to your right if you are faceing the motor and it is almost in the valley. .Checking for an injector pulse if you don't have a noid light. if you have a long screw driver or other thin but solid object about two feet long, have a friend with you. Put the small hopefully the size of a screw driver tip, on the top of the injector, put your ear to the other end and have your frienf crank the engine and listen for a clicking sound. You can check all your injectors that way. (I have Parkinson's disease, so I may be redundant on things, push enter before I have a chance to proof read things. I'm in my 60'svery experienced , especially when it comes to DATSUN and Nissan (one of the same) I am a certified Nissan Master Technition which allows me to pass along my years of expearence. I do have a lot of technical data,some going back into the late 60's The later technical data I have stored in one of my external hard drives. A lot of questions I could answer of I can access the hard drive(it's Hmmmm I drifted of the subject! Your problem.You see, I just looked at the top of my screen and rolled it further up and here I was thinking Ieas answering a question on a 280ZX when in fact your's is a 300Z! For the most part the principals are the same. Pull the coil wireoit of the center of the distributor, with a friend helping you, hold the wire close to a bare metal object and heve tour friend crank the engine. Look for a spark. If you don't get a spark, chances are, your injectors aren't going to pulse either. No ignition, no fuel injection operation. If the distributor doesn't turn, the injectors won't pulse. Computers do fail, but I don't run into many 300's which the computer's have failed on. I race 300Z's and through raceing, I have done a lot of experimentation with computers which will work to the extentt where my car will start and run. Even though my race car is an automatic, I can plug a computer into the race car from and automatic and it will run. I won't use it for raceing, but I have a cabnet with used Nissan computers, relays and other components will usee , for testing and will try what ever spart we have which is a known good one, to see if it resolves the problem if we haven't found it another way. Any computer from a 6 cylinder 300Z from 84-86, if the plugs match, I haven't tried any computer's from later models past 86, because I haven't had the need to try,should alloww the car to start and run. most of the circuitry is the same. If your car starts, you know for sure it's the computer. There is also a main relay, an injector relay if memory serves me right which is located on the right inner fender. along with headlight relays. All are located in a black box which you can remove the cover on.. On top of the box cover, it shows the relay locations.inside the box. OH, in the test where you are looking for spark in listening for ijnectors clicking, if you hav gone through all of that,know you have allth blackwires from the wire harness nad you do'nt have a clicking, it's probably the computer. In our trade we have a saying to the newbe's KISS!
KEEP IT SIMPLE STUPID! In my shop, I get more cars when they have been tampered with by their owner's and the owner he's thrown a $1,000 plus into trying to fix his car.I love the ones where ,before the car has made it off the flatbed,I open the hood, spot the problem and have it running before it is unhooked by the driver of the truck.Wow did I get off track. Maybe I did help you or help a few who have read my rattling on. "there are a lot of it could be's, but do your basic homework before getting into the more complex and sometimes expensive tests. If you need a computer, often you can buy them from a salvage yard with a warranty. good luck

Posted on Jul 03, 2014


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SOURCE: fuel pump relay

Try drivers side in rear hatch, ahead of wheel well area, behind trim panel.

Posted on Jul 20, 2009

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SOURCE: 1982 Nissan 280ZX injectors will not open.

you need to check with a noid light and you must have a pulse or yuo have a computer problem they had a lot of difficulty with their injector plus too

Posted on Sep 13, 2009

  • 170 Answers

SOURCE: how much is it to change a fuel injector

Oh this is fun...

I have a 1993 300ZX N/A and have had two injectors go out on me at different times. This is an expensive fix for two reasons; 1) the injector. 2) the installation process.

If you're lucky you can find a shop or eBay seller with new or reconditioned injectors at an affordable price. $150~$275/injector is steep. Worse is the cost of removal and installation since the upper plenum and fuel rails must be removed. This is a design flaw by Nissan since you can see both screws to remove the injectors, but one is partially covered by the aliminum upper plenum (big silver colored aluminum air intake over the block). There are some sites that will talk about drilling or filing the plenum to allow access to the second screw, but this is highly frowned upon and you run the risk of putting a hole in the plenum. Best to leave this as-is.

It's cost effective to replace these yourself if you're handy with a wrench and a screwdriver. the cost for a shop to do this job is between $600 and $1000 for one injector. Most of the cost is the labor to remove and replace the plenum and fuel rails.

If you want to do this yourself, start with using a voltmeter and check each injector to find the bad one. Set the voltmeter to Ohms, disconnect the electrical from the injectors, and check the resistance between the contacts of each injector. They should read between 10 and 18 Ohms. Here's how:

Here's a step by step process for replacement:

Like I said, I paid for this twice and never again. Too much money for such a small part that I can do myself in my spare time.

Hope this helps!

Posted on Apr 13, 2010

  • 1 Answer

SOURCE: gas gage dont work on my 1985 nissan 300zx

there is a sensor for the gas gauge in the hatch of the car its a little 4x4 metal box about 6inches up from the access for the fuel pump. the cmmon leaks in the car seem to target this guy

Posted on Jun 29, 2010

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