Question about 1988 Nissan 300ZX

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I have a 1988 300zx non turbo 3.0 just replaced the ecu thinking it was the problem but its not. My car will turn over and it sparks, tested the fuel pressure and it makes 42lbs so thats not the problem the injectors just wont spary. The self diagnosis lights on the ecu dont come on. Makes me think its not getting power is there a hidden fuse, relay or fusible link before the ecu? Completely lost

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  • snakeeye253 May 30, 2011

    earth pulse? does that mean it grounds on one side? Can i test that with a test light?

  • snakeeye253 Jun 01, 2011

    I will try while cranking it over. I unhooked the wire clip onto the injectors and tested with a light both sides are constantly hot even with the key off I will go try it while its turning over and post results. I am not sure if both wires are supposed to test hot either. The ones that go to the injectors the green and red ones both light up the test light, on both sides of the engine even when the key is off. It ran perfect I had a stage 2 clutch put in it. It drove 2 miles home and the fuel pump would not shut off, It drained the battery i recharged it and found a short that was keeping it on in the trunk and now the injectors wont spray. Have pressure in the fuel rail and spark. checked the timing belt that is still good. completely lost any help would be appreciated.

  • james mcgrath Jun 12, 2013

    if you download the work shop repair manual it will show you how to test every thing and tell you what the problem is ok i have the same problem i did this test and it came back as the idle switch sensor so if you go to the car turn the on to dash lights then on the bottom of the compute

  • james mcgrath Jun 12, 2013

    if you download the work shop repair manual; and go to the diagnostic procedure it will show you what to do ok this is what to do go to car turn it on to dash light then on the bottom of the computer turn the screw all the way around then count how many times the red and green lights flash the red flash are lots of 10 the greens are 1s

  • james mcgrath Jun 12, 2013

    if it flashs 2 red and 3 green that is 23 this will tell you what is wrong so download the manual you will sort it out i have the same problem i did this and it was the idle switch sensor



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The pulse to switch the coils comes from the crankshaft sensor via the ecu. Pulse to switch injectors comes from the CAMshaft sensor via the ecu. Check injector wiring plugs and confirm there is an ignition live of 12v at one side. Other side should have an earth pulse when cranking.Once you know which is missing you can trace the fault backwards. ( if no ignition live then check wiring, relay, fuse etc) if no earth switching check camshaft sensor and wiring.

Posted on May 29, 2011

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  • snakeeye253 May 30, 2011

    I used a 12v test light and my injectors on one side have power even when the key is off. Is that right?

  • Martin
    Martin May 31, 2011

    Yes. That means it will have ignition +ve at one side and a flashing ground at the other side while cranking.
    You say constant power at one side. Do you mean it has a +a2v or a ground. Do you have a flashing ground at either during cranking?

  • Martin
    Martin Jun 01, 2011

    Hi we need to be clear about this.
    Disconnect one of the injector plugs. ( 2 pin plug)
    Switch on ignition and immediately probe the plug and find the positive side..
    One pin should be ignition live (+12 volts)
    Then probe the other pin whilst cranking the engine.
    This side should show a pulsing earth (ground).
    Ideally you should be using an led test light and not a filament type test lamp, as the switching current may not operate a bulb type. If you are using a single polarity led test lamp, remember to connect the clamp end to ground to probe for a +ve and vice versa.
    Let me know what you find.

    In answer to your earlier question...No you should not have power ot the injector when key is off. Thats why i'm wodering what kind of tast lamp you are using and if perhaps you are connecting the clamp end to +ve and probing and finding a ground.



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Will not start, fuel problem

ok, ill guess it cranks perfectly.
fact 1, there will be no fueling unless the ECU is happy.
happy means:
  1. ECU thinks spark it good. (it has a pin a1 monitor)
  2. Spark is good.
  3. Throttle not stuck (TPS errors) wide open throttle.
if spark is good, IS IT? on all 4 ?
then try test fuel, if it runs for 3seconds on test fuel then the cam belt is not slipped, and there is spark.
if it does not run on tests fuel there is no spark or timed wrong, or the cam belt slipped. (very common on zero serviced cars)
if timing is still correct and runs on test fuel then we attack the ECU inputs. and outputs (the single injector)
this all sounds complex and is not
lets play that out.
  1. ah dizzy rotor turns , cam belt not snapped.
  2. ah, the spark is good but is way off time the belt slipped....
  3. The engine runs on test fuel, wow sounds snappy too.
  4. ok , i use a NOID light on INJECTOR pins 1and 2.
  5. the lamp is good, the fuel pressure , hark , is 0psi or 10. wrong
  6. the NOID fails, i then check TPS input voltage to the EDC
  7. its good, i find the tacho pin dead. OMG.

this year car the Distributor makes all spark the ECU does NOT.
but the ECU watches it like a hawk.
if pin A1 goes dead, ECU cuts fuel, ending crash and burn like seen on TV.

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one of the best posts ever, of 4000. even EX model and dizzy maker.
wow. !
my guess, is it passes a time 4 spark tests.
the 1st rule of all EFI systems is.
1: if the ECU even THINKS (sic) there is no spark it MUST cut fuel.
the ECU has 3 ways to find bad spark (not all ways)
A: spark read back signal dead. (dtc 8? or 15)
B: CMP dead,
C: CKP dead.
the ECU will in fact flash the codes out to tell you which of the 3 are dead, if dead. ever do that yet? (code 4,8,9, 15)? others?
this is called by me, "crash and burn logic", (EFI Rules)

So never ever, troubleshoot fuel loss. with out doing all the above first.
1988 to 2013 cars, all work the same.(EFI)
some cars only activate the fuel pump cranking and running.
that be rule 2:

the ECUis covered in the FSM>
here is a free FSM.

test for spark using a test spark plug x4 (and at coil if easy)
do the scan, of the ECU, the winky blinky test, using the JUMPER.

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I have a 1997 delsol which has started perfectly everytime I have gone to start it until the other day. I was able to push start it and it ran fine till i shut it off at home. After testing with a...

its an old car, why not get the real FSM to keep it going. DIY
it only takes 3 things to run,. one is bad, and find that 1 failure
and take it to the logical conclusions (vast)
1:Good engine, 150psi compression all cylinders. W.0.T.
2: good spark ( and timed right too.) (timing light and test spark plug)
3: good fueling (not too much or too little) (lots of tests but are the spark tips wet? dripping in fuel or dry as a bone. )

if the engine was good and spark , then test fuel test would pass.
does it?
fuel at rail means zero. only the proper pressure works in EFI.
my guess, is you did the dribble? tes?t a the the rail?
that dribble test only finds 100% DOA pumps. nothing MORE.

if the sparks are dry, and you did a proper tuneup. did you, and did you put the new spark plug wires back 1 by 1, no?
then test fuel works and runs for as long as you squirt it.
if test fuel runs say for 3 seconds for each time then you lost fuel..
most cars cut fuel injection if spark is lost. or it even thinks it is lost. ECU monitors spark and cuts fuel
this is classic, and is easy to see with any NOID lamp test
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Ok guys I have a 97 lhs the fuel pump went bad replaced it car ran great again but now it wont start turns over have replaced the fuel filter and the coil pack and still it wont start im stumped please...

this is not unique to chrysler, at all, its EFI.
all EFI works alike , the shapes change to fool the non tech.

i dont know about you, but in my shop
i check fuel pressure and you found it at zero
then put in a new pump and didnt check pressure.
why would you do that? after all it was zero.
and you do that and its still zero. then find a bad wire /connector
in the fuel pump power feed or the fuel pump relay.
or ? a inertial cut out sw, or rollover switch. (i said generic)
now rule 2: if spark is bad, the ECU cuts fuel,
BY DESIGN. that dont mean spark really is bad, but does mean
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All ECU monitor spark 1 way or the other, and if that fails.
there WILL BE NO INJECTION period.
use your scan too to see DTCs while cranking and dead RPM cranking for 5 seconds, release key and look for crank or cam
sensors errors, key key on for 1min to see them pop up.

your are stumped because you are not troubleshooting, only guessing. and will make you broke fast.
here at the simple tests, in the proper order.
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the cam timing is way off. no motor will run like this.
2: spark check for spark. ! at all spark plugs, not just one.
3: make sure the ECU is happy about spark, RPM moves cranking , etc.
if spark tips are dry at this moment test fuel can be used.
does it start now then stall as the the test fuel is consumed.?
4: check for injection.
do the injectors click , do all of then click , cranking>?
if all fail, i can assure you the ECU is CUTTING FUEL!!!
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but take to bank, can witness the drop in pressure and know the injector does in fact inject.
that way or by looking at fuel soaked spark tips.

the injectors can fail in many a way, they are fuel cooled.
A:shorted coil, open coil
B: ecu driver dead.
C: injector clogged or leaking (leaking causes flooding)
the injector has inside 10 micron screens. tiny,
d: bad fuel. cant burn or clog s screens.

you are now totally confused (above) or are un-stumped.

if you dont understand EFI at all , then lets go back to 1920.
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