Cyrillink

280z 78 Wont idle, Running Rich, out of ideas.

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    Hey Team

    I have spent a lot of time on this  forum and i want to say thank you all so much this is an incredible community.

    I have hit a brick wall and looking for a little help.

    Background story; I'm helping a friend of mine fix his 280z with 30,000 miles on it all original. Car has been garage kept all its life. Really really well taken care of. Apparently some one A-hole mechanic tried before me and failed miserably and i don't know what he/she messed up or touched. After them the car didn't even start. Fixed that issue. (FACE PALM) 🤦‍♂️  

    When you try to start the car it tries to start but never does on its own. If you give it gas than the car starts but it is runs rough(motor shaking). Have to keep the gas paddle pressed in just a little to keep it running. Car smokes white/bluish smoke from the tail pipes. (running rich) ( Gas smell). Changed the oil after the previous Mech worked on it smelled like gas was in it.  Did a double flush much better now.  

    Things i did and tested on the entire car:

    Spark Plugs - New

    Spark Plugs Wires - New

    Battery -  New

    Battery Terminals - Cleaned  

    Distributor cap - Cleaned and polished

    Dizzy - Cleaned and polished

    Pick Up - Adjusted to correct distance from roller according to 0.08in or 0.2mm

    Distributor Vacuum - Good

    Ignition Coil - NEW (built in resisters original ceremic resistor was missing) (https://www.holley.com/products/ignition/ignition_coils/street/super_stock/parts/8140C)

    Fuel Pressure - 22-25psi in when engine is off,  while the car is running at low rpm 30psi+ ( 700 to 1k)

    Smoke test - No leaks

    AFM - Refurbished still sealed was installed last month

    AFT Idel screw - Did not mess with

    Throttle Body Screw - NO EFFECT when turning clock or counter clock

    Electrical - 12V all over from Body, Engine, - All good

    Ground Connectors - Clean

    Coolant Temp Sensor - Ordered Arriving tomorrow (CANT IMAGINE ITS THE REASON)

    Timing - Seems good 10 degrees of from original zero marking

    Cylinders Compression Test - 125 + on all Cylinders  

    Injectors connections - look good

    Injectors - listen to them with stethoscope sound health strong tick

    HELP!!!?

    Thank you again for reading. I will be testing tomorrow. 

     

     

     

     

     

     

     

     

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    43 minutes ago, Cyrillink said:

    When you try to start the car it tries to start but never does on its own. If you give it gas than the car starts but it is runs rough(motor shaking). Have to keep the gas paddle pressed in just a little to keep it running. Car smokes white/bluish smoke from the tail pipes. (running rich) ( Gas smell).

    Coolant Temp Sensor - Ordered Arriving tomorrow (CANT IMAGINE ITS THE REASON)

    The coolant temperature sensor is the most likely cause, based on your symptoms.  You need to measure the resistance at Pin 13 of the ECU connector to ground to know for sure.  Installing a new one won't help if the wires aren't connected to the ECU.

    I just now realized, after many years of browsing through FSM's and Fuel Injection Guides, that this drawing has the pins numbered, right in the drawing.  I never looked closely enough before.

    image.png

    image.png

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      Installing a new one won't help if the wires aren't connected to the ECU. - Zed Head

    _________________________________________________________________________

    Thank you for confirming my suspitions. What do you mean if the wires are not connected to the ECU.?

    Do you believe that cables broke, just dirty inside or disconnected? Should I  not even take out the coolant temperature sensor and clean it or even bother replacing it even  i have it?  Sorry for the weird question.

    Edited by Cyrillink
    didnot add the quote

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    5 minutes ago, Cyrillink said:

     

    2 hours ago, Zed Head said:

    The coolant temperature sensor is the most likely cause, based on your symptoms.  You need to measure the resistance at Pin 13 of the ECU connector to ground to know for sure.  Installing a new one won't help if the wires aren't connected to the ECU.

    I just now realized, after many years of browsing through FSM's and Fuel Injection Guides, that this drawing has the pins numbered, right in the drawing.  I never looked closely enough before.

     

     

    Installing a new one won't help if the wires aren't connected to the ECU.  - reply

    thank you for confirming my suspitions.

    What do you mean if the wires are not connected to the ECU.?

    Do you believe that cables broke, just dirty inside or disconnected? Should I  not even take out the coolant temperature sensor and clean it or even bother replacing it even  i have it?  Sorry for the weird question.

    And thank you for attaching the exact connections with pins

     

    Edited by Cyrillink

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    The only way to be sure that that the wires are intact from the coolant temperature sensor to the ECU is to measure resistance at the ECU plug.  If you do that you are testing the wires, the sensor, and every connection along the way.  I would not do anything to the coolant sensor, not even remove the plug at the sensor, until I measured resistance at the ECU plug.  Start at the the end, not the middle. 

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    9 hours ago, Zed Head said:

    The only way to be sure that that the wires are intact from the coolant temperature sensor to the ECU is to measure resistance at the ECU plug.  If you do that you are testing the wires, the sensor, and every connection along the way.  I would not do anything to the coolant sensor, not even remove the plug at the sensor, until I measured resistance at the ECU plug.  Start at the the end, not the middle. 

    Hey Zed,

    Tested the resistance and i was able to get a reading back, the reading was similar to when the sensor was pulled out of the car for cleaning.  Took out the plugs cleaned them to make sure everything is well.

    Car did the same thing. Blue smoke, rough idle while only holding the paddle down. 

    Going to do another smoke test just to triple check.

     

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    2 minutes ago, Cyrillink said:

    Hey Zed,

    Tested the resistance and i was able to get a reading back, the reading was similar to when the sensor was pulled out of the car for cleaning. 

    Without the actual number and knowing where it was taken, can't really tell what you're saying here.  It might the the most important measurement you can make on the EFI systems.  "a reading back" doesn't read well.

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    5 minutes ago, Zed Head said:

    Without the actual number and knowing where it was taken, can't really tell what you're saying here.  It might the the most important measurement you can make on the EFI systems.  "a reading back" doesn't read well.

    I am getting a better snapon Multi meter right now going to test it again and get back to you.

    Thanks again

    Edited by Cyrillink

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    Not to throw you off the troubleshooting track that's been laid out, but is there a chance that the guy who worked on it before you removed the injector connectors and cross connected them, or in other words, put the wrong connector(s) on the injectors?

    Sent from my Coolpad 3310A using Tapatalk

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    23 minutes ago, Zed Head said:

    Without the actual number and knowing where it was taken, can't really tell what you're saying here.  It might the the most important measurement you can make on the EFI systems.  "a reading back" doesn't read well.

    car is indoors with the heat on to 60f 

    sensor reading from the ECU Harness 2.07k Ohm.

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    8 minutes ago, Reptoid Overlords said:

    Not to throw you off the troubleshooting track that's been laid out, but is there a chance that the guy who worked on it before you removed the injector connectors and cross connected them, or in other words, put the wrong connector(s) on the injectors?

    Sent from my Coolpad 3310A using Tapatalk
     

    Interesting Idea, let me double check the correct wire pattern

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    14 minutes ago, Cyrillink said:

    Interesting Idea, let me double check the correct wire pattern

    Checked the injector harness looks to be plugged in correct

    IMG_3791.jpg

    IMG_3792.jpg

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    The injectors all open at the same time.  You can switch plugs at will.  

    The throttle valve switch is a possibility.  Stuck at wide open.

    Another piece in the meal.

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    1 hour ago, Cyrillink said:

    Yes, plugs had moisture on them.

    What I meant was are the carbon fouled? Also how is the ign timing set?

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    11 minutes ago, Dave WM said:

    What I meant was are the carbon fouled? Also how is the ign timing set?

    I tossed in a new set of plugs first thing i did. and timing was set by some one else. i am about to get a timing gun and double check it my self.

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    I had that issue. And I pulled the water temp sensor plug off. Jumped it with a paper clip to close the loop and it ran like a dream. $18 later for a new sensor and all good...... at that time. It thought it was cold and was dumping extra gas from the cold start injector. 

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    4 minutes ago, Dodd23 said:

    I had that issue. And I pulled the water temp sensor plug off. Jumped it with a paper clip to close the loop and it ran like a dream. $18 later for a new sensor and all good...... at that time. It thought it was cold and was dumping extra gas from the cold start injector. 

    Thanks for the recommendation going to try the paperclip.

    Already have the new sensor installed as well. 

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    3 minutes ago, Cyrillink said:

     

    Just checked, Looks good to me

    IMG_3793.jpg

    Just like the coolant sensor.  You have to get the numbers at the ECU plug.  The ECU determines how long the injectors stay open.  They do that based on what's coming in through the connection to the harness.

    You're on the very well-worn path of people new to the Datsun EFI.  Trying one thing at a time.  By the end you'll have measured all of the things you need to measure, just in two weeks time instead of two hours.  No offense, it is very common.

    Your symptoms are also what happens when the ECU goes bad, or the connector gets loose.  People have fixed it, temporarily, by banging on the side of the ECU.  If you had all of the test results and they were in spec. then replacing the ECU would be the last resort.

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    25 minutes ago, Cyrillink said:

    I tossed in a new set of plugs first thing i did. and timing was set by some one else. i am about to get a timing gun and double check it my self.

    The reason I asked if they are carbon fouled was the early post about running rich. Wet does not mean rich, could be just not igniting. I just wanted you to confirm the initial diagnosis that its running rich. Smelling fuel could be a fuel leak somewhere. I like to start with a new set of plugs, then run it for a few minutes, under varying loads if its drivable, maybe put 10 miles on them, and then pull and examine. A properly setup EFI on a 280z should result in nearly white insulators given that test. I just don't want to be chasing a false premise.  Poor running could be a massive vacuum leak that may not show up as leaking smoke under the hood, say if its a stuck EGR as an example.

     

    Edited by Dave WM

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    also, did you ever try removing the oil cap while it was running? normally it should stumble and perhaps die while idling. This will help find if the mixture is set incorrectly as well since unmetered air into the system in a correct working system tends to lean out and die. Again this assume all the EFI is in place and properly hooked up.

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    2 hours ago, Dave WM said:

    The reason I asked if they are carbon fouled was the early post about running rich. Wet does not mean rich, could be just not igniting. I just wanted you to confirm the initial diagnosis that its running rich. Smelling fuel could be a fuel leak somewhere. I like to start with a new set of plugs, then run it for a few minutes, under varying loads if its drivable, maybe put 10 miles on them, and then pull and examine. A properly setup EFI on a 280z should result in nearly white insulators given that test. I just don't want to be chasing a false premise.  Poor running could be a massive vacuum leak that may not show up as leaking smoke under the hood, say if its a stuck EGR as an example.

     

    Hey Dave,

    Thanks for the feedback. I am going to put this thing together entirely and take it for a 10 to 15 mile spin warm it up properly.

    than i will pull the plug send a photo.

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