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zclocks

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zclocks last won the day on April 5 2018

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About zclocks

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    http://www.zclocks.com

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    Seal Beach, CA
  • Occupation
    Engr

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  • About my Cars
    75 280Z

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  1. FOUND SMOKING GUN!!!! I finally found the source of my miss and sometimes backfire thru AFM. With all the things I had done I didn't look at the spark at the plugs. So...... I removed the spark wire at each plug, plugged in a spare spark plug and started the motor. Each plug was firing, but VERY weak. To cut to the chase the ignition coil was the problem. Let me rephrase that....I was the problem. I remove and replaced the coil many years ago for whatever reason. The Primary side coil resistance is supposed to be 0.40---0.55 ohms, per service manual for the 75. The Fire ball I put in there many years ago was 1.6 ohms. This might not seem to be a big change , but when I replace the coil with a "Flame-thrower -2" what a difference. The new coil has a primary resistance of 0.6 ohms , but try and find a coil today which is 0.4 ohms is not possible. I know I have my OEM coil , but at the moment I can't locate it .BTW this new coil is used with the OEM ballast resistor. This is a good day!!! PS : I should give credit to a u-tube guy with a site called "Restoration for beginners". He seems to have good understanding of basic mechanics and after watching his segment on ignition systems, which covered coil replacement, he ran into the same problem with selecting coils. Oh yea his car is a 78 280z.
  2. Time Left: 29 days and 16 hours

    • FOR SALE
    • USED

    For sale is a very nice 280z clock that keeps excellent time. The circuit board was rebuilt , mechanical internals cleaned , lens polished , set knob re-blacked and lamp replaced. Thanks for looking......Ron

    $155.00

    Seal Beach, California - US

  3. View Advert 75-76 280Z Clock For sale is a very nice 280z clock that keeps excellent time. The circuit board was rebuilt , mechanical internals cleaned , lens polished , set knob re-blacked and lamp replaced. Thanks for looking......Ron Advertiser zclocks Date 07/19/2019 Price $155.00 Category Parts for Sale  
  4. You may have just ruined the clock motor and the other bearing parts made of nylon and plastic. Most brake cleaners contain Tetrachloroethylene , ACETONE and chlorine all of which are great grease and oil removers, but detrimental to most plastics. Just a FYI
  5. Time Left: 27 days and 22 hours

    • WANTED
    • NEW

    WTB clocks from 77-78 280z and 79-83 280zx . Please e-mail quantity and price. Thanks....

    NO VALUE SPECIFIED

    Seal Beach, California - US

  6. View Advert WTB Quartz clocks WTB clocks from 77-78 280z and 79-83 280zx . Please e-mail quantity and price. Thanks.... Advertiser zclocks Date 07/17/2019 Price Category Parts Wanted Year 0 Model 280z  
  7. Hey Dave, I was going thru a few boxs of Z parts and found a 75 transistor Ignition. It's completely made by Hitachi . They were one of the big part swingers of the day. I'm impressed with the design and construction. Looks like the main power transistors were also from Hitachi. As soon as I can i'm going to install it and see if it makes any difference in my car. If not then I could have a spare or something else to repair.
  8. Dave, Yes, caps have a limited life and so do power transistors. No telling what material they used. If I can get a transistor unit I'll see about replacing the transistors and caps. Ron
  9. Yes, I should know better. I've seen so many corroded connectors on clocks that I just replace every wire /connector. The thing that fooled me is that the connectors didn't look bad, but corrosion is resistance. Thanks again for the input. Ron
  10. Dave you are correct there are 2 transistors in the control unit that are associated with the pulse to the injectors (FSM EF-51).One transistor is associated to injectors 1-2-3 and the other with injectors 4-5-6. I did this check with the 3 volt lamp as indicated in the manual and both transistors check out. This isn't an exact performance evaluation , but rather an overall output check. Funny I remember many years ago I had a lamp that was provided with a FI meter I purchased and no explanation of what it was for. I don't know what happened to it, but that was the lamp as mentioned in the manual. I also pulled the dropping resistors and cleaned everything including the connector contacts on both sides. All the resistors measured 6.5 ohms. After I reinstalled I checked that the power relay was working and there was battery voltage at the control unit pins for each injector. The car is running MUCH better and no backfire thru AFM. The drop outs are farther apart and very small compared to previously. I went back and retested with my Colortune unit and the visual blue flame is much better on cylinders 1,2,3. There are still some drop out or miss fires, but not as many. The intensity of the Colortune flame is much brighter. Cylinders 4,5,6 are unchanged, bright in color intensity and no drop outs. So, I think part of the problem may have been with the connectors on the dropping resistors or the control unit connector. What I am going to do is remove and clean all connections on the distributor, transistor ignition unit, and injectors. All my injector connectors were replaced about a year ago and I still have to replace the AFM connector. It looks good but the boot has deteriorated. I would like to dig into the transistor ignition unit and see what's going on there. I need to hunt down an OEM unit for testing. Anyone have a spare they would like to part with? I still believe there is a slight problem, but I think I'm on the right path. Thanks for all the inputs it's really helped. Ron
  11. I haven't swapped injectors, not my favorite thing , but that's just about all that's left. My car use to idle very smooth and had quick throttle response. I know there's a definite miss in 1-2-3. Could be the injectors not working correctly although they sound good . What are the chances that just 1-2-3 injectors are bad? Ok, thanks for the input and I will proceed with my quest. Ron
  12. Thanks Mark. I'll take a look at all 3 again. Yes, the plugs are BP6ES, NGK plug wires and Nissan cap / rotor.
  13. I have not driven the car . The problem is the miss at idle and I know it will be a problem when I do get it on the road. It should have a smooth idle. Problem is the miss in 3 cylinders.
  14. Ok, I am officially stumped on this one and need some help. Car 75 Calif 280z with only 80 miles on a rebuild 14 yeas ago. I know it's along story . Problem: 1-I have a small back fire thru the AFM only some times when I crack the throttle. 2- cylinders 1,2,3 have a small drop out(loss of spark). 4,5,6 look very good using Colortune. What was checked: 1. Originally the car would not start. Fuel pump was bad and replaced. Idle pressure 32psi and pump head pressure is 40. 2. Checked pressure regulator and not leaking at vacuum port. 3. Plugs replaced as they looked very dark. 4. Vacuum is 17mmhg and steady. 5. AFM boot cracked and was replaced. 6. Adjusted valves (cold and hot). 7. Checked timing , 10 deg btdc 8. Air/fuel meter indicates I am now running slightly lean (at operating temp) and rich at start up. 9. Checked timing chain mark on cam shaft sprocket . Is just to left on mark #2 10. Cap and rotor inspected and no cracks or discoloration. 11. checked resistance of plug wires and all within 500ohms. 12. checked all 6 dropping resistors. All measured 6.5 ohms Observations: 1. I have a shut off valve on the fuel line and can isolate pump pressure from fuel rail. The gauge is after the shut off so I can check pressure between the gauge and injectors. I might have one or several injectors leaking as the pressure drops off in about 30 min. 2. Using Color tune plugs 1,2,3 have a weak spark , some misses in spark and are slightly blue(good color) 3. Plugs 4,5,6 have a bright spark, consistent firing and no misses. So what it looks like is that plugs 1,2,3 have a weak spark which could be causing my backfire. The only common point I see between the plugs would be the dropping resistors, which all measure the same 6.5 ohms, spark plug wires, coil, and distributor. At this point what am I missing? Any help would be appreciated. Ron
  15. Sorry I didn't see this thread earlier, but through I would throw in a little more knowledge about AFM meters. The air flow meter is a very very sensitive instrument and has several known weakness. One of which is the temperature sensor. If this drifts the signal sent to the Control Unit will change which in turn will change the air fuel mix. And create a cascade of changes/problems. Second the substrate, called thick film ,has resistors that will drift over time. The resistors are ruthenium dioxide (look and act like glass )when centered or fired at high temperature. The exact resistor value is trimmed with plunge cuts into the ruthenium via a laser and the value desired monitored by an ohm meter. This all sounds good, but the problem comes with time when cracks develop at the end of the laser cuts. In essence the cracks grow and the resistor changes value. This can be minimized if the substrate with resistors are cured and the resistor values rechecked. This costs big $ for commercial products so they eliminate this step. In addition, the white substrate is alumina (aluminum oxide), very brittle and prone to cracking if not attached to a very rigid surface. One word of warning NEVER REMOVE the screws from the substrate. You will crack it. My 75 OEM AFM has a thick film substrate made by BUORNS and the one currently in my car is made by OHMIC?? So we have resistors and temperature sensors that change over time, gas which is been reformulated, and different manufactures of the resistor substrates . My original AFM in my 75 would intermittently quit working and at the time and I had no idea what was in the AFM. I was told that it, the AMF, was bad so it was replace. What I discovered was that the air temp sensor was slightly out of speck. The resistor substrate is just fine. This OEM AFM always caused my engine to run rich as well as the current AMF I have on my car. What I believe is the gas has changed in CA and the AFM as adjusted for the 70-80 vintage gas is the problem. For many years I have had to adjust my AFM to the leaner side to get through smog testing. Nothing has changed in my AFM , but the gas has changed. As I discovered recently the boot between the AFM and the TB must be air tight. I struggled for days tuning a new motor only to find I had several small cracks in this boot. Once the cracks were sealed what a difference. Ok one more thing to pass forward . The engine water temp sensor next to the AFM air temp sensor are the two most important parts of the FI Control Unit inputs. If either of these two items drift or change it throws everything off. The change I speak of is a slow drift out of specification. Particular attention to their performance is key. Well this is my 2 cents worth and I hope it helps someone trying to learn about the FI process. Also check out the enclosure. Ron
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