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chaseincats

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    280z
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    1978 280z stock l28 - Dallas TX

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  1. The main efi relay had some resistance so maybe the efi system wasnt getting full power? My main guess is the fuel pump relay had resistance, so maybe it took a little bit longer for power to push its way through the corrosion to turn the pump on? Who knows - all I do know is everyone should test the relays for resistance. The only reason I resurected this old thread was for that PSA haha
  2. I cleaned 2 things - 1) the "teeth" that sit outside of the relay housing (the things that plug into the harness). After cleaning the teeth I took resistance measurements between the circuits. For example (I didn't need to clean this one but it's easy to explain this way) - the fuel pump control relay has 4 teeth. By activating the relay by touching a 9v battery to the left 2 of the 4 teeth the relay will click, I then measured the resistance of the high power circuit (the side which is actuated by the relay itself) 2) if resistance is found (anything over 0.02ish on the multimeter's ohm setting), I opened up the relay by bending the locking prongs back to pull the top of it off. Once open you'll see 2 contacts and rocker looking like this: \ |/ when actuated, the relay arm will shift to \| /. For relays that had resistance, there ALWAYS was some sort of black marks either on the contact side \ / or the relay rocker arm side | Using sandpaper i cleaned them all up and took another measurement confirming there was no more resistance. Top tip: the screw at the bottom of each relay has nothing to do with opening the casing, it screws the relay electrics to the bottom plastic base. Unscrew that screw to pull the articulating arms out of the contacts, it makes it WAY easier to clean both sides that way and screws back in easily.
  3. Long term update. It wasn't the injectors and for the hotter part of the summers that followed, I had the long cold starting issue. A few months back I added a manual switch in the cabin to bypass the Thermotime switch to get the car to start up on crank 1 or 2 regardless of weather which is awesome and works like a charm. That said, I replaced my fuel pump a week or so ago due to it being old as heck and pooping out once. While the car ran great once started, it still had that long cranking issue when it was hot out. I took the relay bracket out and cleaned the teeth of all of them then used a multimeter set to resistance (ohm) and checked the circuits from the teeth and low-and-behold found resistance. I pried open the relays that had resistance (fuel pump and main EFI relay - the fuel pump control relay was fine) and found black corrosion on the relay's rocker arms and tabs they connect to once triggered. After cleaning all of that off, I took another ohm measurement and got basically 0. I put them back in the car a few days later and without using the what I started calling the 'quick start switch' the car roared to life on crank 3. I was absolutely floored. All that to say, take your relay bracket out and take some ohm measurements of the circuits in each relay (after cleaning the teeth with a dremel wire brush or something). If you find anything but "0.02" or below resistance, pry them open and sandpaper off the black corrosion which is no doubt there.
  4. Is there any possibility this is ECU related, and if so how would he test it?
  5. Thanks I'll give this a shot. I have teflon tape laying around so that should do it then.
  6. Was trying to track down a leak and I think I've narrowed it down to oil sneaking out of the threads of the oil pressure sending unit. The unit works great outside of the small leak. Is there an o-ring between it and the block that has gone bad or do they seal to the block in a different way?
  7. Thanks for writing this all up, I'll try and answer them individually No leaks - we've smoked and sprayed it multiple times EFI temp sensor is brand new and in spec Every cylinder is firing spark and fuel (pulled spark plug wires 1 at a time then did the same with the injector power connectors Last time we checked we set it at 10 but even when it was higher as we were setting it the stumble remained The car sounds like its much more similar to your situation since its not bogging/missing it just doesnt want to rev and WILL pop loudly out of the intake if you press the accelerator all the way down and hold it at idle
  8. Normalized meaning the car no longer has a stumble when you hit the accelerator and revs/falls how a normal car should.
  9. Seconding @Ogs Classics's question. My stock 280 has the same cone filter his had and didn't need the stock airbox to run properly. Why would that be necessary for his car?
  10. Moving this over from the "strange intake noise" thread since that's solved. My friend's 1975 280 is having a strange problem where it stumbles every time you hit the gas. We installed an air fuel gauge and when you hit the gas it will go into 'off the chart lean' numbers and then stumble up to catch it. Once it's in a high enough rev range it's responsive, but getting it into the 2.5-3k range is difficult to say the least (see video below). It's also worth noting that it idles fantastically, but it's literally just when you hit the accelerator that the jetronic EFI doesn't throw enough gas at the engine to keep up. The only way to get it to run well(ish) at all is to richen it WAY up using the AFM gear. Another interesting thing is when you pull the plugs they are black but the idle number on the air/fuel ratio gauge says 13.5 when the big gear is set back to the stock tooth (we marked it before messing with it). Mid-13s is the number I have on my '78's afr gauge and my plugs are clean. Here is what we've done so far: Gone through the entire fuel injection bible testing everything it recommends and all values came up properly Cleaned all connections/connectors/grounds according to atlanticz's page Changed EFI temp sensor (it was dead) Change EFI connectors on injectors and temp sensor Cleaned injectors using carb cleaner and a 9v battery to push the cleaner through Put a fuel pressure gauge on it between the filter and rail (36psi) Put a new fuel pressure regulator on it (the old one was hissing, the new one doesn't) Tried a different throttlebody Tried a different AFM (with stock settings) New head & intake manifold gasket (unrelated past problem) Smoke tested the engine for vacuum leaks and capped them all then sprayed the engine with carb cleaner and the idle didn't change indicating we got all the leaks Completed entire 'engine tuneup' chapter of the fsm including timing and valves New fuel filter Here's a video of how it's behaving here - any ideas? My friend is making an account and will take it from here
  11. Thanks, wasn't sure if the colors were just for the links in the 2 pods
  12. Does anyone know the what the amperage is of the EFI relays (the ones in the plastic bracket clip on the battery-side of the relay bracket? This is the fusible link that comes off of the positive terminal of the battery and not the links that are in the 2 pods with the white caps.
  13. Sorry, you're absolutely right - opened the '75 manual for his car and found it there. I'll relay the message thanks Zed
  14. We ended up slightly bending the main metal arm that connects to the circuit board contact which touches the wiper arm's single point towards the top and then we got a reading. The car still stumbles on acceleration however. After all this I just advised my friend to take the car to a shop and be done with it.
  15. My FSM only goes up to page EF48 (1978). Are you looking at a ZX book? Sorry, I meant to say we sanded the wiper contact - we put sand paper between the carbon trace and wiper with the soft side sitting on the carbon.
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