brandon Posted May 12, 2004 Share #1 Posted May 12, 2004 Hello all. I'm a newbie to the Z world-- just bought a very nice 76 280Z: http://devnulled.com/gallery/280Z-calitocolorado I've worked on / modified DSM's for around 5 years, and can do about anything on them without a problem except rebuild engines, trannies, etc by hand, but decided it was time for something new. Anyhow, on the drive home, I noticed it was running very rich. I had an emissions test done today, and they also confirmed that it was rich. Being that it's fuel injection, I'm not quite sure where to start. I would assume that perhaps the spark is not strong enough? I have some new Taylor wires and NGK plugs to throw on this weekend, so that's a start. Any other suggestions on how to get the car running at stoich? Also-- what is the torque spec and gap for the spark plugs? I'll order the CD Manual soon so I won't have to ask dumb questions like those last two soon. Thanks, - Brandon Link to comment https://www.classiczcars.com/topic/11678-280z-running-rich-how-to-fix/ Share on other sites More sharing options...
brandon Posted May 12, 2004 Author Share #2 Posted May 12, 2004 I should mention that switching to carbs is not an option for me. I love fuel injection. Also, the fuel system in the car was totally replaced within the last couple of years.. all new injectors, hoses, etc. Link to comment https://www.classiczcars.com/topic/11678-280z-running-rich-how-to-fix/#findComment-80700 Share on other sites More sharing options...
venom42 Posted June 9, 2004 Share #3 Posted June 9, 2004 I have a '75, and some similar questions to yours. I am thinking that the "cold start" injector may be the culprit in my case. I am not sure though. Anyone know if it will cause any problems if I disconnect the cold start injector (leave it in place, but remove its electrical connection)? Link to comment https://www.classiczcars.com/topic/11678-280z-running-rich-how-to-fix/#findComment-84493 Share on other sites More sharing options...
TomoHawk Posted June 9, 2004 Share #4 Posted June 9, 2004 You "should" be able to run the engine sans cold-start injector, but it should not start up and run well until it's warmed up. That's what the cold-start injector does- extra fuel to start or run when cold. It's controlled by the thermotime sensor/switch.Maybe you could try starting the engine, then disconnect the cold-start injector? Make sure it's not stuck upen first! Link to comment https://www.classiczcars.com/topic/11678-280z-running-rich-how-to-fix/#findComment-84515 Share on other sites More sharing options...
sblake01 Posted June 9, 2004 Share #5 Posted June 9, 2004 The cold start valve gets it's signal from the thermotime switch if the engine is cold enough when you turn the ignition to the start position. The signal only lasts for about 8 seconds then the thermotime switch opens. If you're still getting fuel from the cold start valve at that point then it's leaking. But that is rare. Usually, the culprit in that circuit is the thermotime switch. Disconnecting the cold start valve only eliminates that part of the cold start system. Check the two terminals on the thermotime switch for continuity when the car is warm. If you have continuity at that point then the switch is bad. Richness can also be caused by the AFM being out of adjustment. Link to comment https://www.classiczcars.com/topic/11678-280z-running-rich-how-to-fix/#findComment-84525 Share on other sites More sharing options...
venom42 Posted June 9, 2004 Share #6 Posted June 9, 2004 Is the thermotime switch something that commonly fails? What temp does it stop telling the cold start injector to open at? Link to comment https://www.classiczcars.com/topic/11678-280z-running-rich-how-to-fix/#findComment-84550 Share on other sites More sharing options...
TomoHawk Posted June 9, 2004 Share #7 Posted June 9, 2004 It just gets worn out sometimes, or gets stuck. Link to comment https://www.classiczcars.com/topic/11678-280z-running-rich-how-to-fix/#findComment-84553 Share on other sites More sharing options...
sblake01 Posted June 9, 2004 Share #8 Posted June 9, 2004 Originally posted by venom42 Is the thermotime switch something that commonly fails? What temp does it stop telling the cold start injector to open at? They don't fail very often but they seem to have a tendency to be bad on cars that have sat for a long time without being started. The temperature is not as important as the signal. The one I'm looking as says 35 deg. C.-8 sec. Meaning that if the temp is below 35 the signal will be sent for 8 sec. If the temp is above 35 the signal won't be sent. When they stick they continue to send the signal and the car will run rich to the point of being undrivable because of the extra fuel. Link to comment https://www.classiczcars.com/topic/11678-280z-running-rich-how-to-fix/#findComment-84576 Share on other sites More sharing options...
TomoHawk Posted June 10, 2004 Share #9 Posted June 10, 2004 I tried disconnecting my thermotime switch today. It seems to be running a little leaner, with more power/acceleration, and it seemed to go easier on the freeway. Much less effort to go from 60 to 70 MPH.I don't know what effect it has on starting as the engine was already warm when I tried the experiment. I will try starting it cold in the morning.I also tried starting/running the engine with the cold-start injector wires disconnected, aswell as the TPS switch disconnected. Disconnecting he thermotime switch had the biggest effect. Link to comment https://www.classiczcars.com/topic/11678-280z-running-rich-how-to-fix/#findComment-84665 Share on other sites More sharing options...
sblake01 Posted June 11, 2004 Share #10 Posted June 11, 2004 Once the engine starts or when the engine is warm, the thermotime switch and cold start valve have no affect on performance unless there is a problem with one or both. Link to comment https://www.classiczcars.com/topic/11678-280z-running-rich-how-to-fix/#findComment-84702 Share on other sites More sharing options...
venom42 Posted June 11, 2004 Share #11 Posted June 11, 2004 I have some "tinker time" tomorrow, so checking the thermotime switch is one of the things on my list. Link to comment https://www.classiczcars.com/topic/11678-280z-running-rich-how-to-fix/#findComment-84709 Share on other sites More sharing options...
TomoHawk Posted June 11, 2004 Share #12 Posted June 11, 2004 I'm able to start my engine easy in the morning with the thermotime switch disconnected, but it runs really bad until it gets warm. Bogs really bad. It's OK after it gets warm.Any ideas? Link to comment https://www.classiczcars.com/topic/11678-280z-running-rich-how-to-fix/#findComment-84802 Share on other sites More sharing options...
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