One step forward and two steps back...

[Lani Kai]

Here's my story. Sorry it's a bit long.

I've had a 1978 280Z for just over two years now, and it's always been a work in progress.

At first, it ran super rich. I found some of the injectors were leaking, so I replaced all of them. Then I found the cold start valve was leaking, so I replaced that too, but then discovered the thermotime switch was also bad, and was leaving the cold start open. I decided to just unplug the cold start connector as a temporary fix (before, when the valve was leaking, unplugging the connector didn't change anything). I figured as a Southern California car, it wouldn't really need it anyway. I also replaced the air flow meter, and it finally stopped smoking and ran brilliantly.

I then worked on the body, brakes, and suspension, getting stuck on each but finally got it ready to take to the paint shop.

I had no issues driving to the paint shop, but leaving the paint shop, the car wouldn't start. Eventually I tried plugging the disconnected cold start back in, and it started up but was running super rich again.

Once home, I replaced the temperature-related bits that I'd put off: temp sensor and thermotime switch. The car has not shown any improvement.

Currently, the car does not start with the cold start valve unplugged. Once started, when the connector is unplugged, the revs go up to about 2000 for about 10 seconds, and then the car stumbles and dies. This is the part that confuses me the most.

To sum up,

Rebuilt engine (<100 miles)

Replaced parts:

-injectors

-cold start valve

-air flow meter

-thermotime switch

-temperature sensor

Checked:

-timing (10 degrees BTDC)

-fuel pressure (~35psi)

-TPS contacts

-thermotime/temp sensor connectors: tried switching them around, but no change

Someone help!

[Zed Head]

Sounds like you've lost power to your EFI harness (maybe, I don't know if the CSV is on the that harness or not). You should check for power at the injectors and at the ECU connector (Pin 10 I believe) with the key On. Check your EFI fusible link at the battery also, first actually, maybe the paint shop disconnected your battery to keep it from discharging and messed up the connection.

It's probably running off the CSV alone, with no gas from the injectors. Find out why the injectors aren't firing.

[Lani Kai]

I'll look up the pin(s) in the FSM, but I'm pretty sure I hear the injectors clicking. Besides, I'm not sure exactly how much gas the cold start injects, but wouldn't this cause the engine to run lean?

I'm also unsure why the cold start is staying open. Does this mean either the cold start or thermotime is not functioning properly?

[hr369]

you reversed the wiring on the temp and thermotime? to take the guesswork out

of it you should test the pins and make sure that you're plugged into the right sensor.

Edited October 3, 2011 by hr369

[grantf]

I second hr369.

[Lani Kai]

Well, I verified that the sensors are plugged in correctly. I also pulled the AFM off and cleaned the contacts, checked the auxiliary air regulator just in case, replaced my blackened spark plugs and... Now it won't even start. Head, meet wall.

Plugs are gapped at 1.1mm, and putting the old ones back in didn't work either.

Edited October 9, 2011 by Lani Kai

[Zed Head]

Maybe you had the AAR plug switched with the CSV plug, and your recent work put themback where they belong. The AAR is powered when the engine is running. The plugs are in the same vicinity and are of the same type. I don't know how much gas the CSV puts out, but I think it's more than a typical injector. I have read reports of these engines running on the CSV alone. If you had the AAR plug connected to the CSV, the CSV would stay open as long as the engine was running. When you unplugged it, the engine burned off the excess gas, leaned out and died.

From where you're at now, I would confirm spark, and make sure that you have 12 volts at the injectors. If you have those two, then confirm that the injectors are firing, through the ECU ground.

[Lani Kai]

Hmm, I'm pretty sure I didn't have the two plugs off simultaneously, but then again I can't be 100% certain they weren't reversed in the first place. I'll try testing the CSV outside of the intake manifold to see what it's doing.

[hr369]

"Then I found the cold start valve was leaking, so I replaced that too, but then discovered the thermotime switch was also bad, and was leaving the cold start open"

Wrong.......

a malfunctioning thermotime switch can't cause the cold start valve to stay open. It only gets voltage when the key is turned to the 'start' position. So even if it were stuck closed once the voltage was removed the csv would not have voltage to stay on. Basically there are two modes of failure of the T-time switch. Stuck open- csv will not operate at all. Stuck closed- csv will operate everytime you turn the key to 'start' regardless of temperature.

first you need to read up on each efi component and how it operates and second its very very important

to have EVERY connection clean. i mean shiny contacts. from the ecu down to every injector.

The problem of fouled plugs is sometimes in the coolant temp. sensor circuit, . When the electrical connection to the sensor is weak, or the sensor is bad, it tells the ECU that the engine is cold and it dumps a lot of fuel into the engine.

[Lani Kai]

Logically, yes. It didn't make sense to me either but unplugging the CSV made the car run better at the time, even after warmup.

I've made several rounds though the contacts with DeOxit but maybe there is something loose from when I cleaned things the other day?

Between when it was running rich and not starting at all, I replaced the plugs and cleaned the contacts on the AFM, AAR, CSV, thermotime, and TPS. The problem that is causing it to not start HAS to lie somewhere in those components that I touched. Now, of those, I'm thinking the ones that can possibly cause the car to not start (in warm SoCal weather) would be the AFM or the TPS. Is this a reasonable guess?

Edited October 9, 2011 by Lani Kai

[jkeese01]

With it running rich, can you rev up the engine to say 5000 RPM and keep it running?

[Lani Kai]

Well, I got it started again. One of the retaining nuts on the terminal block was loose.

So I'm back to where I was a few days ago. It runs rich and smokes quite a bit, and if I unplug the CSV while it's running, the idle goes up to about 2000 for about 15-20 seconds and then the car starts to stumble. As far as I'm aware the CSV shouldn't even be doing anything after the first 12 seconds or something, so I don't know why this is making a difference in operation.

As for revving the engine up to 5000, I didn't try that... Wouldn't the TPS enrich it even more and cause the engine to really bog down?