One step forward and two steps back...

[jkeese01]

First mine was running too rich. Tested the temp sensor with a multi-meter and it read infinity, which indicated it was broke and flooded the engine with fuel.

Replaced the temp sensor and could get the car started. The car ran very rough, smoked, but could keep running when I rev the engine. (Sea Foam was in gasoline so that may have caused the smoke)

Next the car was running too lean. Tightened the hose clamps on the Air Flow Meter and inspected the hoses for cracks. Replaced all the vacuum hoses on the engine. Also thought it was a good time to inspect all the electrical connections for corrosion. Cleaned the connections with a small file.

Cranked the car, it smoked, ran rough for a minute or so, then started running great.

Later that day, the fuel pressure gauge I connected to the fuel line showed the fuel was not holding pressure when the engine is off. The car should crank immediately, but was taking about 5 seconds.

Found that the check value on the fuel pump was leaking fuel back into the gas tank. Added a new check value and the car cranks up immediately and runs very smooth. Fuel pressure held for a week (weekend to weekend), so great that my fuel injectors are not leaking.

If you replace vacuum hoses, do them one at a time to make sure they get connect back correctly. Cost less than $20.

[Lani Kai]

Well, I've done some more fiddling around and basically, the CSV is getting voltage when it shouldn't be. This seems to imply that it's constantly getting a start signal?

[jkeese01]

Have you check the 1978 280z Datsun Factory Service Manual for instructions on diagnosing problems with the fuel system?

If you don't have one of these printed books, free .pdf format ones are easily found online with a google search.

[Lani Kai]

Yup, I've studied the FSM and the EFI manuals quite a bit over the last couple of years.

[FastWoman]

Sounds like you have multiple problems going on. To get my own engine straight, I just went from end to end, pulling everything apart, testing, verifying, cleaning, refurbing, etc. I found numerous problems, even though the engine was running "OK" before I started. Sometimes it makes more sense just to assume multiple things are wrong and to go through EVERYTHING than to try diagnosing individual problems.

Regarding your CSV: Your CSV should be wired in parallel with your thermotime switch connections, so you can do simple continuity tests to determine the identity of these two connectors. Once you figure it out, you should put little zip ties around these connectors to identify them in the future.

If you've definitely got the right connectors, and the CSV stays energized, then there's definitely something wrong. First, this would suggest that the CSV circuit is powered by the wrong circuit. It should only receive power when the key is in the START position, but it's probably receiving power from the IGN circuit. As a quick test, check for continuity between the +12 wire of the CSV and the small starter wire with the ignition key in any position other than START. You should have continuity. If not, the CSV is getting power from the wrong circuit.

Assuming you have power from the correct source, there are only two possibilities for how the CSV and thermotime switch would work. If the thermotime switch is wired backwards, you'll have a short to ground in cold temperatures, and the CSV will be grounded through the thermotime switch's heater element. This might cause it to hang open. Then when the coolant temp dips below 50F (?), the short will cause bigger problems.

If the thermotime switch is wired the other (correct) way, the ground to the CTS should be open at temps > 50F. The CTS will receive +12 whenever the key is in the START position, but it won't be grounded. At colder temps, the ground will be closed; however, the heater in the thermotime will soon interrupt the ground path.

As for the other problems, dunno... I'd just go through the system from end to end:

-- vacuum leaks? Fix everything you can find, and verify with what I call the "yogurt cup test." Remove the AFM, stuff a plastic cup into the rubber boot to close it. Pull off the vacuum booster hose, and blow into the intake like you're blowing up a balloon. The intake should hold pressure, leaking it off very slowly. If you have any leaks, it should be obvious.

-- electrical connections -- verify all of them

-- distributor -- remove the cap and rotor, and try turning the braker plate underneath by hand. It should turn smoothly, but it probably won't (common problem). Try timing it to spec (10deg BTDC).

-- fuel pressure -- should be about 36 psi static pressure without the engine running.

-- Consult the FSM to ensure that all your sensors are within spec.

If you get that far, your engine should at least run, albeit maybe not well. There can still be other problems. Sometimes our old ECUs go a bit wonky over time, but we can do mods to compensate.

Hope that helps.

PS I take pics too! www.graphic-fusion.com. Next stop, I'll check out your website.

EDIT: WOW! Awsome work!

Edited October 23, 2011 by FastWoman