car turns over but wont start. 78 280z please help!

[Nightscraper]

replaced coil and it started up again but its running kind rough.

[grantf]

But it's running

[FastWoman]

Is it a steady, "chug, chug, chug" sort of rough, that would suggest a cylinder or two that consistently isn't firing? Or do you have a random, irregular miss?

Try richening the mixture by pulling the vacuum hose off of the fuel pressure regulator. Block the hose to seal the vacuum leak. Better or worse?

Try leaning the mixture by pulling off the vacuum hose to the HVAC system (next to the brake booster vacuum hose). Better or worse?

[Nightscraper]

up one down another it started (good) now it just idles low then when its reved up it sputters then dies. any advice?

[SteveJ]

Did you try what Sarah said to do? It would be good to check your fuel pressure with a gauge, too.

[240260280z]

If your plugs are black then it is possible the connections to the water temp sensor need attention.

[Nightscraper]

i was going to but it refuses to start again. and ill take a look blue thanks

[Nightscraper]

i checked the sensor and fiddle with the wires a bit and lo and behold it started up again. i think i might have a problem there

[Nightscraper]

if there is something wrong with that sensor. aka bad connection/ wire it would cause it not to start right?

[FastWoman]

If you have a bad connection, the car might start, but it will run really rich, with black smoke out the exhaust. If the sensor is shorted, the engine will run very lean. I don't know whether it would start that way. The best way to check your sensor and connections together is at the ECU plug. As I recall, you need to check resistance between pin 13 and ground.

Try starting the engine with the fuel/air mixture modifications I suggested, and see if either one gets the engine running any better. Of course this is just for diagnostic purposes.

[Nightscraper]

Big update! thanks for all your help guys i did alot of wire checking and everything you guys told me but all it took was an extra pair of eyes. My dad came over today and we spent a few hours on it and found that the wires going to the pick up coil in the distributor were melted! so we took the wires off the distributor, cut off the melted portion and rewired them and it runs fine now! thanks again for all your help FastWoman, SteveJ, blue, jimbob_racing, and grantf!