78 280z flooding when starting

[Dogariffic]

Have owned it about 6 months. She always ran rich a bit and over time I have replace a lot of items to address this. Over the past two weeks after we added a  new  2.5 exhaust system and cherry bomb .... I know we are looking for another option.... the over fueling began to get worse. Finally two week ago she started flooding out at starting and we have been unable to get a handle on it.

so things we have done to address  the issue.

new fuel pressure regulator, Thermo time switch and cold  start valve and temp switch, New plugs and plug wires new injectors  and injector wiring, All new fuel filters, all new vacuum hoses, high flow air intake, new started  and alternator new engine gaskets, new fuses valve adjustment.

this morning I pulled he plugs and they were wet. I clean them and she started right up. Went to get  ew plugs an then to fill up with non ethanol 91 octane gas and she flooded again .

thoughts are welcome.

[siteunseen]

Shot in the dark but the vane in the afm could be stuck or in the tps. Spider webs got mine one time. 

[Zed Head]

Ya gotta measure stuff.  Fuel pressure, coolant sensor resistance, etc.  If all of the measurements are right, another possibility is a bad ECU.  People have temporarily fixed them by knocking on the side or wiggling the connector.  You'll want to take your measurements at the ECU connector so that act alone might solve your problem.

You can test site's suggestion by removing the black cover on the side of the AFM and watching the weight while it runs.

[rcb280z]

Wow! That's a lot of money to just throw at parts not knowing if it really requires it. Do you have a FSM? It has a lot of good info. And if you do post some numbers so we have something to look at to better help you solve the problem(s). 

There are some knowledgeable people on this site but they can't help you without some true numbers.

Mine ended up being a couple things. Bad injector pig tails and IIRC a bad coolant sensor. But I was just a little rich, not flooding out.  

[rcb280z]

2 hours ago, Dogariffic said:

this morning I pulled he plugs and they were wet.

Was this before starting it? Im assuming it is. Strange. Hope you don't have much fuel getting past the rings.

[Dogariffic]

One question I have relates to the choke. Today is a hot day. Drove the car 15 min. It warmed up. Then after filling with gas. It flooded. Once it did start it had a fast idle. And after about 60 seconds it idled down as if the choke was on. Is it not unusual for the choke to come on in that circumstance.

[ramsesosirus]

If your car is a 280z and fuel injected, I didn't think fuel injected cars could "flood".  Maybe you have a weak spark/ignition.  Possibly adjust your Full Throttle switch also.  Clean all of your electrical connections, especially if they are "green".  

[ramsesosirus]

1 hour ago, Dogariffic said:

One question I have relates to the choke. Today is a hot day. Drove the car 15 min. It warmed up. Then after filling with gas. It flooded. Once it did start it had a fast idle. And after about 60 seconds it idled down as if the choke was on. Is it not unusual for the choke to come on in that circumstance.

Do you have fuel injection?  You should, all Z's after 1975 came stock with it.  Which means you shouldn't need or have choke.  I don't even have the lever in my 76 FI 280z.  Have you cleaned or had your fuel tank cleaned?  Mine was rusted and blocked.  

If I am correct, choke is exclusive to carbs.  Does it idle ok in gear?  Mine idles high in park, but come down to around 1000 in gear (I set it for 700, as per the hood sticker).  Is your exhaust leaking by the Tstat housing?  (that is where the sensors are, too much heat might mess them up...)  

[rcb280z]

I think this is a dead giveaway that he has EFI

4 hours ago, Dogariffic said:

Thermo time switch and cold  start valve and temp switch,

 

[ramsesosirus]

Download the Factory Service Manual if you haven't already.  Very good resource, available for your specific year Z.  If you google "19XX 280z Factory Service Manual", you'll find it.  Xenon .com or something.  You have to follow the procedures if you want the Z to run right.  But it will be worth it.  Promise.   

 

[EuroDat]

No need to go to another site, you can also download the FSM for this site too.

http://www.classiczcars.com/files/category/13-280z/

Wow. Stand back and throw money at it. I tried that once on an Escort. In the end my pockets were not deep enough and I had to resort to diagnosing the problem and then fix it. I say that jokingly now, but it cost me a lot of money for an eventual $30 fix. I can imagine you have spent a lot on the parts and the problem is disappointingly not solved.

Most people have trouble with running lean. What a lot of people call ecu drift.

You need to start diagnosing stuff and cross it of the list. The things you can check, for starters, are:

1. Is the system holding fuel pressure. You changed the injectors and the csv, but you can't be sure one or two (new or refurbished?) Injectors are not leaking or sticking. I wrote a test procedure on a thread here somewhere. Ill try to find it and post it here.

2. Check the temperature sensor resistance at the pin 13 & 5 in the ecu connector. Check that with the FSM and the 1980 efi supplement (bible) on this site.

3. Check the ignition for good spark while cranking the engine. You can do tests on the ingnition, but a faulty tiu is a process of elimination.

When you do tests, write down what you do and the test results. People like to see figures, it also helps with feedback.

 

[esmit208]

There is a link on the home page for EFI issues. To be honest most or (some) owners converted to carbs because of issues (headaches) with EFI systems. I owned  a 77 for a while and it was the only car I was happy to get rid of. After many poor running issues I was able to isolate it to the ECU on the kick panel by your left foot. I frequently had to put pressure on the plug to get it to run smoothly and had the same fuel consumption issues you described, although no flooding issues. I called several places that sell ECU'S for that model but I was never quite sure I was getting something better than what I had so I got rid of the car. But good luck.