skip3535

1981 280zx runs for about 30sec after starting but then dies as if the key was turned off. It wont start again until the next day. I first thought it was flooding but pressure is good also CHTS and AFM checked good. I was thinking that the IC ignition unit may be bad. Has anyone had this problem ?

NismoPick

An engine needs 3 things to start:
-Proper fuel delivery
-Proper spark delivery
-Proper compression.

Since it starts then dies, you need to figure out if it's getting no fuel, flooding, or getting no spark. Then diagnose why.

skip3535

There is fuel on the plugs when I pull them out. That's why I thought it was flooding. I checked the fuel pressure and it was 30 psi. It starts right up and runs great for 30 sec then shuts down. it doesn't sputter just shuts down. Ill try and check the spark after shut down. Thanks

rogerz

put a fuel gage in the fuel ring. only way to monitor fuel delivery. plugs wet mean nothing except maybe your cold start valve is stuck open. pinch off the hose going to it and then see if your problem is gone

skip3535

plugged off cold start valve. fuel pressure about 40 psi when cranking then drops down to 33 psi when engine begins to start. I pulled a plug and it is firing. It will attempt to start when I use starting fluid. If I let it sit for a day or two it will run for about 30 sec then shut down. The last time I did this I held the throttle at about 1500 to 2000 rpm and again it just shut down

rogerz

sounds electrical. is it a repeatable verifiable 30 seconds or is that just I think so. check into that thermotime circuit never had to dig into it but folks have had problems in the past. you shouldn't be getting 40 psi fuel if your fpr is working properly. possible problem??? pull the vacuum hose on it and see if fuel squirts out. if the diaphragm is ruptured you could be getting too much fuel that way.

skip3535

yes it always dies at about 30 sec. thanks I will check the thermotime circuit. I did look at the fpr and no fuel in the vacuum line. This car had been parked for about 7 years. There was no fuel in it at all. I thought fuel injectors normally become clogged over time. I have read were people say that they can go bad and flood the car. What do you think ?

rogerz

unlikely stuck closed maybe but not stuck open. try disconnecting the fuel pump electrically. put gas pedal to floor and hold it there. Crank it and see what happens. You maybe just have flooded it by trying to start. you should get a few pops and maybe a few run seconds. do it a couple times. then reconnect pump and try a start. you have to have a GOOD fully charged battery for this. Have you had your battery load tested? are your cable terminations tight and corrosion free.

skip3535

Thanks. Its a new battery 700 ca and I recharge it every night. I tried pulling the #2 fuel relay and there was no fuel pressure showing on the gauge. put pedal to floor and nothing so I tried starter fluid and it tried to start. I reinstalled the relay and fuel pressure came up to 32 lbs when trying to start . It tried to start a few times but then nothing. I tried starter fluid again and would try to start but wouldn't run. I took the relay back out and tried to start again 6 or 7 times and still no but I did notice that fuel pressure only dropped to 28 lbs. I would think it would have dropped to zero. I know the computer runs the injectors . Is there a easy way to check them without pulling the fuel rail ?

rogerz

disconnect at the pump forget the relay. then try the open throttle (WIDE) and crank while holding it open. You need to be sure you have cleared out all the unburned fuel sitting in the manifold. it won't start and run but probably get a few pops. on 2nd 3rd try it may run a few seconds.

skip3535

I ordered a used computer off E-Bay and now runs great. The old computer looked good. I opened it up and didn't see anything that was burnt. I did notice it had quite a few IC chips and unless you have a bench to check it you wont know if its good or bad. I checked just about everything else and all was good before I decided to change it. Thanks for the feedback.