Need assistance from the Zed Collective Conscience!

[ZCurves]

I have often touted the 'Power of Many' on this site. Time after time the 'Zed Collective Conscience' has helped solve each others problems, so now I am seeking some answers...

I have a stock 1978 280z that I have restored a few years ago. Everything has been fine except recently after the car gets warm (not even hot) the engine just dies. When the engine first starts, it is immediate and idles fine but is a little rich (although that may have been corrected with the recent TPS adjustment). Once the Z warms up -as in less than two miles of driving - it dies.

It does not diesel or pop, which would make me think fuel or AFM. It seems more electronic as if someone disconnects the battery. This last episode, the engine did dump a bunch of fuel leading a nasty smokey death spiral -seemed to be in a 'flood-condition'. The next day she started right up only to repeat -except I left her in the driveway rather than take a chance on being forced to call Hagarty for a rescue.:mad:

Using the FSM and Fuel Injection Bible -I have done the following:

• Replaced Ignition Module and the Keylock/Ignition switch (needed done anyway).
  
• Checked the Water Temp Sensor and Thermotime switch and made sure they are correctly plugged in.
  
• Checked the Cold Start Valve and it appears to function properly.
  
• I have adjusted the TPS to factory spec.
  

Here is what is next on my inspection list:

• Check Timing.
  
• Check Fuel Pressure - even though I have installed a new fuel pump including a clear fuel filter in-line between the tank.
  
• Check Fuel Injection Relay.
  
• Check Fuel Pump Relay.
  
• Check AFM.
  
• Check ECU.
  
• Check continuity between ECU and Engine.
  

I am even checking the "Cold" conditions vs. those after the Z warms up. In short - I am fricken frustrated and invite each of you to chime in with anything that I may have missed - or need to re-check. Just because I have had this model of Z for close to 30 years doesn't mean I haven't overlooked something. I guess I am loosing my touch or haven't had enough beer yet.

[Hunter260Z]

I had a problem just like yours,on a 510 and it was a bad coil.Just a thought.

[zKars]

The trick with this type of diagnosis is to have a way to monitor the system inputs and outputs, and then watch which one goes away at failure time.

With a fuel pressure gauge you can see if the fuel supply stops or is too low to support combustion. With a volt meter on the + side of the coil, you can tell if the power supply to it goes away. With a timing light, you can tell if the spark goes away, indicating a distributor or ignition module failure (not firing the coil).

Imagine duct taping the fuel pressure gauge, voltmeter and timing light (with flashy end pointing at your face) to your hood then going for drive to see which says DEATH first when the car quits. Of course in your case, it will happen over and over at idle in your drive way, so should be easy to spot. You are quite lucky in that regard.

Another key indicator is the speed at which the car goes from "working" to "not working", at least for cars with carbs. Electrical failure happens immediately, while fuel starvation happens slowly. Fuel injection unfortunately also can turn the car off in a heart beat if the injectors stop firing (ECU), but can happen more slowly if the fuel pressure drops off from full to none over a period of several seconds.

Common failure components here are ECU, the coil, distributor reluctor pickup windings, Ignition module (under pass dash), power to coil, fuel pump, plugged lines and or filter, or just a loose wire that moves just enough when it or something connected to it gets a bit warm.

Happy hunting.

[Captain Obvious]

My first blush advice would be to start simple. Attempt to determine if the problem is spark or fuel. When the problem is occurring, pull the coil wire and see if you have spark.

I couldn't tell from your description... When the engine dies, does it restart or does it just crank and crank and not start?

[ZCurves]

When the engine dies, does it restart or does it just crank and crank and not start?

Thanks Man, Just cranks - Nothing else. Wait awhile- like an hour, then it will restart. This last time it was a missing smokey mess.

[ZCurves]

Imagine duct taping the fuel pressure gauge, voltmeter and timing light (with flashy end pointing at your face) to your hood then going for drive to see which says DEATH first when the car quits. Of course in your case, it will happen over and over at idle in your drive way, so should be easy to spot. You are quite lucky in that regard....Happy hunting.

Well I guess it is time to go hunting... I just dont want to end up shooting my Z. Thanks for the tips....

[Captain Obvious]

Gotcha. On the good side, the fact that the problem persists makes it easier to find.

So with what you have described, it could be a huge scope of things. Could be fuel or spark. Anything from an intermittent electrical connection inside the ignition module to crud in the fuel tank blocking the pickup screen.

Next time it happens, check for spark. That could narrow the scope significantly.

Like zKars described it's a hunt, but the hope is to narrow the hunt as quickly as possible.

[Zed Head]

When the engine first starts, it is immediate and idles fine but is a little rich (although that may have been corrected with the recent TPS adjustment). Once the Z warms up -as in less than two miles of driving - it dies.

It seems more electronic as if someone disconnects the battery. This last episode, the engine did dump a bunch of fuel leading a nasty smokey death spiral -seemed to be in a 'flood-condition'. The next day she started right up only to repeat -except I left her in the driveway rather than take a chance on being forced to call Hagarty for a rescue.:mad:.

I had a very, very similar thing happen to me when I was checking a spare ECU that I had (coincidentally from a 1978 parts car that I had picked up). I installed the ECU, the engine started right up, I hit the road for a little test drive and it hiccuped once after a Stop sign, then died before I could turn around to get home. Within about a mile. It started again and made it about 1/4 mile before dying again, then another 1/2 mile, then wouldn't restart. The guy who helped me push it in to a parking lot said it smelled like it was flooded. I ran home and got the old ECU, replaced it and drove home. I reasoned that the transistors that drive the injectors had crapped out and replaced them, and it seems to work right now, although I don't trust it and only keep it around as a curiosity..

Flooding from a bad ECU has been documented a few times. I can't remember the guy's screen name but one member re-flowed the solder joints at the ECU connector to fix a similar problem.

Summary - it might be your ECU.

Edited October 29, 2013 by Zed Head

[ZCurves]

Summary - it might be your ECU.

Thank you. Easy enough to check as I have like a half dozen ECU's that I have been hoarding. I have my plate full now with Captain Obvious and zKars recommendations.

[Dr. 240Z]

Just a suggestion: Check/replace the coil before all else

[FastWoman]

Andrew, before swapping out anything, you should really check for spark vs. fuel. I like to rule out fuel by spraying a bit of starter fluid into the intake manifold (through a vacuum hose nipple) to see if I start the engine briefly. If it starts, then your spark is intact, but fuel is not. A great way to test whether the ECU is responsive is to plug a Christmas tree light (or a noid) into an injector connector and try cranking. Does it flash? The beauty of these tests is that you're disturbing the system minimally. If you have an intermittent, heat-related electrical issue, you might ruin your chances of finding it by swapping out too many things, wiggling connectors, etc.

[2fiddyz]

I have had a similar problem with more than one of my Z's but they were all 240's. In each case it was a (very) slightly corroded Coil Lead. After everyone else's suggestion of checking spark when it fails again, pull the simple spade connector off the coil scuff with scotchbright, and use needle nose pliers to crimp that connector a tiny bit tighter (don't crush it closed) so it more solidly/positively engages the spade fastened to the coil, and see if that works. Also check the coil for any oil around it. Older coils used to start leaking before they completely failed.

You are a braver man than I trying to keep that original EFI running. My hats off to you. GOOD LUCK SIR!!!