78 280z flooding when starting

[Dogariffic]

Thanks Euro...I saw the calibration article earlier and read it. Good info. I think my issue lies elsewhere though since mine has not been touched.   I have also seen your write up on the HEI module and that may be part of my solution....thanks again.

[Zed Head]

43 minutes ago, Dogariffic said:

The transmission was in gear, but I put the clutch in so I could coast.....but the clutch was out and engaged in second gear when it popped off.

My point was that if the engine is turning over and the key is still on then you should still see the tachometer showing RPM.  It's a spark counter.  If the tach goes to zero and the engine is still rotating because the car is moving and it's in gear, then there's no spark.

In short, if you're driving down the road and the the engine loses power with the tach going immediately to zero then you probably have either an ignition module problem or an ignition system power problem.

[Dave WM]

I recently opened up my OE Ign module. there were several electrolytic caps in there. In vintage electronics these are often a problem. I have a spare that works well, I may end up replacing the caps in my OE just to add another 40yrs to its expected life. I will use good quality (Nichicon) hi-temp low ESR stuff. These caps use a chemical base to form a very thin insulator IIRC, giving very high capacity in a small package. The problem is the paste can dry out or fail in some other way. My guess is the caps used back in the day were of excellent quality (70's Japan) but still I am sure no one thought they would still be used 40+ years later.

[Zed Head]

When my 76 module was going bad the tachometer would show about 50% more RPM than actual.  I'd guess this might trigger the injectors 50% more as a result.  Just a thought on why the flooding might be happening.  I didn't notice flooding on mine, but mine would only fail after about 3000 RPM, then it would keep working but with a bunch of extra sparks.  Keep an eye on the tachometer while test-driving.  It's typical for them to fail, then start working again after a cool-down.

We have several threads about replacing the OE module with a GM HEI module, and a nice writeup in the Downloads area..  1978 is good for it since there's only one electronic pickup in the distributor and circuit in the module.  It's a cheap fix, almost worth doing just as a test and to be ready for eventual failure.

[Dogariffic]

And my Tach has never worked well....It usually only goes up to about 3,000 rpm.....I have also seen the crane xr-3000 at the Z store.  It claims to be a plug and play solution and although it sits in the engine is not impacted by heat, moisture, vibration, and dirt....Compared to the GM HEI is it probably a bit more expensive at $137.00 

[Dogariffic]

Ok some evaluation ad testing going on today.

So far we have opened up the ECU and cleaned connections.  Went ahead and opened the whole thing up to see if anything was burned up.  All looked good. Photos attached for those that like photos....

. Also opened up the Ignition Module on the passenger side by the fuse box.  cleaned connections there as well and went ahead and opened it up to check things out.  I have read they cannot be repaired but was curious to see what was going on.  Nothing burned up in there either.

After this, we started the car to make sure we had not messed anything up and she is running normally.  I am considering letting her idle and run a bit in the driveway to see if she shuts off.

Edited to add...Pulled the plugs and they are getting soot on them.

Next moving on to more testing with the FSM.

 

Edited June 25, 2017 by Dogariffic

[Dogariffic]

Added an in-line fuel pressure gage between the fuel filter in the engine bay and the stock fuel rail. During start... when I turn the key to start and engage the starter and there engine begins to turnover she registered about 37. Once she engages and begins to run she registers 30. If I rev her pressure jumps to about 35 and then idles down to 30. Once I cut her off pressure drops to 0 quickly.

[Zed Head]

That sounds right, except for the rapid leak-down after shutoff, which is really just an inconvenience.  The numbers, 37 and 35 and 30, for the conditions you described, all look about right. 

[Dogariffic]

Thanks for the confirmation Zed.

Still after the elusive reason she cuts off at random when warm and is difficult to start and appears to flood. 

Next time she floods or is hard to start I will be able to monitor fuel pressure.

Just ruling stuff out.

[Zed Head]

That's the way to do it.  But keep your eyes open for a cheap ECU.  Most of us out here have a spare or two because the old electronics generally seem to be drying out and dying.  Ignition modules and ECU's.  I had a bad ECU myself and it was supposed to be a spare.  A few others have had bad ECU's over the years.  And they tend to flood out as part of the dying process.

[Dogariffic]

How do you identify a "good" ECU? I have see rebuilt ones on Motorsports site. Is there a way to refurbish one?

And I am considering the crane XR3000 and the crane ps60 coil that goes with it to replace my injector module.

Also does anyone think vapor lock may be my issue with hard starting after running and even possibly the single time the car cut off doing 75 on the freeway. I live in Mississippi and it is getting hot here now. This is my first summer with the car.

If vapor lock is a possible culprit I am considering adding a 280zx injector fan or possible insulating the fuel rail like the old 240Zs.

[Dogariffic]

So another update 

I have cleaned some more connectors. The AFM, the mass air sensor and all of the fuel relay sensors.

Decided it was time to take her out again today because she is just fun to drive.

Had a follow car with a tow rope if needed.

She ran great at idle and the tail pipe was looking cleaner that before so I was encouraged.

After about 30 miles she cut off while doing 70 on the freeway. The tach was jamed at 2500 and this is standard. With the engine engaged and no power the tach stayed locked without movement. Popping the clutch would turn her over but she would not catch. As if  no spark. And again the tach remained frozen.

Got out and had all my tools prepared to test various things. The first test was fuel pressure as I have the new online gage. Pressure was at 25. This is lower than the 32 at idle before we began the trip. Checked spark at the coil by jumping a spark from the coil wire to the distributor to a strut nut and we had spark.

Was about to Check spark to a plug and asked my son to turn her over and she caught and ran. Seemed to be rich based on exhaust smell.

Jumped in and drove about 15 miles to the house. She began to backfire while accelerating with a single pop coming out of first and then double popped while down shifting from third into second. Once home the tail pipe had some soot in it. She also had a bit rougher idle compared to when we began the trip.

I still believe we have an electrical issue and will check ECU connection readings. Will also take a look at the fuel pump this evening and all connections there and check out the fuel filter entering the pump.

Still considering another ignition module and coil as mentioned earlier.

Will post later with more info.