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.

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.

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.

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.

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.

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

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.

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.

Thanks Dave. I jumped on this just before doing the other tests I mentioned and saw no spark from that lead.... Edited to add...I do have spark. I did not have the lead close enough to the shock mount for it to jump....Edited again to add...I have spark sometimes and sometimes not...

ok. Beginning a few tests. The goal is to determine my over fueling issues and the reason the Z has begun to simply cut off. To catch you up.....I started the car yesterday and let it idle for about 15 minutes then pulled the plugs. It hesitated ever so briefly before firing off and idling smoothly. The plugs were dry but covered in black soot. Not a surprise after the car cutting itself off the previous day. I pulled the plugs cold this morning and there was no change. No additional wetness etc. I then started the car and again it briefly hesitated before firing off an idling smoothly. I then checked the AMF and manipulated it a bit at idle and 3,000 RPM. It ran slightly better moving it only a mm or 2 clockwise at idle to lean it up. Manipulating it counter clockwise made the engine run rough at idle. I did not notice a difference at 3,000 RPM when manipulating it clockwise but it ran rough counterclockwise....... I have the glue on my AMF by the way. It has never been adjusted. I then decided to take my tools and take the car around the block. She ran like a champ. After 5 minutes I turned back toward the house ...not wanting to challenge the Z gods. About 100 yards from the driveway she cut off. No heads up. No miss-fire. The Tach went to 0. I was able to coast back to the garage and immediately gave thanks I was not stuck on the freeway again. I then pulled the plugs. Photo attached. If I had run it longer more of the soot would have burned off in my opinion, but the tip was hot and clean. So I am determining that I don't really have a fuel issue that is leading to flooding and the car simply cutting off. I will now move to searching for an electrical gremlin. I believe I will begin with the ignition module buy will also check connections in the ECU. Thoughts?

When I say no spark what I mean is that the engine would turn over but it was not trying to catch.....like there was no fire. At the time I did not remove the plugs to look at them. I foolishly did not have my tools with me.

I am planning to execute several tests this weekend to work and nail down the flooding issue but wanted to pass along a bit more information. Yesterday I noticed a loose wire on the Water Temp Sensor. I loosely connected it and started the car then pulled the wire and disconnected it. The car tried to die so I reconnected it tightly and took the car out for a spin.... I thought I was on to something but after about 20 minutes of driving on the freeway at 70 she suddenly died. No noise just dies. I popped the clutch a couple of times but nothing. After stopping she would turn over but no spark. After about 45 minutes she roughly kicked over but was trying to flood again. I was able to work the fuel out of her and she fired up running smoothly and I went back to the house. Looking forward to the results of the tests and figuring the issue out. She runs well without this issue!

I had seen that test written about before. Good suggestion to test the issue.

Thanks

Dumb question, but If I remove the cold start valve, how do others fill the hole that remains to keep the vacuum?

I considered that and will give it a shot. I would rather find out why the valve is staying open....if that is the case..... but if unplugging it solves the problem....

This will be helpful thanks and I replaced all of the vacuum hoses so that is good.

Thanks for the photo. I think I am good here. Earlier today I found one of the 4 wires was loose and I reattached, but that did not change anything.

They were wet after trying to start... fuel.

All good suggestions thanks

It will be a good test.

Appreciate the book . It will be helpful. I plan to test a bunch this weekend.

Spark appears fine...

Thanks Site. I had not seen the information in this format.. It is helpful!

Thanks for the suggestions....and yes I have the factory service manual.....but sometimes it is nice to reach out to the group here to get opinions and thoughts. If I only used the factory service manual I would miss out on all the good advice and banter, right? And yes I have purchased new parts for the car. She is 40 years old and I want her to be as reliable as possible. I would rather replace something today that many have had issues with and move on with it....instead of something breaking today and then next week something else. So far things are going fairly well and if not for this flooding issue... that has recently popped up... she would be running great. Again appreciate the suggestions and I will touch base as I move through the steps to identify this specific problem.