fuel rail and pressure regulator suggestions-78 280Z

[Yarb]

Well that did the trick it’s idling now!!!! I only ran it for a minute. Want to make sure the permatex has time to dry completely It’s running rich, I guess my next step would be to check the air bypass screw on the afm. When I originally looked at it was a little over 4 revolutions out. I’ve completed all the preliminary measurements that are static tests. Can anyone suggest where to start? The temp sending unit and harness has been replaced. From what I read this is the main threshold the ecu monitors for fuel delivery.  Any help would be greatly appreciated. Thanks to everyone on getting the idling issue resolved.

[Zed Head]

What is your new goal?  Generally, for anyone with a 280Z, running through the electrical checks in the 1980 EFI Guide is recommended, along with verifying fuel pressure, and giving the engine a solid tuneup.  Valve lash, timing, etc.  Problems with the 280Z engines are usually a collection of small things, rarely just one big thing.  Each correction of a small error closer to specification will make the engine run better.

[Dave WM]

1 hour ago, Yarb said:

Well that did the trick it’s idling now!!!! I only ran it for a minute. Want to make sure the permatex has time to dry completely It’s running rich, I guess my next step would be to check the air bypass screw on the afm. When I originally looked at it was a little over 4 revolutions out. I’ve completed all the preliminary measurements that are static tests. Can anyone suggest where to start? The temp sending unit and harness has been replaced. From what I read this is the main threshold the ecu monitors for fuel delivery.  Any help would be greatly appreciated. Thanks to everyone on getting the idling issue resolved.

The idle bypass only has a very minor effect on the fuel mix, and only on the idle mix. How are you determining the running rich? If it is indeed rich you will want to 1st verify the ECU temp sensor is tracking the temp curve, see the FSM for resistance measurements to temp reading. Use a thermometer in the neck of the rad to confirm your temps. Take the readings AT THE ECU 36 pin connector. 13 and chassis ground IIRC. resistance in the connectors both at the sensor and the bullet connectors on the sub harness must be clean and free of corrosion. A high resistance will result in a rich mix.

If that check you need to confirm fuel pressure, should be about 36-38 psi with the engine off pump on. With normal manifold vacuum (about 17-20 in hg) you should see around 29-31 psi (engine running idling after warmed up). The fuel pressure should track with vacuum, so as you open the throttle quickly the fuel pressure should momentary rise, the drop back when throttle is released. higher vacuum less pressure is the key.

Depending on the outcome of those there are more things to look at, but those will be the problem most of the time, assuming no one as monkeyed with the AFM spring settings.

As to the orig question about the bypass, I had some luck with setting it by using a vacuum gauge on the intake manifold, letting the engine warm up an settle down, making sure everything else was right (timing/fuel pressure/temp sensor) I found that I could tweek that adjustment to max out the vacuum (best eff of the engine at idle indicated by best vacuum I could pull) I then leaned it some (CCW) until I could see the vacuum start to drop off. This setting seemed to get me right to the oil cap off test.

the oil cap off test will be when it idles well but as soon as you remove the oil cap it will start to miss and quickly die. This is due to unmetered air causing a over lean condition. If you remove the cap and nothing happens you are a bit rich at idle but will look the best on the vacuum gauge. if you remove the oil cap and it speeds up you are too rich to the point where the engine is no longer at optimal mix even for best vacuum. Again I use the vacuum reading as a way to determine if the engine is operating at peak efficiency.

 

[Yarb]

I’ve yet to get it to operating temperature since I began this project. Today was the first time it’s cranked and idled. I found the afm had been messed with before I cracked it open. All three mounting bolts were missing and the ground wire just hanging there. I followed “Atlantic’s” thread point by point. The result was the flap was not completely closing not allowing the fuel pump to disengage. Corrected that by bending the tab per the instructions. Flaps closes completely, pump circuit opens. All other measurements checked out. Fuel pressure is good now with OEM pump and regulator replaced. Installed a pressure gauge between the filter and fuel rail. Isolated the cold start valve. Tested it by the fsm and it checked out. Injectors were sent out to HPI and refurbished. Temperature harness replaced with sending unit as well. Haven’t checked valve lash or timing yet. The reason I was asking about the aar is by reading that thread the engine receives more air at start up until reaching operating temperature. I hope I understood that correctly. Ignition components replaced. Air gap checked out on the distributor. Verified measurements at the ignition control box at passenger side. I know it sounds like I’m bouncing around here. It’s been sitting for 12 years. I’ve cleaned every contact and replaced all fuel,vacuum,boots etc. when my dad drove it for years running extremely rich. Bumper is black at the exhaust tip. I’m sure it’s got some serious carbon buildup going on.

[Dave WM]

before making in conclusions it sound like you are almost done with the normal stuff. Just get that timing set, and confirm the temp sender resistance readings (don't think I saw that in your response).

Make sure thermostat is working and you are getting up to correct operating temps. Once all that is covered buy some new plugs (ngk) install and take for a short test ride, like 10 miles of normal driving. pull the plugs and post up the pics. They are the best indicator short of a gas analyzer of the fuel mix.

[Yarb]

Thanks Dave, just noticed your in Central Fl. also. I’m in over in Lakeland. The car is in Haines city in my families warehouse. I dropped the tank and had it cleaned and coated. Been running out of a gas can. Was holding off installing it until I swap the AT to 5 speed and r200 diff. Thought it would give me a lot more room to work with. Not to mention brake issues so driving it might be a problem for now. Thermostat and plugs are new as well. I’ll get a chance to run it tomorrow for the first time and get it up to temp. Now that the bcdd issue is resolved I can at least let it idle for awhile.

[Dave WM]

have you got the stuff you need to do a swap? the pedal box and trans/diff/drive shaft?

That should be fun, if you want some help, I am not far from Lakeland will pm you later with contact info.

[Yarb]

Awesome, I have the full drivetrain from a 83zx. That would be great send me a pm. Have a great day! Oh.. I still need the pedals. I assume I could use the same pedal box. To tell you the truth l haven’t looked.

Edited November 21, 2019 by Yarb
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[Dave WM]

I am going to try and meet up with Yarb soon to see if I can help figure out rich running.

so I don't forget, one of the test I want to run is a power test, disable on cylinder at a time (disconnect the injector plug) and listen to the engine for a change in RPM. Yarb let me know if you have already done this. If not def a good start to see if all the holes are working as they should.

The plan is to do a compression check/base time set/overall look over and check some basic readings. I will have my car so we have something to compare to as well. I will also bring my spare ECU just in case that is an issue. I have a spare AFM as well, its a earlier model so not sure if that will be an issue.

[Yarb]

Sounds great, I have not tried disabling/injector test. Looking forward to bringing this Z back to the road.

[Dave WM]

I was trying to make a video until my sd card was filled.

I started the test engine on the stand, put a meat thermos in the rad idled for a few min until the temp stabilized. Reading was right at 160f, which maybe the temp of the stat I put in, I presume so. I got a reading on the gauge bout 3/16 left of center for what that is worth.

shut down the engine and read the resistance of the temp sensor harness (at bullet connectors) got 500ish ohms. For fun I inserted my 500 ohm rheostat  in place of the temp sensor. started the engine and observed the vacuum (my way of reading mix of engine besides just listening to it). I could tell NO change when adjusting from 0-500 ohms so I presume that it must ignore that sensor at that low of a resistance. IIRC its supposed to stop listening to it at about 150f so that makes sense.

So another test will be to read that sensor once you get up to a min of 160f. Just trying to keep some more notes for comparison.

 

[Yarb]

I’ll go back and check the new thermostat I put in. I’m thinking it was 180 degree. I’ve kept all of my receipts. I’ll dig through and let you know.