1976 280z engine runs rough then dies, will not idle.

[siteunseen]

here's some good glue blob shots also.

http://atlanticz.ca/zclub/techtips/afm/index.html

 

[mbz]

Siteuseen, thank you for the clarity on the glue blobs.... I was way off base on my understanding of this. I'll read up on it tonight.

10 minutes ago, Zed Head said:

Working on the EFI system is really just taking measurements and comparing them to a check list.  Measure-check-measure-check....

Got it. If this weekend's round of diagnostics don't result in improvement or a fix, then measure-check-fix-measure-check-fix, etc... is in order for next weekend.

10 minutes ago, Zed Head said:

Often-times people adjust things to out of spec. trying to fix other out of spec. things.

Hoping that's not the case, but have already realized this may be what I'm dealing with.

Like I said, I plan on keeping this car for a while, so it's best to get the EFI sorted out now before moving on to other issues. (like suspension, AC, heater core, radio and other electrical gremlins). ?

Thanks again for the feedback, I really appreciate the help!

Edited March 22, 2019 by mbz
self correction.

[Dave WM]

ah yes suspension you will get a lot of advice there. Your biggest decision will be stock or modify. I find stock very satisfactory as I am more of a driver vs a racer. in the stock configuration the ride is pretty rough, its a very connected to the road kind of car. Making it stiffer for "performance" would be unbearable to my old bones. I never hear anyone mention a smoother ride with suspension upgrades.

AC is some fun stuff, its a very very simple system, works marginally well (not great but much better than the old 240z  pull thru evap). you got to decide if you want to stick with R12 or 134a, The only real upgrade you could do is maybe a PF condenser. brand new evaps are available but expensive. The biggest complaint seems to be the volume of air flow in really hot climates. here in the sub tropics middle of summer (95f 80%humidity) can really require more than the system can handle, at best you will not sweat in the car. In LA you should be ok with the lower humidity.

Looking forward to some threads on these topics once you get the current problem worked out.

 

[gwri8]

7 hours ago, mbz said:

Thanks for the tip.... to confirm, it's item 14 in the diagram?

Yes, that one.  It's not obvious visually, but it has easy access to it.  It lives in a high heat area and can often turn hard and split like your valve cover hose did.

[Dave WM]

you also should make sure all the heat shielding is in place, will help a lot with the splitting.

[mbz]

OK so here's the results of today's testing so far.

•  DISTRIBUTOR: Distributor cap checks out OK. Inside contacts look a bit worn, but all functioning OK. No cracks or moisture in cap. Checked rotor, looks good. cleaned up contact surfaces a bit just for good measure while I was in there. Tested spark plug wires as well, each cable functioning properly. (see photos).
• IGNITION COIL: Ignition coil test results are: Voltage to coil = 11.93 volts ( a bit low, probably the old battery), Primary resistance: 2.3 ohms (a bit high but fine), Secondary resistance: 10.92k (fine)
• FUEL PRESSURE: Checked fuel pressure: 38.5 PSI with engine ON, 33.5 PSI with engine OFF. (see photos AND video)
• FUEL INJECTORS: Checked fuel injectors with stethoscope, all are working fine.
• HOSE CHECKS: Also checked hose connector to PCV valve, it is fine.

Also, see last photo, it shows the crap that spews out of the exhaust. Any thought on this?

I still have to check the following:

• Check Water Temperature Sensor. (resistance test to follow next)
• Check glue blobs on AFM for signs of tampering.
• Check boot from AFM to Throttle Body for cracks.
• Check Cold Start Valve. (not sure I need to do this as I am not having trouble starting engine unless it's flooded).

Any comments or feedback on today's results?

Any advice on what to check next besides Water Temperature Sensor, glue blobs, boot from AFM to Throttle Body, and CSV?

Any other photos or video that would be helpful with diagnosis?

As always, help is much appreciated.

Thank you!

[Dave WM]

that fuel pressure is way too high.

did you check it with the engine OFF and the fuel pump running. do this by removing the start solenoid spade connector (so the starter will not operate when turning the key to the START position. while holding the key in the start position get a reading. You should hear the pump running.

Note the fuel pressure. Should be 36 psi.

Do that and report back. One step at a time. I have some ideas as to what the issue is, but its best to not speculate with possible solutions until test results known.

I am guessing the last pic is after shut down and bleed off of some of the pressure with the pump NOT running.

Edited March 25, 2019 by Dave WM

[Dave WM]

This is how it should behave, starter disabled by pulling solenoid spade off, turning key to START. We need to know the pressure with the engine not running but the pump running. This is to check the fuel pressure with the FPR reading NO vacuum.

 

Don't worry about the bleed off discussion, if it holds for even just a few minutes its fine. A problem would be a very quick (1 min) drop to zero. I would guess that would be a leak, but having no serious leaks to detect I am guessing about the time. There is VERY little fuel in rubber hoses that could expand and  hold pressure so I would not expect it to last for a very long time. At this point no need to concern until the fuel pressure is correct per the above video, engine off pump on.

Edited March 25, 2019 by Dave WM

[madkaw]

You really the pressure is “way too high”. 2psi could be a gauge . Doubt that is any issue with his engine running poorly . 

[Dave WM]

don't bother with any other checks until this is resolved.

[mbz]

1 hour ago, Dave WM said:

did you check it with the engine OFF and the fuel pump running.

DaveWM, that was my bad.... I did not check fuel pump with engine OFF. I figured that if the fuel pump wasn't working there would be no fuel pressure at all. I will do that on the next chance to test it and will report results.

1 hour ago, Dave WM said:

I am guessing the last pic is after shut down and bleed off of some of the pressure with the pump NOT running.

Yes that is correct.

 

Edited March 25, 2019 by mbz
edited for clarity

[madkaw]

How do the plugs look?