mbz

CO, I think you are right on all accounts and what I'm dealing with is a number of problems inherited from the PO, where they just kicked the can down the road on these issues to be dealt with later.... well later for the PO seems to be now for me. I have read through the service notes from PO's Mech (pretty extensive), and it indicated that the engine was running rich (failed smog), and that there was a vacuum leak that was repaired, which would have made it run lean (although I do not have details about that yet - going to put a call into the PO's Mech and see if I can get more info about this). However PO's Mech. indicated that he leaned out the engine to pass smog. The car did pass smog and was driving OK (I've put about 150 miles on it since purchased at end of January 2019, half of which was driving the car home after the initial purchase), up until this problem just presented itself when the car refused to start while out for lunch about 5-6 weeks back. DaveWM's advice has been pretty spot on thus far, so I'm sticking with the next round of tests he indicated yesterday, which is: 1). Clamp off the fuel supply to the cold start valve to be sure it is not providing excess fuel into the engine if it is malfunctioning. 2). Check Water Temp. Sensor at 36 pin connector. 3). Check AFM air temp sensor and the Static reference resistance readings. 4). Check that TPS sensor is working per the FSM. I'm reading up on these tests now trying to educate myself so as to be not quite as ignorant, and once I have the knowledge and the time (hopefully by this coming weekend or sooner), I'll be able to perform these checks and report back the findings.

Short answer is.... I don't know. (I'm not afraid to say it) I don't think we need to assume that I'm ignorant after the fuel pressure gauge debacle.... ? But kidding aside, I really don't know if that makes sense or not. How is it supposed to perform?

Yes the conversion looks correct, I checked it here: https://www.convertunits.com/from/in+Hg/to/psi

Zed, I knew you'd be back! I have GREEN INJECTORS. My 280z is a 1976 (built in 1975)..... it's right there in the title of this very, very, very, very long thread. (which at least 2/3 of it can be attributed to the bad fuel pressure gauge). ? I have both the FSM & FI Bible (actually printed them both and put them in a 3 ring binder as well - I was feeling ambitious and bored). Are you having waffles with your chicken? (it's very good)

When at idle, NO / negligible. When RPMs are increased, YES.... LOTS of BLACK smoke.

I have results from the loaner fuel pressure gauge..... they're good. My fuel pressure gauge was way off. (chicken dinner for Zed) ? Here's the results: Fuel Pressure with Fuel Pump ONLY: 36-38 psi (hard to tell from angle of camera, but well within spec) Fuel Pressure with Engine Idle: 34 psi (RPM = fluctuates between 400-500 at idle) Fuel Pressure with Engine Idle and OIL CAP OFF: 32 psi (RPM = fluctuates between 600-1,000 at idle) When idling, if I open the throttle.... initially the engine hesitates then starts to rev to higher RPMs. With the oil cap OFF the engine will return to idle. With the oil cap ON the engine will drop to idle, then stall and will not start. Only_Fuel_Pump.MOV Engine_Idle_Oil_Cap_ON.MOV Engine_Idle_Oil_Cap_OFF.MOV

Maybe it's time to take it to an expert for correct calibration? Or perhaps the AFM is better off being replaced?

Thanks for your help Zed, have a good one. DaveWM, I'll check back in tomorrow when I have a different fuel pressure gauge. I'm going to go clean up.

Not trying to win anything Zed, just trying to fix my car. It's not a competition.

OK so as to the gauge and it's consistency..... I GET IT. I will borrow one from Pep Boys tomorrow and see if I get different results. Flogging a dead horse on that point.

Well I'm trying to provide relevant info. What other tests and results would you like to see?

Like I said, it was the angle of the dangle.

I'm checking service records now, looked back to 2008 and did not see any mention of fuel pump replacement. I'm going to button her up for the night, then do a deep dig on service records to see if I can find out when it was last replaced. What's the next step....? New fuel pump? Testing the vacuum from the intake manifold to the FPR? Kinda stumped here. Thanks for the help today guys, I appreciate you putting up with my amateur BS.

OLD FPR - fuel pump only = ON pressure is 45 psi !!!! (See video.) Photo is for test configuration reference. IMG_1877.MOV

Again......

OK I get it. I'll borrow a gauge tomorrow and see what happens. However, gauge or no gauge, the problem is still persistent. That's pretty high pressure. Not sure what's next......

Zed for your edification, here's a head on, dead on shot of the gauge at zero.

I couldn't see. I was in the driver's seat turning the key. I didn't hear Niagra falls over by the bucket, in other words it didn't sound like it was gushing or anything. Just for shits and giggles, I could hook up the original FPR and see what happens. So what's the next step from here....? Borrow Fuel Pressure Gauge from MMJ? Buy a Vacuum gauge and see what kind of vacuum is present? Am I jumping the gun again? I'm not sure what this test told me other than my Fuel Pressure Gauge is a POS.

Yes it goes to zero, it's just the angle of the dangle in the photo that's making it look like it's starting at 2-3 psi.

I get it..... I need to borrow a gauge from Manny, Moe & Jack and see what results I get with a different gauge.

OK I did the Fuel Pump only to FPR test and got 42 psi with key on and 38 psi with key off. ( said 40 psi in the video but couldn't get a good reading until I saw the video). To be sure I got the test set up and performed correctly..... See video #1 for test results. See video #2 for test set up & configuration. IMG_1874.MOV IMG_1873.MOV

OK I did the test and got 5 psi. To be sure I got the test set up and performed correctly..... See video #1 for test results. See video #2 for test set up & configuration. IMG_1870.MOV IMG_1869.MOV

OK, I'm going to use a short length of hose to loop the fuel rail to the fuel return. Then run the fuel return hose line to a bucket where the fuel return hose connects to the metal return line under the car. (return will not be going to tank). Then check fuel pressure with JUST THE PUMP. Stand by while I rig it up and get results....

I used a long length of hose (like 3 feet)

Also, I just went and took the gas cap off and it sounded like a vacuum being released. Not sure if this helps confirm or debunk diagnosis. - - - ALSO - - - After depressurizing the fuel tank, I took the clamp off the fuel return hose that was draining to the bucket. No more back pressure. So I connected the other end to the fuel rail, and checked the pressure with just the fuel pump cycling fuel through the fuel rail and back to the fuel return without the FPR inline. The fuel pressure was 8 psi.... consistently. (I tried it 5 times) So maybe it's not a clogged fuel return line after all.....?