78 280z Severe Driving Problems

[Dave WM]

another reason the psi could be high is a "stuffy" return line. try letting the return line drain into a holding tank with some long fuel hose.

[kinser86]

12 minutes ago, Dave WM said:

did you see the fuel pressure change with the vacuum? as manifold vacuum decreases (less vacuum, no matter how say it does not seem right) FP should go up. with the engine off (no vacuum) pressure should be about 36 psi, idle should be 29psi, should vary between those with throttle, go even lower than the 29 psi as you snap the throttle closed and the vacuum shoot to 25inhg.

 

11 minutes ago, Dave WM said:

another reason the psi could be high is a "stuffy" return line. try letting the return line drain into a holding tank with some long fuel hose.

I am starting another to-do list, this will on the top. I did blow through all hard lines on the car and verified air was going through from the front to the back of the car. When I had the rail out, I also blew air through it.

• Record FP/Vacuum /RPM simultaneously

Here is the video of it moving under its own power, it was a short drive.

 

[Dave WM]

you need to figure out why that pressure is so high, the EFI on this car has no  Oxygen sensor so it has no idea if running rich or lean, so can not compensate with on/off time of injectors. So everything has to be right, sensor resistance, and fuel pressure are critical. I would not touch the AFM until you get that dialed in. You could test the FPR by hooking up a vacuum source like a brake bleed hand vacuum to the FPR, energize it using what ever means works (like solenoid off, key on) and read the fuel rail pressure, starting at atmospheric and then working the hand pump down to 18inhg to get to the 29psi. Do one thing at a time, start with that, then try a return line to a holding tank, eliminating one variable at a time.

Main thing is to resolve on problem before moving on. Compensating for a fuel pressure problem with the AFM is not going to work, at best it may be ok for a range of RPM but not likely to work as it should.

Edited August 31, 2018 by Dave WM

[kinser86]

48 minutes ago, Dave WM said:

You could test the FPR by hooking up a vacuum source like a brake bleed hand vacuum to the FPR, energize it using what ever means works (like solenoid off, key on) and read the fuel rail pressure, starting at atmospheric and then working the hand pump down to 18inhg to get to the 29psi. Do one thing at a time, start with that, then try a return line to a holding tank, eliminating one variable at a time.

I will do just that. I have a hand vacuum pump I can use.

[Zed Head]

Just watched your last video.  Very informative.   I don't think it's firing on all cylinders.  Could be several reasons.

I would confirm that firing order AND rotation direction are correct.

Check all of the injector connections.

While it's idling pull one injector connector at a time.  Each one should cause a change in idle speed.  Pull the connector, confirm idle speed change, put it back on.  If you find one that seems dead, switch it with the one next to it.  They all fire at the same time, there's no order.  If the problem follows the injector connector it's that, if not it's the injector.

 

We got way ahead of your actual problem I think, although everything you've done so far will probably help with the fine tuning.  But you need to get each cylinder firing first.  Another reason for cylinder misfire is bad cam lobes.  Could also be improper lash setting.  You might check your lash again and/or do another cylinder pressure check.

Edited August 31, 2018 by Zed Head
Don't not problem.

[Zed Head]

Another way to say it is it should be running much better and differently than the problems you have suggest.  I've had the lean problem and it wasn't like yours.  It popped back and bucked when you tried to give it gas.  Yours is running like it's on 4 or 5 cylinder.  It could be fouled plugs but these engines can run really rich, enough to make your eyes burn, and still not foul plugs.

[Dave WM]

good point about the power balance test.

[Zed Head]

Just watched the video again.  I wonder if the AFM is even plugged in.  You can check the pins at the ECU connector.  Sometimes the plug falls off the bottom when you're reinstalling the AFM.

Or maybe the TVS is stuck at idle setting.   Something odd going on, it sounds good with no load.

 

[Dave WM]

forgot to ask, where those new plugs with only a few miles on them? I like to read plugs that are brand new. Regarding ZH comment, you should make sure you are getting the resistance test for the AFM at the ECU 35 pin connector, that would make sure the wire harness is not an issue. I still think you should focus on getting that fuel pressure issue resolved 1st, no reason for it to be high like you were seeing.

[Captain Obvious]

There is lots of expert help already on the case, so I'm going to stay in the wings as much as possible, but before I go back to my hiding spot, there are two things that have caught my eye.

First is this... On your to-do list was to return the AFM gear to it's original position by turning it six teeth counter-clockwise. The implication of this is that you had previously turned the gear six teeth clockwise. (Haha! Big intellectual leap by me, huh?) The POINT is... If think you are chasing a lean condition, then turning the AFM gear CW will only make it leaner:

On ‎8‎/‎27‎/‎2018 at 6:51 PM, kinser86 said:

to-do list:

• Turn AFM 6 teeth counterclock wise back to previous spot.

The second thing that caught my eye was the way you have the vacuum gauge and the vacuum advance connected. Something is wrong with the following:

7 hours ago, kinser86 said:

Vacuum reading was taken between the vacuum advance and intake.

The vacuum advance signal for the distributor is not supposed to come directly off the intake manifold. It is supposed to come off a ported source from the bottom of the throttle body. And that vacuum source should be zero vacuum at idle. So something is screwy there, and your fuel pressure readings and ignition timing numbers are suspect until you get to the bottom of that.

If you have the distributor connected directly to the intake manifold, then your base timing is wrong. Or if you have the vacuum gauge connected to the ported vacuum source, then your throttle plate is open waaaaaaaay too far at idle. Potentially because the thing just won't run at anything less. Also, if you're using that ported source for the gauge, then your FPR numbers may be correct because you can't do the subtraction for manifold vacuum correctly.

And I agree with Zed Head... It just don't sound right and I agree that you need to double check the firing order. Also check the injector clickety-clicking with a stethoscope.

[Chickenman]

On 8/26/2018 at 12:27 PM, kinser86 said:

• Fuel:

  • New fuel injector connectors

  • Injectors reconditioned from Fuel Injection Services (confirmed working)

  • New Walbro 255 fuel pump

  • Tank removed and checked for rust

  • Fuel hard lines cleared with compressed air

  • New fuel filters (pre and post pump)

  • Inline gauge added between filter and rail

•  

May as well throw my hat into the ring.

From my experiences tuning Mega squirt units, the Factory Nissan FPR can not properly regulate the extra Volume and Pressure that aftermarket  Fuel pumps put out. The return orifice inside the Nissan OEM FPR is simply not large enough to allow consistent regulation. .

FWIW, I would highly advise upgrading to an Aeromotive EFI Bypass FPR. Part # 13129. I've had about 6 customers switch out their OEM Nissan FPR's  to the Aeromotive unit. All were running aftermarket high performance Fuel Pumps and all were experiencing Fuel pressure issues. Switching to a proper adjustable FPR solved these issues in every case. Note; There are some crappola FPR's available. Aeromotive and Fuel Labs make excellent quality units. All made in USA and all very accurate. Even some brands such as Holley and Mallory are made in Chinea crap these days. 

[Zed Head]

That's a good point about the Walbro.  Beside that it is way overkill for a stock 280Z engine.  I've read about noise but not many overpressure problems though, with the 280Z lines.  The 240Zs have problems for sure.  Easy to check.

The one major problem for a daily driver with the Aeromotive FPRs is that they leak down immediately on pump shut down.  This can make hot start problems worse, and next day cold starts also.  Even the factory FPRs are a pain when they leak down.