I'm About Done With The %**&ing Efi

[Zed Head]

Where's 7-8?  U?  U = ?

[mjr45]

Thanks FastWoman, I knew you would chime in with some good info. I'll try cleaning the wiper and test it again and see what happens. I've looked at the vane before and it didn't appear to be bent and it moves easily. I haven't had a front fire but that doesn't mean it couldn't be bent.

 

Blus, I may try to tighten it up after doing what Fastwomwn posted. Thanks for that diagram, it helps a total electrical novice like me to kinda get the idea.

 

rcb, you're correct there is no altitude swicth or at least not one that I could find.

 

Thanks

Edited March 20, 2015 by mjr45

[240260280z]

I made some measurements a long time ago:

pin 6 is near or at ground potential

pin 9 is around 2V below battery voltage it seems to be from a voltage regulator or current source in the ECU

pin 8 is the voltage across a fixed resistor that is supplied by pin 9 (193ohms in an AFM I profiled, 100ohms in the picture)

pin 7 is the voltage picked up by the wiper (voltage changes with its location in sweep)

Voltage U is the voltage between pins (7-8) or it is the resistance (for a current circuit). It decreases as the wiper moves towards WOT

Voltage Ub is is the voltage between pins (6-9) or it is the resistance (for a current circuit). It is fixed.

[240260280z]

AFM Measurements taken on a 77 280z referenced to chassis ground.

test

point 39 | 36 | 6 | 9 | 8 | 7 | 27 | Vreg | temp C

rpm

_800 13.93 13.93 0.01 11.59 7.48 3.22 5.09 14.04 6

1000 13.92 13.92 0.01 11.64 7.52 4.14 5.14 14.08 6

1200 13.98 13.98 0.01 11.7 7.56 4.68 5.23 14.15 6

1400 14.03 14.03 0.01 11.76 7.59 4.99 5.21 14.18 6

1600 14.35 14.35 0.01 12.06 7.78 5.41 5.25 14.49 6

2300 14.32 14.32 0.01 12.05 7.75 5.82 5.25 14.45 6

Edited March 20, 2015 by Blue

[hr369]

hr369, I've looked and looked for that ground wire and the FPR is new, look at my reply to Zed.

 

Zed,there is no cam, just stock. The FPR is new but that's not to say it can't be bad, my fuel pressure drops to zero in about 8 minutes after shut down, so its loosing pressure somewhere, I suspect there is a microscopic hole in the fuel rail under the #1 injector, there is some brown goo dried on the heat shield that I've cleaned off a buncg of times but keeps coming back. With all that said, that shouldn't cause it to run rich I don't think. The CSV is new, but could be a problem, maybe its leaking, but taking it out of the circuit electrically doesn't make a difference, Thanks

Mike

 

You can't find which ground wire? the one on the top or bottom?

[rcb280z]

Isn't that the engine to body ground? 

Edited March 21, 2015 by rcb280z

[Zed Head]

The EFI harness has its own ground wire, connected directly to the negative battery post using a plastic covered metal blade type connection, male to female.  It's right next to the battery, off the firewall, in the stock configuration.

 

Post #19 here shows it, with a little picture.  Upper left of the illustration - http://www.classiczcars.com/topic/40658-fuel-pump-and-relay-problem/

 

 

After thinking about it, I think that somebody pointed out in the past that the EFI harness ground wire might actually just connect to the bolt on the intake manifold that is also a ground connection.  Not positive.  Multiple gorund paths would be good.

 

Really though, ground paths should always be confirmed as low resistance paths back the battery, and the alternator body, using a meter.  If the ground strap does the job, that would be enough.  There are many pins in the ECU connector that can be measured to ground.

Edited March 21, 2015 by Zed Head

[FastWoman]

Sorry about that!  The description in my '78 FSM of the direction of wiper movement was a bit ambiguous.  ("When the flap deflects along with a change in the intake air flow rate, the terminal 7 mounted to the flap shaft slides on the variable resistor R from R1 to R9, causing the voltage across terminals 7 and 8 to change.")  It implies the opposite of what it actually seems to be, as R1 is closest to contact 8 on the potentiometer trace.  Go figure!

 

Irrespective, Blue always has great diagrams and trustworthy info!  Given that the wiper movement is opposite what I thought, the resistance measurements seem to indicate at least 30 Ohms of extra resistance between the potentiometer trace and the wiper, suggesting the contact still might be dirty or oxidized.  Cleaning might improve things, but it wasn't the smoking gun I thought it was.

 

Zed Head: Edit - I don't find any indication of "should be low reading" on 7-8 in the FSM.  Some would consider ~200 ohms to be low.  7-8 is only called out as continuity, but not detailed later in the FSM.  Anyway, I'll see what mine show, they all worked.

 

 

p. 50 of the Fuel Injection Guide: Leads to pins 7-8 should read: "Continuity (Small resistance)"

 

The FSM suggests powering the thing up and looking for smooth voltage changes throughout range of vane movement.  Note:  This should be done with an analog meter!  You won't see jitter from dirty traces very easily with a digital meter!

Edited March 21, 2015 by FastWoman

[rcb280z]

Just a couple questions:

 

Stumbles at 5800 rpms, How often do you run it like that?

15 degrees timing with NO advance? Whats the terrain like, hills and mountains? or flat land?

 

Isn't that enough to cause very poor gas mileage?

I know when I run mine hard WITH vacuum advance on "flat land" I get poor mileage.

 

You can run it hard like you do, shut it down right away and check the plugs to see if they are still fouled (Sooty). Might tell you or the members here a little about whats going on.

 

And maybe just drive it around without running it at 5800 rpms and check the plugs. This is how I found I had a rich idle only, and was lean at WOT.

Edited March 21, 2015 by rcb280z

[240260280z]

FW I was lazy and never probed the AFM circuit board with the carbon trace enough to tell how much resistance it adds to the chain of surface deposited carbon resistors (dark rectangles)

I am guessing the carbon trace has some resistance like a regular "pot". Especially when looking at the funky sawtooth traces

[mjr45]

Zed, I do have the ground wire that connects directly to - post of the battery

 

hr369, I don't have either of those ground wires, I do have a ground wire on the battery side to the car body, but I believe it comes from the other wire harness in the engine bay that goes to the interior, not the EFI, but I'll check it to be sure.

 

rcb, I don't very often run it up to 5800, usually just about to 4000 when accelerating and normal cruising around RPM. The plugs have always been sooty black even when I checked them after running hard. I live at 9000' up in the Rockies, lots of hills and twisty's not much flat terrain around here. The altitude also gives some low numbers on vacuum and compression, but when corrected for sea level they are pretty much right on.

 

Blue, Fastwoman, my carbon trace doesn't look quite that clean and there is a slight wear spot on the carbon trace from the wiper, so maybe when I clean it, it just may help at least a little.

 

Just as another note, I've always had a rich condition. One time caused it to die from over fueling, but that was due to a faulty connection to the CTS which I corrected and check on often to make sure its OK.

 

I'm trying to get her running prefectly to sell it on to raise money for my son's cancer treatment as much as I hate to part with her, but you gotta do what you gotta do. You guys are awesome and I appreciate all the help.

Mike

Edited March 21, 2015 by mjr45

[240260280z]

Maybe bending the wiper so that it touches a different part of the trace (where it is not worn) will help.

Prayers for your son this week at church.