1977 280z EFI Nightmare

[ckurtz2]

UPDATE 2: Resistance Checks at 35pin connector 

Well it looks like we have some work ahead of us. The things that I know failed were one of the AFM tests and the water temp sensor. However, any test where I grounded one of the points to the car it failed. I just grounded it to the bolt on one of the kickplates. Is this how I am supposed to ground it?

Idle throttle switch PASSED? Proper spec should be continuous and not continuous

throttle released it read 0.6. I think that is ok. Throttle depressed it read 1. Not continuous 

Full Throttle Switch  PASSED Proper spec should be continuous and not continuous

full throttle: 0.1 which is close to continuous enough

part throttle: 1 Not continuous

AFM#1 PASSED should be about 180

it read 182

AFM #2 FAILED should be continuous

it read 184

AFM #3 PASSED should be about 100

 it read 101

AFM#4 PASSED there was a wide range depending on temperature. Did just fine within specs

read 1411

AFM#5 PASSED AFM flap at rest should be not continuous. Fully opened should be continuous.

Read 1 so not continuous. Then read 0.1 so continuous

Water Temp Sensor FAILED should read within temp specs

I got 1, so it had no continuity

Control unit ground #1 FAILED should be continuous

62.9k

control Unit ground #2 FAILED should be continuous

62k

control Unit Ground #3 FAILED should be continuous

62k

Control unit ground #4 FAILED should be continuous

62k

Air Regulator and Fuel Pump Relay FAILED should be continuous

64k

Fuel Pump Relay FAILED should be continuous

read 1 so not continuous

 

Let me know your thoughts!

 

[ckurtz2]

11 minutes ago, Zed Head said:

Could be a pressure plate issue.  The levers/fingers that the TOB sits on might be unbalanced, or stuck.  The TOB should be centered on the pressure plate fingers by the nose of the front cover.  Although if the TOB wasn't seated on the fork correctly it might be pressing sideways on the fingers, kocked.  Interesting puzzle.

Bummer though.  The trans must come out.

Yip, was very disappointing when I felt it do that. Problem for another day though, just won't use the clutch while I try to get the engine running properly:) 

[Zed Head]

9 minutes ago, ckurtz2 said:

Water Temp Sensor FAILED should read within temp specs

I got 1, so it had no continuity

 

10 minutes ago, ckurtz2 said:

I just grounded it to the bolt on one of the kickplates. Is this how I am supposed to ground it?

That usually works.  These old cars lose their grounds though, just through rusting connection points.  You can add wires to create better grounds, to battery and engine block.  Looks like you should spend some time fixing your grounds.  They are as important as power supply.

Your running rich problem would be the water temp sensor.  Next step is to check the sensor itself at the thermostat block.

[ckurtz2]

With all of those tests failing when grounded it makes me believe I have the harness royally messed up in the engine bay. I am fairly confident I have everything right besides these two wires. When I got the car they were messed up, and I am not confident I put it together right. Do you have any idea how these are supposed to be hooked up? 

I had one running to ground on the battery, and the other leading to the positive terminal on the battery. This definitely could have been wrong

In addition, I tested the resistance of the water temp sensor at the housing. It read about 1300ohms which sounds about right, because the water still is a tad warm inside. So does this confirm I have a harness problem?

 

Edited May 1, 2021 by ckurtz2

[Zed Head]

The fact that the engine started means you guessed right.  Check the ground junction on the manifold, by the throttle body.  There's an eyelet with a bunch of wires attached.

 

 

 

Edited May 1, 2021 by Zed Head

[ckurtz2]

@Zed Head

interesting, my connection on the intake looks good. However, the little tower that the two grounds were connected to was painted where it touches the intake manifold. Would that ruin the ground?

[Captain Obvious]

What he said, and you're right. One of those big red wires goes to the positive battery terminal, and the other goes to the negative.

If you're looking for confirmation about which one goes where, the one that has low resistance to the ECU ground pins (5, 16, 17, 34, 35) should be connected to the battery negative. And the other one should be connected to the battery positive.

So you guessed right before, or the car wouldn't run (and you would have probably fried your ECU), but just to double check, I'd measure some resistances.

Also note that the big red wire that goes to the battery positive is supposed to have a fusible link on it. Yours probably turned to dust some years ago.

[Zed Head]

9 minutes ago, ckurtz2 said:

Would that ruin the ground?

Meter meter pumpkin eater.  Where's your meter?  Start probing and poking.  That's why most meters have long leads, so you can reach way over there to get a reading.  Take a reading, clean a connection, repeat.  Each small decrease in resistance will help.

[ckurtz2]

So I did as recommended and toyed around probing and poking. I realized that nothing was grounding, because I did not have the battery ground connected before. Gee I am so smart.

It seems like all the grounds in the engine bay are good. Everything read 0.1 to 0 ohms. I tested from across the engine bay on a harness ground to the battery, from the manifold to the battery, and every which way around and it all seemed solid. 

So I went and redid the harness pin test for the ones that failed and here were the results

AFM #2: Fail

183 ohms. Should be 0

Air Regulator and Fuel Pump: Fail

60 ohms. Should be 0

Fuel Pump Relay Circuit: Fail

60ohms. Should be 0

Water Temperature Sensor: Pass

It was within spec

Control Unit 1: Pass

0ohms

Control Unit 2: Pass

0ohms

Control Unit 3: Pass

0ohms

Control Unit 4: Pass

0ohms

 

So I think I can confidently say that the harness grounds are not the issue, at least in the engine bay. So What exactly would this mean? I think a rebuilt AFM is justifiable due to failing that test.  However, what the heck could be the problem with the circuit surrounding the fuel pump, air regulator, and fuel pump relay. I checked the ground between the air regulator connector and the battery. It checked out good. I also have an aftermarket fuel pump, would this account for the resistance? The resistance at lest dropped thousands of Ohms when I hooked up the negative terminal on the battery. I wonder if I should run a ground between the chassis and the ground on the starter motor. 

Edited May 1, 2021 by ckurtz2

[ckurtz2]

Here is my next update. Did some of the circuit tests for voltage. Everything pretty much seemed like it was receiving voltage, the only one in question was the AAR. It was supposed to slowly warm up to voltage, but it first read a lower voltage and immediately spiked to the battery voltage. My battery voltage said 27v. ?What the heck? What would that voltage indicate?

I attached the sheet of tests I did today off the EFI bible. Let me know your thoughts.

In addition, I decided I would record a video of how it runs so everyone can see. Here it is. I noticed for the first time a hissing noise coming from where the thermostat is. Could that be a vacuum leak. I ran a vacuum test and it literally read zero. To confirm this I pulled a few different ports while running and put my finger over them. I felt no suction and the way the motor ran made no change. However, I must be getting some vacuum, because the AFM meter moves. Before I fixed all the vacuum leaks that @Captain Obvious mentioned I could not rev the car at all, but this time I can. So i must be getting closer.

Could a bad injector seal at the manifold cause this big of a vacuum issue? Or perhaps the intake gasket itself? Fyi the exhaust leak you here is a big one between the mid pipe and the header. Problem for another day.

 

[Zed Head]

When you moved the AFM vane you were adding fuel.  Seems like a vacuum leak somewhere, or the typical "lean AFM/electronics" problem.  The "temp sensor tweak" is the cure for that.

Not sure what's going on with your voltages.  Are you sure there's not a decimal on the display?  What kind of meter?

http://www.atlanticz.ca/zclub/techtips/tempsensorpot/index.html

[ckurtz2]

@Zed Head

I cleaned the afm where it hits the carbon trace to see if that is why it had a high ohm reading. No change, if anything it read a few ohms higher.  I can hear the hiss of a leak from the fuel injector area/ intake manifold. Looked closer and realized that the injector seal wasn't in all the way. Seems to be like that on a lot of them, so I am just going to redo the seals.  In addition, what are the torque specs on the intake manifold gasket. It seems that I possibly over torqued it really bad, and that could be another cause for leaks.

So I think I knocked down my vacuum problem to the injector seals or intake gasket itself. Every other connection I know is solid.

Also I did a fuel pressure test and it tested perfectly fine. 

After I replaced the gaskets I will listen for the hiss again. If that fixes the vacuum and the car still runs poorly I will know it is down to the AFM that is ruining how the car performs. What is the "temp sensor tweak" you mentioned? I was just going to get a rebuilt unit from zcarsource. 

Regarding battery voltage I am just using a standard multimeter I got from ACE, I am positive there are no decimals. The voltage from the car's gauge reads about 13, interesting.