78 280z Severe Driving Problems

[Dave WM]

sorry kind of lost, are you getting 36psi with engine off (pump on), are you getting 30psi with engine on and measured vacuum at about 17inhg?

If so I would install a new set of plugs go drive it 5-10 miles and then look at them. should be nearly white. Not a fan of trying after market parts if you are having a problem. the OE stuff should work fine. Assuming other stuff has been covered, like air filter as an example.

Might want to step back and re check some of the earlier stuff. really need to figure out one thing at a time, if fuel pressure is off, no reason to go further until you have that worked out. There has to be a reason if its not right.

re pump swaps, I had an aftermarket style pump that would do 90psi, car ran fine, I replace it with an OE style pump that has a built in limiter (think its 40psi, but not sure). I did it since I like OE stuff, it made NO difference in the performance of the car. So from that I gather the pump would not be an issue.

Edited September 18, 2018 by Dave WM

[Zed Head]

His video in Post #26 kind of sums it up, it's not really drivable.  And in some of the others, #74 for example, he reports 42 psi with just the pump running, his injector flow test.  Several odd things going on.  Still haven't confirmed that the gauge is good.

Several simple things could be knocked out to make the overall situation more clear.

[Dave WM]

did not see any pig rich black smoke on the video #26 kind of wonder if its even fuel related. Oh well the plug test will tell for sure.

[JSM]

What is the number on your Ecu? I may have a spare from a 78 you can try. 

[rcb280z]

11 hours ago, Dave WM said:

did not see any pig rich black smoke on the video #26 kind of wonder if its even fuel related. Oh well the plug test will tell for sure.

I didn't either and if it is rich at idle you would have seen a puff of black smoke coming off of idle for sure.

[kinser86]

On 9/17/2018 at 9:20 PM, Zed Head said:

Take the FPR out of the picture.  Connect the fuel rail supply line to the fuel return line, with the gauge plumbed in.  Run the pump.  If you don't have pressure then it's not the pump.  It might be the FPR.  Or a restriction in the rail.  Bypass the FPR on the rail and run another test.  Break the system down in to its parts and something will show up.

Hopefully, eventually, as you're working on the individual sub-systems you'll have a realization about something that's not right.  You've kind of gone past the original finding that swapping injector connectors had no affect.  Which might have been a clue that you had some injectors not opening completely.  Which might be supported by the varying flow rates at wide open.  One or two might be gummed up.

I have my old BWD injectors from OReilly Auto with 10,000 miles on them.  Kind of waiting to see what your plan is.  Did you contact the rebuild guys?  Seems like they owe you something.  Maybe they have a couple of injectors that they can give you to make up for the bad ones they said were reconditioned.

Those are some good suggestions regarding the test with the fuel pump and bypassing the FPR.

The company that serviced the injectors documented the results. They did a Open flow and Pulsed flow test. I need to confirm the number in the result, more than likely volume but they did not deviate as much as they did on the car. Unfortunately, the injector number in the test do not coordinate with the injector cylinder number on the car and in my test. Given this information, it would appear the injectors are operating close to each other, no obvious outliers as identified in my test.

Open Flow | Duration: 30s
Injector	1	2	3	4	5	6
	109	110	110	108	107	107
Pulsed Flow | Duration: 80s | RPM: 2400 | 6ms
Injector	1	2	3	4	5	6
	116	116	116	116	117	120

At this rate, I can disassemble to fuel rail and check for debris again since it is already out of the car. I can document it along the way. I figured since I have the rail out and ease of access to replace the FPR. Maybe the diaphragm has become rigid from age and degradation.

Regarding injectors, I was thinking of buying two injectors and seeing if they flow the same as the others using the same test as before. If they don't differentiate by much in volume then I don't see the need to buy 6. If something looks suspect (spray pattern or volume) I would probably buy four more and run another flow test again.

On 9/17/2018 at 9:37 PM, Dave WM said:

sorry kind of lost, are you getting 36psi with engine off (pump on), are you getting 30psi with engine on and measured vacuum at about 17inhg?

If so I would install a new set of plugs go drive it 5-10 miles and then look at them. should be nearly white. Not a fan of trying after market parts if you are having a problem. the OE stuff should work fine. Assuming other stuff has been covered, like air filter as an example.

Might want to step back and re check some of the earlier stuff. really need to figure out one thing at a time, if fuel pressure is off, no reason to go further until you have that worked out. There has to be a reason if its not right.

re pump swaps, I had an aftermarket style pump that would do 90psi, car ran fine, I replace it with an OE style pump that has a built in limiter (think its 40psi, but not sure). I did it since I like OE stuff, it made NO difference in the performance of the car. So from that I gather the pump would not be an issue.

42 PSI engine off, key switch on, oil pressure sensor disconnected. This is 6 PSI greater than it should be and I am trying to find out why.

On 9/17/2018 at 9:48 PM, Zed Head said:

His video in Post #26 kind of sums it up, it's not really drivable.  And in some of the others, #74 for example, he reports 42 psi with just the pump running, his injector flow test.  Several odd things going on.  Still haven't confirmed that the gauge is good.

Several simple things could be knocked out to make the overall situation more clear.

I will test the gauge with compressed air to validate its functioning/not sticking/accurate.

On 9/17/2018 at 10:19 PM, JSM said:

What is the number on your Ecu? I may have a spare from a 78 you can try. 

AFM Number: A31-605

ECU Number: A11-601 000

I have read a number of times these two are supposed to be from the same batches (not sure how true that is) which is why I always look for sets. Right now the rail is still out the car until resolve this high fuel pressure issue but I will keep that in mind when I get over the hump if the numbers are compatible.

[Captain Obvious]

9 hours ago, kinser86 said:

42 PSI engine off, key switch on, oil pressure sensor disconnected.

What does the fuel pressure do when you let go of the key?

Does it drop to zero, or does it stay up? And if it does maintain pressure, what pressure does it maintain?

Answers to those questions could help determine if the FPR is being overwhelmed or if something else is going on.

[Dave WM]

will take one last crack at this.

the assumption is the poor engine behavior is fuel related. Further the assumption is the fuel mix is too rich.

IF that is the case the new spark plug test could quickly confirm. The problem with the assumption is lack of black smoke noticed in the video tends to point away from a rich mix.

But again you may have issues with correct readings. The gauge could be incorrect, the video lighting may not show smoke. Test equipment must be tested to make sure its accurate before completely trusting the readings.

IF the new spark plug test confirms the condition is overly rich, then the indicated too high a fuel pressure can be part of the problem. If not then you can spend a lot of time chasing the wrong issue.

I did not go back and re read everything but if this is the car with the super high compression, then there could be further evidence of long term over rich (and therefore excessive carbon build up on top of the pistons raising the compression ratio).

The new spark plug test is super easy to do please try that before continuing to chase any other issues. If they come out black then at least you can be SURE its a fuel mix ratio issue. I invested in a "color tune" clear plug just so I could see the combustion process when I was trying to diagnosis a lean misfire at idle. Not saying you need one of those, but if you had one it could substitute for the new plug test.

If I was 100% sure its too rich, I would start by substituting a rheostat for the temp sensor (bullet lead to ground thru the rheostat) so I could REDUCE the resistance, which should lean out the ECU. Most of the time I see folks adding resistance to cure a too lean condition, which would be to insert the rheostat in series with the bullet lead.

I like your resolve to get to the bottom of it, I am sure you will ultimately be rewarded with a fine running car. I can tell you that when they are sorted they start easy, get good gas mileage, and run great. I just got back from another 800 mile trip with no issues and got about 25mpg going freeway speeds most of the way.

 

 

 

 

 

 

[JSM]

18 hours ago, kinser86 said:

 

ECU Number: A11-601 000

I have read a number of times these two are supposed to be from the same batches (not sure how true that is) which is why I always look for sets. Right now the rail is still out the car until resolve this high fuel pressure issue but I will keep that in mind when I get over the hump if the numbers are compatible.

That is the one I have.  If you want it, I'll ship it to you for you to try.  If it works, pay me what you feel if it worth.  If not, you can ship it back.

[kinser86]

Alright, before I address the recent posts let me state an update. I contacted the injector shop here and asked about the tests. They confirmed the volume was in milliliters. I brought up that my test showed two outliers vs their results. They said to bring them back and we can set them up on their tester and run the test again to see if that is true. I told them that next week sometime will be the earliest so I will document the trip and report back findings.

11 hours ago, Captain Obvious said:

What does the fuel pressure do when you let go of the key?

Does it drop to zero, or does it stay up? And if it does maintain pressure, what pressure does it maintain?

Answers to those questions could help determine if the FPR is being overwhelmed or if something else is going on.

It stays up, I don't have a number to support this but it does not drop to zero immediately. Give it 24 hours, it'll drop to zero. When working on the car, I could go away 30 min at a time and glance over the gauge and see its not at zero when going back to start it.

9 hours ago, Dave WM said:

will take one last crack at this.

the assumption is the poor engine behavior is fuel related. Further the assumption is the fuel mix is too rich.

IF that is the case the new spark plug test could quickly confirm. The problem with the assumption is lack of black smoke noticed in the video tends to point away from a rich mix.

The new spark plug test is super easy to do please try that before continuing to chase any other issues. If they come out black then at least you can be SURE its a fuel mix ratio issue. I invested in a "color tune" clear plug just so I could see the combustion process when I was trying to diagnosis a lean misfire at idle. Not saying you need one of those, but if you had one it could substitute for the new plug test.

If I was 100% sure its too rich, I would start by substituting a rheostat for the temp sensor (bullet lead to ground thru the rheostat) so I could REDUCE the resistance, which should lean out the ECU. Most of the time I see folks adding resistance to cure a too lean condition, which would be to insert the rheostat in series with the bullet lead.

I do have new plugs ready to go in and I will put the old ones aside. Right now I am looking for the high fuel pressure culprit and outlier injectors.

1 hour ago, JSM said:

That is the one I have.  If you want it, I'll ship it to you for you to try.  If it works, pay me what you feel if it worth.  If not, you can ship it back.

This is good to hear! ? I will keep this in mind again once I have the car completely back together (if you still have it at that time).

To Do List:

1. Take Injectors off rail
   1. Inspect fuel rail for blockage
   2. Bench flow injectors at shop in town that serviced them
      1. If the flow is even on the bench.... replace fuel rail? ? (I am not sure, this would stump me)
      2. If uneven, replace known bad, repeat flow test to confirm even
2. Test fuel gauge accuracy/precision
3. Plumb fuel supply to fuel return with confirmed working gauge in between to test for restrictions
4. Plug test, which will be heavily documented with video and everything. I am familiar with plug/chop test on motorcycles, never performed one but don't think the car is capable of safely doing this under load.

Hopefully I got everything...

[Dave WM]

don't worry about the plug /chop, just a few miles of normal driving. the way it runs now, that should be enough to see an obvious problem. I just want to absolutely confirm the condition is an over rich fuel mix.

[kinser86]

57 minutes ago, Dave WM said:

don't worry about the plug /chop, just a few miles of normal driving. the way it runs now, that should be enough to see an obvious problem. I just want to absolutely confirm the condition is an over rich fuel mix.

Got it.