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Discussion Starter #1
I got an 87 z31 na. And right now, in order to get my car to operate normal for a short period of time I have to unplug the fuse to my fuel pump and plug it back in after about 4 seconds. I have replaced the pump, fuel filter, plugs, cables, and got a FPR from the local pull a part. I also replaced the o2 sensor
When I go to accelerate my engine bogs and stumbles very bad, then I take the fuse out and plug it back in, and things run smooth for a short period of time. I have ran the diagnostic codes and I get the fuel pump circuit code, but I thinks that is vague since it could be anything with the fuel system aside from the injectors.
I am brand new to working on cars so I dont know much. But I am willing to learn if anyone can give me some insight on what this might be.
 

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I am assuming you already have the Factory Service Manual for your Z31. If not, go get it here.
Have you ran through the FSM's Fuel Pump code 22 inspection chart? See FSM section EFEC.
You will want to do this when the car is misbehaving.

Other than that, I would check that ECU is well grounded. Make sure ECU is bolted firmly to the car body, and that there are some body grounds in good shape. Take a close look at the ground strap from the battery ground to the car body.

Questions for curiosity sake:
  • How long after you pull the fuse does the car behave correctly?
  • Will the car continue to run/idle once the problem starts?
 

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Discussion Starter #3
I am assuming you already have the Factory Service Manual for your Z31. If not, go get it hear.
Have you ran through the FSM's Fuel Pump code 22 inspection chart? See FSM section EFEC.
You will want to do this when the car is misbehaving.

Other than that, I would check that ECU is well grounded. Make sure ECU is bolted firmly to the car body, and that there are some body grounds in good shape. Take a close look at the ground strap from the battery ground to the car body.

Questions for curiosity sake:
  • How long after you pull the fuse does the car behave correctly?
  • Will the car continue to run/idle once the problem starts?
I have a PDF of my FSM. Should probably get the book.
The grounds to me ECU look good.
The car continues to run bad until I plug the fuse back it. So after the pulling of the fuse it still stumbles a bit, but as soon as I plug it back in, everything is good for about 10 seconds. Then starts to lose power.
I thought it could be my MAF so I pulled it and c leaned it. With no change to the performance. I know she isn't in limp mode since I can accelerate to 4k rpm after I plug the fuse in.
And she does idle rough most of the time, but she starts up first try everytime
 

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Discussion Starter #4
When I replaced the fuel pump, I reused the hose from the old pump. I believe the problem is in the hose being old and flimsy. So whenever the gas gets sucked through there it might be collapsing the hose and not allowing the fuel to get through at high acceleration.
 

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You should do a fuel pressure check to verify you have a fuel pressure issue. This is relatively quick, easy, and cheap.

Generally the fuel pump is at the bottom of the gas tank and all hose from it is under pressure not vacuum. Was your gas tank clean, any debri, gunk, or water, when you replaced the pump? Perhaps check the fuel filter.
I don't think any of the above problems would cause a code 22 on ECU. I don't know if your after market pump would cause the code.
 

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Discussion Starter #6
I figured out what it was. There is a little orange hose connected to the sock of the pump. And it was disconnected. I went to take the pump out and the ring the lid screws into cake out with the lid. And now I can't get the ring back into place to screw the lid to my pump down. Any advice for that? Please help.7
 

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Discussion Starter #7
And yes
I am assuming you already have the Factory Service Manual for your Z31. If not, go get it here.
Have you ran through the FSM's Fuel Pump code 22 inspection chart? See FSM section EFEC.
You will want to do this when the car is misbehaving.

Other than that, I would check that ECU is well grounded. Make sure ECU is bolted firmly to the car body, and that there are some body grounds in good shape. Take a close look at the ground strap from the battery ground to the car body.

Questions for curiosity sake:
  • How long after you pull the fuse does the car behave correctly?
  • Will the car continue to run/idle once the problem starts?
The car does continue to run idle when the problem starts, although it does stutter pretty hard. Almost dying
 

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Discussion Starter #8
Well what I thought was the problem was not it. Or maybe it was, but now the lid to my fuel pump won't seal closed. But my car is still running the same. Bogsout after 16 rpm.
 

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Have you tested the airflow meter? If it bogs down after 1600 rpm or so, it may be going into that limp mode thing they do. I had an issue with mine not pulsing the injectors, and I found the problem in the attached pictures. Oddly enough, the diagnostic part of the computer was working fine, and didn’t identify a problem!
 

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Discussion Starter #10
Have you tested the airflow meter? If it bogs down after 1600 rpm or so, it may be going into that limp mode thing they do. I had an issue with mine not pulsing the injectors, and I found the problem in the attached pictures. Oddly enough, the diagnostic part of the computer was working fine, and didn’t identify a problem!
I haven't tested the air flow meter. What's keeping me from believing it's my MAF s the fact I have to unplug the fuse to my pump to get it to run correctly.
I have cleaned my MAF thought and nothing really changed.
Are those pictures of your ECU
 

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I haven't tested the air flow meter. What's keeping me from believing it's my MAF s the fact I have to unplug the fuse to my pump to get it to run correctly.
I have cleaned my MAF thought and nothing really changed.
Are those pictures of your ECU
Yes, that’s the ECU. I have no ground to my fuel injectors, but the rest of the ecu seems to work fine. Super weird. I thought you had solved the fuel pump problem, so I apologize. I would say get an inline fuel pressure gauge and see what you operating pressure is. It should be about 49 psi. If it’s not, the pump isn’t functioning correctly. If it is, take a look at your fuel pressure regulator. It may have gone bad.
 

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Discussion Starter #12
Yes, that’s the ECU. I have no ground to my fuel injectors, but the rest of the ecu seems to work fine. Super weird. I thought you had solved the fuel pump problem, so I apologize. I would say get an inline fuel pressure gauge and see what you operating pressure is. It should be about 49 psi. If it’s not, the pump isn’t functioning correctly. If it is, take a look at your fuel pressure regulator. It may have gone bad.
Would my lid not sealing properly cause issues as well? When I took my fuel pump out the last time the ring that the lid screws into to hold it in place came out and I couldn't get it back in correctly...😭
I swapped my FPR with one from the junkyard, so maybe that could be the problem.
 

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It doesn’t matter if the tank isn’t sealed per say, although if you don’t have the pump sealed all the way down, you’ll have an explosive gas vapor situation inside the car... I’d definitely fix that. It will not however affect the fuel pump operation. It just pulls from the bottom. Either you have a clogged pump, clogged fuel sock or a bad fuel pressure regulator
 

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Discussion Starter #14
Well the
It doesn’t matter if the tank isn’t sealed per say, although if you don’t have the pump sealed all the way down, you’ll have an explosive gas vapor situation inside the car... I’d definitely fix that. It will not however affect the fuel pump operation. It just pulls from the bottom. Either you have a clogged pump, clogged fuel sock or a bad fuel pressure regulator
Well the pump, filter, and sock are brand spanking new. Installed it in July. So it would have to be the FPR since I replaced the old one with another old one. I guess my next move is getting a new one.😂
 

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Have you done a fuel pressure check? Do you know that you have a fuel pressure issue? It should be above 30 psi after you turn the ignition on (before starting the car). At idle it should hold 30 psi, and when you open the throttle it should rise to about 37 psi.

You have not mentioned it, but does your car have stock fuel pump wiring?
 

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I agree that an inline fuel pressure test is the next step! You can borrow a tester from an auto parts store, or you can make one pretty cheaply.
 
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