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Discussion Starter · #1 · (Edited)
My truck is a manual Nissan d21 or hardbody. It’s a v6 se model. I was having a problem where my trucks rpms would drop and it would rev super low and almost die. It got to where I couldn’t even tap the gas to get the rpms up as it would kill it almost instantly. The only thing I could do was start it and be pressing the gas. Even if I took it out of gear it would try to die. I had to keep the rpms up for it to keep going. Now it’s to where it will not turn over. Was able to spray brake cleaner into the throttle body and that would keep it going. So I believe the issue is a fuel pressure problem. Was able to get the bed off and test it by the fuel pump and was getting about 40 fuel pressure before it dropped. I’ve researched it a bit but wanted to see if anyone knew anything about it. I’m thinking it might be a fuel pump that’s going out or a fuel pump sensor. Thanks so much for your time. If you have any questions let me know.
 

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Was able to get the bed off and test it by the fuel pump and was getting about 40 fuel pressure before it dropped.
It's definitely a starvation problem if it runs on Brakleen, and if you're seeing pressure drop at the tank then chances are it's a tired or binding pump motor that's losing torque and speed when it gets warm. It won't be a blockage because you'd see rising pressure and not falling. I don't recall if D21's had a return-type regulator, if so it's possible that's causing a drop. You can check that easily by temporarily pinching off the return line to see if its disposition improves. Otherwise, just check voltage drop on the power and ground wiring to make sure that isn't the issue before condemning the pump. If your pump power is good then it sounds like a bad pump is the correct diagnosis.
 

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Discussion Starter · #4 ·
I have yet to check the pressure at the injectors. I’ll definitely check that. Will do. I’ll definitely check those both. Yeah the pump cost a bit. Wanted to make sure before replacing it. Thanks so much for the reply.
 

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I have yet to check the pressure at the injectors. I’ll definitely check that. Will do. I’ll definitely check those both. Yeah the pump cost a bit. Wanted to make sure before replacing it. Thanks so much for the reply.
The 40 psi at the tank is already way low. Normal is about 56 and I think factory minimum spec is 51. It won't be any higher at the engine, so there's little point in a downstream measurement.
 

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I have yet to check the pressure at the injectors. I’ll definitely check that. Will do. I’ll definitely check those both. Yeah the pump cost a bit. Wanted to make sure before replacing it. Thanks so much for the reply.
Since you didn't specify the year of your D21, if it has the V6 engine , then it must be older then 1996. That being the case, it has a fuel pressure regulator at the fuel rail and a fuel filter in the engine compartment. Tee-in a temporary fuel pressure gauge between the fuel filter and the fuel rail. The readings at idle should be as follows:
  • with vacuum hose connected to the fuel pressure regulator: 34 psi
  • with vacuum hose disconnected from the fuel pressure regulator: 43 psi
If the pressure is out of spec, the pressure regulator may be bad or the fuel filter may be plugged up; they're OK, then the pump is marginal.
 

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Discussion Starter · #7 ·
Thanks for all the reply’s. It’s a 1989 d21. Did a couple checks on it and when I when I plugged the return line at the tank I actually had a rise in pressure to almost 60. And it was still losing pressure but this time it was a lot slower then when it wasn’t plugged. It’s making me think the problem is most likely the fuel pressure regulator. I replaced the fuel pump and even tested it with out the fuel filter and it was doing the same thing. It also will only start when I’m spraying brake cleaner into the throttle body and keep running if I keep spraying it. As soon as I stop it dies. I was researching them but I found that a lot of places had them discontinued or they were for a 90’s d21. Would a 90’s part work for this? I found the part numbers 22670-88G00 and 16240-03G15. Thanks a bunch for all the help.
 

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Discussion Starter · #9 ·
Possibly. I’ve had the fuel filter in it for awhile. Got a new one on it now and it’s still the same. I also tried plugging the return line to check the pressure regulator but still nothing. I’m pretty positive it’s a fuel issue and it’s not getting to it. Could it possibly be the injectors not misting properly? I also put a new fuel pump on it.
 

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Discussion Starter · #10 ·
Oh and I completely forgot about it. I the check engine light on when I got it. Fixed it and got the check engine light off. But it had two codes reading even with the check engine light off. They were 23 and 45 which are idle switch and injector leak. My truck was running really good and the one who was helping me said it would be good. I’m thinking could this possibly be due to the injector leak. Weird thing is the check engine light still is not on. Could these effect it? Thanks a bunch
 

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The 60 psi with the return line pinched is healthy, and 40 with the return open looks to be normal for your old horse. The fact that the regulator return drives the pressure up means the flow is unobstructed in both directions. I doubt it's clogged injectors, because only running on Brakleen, it would have to be all of them. Injectors don't all clog at once unless there's sugar in the tank, and that clogs the pump and filter too.

I did find a bulletin, apparently there's a potential open-splice issue on '87~89 D21's. I can't find the bulletin itself, but here's the synopsis:

Vehicle:
1987 - 1989 Nissan D21 3.0
1987 - 1989 Nissan D21 2.4
Symptom: No start and no injector pulse.
System: Emissions/PCM/Fuel
Problem: No power to terminal 114 at the ECU.
Test & Fix: Terminal 114 is the battery feed to the computer. The wire is White/Red. Check for a splice problem in 2 possible locations. Check the splice under the hood in the harness about 8" from the Throttle Body Injection (TBI) connector going toward the passenger fender. Then check the splice located in the harness behind the passenger side kick panel. Repair as necessary.
Diagnostic Codes: N/A
 

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Oh and I completely forgot about it. I the check engine light on when I got it. Fixed it and got the check engine light off. But it had two codes reading even with the check engine light off. They were 23 and 45 which are idle switch and injector leak. My truck was running really good and the one who was helping me said it would be good. I’m thinking could this possibly be due to the injector leak. Weird thing is the check engine light still is not on. Could these effect it? Thanks a bunch
The Check Engine Light CEL is reserved for Emissions issues.

Bad injectors are common.
 

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Discussion Starter · #14 ·
I was able to check the wire and didn’t find any issues with it. But I was able to test the injectors. Found out that they were not getting power. Then in the process of trying to test the issue there was one point which it got power but it was only 2v. I also check the power at the ecu for what I believe is the one going to the fuel pump and it was getting 12v there. Gonna check the line running to the ecu and the fuel pump again. Anyone know what might be the issue? Thanks a bunch for all the help.
 
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