Swapped Injectors, Losing Preasure

djburke87

I have been having a misfire issue since I got my car (cylinder 3). So in my attempts to troubleshoot it, I have replaced my fuel injectors with new ones. Since I have replaced them, I have been losing fuel pressure while the car is off. When the engine shuts off, it has about 50-52 psi. Yesterday I monitored it for a bit. It was 45 psi after a few minutes, 35 psi after a few hours, and 20 psi after 10 hours.

When it starts, it takes a couple of extra seconds to start, and when it runs I have no issues at all. But the starting is annoying me. Also, this didn't fix my cylinder 3 misfire, oh well.

So what I am assuming is that I messed up an o-ring when I installed the injectors. Does that sound right?

I have a new set of o-rings, and I am going to replace the ones on the new injectors. Does anyone have any recommendations on how to not screw this up again? Yoh can lube the o-rings, right? I know you need to torque the rail, but is there anything else that I should do? It seemed pretty straight forward when I did it, but apparently I screwed it up somehow.

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2018 Nismo - Z1 Cold Air Intake, Z1 Silicone Hoses, Catalytic Converter Delete, Remark Axleback V1 Exhaust

SonicVQ

The fuel pressure drop you have is normal.
As long as you have 29 psi or more after 30 minutes with the engine off, all is good.

You may want to check the fuel volume. The stock pump is around 120 litres/hour or 1 litre (1.06 quarts) in 30 seconds.

What happens to the crank time, if you turn the ignition on, the fuel pump will run for 2-3 seconds, then switch off, then start the car?

What are your fuel trims?

You could also reset your ECU. Easiest way to to unplug a MAF, start the car, CEL turns on, then turn off the car. Plug it back it, start the car and clear the code.
This will clear/reset the fuel trims. Then start the car and see if it starts quicker.


I have seen fuelling issues that seem to be caused by deleting the cat.
I think from about 2012 the ECU uses the rear o2 sensors to check for a rich/lean bias on the front air/fuel sensors.

djburke87

I'm not saying the fuel pump may not be the problem, but the issue only occurred immediately after I put injectors in. It has been a problem since, and never before. It makes me think it has to be an injector issue that is a result of me messing with it.

If I start the car and it runs for a couple minutes and turn it off, it starts up like it used to if I start it within about 30 minutes

How do you check the fuel volume?

I don't know what my fuel trims are or how to find them. Unfortunately, the previous owner put test pipes on my car. I have ordered HFCs, but they won't be here for another month. I also have new o2 sensors, both upstream and downstream, to put in when I do the HFCs.

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2018 Nismo - Z1 Cold Air Intake, Z1 Silicone Hoses, Catalytic Converter Delete, Remark Axleback V1 Exhaust

Rusty

Do not install the new O2 sensors until you have installed the hfc first. Use new oem O2 sensors. There have been problems with other O2 sensors in the past.

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SonicVQ

Let me back up to understand the background:
You had a misfire and replaced all the fuel injectors. Since then, the car will crank more than usual before starting ONLY if it has been sitting.

Is the misfire gone with the new injectors?
Where did you buy the injectors and what brand are they?
(There are MANY fake/cheap/counterfeit parts available today that cause endless problems)

Your fuel trims can be seen using any OBD scan tool, even a $10 EL327 and a $7 app will show you.

Just to cover all bases, the fuel trims will tell us if the engine thinks a bank is rich or lean and by how much. Very useful for troubleshooting air/fuel problems.

From a troubleshooting perspective, what tests did you do that lead you to replace all the injectors?
There are tests that can be done that can tell you which injector is bad or which ignition coil...

AND they are much cheaper than throwing hope/prayers and parts at the problem.

djburke87

Correct

I got them from Rock Auto. They are a "remanufactured" injector, meaning the were rebuilt and tested by GB Remanufacturing. It is an OEM injector that has been rebuilt by a 3rd party. Maybe I should put my other ones back on with the new o-rings I have, since they didn't have this problem.

I have a scan tool, I will see if it has that option after work. Thanks!

I have replaced spark plugs, swapped coil packs(remained on cylinder 3), cleaned the MAFs, done a throttle body relearn, and now replaced the injectors. I am open to advice, but also kind of hoping the issue will be resolved when I put cats back on it and new O2 sensors.

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2018 Nismo - Z1 Cold Air Intake, Z1 Silicone Hoses, Catalytic Converter Delete, Remark Axleback V1 Exhaust

djburke87

That's the plan!

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2018 Nismo - Z1 Cold Air Intake, Z1 Silicone Hoses, Catalytic Converter Delete, Remark Axleback V1 Exhaust

SonicVQ

I've never used "hope" as a strategy, but maybe it will work for you.
Good luck!

djburke87

Okay, so what would your strategy be? Not to put on catalytic converters and new O2 sensors? Just leave it with test pipes and run it with a misfire?

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2018 Nismo - Z1 Cold Air Intake, Z1 Silicone Hoses, Catalytic Converter Delete, Remark Axleback V1 Exhaust