91 300zx TT running poorly, please help!!

[Robert mudd]

Well after driving it all day (about 100ish miles) I think I can safely say that the O ring were the problem. Thank you guys so much for your help, if it wasn't for you guys I probably would have never guessed the rings. I appreciate that you guys would use your valuable time to help me. If anyone has questions about my problem, symptoms, or the process please feel free to ask.
Thanks again,
Robert mudd

[nissanfreak12]

That is fantastic to hear! Its good to see you go this fixed, now enjoy your Z and post some pics of it.

Its good that you decided to look into the oring, because since it was leaking outside of the cylinder, it easily could have started a fire.

[Robert mudd]

Well might have spoken a little too soon, Unfortunatly, the misfire is fixed and it runs very good, however today I was driving it and it seemed to not want to rev over 4.5 -5 K rpms. Sometimes it would, sometimes it wouldn't, it felt like there was a rev limiter there, idled great and had good smooth power up until that point, and I've only noticed it after it had been driven and hour plus today. Also put a bottle of techron in it earlier today when I filled it up.

Thinking Maybe a fuel pump going out? Eventhough I checked the pressure last week, that was when the engine was cold.
Tell me what you guys think?

[nissanfreak12]

Fuel pump, fuel pressure regulator, fuel filter.

Make sure all Vac lines are hooked up first since you just did work removing the plenum. Also Make sure the PVRV solenoid is not malfunctioning if you still have it. Normally it doesn't cause that issue, but it is possible.

Another thing comes to mind, is yours a true TT or a swap? When I did my swap, I used a NA pump, did the same thing at about the same RPM. Granted later I found out the pump couldn't supply enough fuel for a TT with mods, but it's something to think about.

How old is the fuel? Do you smell fuel in the engine bay?

Chances are its just a weak pump, when one thing goes out on these cars, once it is fixed, always seems to be something else.

[Robert mudd]

This is a true TT, I've checked the fuel pressure regulators and just put on a new filter,

Not sure what a pvrv is.

Fuel is brand new, when I checked the pressure it was at the low side of the acceptable pressures, 38 psi. Maybe it can't keep up with demand at higher Rpms, will see it if acts up today.
If I put cheap PCV valves in instead of oem Nissan, could that cause the problem, these valves didn't have a spring like nissans. The PCV mechanism was free floating.
Thanks again for your help!

[nissanfreak12]

PCV valves just keep the pressure from building up in the crank case, worse case is it create a vacuum leak.

Try and check the FPR with and without the vac line attached. It should rise when vac is not attached. If it is possible, drive around with the fuel gauge attached and see if the pressure drops at the higher rpms. If it does it could be, FPR, Fuel pump, or fuel controller.

[nissanfreak12]

Try not to get frustrated with the car, you have to remember, it is a 26 year old car. Anything and everything can go wrong with it at this point.

[Robert mudd]

I won't get frustrated as long as you guys don't get frustrated with my questions lol.

I'm gonna bring her back to life!!

Sorry long day at work so I didn't get to do anything today.

Last time I checked the FPRs no gas came out of the vacuum lines when the car was running, and I don't think the RPMS changed but I will check that tommorrow. It might have but I wasn't focused on that.

Question for you, based off the unit I have I don't think I can drive around with the pressure gauge on. Can I drive around and get it really warm (when it exhibits the issue). Then hook up the gauge and test it with the car not moving? Will it still display the issue while not under the load of me actually driving the car, rather just revving it?

Side note, when driving the car this morning it would rev freely until about 20,30 minutes of driving, when again is would struggle to get above 5k, Again idle is great still and power is very good still up until 5k.

Thanks again, will keep you updated when I do a few tests tommorrow.

[nissanfreak12]

I am not a fan of throwing parts at it, but I know it was stated maybe a CTS may be bad. Worth a shot. I know at the parts store they are what 20-30 dollars?

It still sounds like a fuel pump issue. My thoughts are that the pump is getting too hot, even though being cooled in fuel, that it loses its pumping abilities. I have a tow truck that ran great when it was cold outside, 1993 ford f350, ran great for hours with no issues. Well when the temp got above 85, it would start lagging power. One day, after about 4 hours of driving, it started really being under power. Having issues at higher rpms. So I decided to change the pump because when I switched to the rear tank, it drove fine. So I know it was the pump. Yours has the same signs as mine did, and of pumps that I have dealt with in the past.

Fuel pumps are not what they used to be and just quit. They will work at lower rpm's but not higher(major sign), have enough to start, but thats about it. Just stop completely, but then start working just fine. Act up only when hot, or all of the above.

If I had an extra pump, I would more than happily send it to you, but not a TT pump. It can be an expensive gamble, but it is giving all the signs of a failing pump. The only other thing that it may be is the fuel pump controller. One way you can check it, is wire the pump so it gets 12 volts continuously(basically wired on a relay and fuse directly to a sourced ignition), run it for a good hour or so and see what it does. A day or two like this will not hurt anything if the pump is strong. If the pump is weak, it will fail faster. If it runs with no issues for the couple hours/days, your controller is the issue.

[Robert mudd]

Thanks for the response,
Ya I have an above average knowledge of cars for someone my age, (21) but still not that great compared to you guys.
But from I can tell when driving, it seems like a struggling fuel pump,

I'm a little confused,
so hooking it up to continuous 12 volts will bypass the controller, then if it runs well even when hot then the controller is the issue, if is still struggles, then it's the pump?

Or does this bypass cause the pump to fail if it is weaK?

Or both?

Also how much would you estimate a good quality pump would cost, also how difficult is getting to and replacing the old pump?

Thanks again!

[Robert mudd]

After a quick check this morning if I'm standing in front of the car, taking off the right FPR slightly raises the rpms. While taking off the left FPR lowers the rpms. And the left one lowers more than the right one raises, so when taken off at the same time the idle speed drops just ever so slightly.

Will check pressure later today hopefully

Will try and check pressure later today.

[nissanfreak12]

Basically both. WHat you are doing when you wire a relay to the pump from its own circuit, you are bypassing the controller, just make sure you wire it as close to the pump as possible. Usually at the access port on the fuel tank. This will bypass the controller and give the pump constant 12v.

The TT controller has 3 stages, I think 8v. 10v, and 12v. Na's have 2. To access the fuel pump on a 2+0, its right behind the passenger seat, under the cargo holder. Basically between the two windows. 2+2 are under the spare tire.

A TT fuel pump is roughly $300.
https://conceptzperformance.com/nissan- ... p_1246.php

You can go walbro, aeromotive, or AEM which are universal HP pumps for significantly cheaper.

https://conceptzperformance.com/aem-50- ... p_9730.php

https://conceptzperformance.com/aeromot ... p_4774.php

https://conceptzperformance.com/walbro- ... _p_936.php

There are other options out there as well, these are just a couple.

[nissanfreak12]

To clarify, with the bypass to the pump, if the pump fails its the pump because the controller is not controlling it at all. If it runs with no issue for a couple days or a few hours, then the controller is the issue, again because the controller is not controlling it. Controllers very rarely go bad and are fixable if they do.

The piece on the left is the fuel damper, which smooths the pulses from the pump to the injectors. The piece on the right is the FPR which controls the pressure in the fuel lines.

[Robert mudd]

Okay that makes sense.

Update on symptoms today. My plan was to run it until it got hot, then bring it back and hook it up to the pressure gauge, rev the engine and see if the pressure dropped off at high RPMs.

However what I found was that when hot it would still rev freely in neutral. So I drove it again, first gear was still mostly freely revving when warm, however in 2-5 the engine didn't want to rev above 5k Ish,

So does that mean is wouldn't be the controller because the load the engine is under seems to matter??

Also I found someone locally who could possible have a used oem fuel pump for around 125, what are things worth checking on it, or would you stay away from it completely? (Keep in mind I'm on a college budget lol)

[nissanfreak12]

Free reving and under load are completely different. So, could still be both.

From what described though, more than likely the fuel pump. I would stay away from the local guy for 125, it easily could be a NA pump, would never know. They look identical. For that price, I would pick up an aftermarket pump for about that price. Its new and has a warranty. NOt hard to install either.

[nissanfreak12]

You could always find a cheap fuel pressure gauge and hook it up so you can see it when you drive. That will tell you a what is going on. Like I said, controllers rarely go bad.

[Robert mudd]

Thanks again for your input nissanfreak,

Tommorrow I am going to try and locate a pressure gauge that I can drive around with. That will hopefully shed light on the problem.

Also I'm worried that with an aftermarket pump I will have to modify brackets, hangers and wiring, etc, is there an aftermarket brand that will bolt right into the stock bracket and also the stock wiring, that would make me a lot more comfortable going aftermarket?

[nissanfreak12]

You honestly would not have to modify that much and you can go back to stock if you need to. All lyou really need to do is get clamps to hold the smaller pump in place. No cutting or odd placement. The stock level sensor is in another section of the tank.Like I said, its very easy to "mod" The wiring is splicing the wires, I think some pumps have the same plug, just not sure which ones do. But cut and use butt connectors to attached the wires.

[Robert mudd]

My boss who is very inteligent when it comes to cars, also owns a 90 300zx na. He seems to think that the MAF is the problem. What are your thoughts on that based off my symptoms? I know my MaF is at least functioning however I don't know the extent to which its functioning. Maybe at higher volume levels it doesn't read correctly, maybe that's why 2-5 gears don't want to rev higher?
What are you guys thoughts on this??

[Robert mudd]

After driving the car for about an hour and a half, the symptoms have gotten a little worse. Seems like a little more loss of power. Also my boss drove the car and when it reaches the limit it does start to miss.

After work today I tried to get access to the fuel pump to see how hard it would be. It seems very easy, took my trunk area apart and there were two hatches. Took both hatches off. One passenger side and one driver side. I'm assuming the fuel pump is passenger side?
Any trick to getting it out of there, or is it straight forward?

I think I'm going to go ahead an go with an aftermarket fuel pump. I really think that because it sat for so long before I got it, 2+ years, that the fuel pump is weak, and with the amount I am driving it, it's failing. Any recommended brands or pumps for a pretty stock TT that isn't going to to really be modded that much in the future?

Thanks again.

[nissanfreak12]

Concept z performance has a few that are really well priced

AEM- free shipping about $100
Walbro-no free shipping $85
Grams Performance-no free shipping-$100

All will work great if you are staying stock or want to add small power add ons. They all can handle it.

Is it missing at the higher rpms? If yes, your fuel pump is failing, and having it sit for a couple years will cause issues with the pump, especially if the gas went bad.

Replacing is really straight forward. Relieve fuel pressure, the bolts holding the access to pump are 8mm. It pulls right out. Be careful removing the hoses, it may be stuck on, just take your time. This is honestly the hardest part is the damn fuel hoses. Which side the pump is on, I honestly forget. Remove pump, install new one, splice wires, new hose, etc.

Like I said, its a very easy process.

[Robert mudd]

Ordered the AEM pump kit, was shipped today.
Will install it and let you guys know how it goes.

Thanks again for all your help.

[Robert mudd]

Hello, received the pump kit today and installed it. So far it seems to have fixed the problem. Power seems smooth and revs freely. So this is good

The bad. It appears my tank has rust in it. Should I stop driving the car immediately or is it still okay to drive for the time being because I just replaced the fuel filter?

Also what are my options and what is the easiest way to fix this problem?

Thanks for your input.

[nissanfreak12]

Make sure you have the filter on the fuel pump. No filter on pump and rust will destroy a pump extremely fast.

Only way to clean the rust from the tank is either drop it and thoroughly clean it, take it to a gas tank shop and have them dip it and clean it, or replace it. The tank itself may not be rusty, but the fuel hangers for the pump and level may have rusted enough to cause rust in the tank.

[Robert mudd]

Okay yes I put the filter on the pump, how difficult is it to get the tank out of the car?

[Robert mudd]

I hate to keep changing the topic but, today I was driving it, and While i was not just killing her I was driving a little harder than normal. Three times while driving harder she lost power momentarily. First and second times only lasted about a second. The last time lasted around 8-10 seconds. I pushed in the clutch and the car idled it just wouldnt rev at all during that moment. Resumed driving at a normal pace, and she made it all the way home without a problem.

I'm not really sure where to start when looking for this problem. Could it just be the filter getting clogged because my tank is pretty rusted. Could it be my new fuel pump is not set to the correct height so when I take corners the gas sloshes away?

Any help is appreciated. Thanks