The new guy here, I have recently purchased a 90TT Auto w/77k. The only problem I have in this cars is I smell gas the first time I start it in the morning but after that it's ok. I have talk to some friends that owned one before and they told me that one of the problems of 300ZX are leaky injectors. If this is the case I'm on my way of upgrading the fuel injectors anyway. The question now is what do I need beside the injectors to upgrade my fuel system? Will my stock fuel rails and pump be sufficient enough for the injector upgrade? Need help please.

 

I would check all of your fuel lines first. There is a small peice of fuel line on the plenum at the front of the car that needs to be checked as well. Mine was leaking there. I tightened the clamps on it and it stopped leaking.

 

The leak could be from your injextors but because it goes away it's more likely from a hose around the fuel rail. In cold weather the hoses can loosen enough for a leak if not tightly fastened. As your car warms up the hose expands and seals the leak. Check all of your hoses around the plenum for signs of wear and cracks.

 

The car stumbles also when I drive it at highway speed and it sometimes does it at the stop light. I have recently installed a XBS blow off valve kit for the 300ZX. This could be the problem also. I am having a hard time working on it now because the repair manuals are not readily available. I am about to buy or download the manuals from the site. I am going to upgrade the stock injectors to a bigger injectors for my turbo kit. The question is do I need to reprogam the CPU for the bigger injectors? What else to I need to upgrade? Will the stock fuel rails be sufficient? fuel pump? I looking to get 500+ RWHP? Some advise would really help me alot. Thanks!!!

 

Im not exactly experienced w/ the fuel system on this car yet, but i'd assume that the stock fuel pump should be able to handle upgraded injectors to a degree (how much i dont know), and the stock fuel rails shouldnt be a problem until you start getting into the upper HP ranges. As for the ECU, it would be a good idea to upgrade it anyway if your planning on reaching anywhere around 400+ RWHP let alone 500. You should also be looking at a high flow fuel filter to add to it all, and if your going to be really upgrading, id replace all of your fuel lines and hoses so that its certain you arent leaking anywhere.

If your looking for a service manual, you can download the entire FSM from carfiche.com which should save you some money, and thats probably your best bet since there havent been any manuals put into production by anyone.

I'm curious as to the fuel pump question as well, does anyone know?

 

If you are upgrading your injectors you must get the ECU programmed for it (JWT, ASHSPEC). Stock fuel pump and rail should be fine unless you get into the 800+ hp range.

 

Thanks for the reply, Looks like you have a 90TT auto as well. How is your transmission holding up with the mods you have? My goal is to reach atleast 500RWHP and since Iam new to the Z community I don't know if my stock auto tranny will hold up. I'm sorry for having to many questions.

 

The previous owner had the transmission rebuilt and I havn't put too many miles on it thus far. It seems to be holding up fine though. Getting a transmission cooler will help as far as reliability but I plan on getting a fully built transmission from Specialty Z or SGP in the future. Oh and don't worry about asking too many questions. We are all here to help each other out so ask away.

 

Yes your stock fuel pump will be fine till about 600+hp as well as the stock fuel rail. You absolutely should replace the fuel line, filter and probably the damper and regulator. As stated earlier the ECU must be upgraded to allow for different pulse times due tho the larger injectors. Also a good time to have it programmed for your other mods. The blow off valvles shouldn't be effecting you're driving at speed unless they are venting under low boost and dropping your intake pressure.

 

Thanks for all the information guys.

 

how much does it cost to upgrade fuel injectors. I was thinking about doing the same thing.

 

usually a pretty penny for decent *new* ones.

 

Your looking at about 1300.00 for a new ste of injectors and the ECU upgrade. Plus the blood sweat and tears of pulling the plenum. I have heard that the injector upgrade is basically useless unless you upgrade your turbos and exhaust as well. My Z is missing a motor at this point since I pulled it to put in sport 500's, downpipes back, and 555cc injectors plus the 120 maint.

 

The stock dampner and pressure regulator can handle significant amounts of power. I believe that WAGZ Z incorporates these stock items and he's over 800 ponies.

 

Yep. He has a stock fuel pump as well doesn't he?

 

I had the same problem, only happends when my engine is cooled. Easiest way I found is start up the engine when its cold or when ever you have the problem, open up the hood and if you see wet areas then the problem is some where around there. Hot weather is harder because the gasoline tends to evaporate alot quicker. Becareful though its possible for your car to catch on fire.

Mine is the fuel regulator it was happening for a month. What I saw was pretty damn scary. Fuel was spraying out of it like a garden hose. Costs me $70 bucks to fix. Cheap price and saved the car.

 

I checked it last night. I even took out all the necessary part inorder to check all the fuel supplies. I've seen some wet stuff on the manifold and it was just some oil. I haven't seen any fuel squirting out from any fuel supply parts. I'm taking it to my friend's shop. He use to own a 96 TT but sold it because it has leaky injectors.