IllinoisREI

1990 300ZX NA with two bad fuel injectors. Decided to do a plenum pull, probably the first for this car, and replace them all. Everything is disconnected per the procedure posted in twinturbo.net but plenum only moves about a half an inch?!

I've checked and double checked. Do I need a crowbar? Is there a step for an NA that's not covered in the TT procedure? Anyone else have this problem?

KasbeKZ

yeah i had it. it's always another hose. look under the plenum while you move it and see which hose is moving. it's hard to see them all. but it has to be a hose. that's the only thing there. there are hoses so far down there that you can only see one little bit of them.

ZLover4Life

^ What he said.

Simply look harder. Tug on it *lightly* and see where the resistance is coming from.

And make sure the PCV valves and EGR tubes are disconnected, as well as the fuel damper and fuel pressure regulator.

KasbeKZ

oh yeah that's a good one. that dampener i think it is will just sit on top of the flanges that it bolts to on the plenum, so even though it's loose, it can still hold it down. you have to move it pretty awkwardly if you don't take it off.

ZLover4Life

Btw, based on your screen name, I'm going to recommend you join ChicagoZ.com.

IllinoisREI

Ok. This isn't easy to admit. This step wasn't actually called out in the plenum pull procedure I grabbed from the twinturbo site, but that's no excuse. I never pulled the coil packs, just the connectors. F***'n rock! Good thing I held off on the crowbar.

So now it's off and I've got the rebuilt injectors ordered from injectorwhse.com ($45 per after core exchange), and a new gasket, injector insulators, fuel filter, and a hose I had to cut in half to get out from Courtesy Nissan.

Any suggestions on spark plugs for an old NA?

ZLover4Life

Regular old PFR6G-11's from Nissan. You'd be a fool to go with any other plug.

And while you're waiting, do yourself a favor and practicing installing and removing that plenum. Do it until you're good at it. Why? Because you will be replacing those rebuilt injectors again very soon.

Mark my words: buy cheap, buy twice. And probably continue buying until you wise up and get *good* injectors.

KasbeKZ

word^^^ i spent $1k on my injectors for all 6. $160 a piece. i think they were double marked up though. if you got with courtesy, i think they have the same ones for $140. but i'm glad i did. i've heard bad stories about the rebuilt injectors. i really expect to never have to touch the injectors again except to replace the 0-rings around them.

ZLover4Life

Anybody who has the old style injectors is going to continue having problems with them. People who have rebuilt old style injectors are going to have LOTS of problems with them.

I recommend at minimum the injector rewire with new injectors, and the best option being [authentic] 300Degree rails with new-style injectors.

KasbeKZ

the ones that the dealership would be selling new with red tops would be new style right? would the 300degree fuel rail make any difference? is that just for reliability?

ZLover4Life

No, the new style (pintle-less) have the 94-96 connector and require either a 94+ lower plenum and rails or 300Degree rails (with 94+ connectors obviously) to fit on a 90-93 car.

KasbeKZ

damnnnnn.... so i spent $1 on the old style injectors that probably won't last as long as i'd like them to.... i'm not going to tell dad about that... he paid for them. i hope they last at least 50k or so though.

snwbrderphat540

just avoid anything with alcohol in it... which is hard cause i think almost all gas now has ethanol in it. haha. sucka!



also, pintle-caps blow

ZLover4Life

Do the injector rewire if you haven't already. I don't remember you asking our input on which injectors to go with, did you? And the retrofit isn't cheap (~$1300 for injectors + rails).

Easier method:
http://www.twinturbo.net/net/viewmsg...&msg_id=998981

Harder method:
http://www.twinturbo.net/net/viewmsg...msg_id=1013303

KasbeKZ

sweet. thanks. no i never did ask for advise because when all this happened i was pretty new, and what little i had heard about the new style/old style dilemma, i misunderstood. i was under the impression than any new injectors you bought were the new style. i didn't realize that injectors that fit older cars were the old style. i'll check out the re-wires though. thanks. how well does the re-wire work?

ZLover4Life

That's kinda unknown at the moment. Here's why...

The people who have done the rewire have met success - no reported failures yet (it's only been a short while since that method was determined though). But to determine if it is a solution, we must fully know the problem, and that's not as clear.

There are two suspected causes for failing early injectors... it could be one, the other, or both.

The problem the rewire fixes is called the "constant voltage" problem. Early style injectors are getting power ALL the time... yes, even when the car is off. This wasn't a problem a decade ago when gasoline was just gasoline, but now it has ethanol. The theory is, the constant voltage + ethanol (an alcohol) is causing electrolysis to occur in the injectors when the fuel is sitting (any time you're not driving the car). Essentially, the injectors are rusting from the inside out. There is strong evidence to support this, as there are images of bad injectors under a microscope that are rusted out. The rewire makes it so that the injectors only get a voltage when the car is on. If the car is running when there's a voltage, there's not enough time for the injectors to rust as the fuel is rushing through the injectors rather than sitting, and the problem is resolved.

The other semi-suspected problem is friction. Think of an injector as a valve that opens to allow fuel to flow through it. This valve is lubricated with gasoline (a petroleum product). Ethanol, an alcohol, is a cleaning solvent. This breaks down the lubricating ability of gasoline. As such, when the injectors are opening and closing rapidly, they are wearing out prematurely. If this is true, the rewire won't resolve this.

But the fact of the matter remains... 94+ injectors are immune to these issues entirely. 300Degree rails allow them to be bolted onto early-style plenums, making plenum replacements or machine work unnecessary (they also flow better).

To give you an idea of how susceptible early injectors are to failure, I replaced all 6 of my injectors with Nismo 555's (that's a brand name and all NEW pintle injectors) in 2004. I replaced one in 2005. I replaced one in 2006. I replaced one in 2007. I replaced one in 2008. And my car may have another dead one, since it was on 5 cylinders when it ran briefly last week (but it could also be due to the head gasket, I'll know in a few weeks). If the 300Degree rails had existed at the time, you can bet your *** I would've gone that route in 2004. I ended up spending far more replacing injectors annually.

napoleonzheking

Hmm. I guess I will do this before I put my Z1 ECU in.... the rewire that is.

IllinoisREI

Zlover: I knew I was rolling the dice with the rebuilt injectors but I didn't expect the dice to be loaded. I think I'll try to cancel the rebuilt order and go with the fuel rail mod. I'm not down for an annual plenum pull. Appreciate the advise and info.

KasbeKZ

yeah thanks. i'll be getting on the rewire pretty quick.

ZLover4Life

^ Wise choices, both of you.

IllinoisREI - I recommend buying from Specialty Z (SpecialtyZ.com) or Import Parts Pro (ImportPartsPro.com) since they are both authorized 300Degree distributors and other vendors have been known to occasionally screw their customers.

IllinoisREI

Ok. The refurb order is canceled. Unfortunately, they aren't exactly giving away that 300 Degree fuel rail. Are there any injectors that are less susceptible to the evil ways of ethanol contaminated fuel? I have always run only premium in the 300 and my 350 as well. Would that lessen the chance of early failure?

Appreciate your expertise Zlover.

ZLover4Life

There is as much ethanol in premium as in 87 octane, so no, the fact that you run premium (as you should) doesn't mean your injectors are less prone to failure.

And ANY drop in injector for the old style rails is going to be susceptible to failure. The only guaranteed way out is the retrofit with either 300Degree rails or 94+ rails + machining the lower plenum to accept the rails (the newer injectors are not a direct replacement - that's the problem). If you want to take your chance with the old style and the rewire, be my guest, but as I said before, that's not a guaranteed solution like the pintle-less injectors.

KasbeKZ

i mentioned this to my dad and he said when he was talking to the dealer that he bought them from, the dealer said that the modernly sold old style injectors had a new coating on their valve part that would prevent the issue.

this is pretty much two sets of conflicting info that i'm finding here. i tend to go with zlover over this guy that the injectors came from, but i'm just wondering if you have heard of any improvement in the old style injectors that are sold now

ZLover4Life

The guy at the dealership fed your dad a spoonful of bullshit.

The problem is as abundant today as it was 5 years ago. If you don't believe me, ask on tt.net.

KasbeKZ

no no i believe you. i'll do the re-wire at any rate. i'm curious to see how long these last though.

i got to thinking yesterday when i started it for the first time in a week that every time it sits for more than a week, it always starts on 4 or 5 cylinders and takes a few seconds to get up to 6. i always thought it was connections, but now i'm thinking it may be the injectors sticking. can they do that intermittently like that?