Injector failure

[Q45tech]

This comes from a old 300zxtt forum. It is an interesting concept that the constant +12 volts on injector causes corrosion [ethanol with water conducts a little.The Q constantly supplies +12 and the rail is grounded thus some current could flow? I will test today and report. Easy as there is an injector fuse

"Well, now I know why I keep eating so many fuel injectors. Apparently it's normal for Nismo 555 injectors to last only a year in the 1990 to 1994 300zx...

http://www.twinturbo.net/net/v...35571

Some more comments from Greg @ SpecialtyZ:

We have had many,many,many nismo 555 injectors fail in the last coupleyears and nismo will not do anything. some of the early style injectors are only lasting a couple months. Since the fuel changed with alcohol content they are all failing extremely soon.

I feel for you that your experiencing problems with nismo injectors andyou are far from alone.

What is happening to the injectors is that they are corroding theinternal connection and causing an open circuit. The injectors are not getting shorted coils from running past their duty cycle.

The early style injectors have positive 12 volts all the time. The fuelformula changed a few years ago and they started adding alcohol to thefuel. Since the time the fuel was changed the injector failures of cars withearly style injectors is through the roof, (brand new and original early styleinjectors we are replacing several a week). It is believed the alcoholand having power to the injectors is causing electrolysis and eating up theconnections internally causing the high failure rate. They are nothaving this problem in Japan and they make fuel the way we use to withoutalcohol. The injectors were originally designed for fuel that we do not have anymore.

The stock injectors use to last 10 years easy and we hardly ever hadfailures......Now we are having to replace stock injectors that havealready been changed in less then a year all the time as well as originalinjectors failing almost daily. The late style injectors are wired to the ECU differently and do not have power when the key is off.

By old style, I mean the 1990-1994 year style injectors.The new style injectors that were used in 1995 and newer Z cars arecompletely different in design and require different code in the ECU and donot have power going to them from the ECU until the key is turned on.They also require a different fuel rail to bolt them in.They are not directly interchangeable. It requires different fuel rails andmachining of the lower intake manifold to accept the newer style fuel rail.It also requires changing the injector electrical plugs and ECU chip.

You absolutely have older style injectors because that is all you can usewithout major modification and changing all the injectors to the late modelyear style.Your only option at this point is to replace the one bad injector unlessyour willing to go to the expense of replacing all of them and doing themodifications to change over to the complete new set up.

Nismo is aware of the problem now and we have a lot of documentation.We are hoping nismo comes up with a solution for direct replacements.

I am recommending to people doing upgrades currently to change over to thenew style now they we know there is a problem with the old style injectorscombined with our current pump fuels.For years the Nismo 555cc injectors were a great relieable injector.

Other company's selling injectors for the early application are assembledthe same way and the ECU program for the early style injectors has the ECUsending power to the injector all the time adding to the electrolysisproblem.

Mike Smith and JWT are looking into ways to help the injectors live longerby wiring the injectors differently. This is still in the testing stages andwe are hoping to offer at least a patch of some kind to help with peoplethat have these injectors.

I feel your frustration, I had to change 3 of the 6 injectors in less then ayear on my personal 300ZX that had the HKS 2530 turbos......I replaced themall with the newer style 740's and fuel rails when I put JWT 700 turbos inthis last year.I still have all my 555cc Injectors in my 280z that has the twin turbomotor and Greddy TD05 turbos. I did wire this car myself when I did theengine conversion and I do not have power to my injectors when the car isoff.This just happened by accident because I wired the car and the fuelinjection relay does not have power until the key is turned on.

[Q45tech]

I used a sensitive digital VOM and could not read any engine off current flow to injectors [at fuse location] down to 0.01 milliamperes. BUT there was voltage coming backwards from ecu thru injector referenced to +12 battery terminal. [from switching transistor that grounds injector].

I will need to make a special adapter to read current flow from injector to ecu?

Might just be easier to rig a relay to open circuits when car is off?

I need to determine which terminal on injector opens: the ecu or the battery side. Need to find an industrial xray machine.

Anyone have access to a precision TDR [time domain reflectometer]?

[qship96]

Just install a cutoff switch at battery terminal and shut the entire monster down

[Q45tech]

Then the radio and other circuits loose memory..................a ignition controlled relay [20 amps] in series with injector fuse is the best answer to delay injector failure. IF THE CONCEPT is proven true in the future.

Research on ethanol blends shows fire fighting problems due to ethanol resisting foam and conducting electricity:http://hazmat.dot.gov/pubs/rep...6.pdf

"Gasoline is an insulator, butethanol is highly conductive. The % sensor measures changes in electrical conductivity, temperature, anddielectric constant. It sends a duty cycle input to the PCM that allows a calculation of actual ethanolcontent to be made. The pulse width of the injectors is adjusted accordingly so that the fuel mixture doesnot become too lean. More recently, manufacturers have eliminated the % detector and use a “deductiverefueling logic” to determine what fuel has been added to the vehicle. When the PCM “sees” that therehas been a sudden change in fuel tank level, it deduces the amount of oxygenate from O2 content in theexhaust and makes the appropriate changes to fuel delivery. These include different base injector pulsewidths and different ignition timing curves (more fuel, advanced spark timing). E-85 vaporizes well enoughfor starting down to 10°F. Below that temperature, the engine block heater should be utilized."

http://www.allsafe-fuel.org/TechPaper.pdf

[heywier427]

very interesting!

[Q451990]

By old style, I mean the 1990-1994 year style injectors.The new style injectors that were used in 1995 and newer Z cars arecompletely different in design and require different code in the ECU and donot have power going to them from the ECU until the key is turned on.

Maybe this is something that could be modified in the next phase of the "NICO ECU" if we could bribe Robert or someone else with the knowhow to do it? In the meantime, I can unplug the fuse overnight, since the car is in the garage for days at a time anyway.

Heath

Side Note: Dennis, I'm going to be at T3 (S. Cobb) on Friday at about 4:00 for a transmission flush on the way to see the inlaws in Dalton. If you haven't had time to play with the Bowen/NICO ECU in action with the Consult, please stop by - I would love to get your thoughts on it.
Modified by Q451990 at 3:15 AM 5/22/2008

[Q45denver]

That's the first I heard of that being an issue.

Maybe this something that could be modified in the next phase of the "NICO ECU" if we could bribe Robert or someone else with the knowhow to do it? In the meantime, I can unplug the fuse overnight, since the car is in the garage for days at a time anyway.

Heath

Side Note: Dennis, I'm going to be at T3 (S. Cobb) on Friday at about 4:00 for a transmission flush on the way to see the inlaws in Dalton. If you haven't had time to play with the Bowen/NICO ECU in action with the Consult, please stop by - I would love to get your thoughts on it.

Modified by Q451990 at 8:07 PM 5/21/2008

[greg_atlanta]

Here's my story..... is this a classic case of injector failure?

* 92 Q, appx 238K miles, runs like a dream -- but in ethanol area now

* all injectors removed and cleaned manually about 6 months ago when fuel hoses and injector harness were replaced (tommy at T3 decatur)

* filled the tank last week at high volume bp station with 10% ethanol sticker, was a little suspicious since about half the pumps had a bag over them (tanks low?) prior tanks were either bp or qt.

* for 1st 130 miles driven on that tank car runs perfect

* today make a 4 mile trip, runs great, shut the car off, turn it on 30 mins later and it's running rough if i don't keep rpm at 1000 (rpm at idle in drive is normally around 650-700 rpm and the rpm adjustment is turned all the way up).

* rest of the day making lots of short trips, have to put the car in neutral at stoplights to keep the rpms up and keep engine from lurching/bouncing. seems to run fine above 1000 rpm.

* car sits for 8 hours at work, drive home 6 miles and it's worse that before, also runs rough at highway speed

I'm at 1/2 tank now, will put in 1 bottle of isoheet tomorrow. If I got bad gas, wouldn't the symptoms be sporadic? Should I fill the tank ASAP to dilute whatever's in there, or try to run it dry before I fill up?

If this is an injector failure, is it safe to make short trips the next 3-4 days with the engine running rough? I really don't want to deal with T3 and rental car until after the holiday weekend (I can let roomie drive me around all weekend).

Thanks,

Gregaka injector newbie

[Q451990]

Hey Greg... long time no see!

In my case several years ago, a single dead cylinder felt more like a bounce at idle, but no reduction in idle speed or real driveability issues (except for the vibrations).

So I think either you had multiple injectors crater all at once, or bad gas...

Heath

[greg_atlanta]

Is it safe to assume for now that it's bad gas and just drive it to empty the tank? (which hurts at $3.99/gal!) Or should I fill it up to dilute the gas that's in there?

Since the idle adjust is turned all the way up and Byron at T3 suspects the part may need to be replaced (aac/iac valve, forgot the exact name), could the engine just be stumbling since the E10 has less energy than real gas and causing a lower idle?

[Q45tech]

The E10 energy level is only 3% down so insignificant at idle.

Why not ohm the injectors to see how many bad ones you have today.

If you need an IAC I have a recently cleaned* and tested spare [$85].

* It takes about an hour and multiple solvents and air pressure and tiny picks to clean to as brand new.

Should read 10.0 +-0.5 ohms..........9.9 is the average of 3 I tested. all at 75F.

[Q45tech]

Extended fuel study effects on plastics:http://www.polymerplace.com/ar...s.htm

[Q451990]

Just for convenience, here's the link to how to ohm test the injectors.

http://www.q45.org/ohminjectors.html

Heath

[Q45denver]

[QUOTE=Q45tech]The early style injectors have positive 12 volts all the time. The fuelformula changed a few years ago and they started adding alcohol to thefuel. Since the time the fuel was changed the injector failures of cars withearly style injectors is through the roof, (brand new and original early styleinjectors we are replacing several a week). It is believed the alcoholand having power to the injectors is causing electrolysis and eating up theconnections internally causing the high failure rate. They are nothaving this problem in Japan and they make fuel the way we use to withoutalcohol. The injectors were originally designed for fuel that we do not have anymore.[QUOTE=Q45tech]

Aren't the 90-93 ECU's interchangable with the '94-96 version. So for $50 or the cost of a 94-96 ECU you could solve that as a potential problem. Not sure what they mean by "electrolysis or corrosion" since these terms usually imply metal?

[greg_atlanta]

Just for convenience, here's the link to how to ohm test the injectors.

No luck with that. I couldn't get a reading from my cheapo multimeter. I replaced the battery and the red arrow swings to the right when I touch red and black together, but when I connect the battery and harness leads nothing happens.

Will drop it off at T3 on Tuesday. Same symptoms today.

[Q45tech]

Testing for enough current flow to cause electrolysis inside injector has so far come up negative. So we are still left with the ethanol swelling the plastic and physically pulling the connection apart on the rear of terminal/connector.

Obviously there is a difference between sudden open failure and the progressive slow increase in resistance we use to see before ethanol was added to gasoline.

[greg_atlanta]

Just talked to Ty at T-3 S Cobb and he said he's seeing a lot of repeat customers on injector replacements.... replace one or two, then others fail a few months later (with a lot of repeat labor). He quoted $2400 to replace all the injectors, but there's no guarantee the new injectors won't fail at some point in the future.

A/C is gone on my car, was considering fixing it at some point if the car was in good shape, but now I'm looking at $2400 for injectors plus at least $2000 for A/C..... think it's time to put her out to pasture.

Will be at T-3 Tues 10 am to get an assessment (or a quote to add to the junker fleet).

Any advice?

[Q45tech]

So far Nissan is still warrantying injectors [parts] at the same 12/12k as other parts.

Ty and I discussed what to do about the labor warranty and how we risk significant labor possibility, if a new injector fails within 12/12k.

We may be forced to sell injector replacement insurance to cover the $600+ labor at risk.

This is unique since every other Nissan part historically lasts much longer than 12/12.

[Q45denver]

Personal experience tells me they will probably last thru the warranty period. I think that failure is more time dependent than mileage related. The first set of replacement injectors was installed in my 1990 around 13 years ago. I had two new ones fail within 10K miles but only after two years. Then after a year of sitting all of the used ones put in my replacement engine suddenly failed. I had a hard time figuring out why the car would barely start or run anymore until I ohm tested them.

Apparently this problem was not unique to the Q's, so you would think that after all this time a solution would have occured. Maybe if they were forced to use ethanol in Japan it would have been so by now. So far I have had good luck with my '94-96 phase II's.

If anyone needs a new Deutschwerks phase II adaptor kit at a substantial discount over what I paid for it let me know. I have one I never used.

[greg_atlanta]

My problem is "fixed". Pics soon.

[greg_atlanta]

Was in the Decatur area yesterday about to go browsing at dealers but decided to drop by T-3 first. Tommy tested the injectors and said #7 was dead and two others were likely to fail soon. I had talked to sales guy at the dealer a hour earlier and they happened to have a G sedan without a sunroof -- which is rare find. Robbie repeated what Ty said about all the repeat customers with injectors, often with another injector failing the next day after some of the injectors were replaced.

So I ended up buying 6 new injectors.

Not sure what to do with the old Q, I've had it for 8 1/2 years. Will mull it over for a few weeks. I'll post pics soon. Car is in very good shape other than no A/C and 1 (or 3) bad injectors.

[Q451990]

You've had the "new car itch" for a few years now - I guess now was a good time to scratch it! I didn't know they even made a G without the sunroof. Beautiful car!

I hope you can sell your Q to someone on here that has the time and ability to do some DIY work to keep her on the road. It would be a shame to see another first gen. flagship off of the road.

Heath

[maxnix]

Especially a good one!

[greg_atlanta]

Especially a good one!

Yes, it is a "good one".

I might get over it after a few weeks with the G. Although it's only 13 inches shorter than the Q (same wheelbase) it feels about half the size -- which is perfect for a city car. It's very high strung and jerky, but that may mellow as it breaks in. I'll come up with a likes/dislikes list in a few weeks for others who are considering a G. It's A LOT of car for the money, basically a half price 535i.

[Q451990]

Well... I had my first sign that all is not well with my injectors today. Got a dead miss after about a 15 minute hot soak. It went away as I floored it and pulled into the road. Drove fine for a couple of later trips... but I'm probably on borrowed time. I put a can of BG44K in earlier in the day... doubt that's related. Just ohmed them while they're fairly hot... meter bounces in the upper 14 to low 15 ohm range on all injectors except #5 that shows the upper 17 to low 18 ohm range.

I'll check them again tomorrow when they're cold. I actually pulled the fuel pump fuse after I parked her in the garage... maybe not marinating them in the corn death juice will help somehow. Also pulled the injector fuse in case the above theory has some merit. Who knows if anything will help... not looking forward to the back pain from the plenum job.

I guess at this point I have to decide if I want to try the purple new injectors from eBay - or spring for new 94-96 injectors and rails and subharness from Joe. I'm not willing to risk the remanufactured injectors and retrofit kits... Has anyone found a good deal on NEW 94-96 injectors?

Heath

[Q451990]

Here's a link to a .pdf on JWT's site with the constant 12V theory. http://www.jimwolftechnology.c...E.pdf

[elwesso]

Thats an interesting concept with the electrolysis. Dennis, does the 94 Q work the same way the later Z's do? Seems like the Qs would be the same across the board since the ECUs are all compatible, im not sure if thats the case with Z?

[Q451990]

Thats an interesting concept with the electrolysis. Dennis, does the 94 Q work the same way the later Z's do? Seems like the Qs would be the same across the board since the ECUs are all compatible, im not sure if thats the case with Z?

From the schematics on the JWT .pdf I get the impression that the ECU doesn't control that 12V flow in terms of being swtiched or always on... I think it's more related to which leg of the igniton switch that circuit is wired.

BTW, ohmed my injectors again today cold. They all read about 1 ohm lower... so upper 13 to low 14s on everything except #5 at somewhere in the 16 ohm range.

Wes, does the ignition switch have to be on to ohm the injectors on your Q?

Heath

[elwesso]

if you have anything on in the car it will throw the reading off, but we all know that from ohm's law since the voltage will be a little different..

when you ohm your injectors, you either go across the terminals or from the harness with the + on the positive terminal on the battery and the other end on the pin in the harness!

I wouldnt be too depressed about your readings heath, when was the last time you put into your VOM a new battery?

[Q451990]

I wouldnt be too depressed about your readings heath, when was the last time you put into your VOM a new battery?

Battery is good. I'm not worried about the readings on any of them except #5.

The reason I asked about if you have to turn your ignition key on when testing is that I get no reading between the (+) terminal and the injector harness if the injector fuse is pulled - so I suspect if your later model Q has the switched 12V going to the injectors, you would have to have your key in the on position to test them - while I would not (if my fuse is in). Confusing sentence, but hopefully it makes sense.

Heath