Thought i fixed it. l28 fuel injected

[LouDoova]

Hello all, brand new to the site, and brand new to z's. My name is Lou I live in Knoxville, TN. I wanna start off by thanking everyone on this site, I just joined but have been doing research on here for a while and I love the way the topic's don't just trail off, someone is always chiming in giving useful advice, which is rare in a forum these days. (people just wanna argue). Anyway, i'm having a few issues that i was hoping someone could clear up.

 

- Background

  - Car has sat for over 10 years twice in it's life. The previous owner had let it sit for about 2 years and he didn't stabilize the gas. when he started it up he ran the bad gas through. He had the system flushed, injectors cleaned, gas drained, new fuel pump and filter. Didn't change the lines as far as i know.

 

- Currently

   -When I bought it, it ran fine. The next day i drove it for about an hour with no problems. after shutting down i come back out and try and start it and it wouldn't. Eventually it started. I kept driving it, and it would drive fine with only slight hesitation occasionally. Then it started to studder, and intermittenly lose power through the revs, but idled fine. I started researching, and eventually came down to the conclusion that it was either the gas tank needed a cleaning, or the thermotime and cold start were the culprit. I took the gas tank off and cleaned it as best i could. I just threw some rocks in there and shook it, and flushed it out with water then gas then shook some more then more water and gas. The inside still looks kinda ehh...also one of the vent hoses broke upon removal, so i used a piece of rubber hose and an adapter to connect them back together. and there was some chunky yellow stuff, that felt like moss in the return line. I replaced the line ( but not pump its brand new ). From there i disconnected the thermotime and cold starte valve, put gas in and took it for a spin. It drove awesome, was the first time i really got to drive it since i bought it. I drove it hard to see if it had any kind of studder but nothing. So i'm not sure if it was the gas or the cold start that fixed it. I drove to a restaurant, ate and left. It was still driving fine. But then all of a sudden, as i'm getting on the interstate accelerating, it won't rev past 3k. After applying more fuel, it seems to bog more. Then when i let off the gass it backfires. I got it home by just barely pressing the gas. So thinking it was a kinked vent hose i dropped the tank, but everything was still connected and looked fine. I wanted to drive it again just to see if maybe it had changed something, gotta have hope! I didn't even make it off my street. i literally couldn't give it any gas, but it would idle. When i would try to gas it, revs would drop low and almost die.

 

Do you think this has to do with the fuel lines clogging up, or is there a filter inside the tank that can get clogged. i feel like i remember seeing this. how clean does the tank need to be? My next area of concentration will me the MAF, and TPS when testing the MAF the reading came out just barely off from what FSM says. And that being the direct link to the ecu that what i'm thinking it must be. My car came with a manual that i've read front to back, especially EF and EE. And from what i've read online these are the conclusions i've made. Can anyone clarrify? also thermotime didn't read anything when tested. Thanks for reading sorry for the lenghthyness.

 

 LOU DOOVA

[siteunseen]

You need "atlanticz tech tips". Google it and look under "efi and fuel".

I'm using my phone now, sorry I cant link it for you.

[Zed Head]

But then all of a sudden, as i'm getting on the interstate accelerating, it won't rev past 3k.

Did you wash the engine or get water on it?  This is typical of a wet TVS (throttle valve switch).

 

Also, you should describe what the car does now.  It's hard to tell if it has all of the problems you described or if some of the old ones are gone and it has new ones.  And add amounts of time, like "it drove fine for a week", or only an hour.  You said when you bought it ran fine, then it had a problem, then you kept driving it.  But for how long did you keep driving it?  Minutes or days?

 

If this is the current state - ".i literally couldn't give it any gas, but it would idle. When i would try to gas it, revs would drop low and almost die." - it might be that your AFM (that's what we call it, not a MAF) is disconnected or stuck.  Is the cover still on it?

 

At least it's running,  It shouldn't be too hard to get it tuned up, but make sure that you take notes about everything that you change.  Don't adjust your AFM, don't twist the distributor without a timing light.  People often get lost after making random changes and have a hard time fixing the problems they create.

[LouDoova]

thanks for the reply. well i haven't been doing anything random. anytime i have a thought of what it is i research it first. I've taken the AFM apart because the silicone was crusty. Everything looked as it should so i sealed it back up. But i'm still leaning to this as a problem. After i cleaned the gas tank and disconnected the cold start valve i drove it for aproximately an hour and a half before it started bogging out. which led me to believe that my fuel lines might be clogged and it just took a while for it to clog back up. Is this a possibility?

[Zed Head]

Yes it is.  If you have a fuel pressure gauge, you can check it while driving.

 

You're on the very well-worn path of checking the first things that you see, because someone else did the same thing and wrote about it.  But those typically aren't the problem.  I haven't seen a single instance of a stuck cold start valve.  It looks like a problem, it's easy to get too, easy to disconnect, but it's never the cause.

 

Many, many people try to "feel" their way through the EFI system, but in the end they almost always have to take a few measurements or do a few structured experiments.  Just trying to save you some time.  You have about 100 doppelgangers out there.

[siteunseen]

I been down that road also.  I ended up replacing everything except the hard fuel lines from the rear to the engine bay.

 

If bought another one today the first thing I would do is put a clear filter between the tank and the fuel pump.  Fram G3s are $3.  Here's the details; http://atlanticz.ca/zclub/techtips/fuel/g3filter/index.htm

You'll be able to see if you have particles in there from a trashy tank.  You probably need a $10 fuel filter up front behind the radiator on the passenger's side fender too, it can't hurt if you haven't already replaced it.

 

 

 

 

 

[Chickenman]

^x2    Add a Fram G3 filter as Siteunseen has suggested, and immediately replace the main Fuel Filter if you haven't already done so.  If this is clogged it can cause the symptoms you describe. The factory filters are still available from Nissan

 

 After 10 years storage it wouldn't surprise me if it was clogged full of gunk.

[Careless]

I have a feeling it's your injectors. Whatever is in the return line probably went through them first. The solenoids/coils can occassionally stick open or closed, causing similar symptoms. You can bench clean them with a PWM driver, a 12v battery, and a spare fuel pump with some injector cleaner or gasoline-diluting solvent with a spare fuel pump and one single fuel injection hose to pressurize the injector and run the solvent through it (check voltage of the injectors before using 12v). This is a much better method than running injector cleaner in the tank, because the solvents that actually work are not good for combustion in your motor, so bench cleaning in a bucket is much more worthwhile.

Alternatively, you can have them serviced at many diesel shops at about 15-20 bucks a pop, or you could buy some replacements. But the bench cleaning method costs like 20 bucks and can prevent you from spending money on the injectors before figuring out whether they're the culprit by simply looking at the spray pattern.

[Zed Head]

^{A spare engine I picked up had had water in the fuel and it rusted the inside of the fuel rail.  The filters on the injectors are only meant as a last resort, thy can clog easily.}

 

On powering the injectors for cleaning or testing - I run six on a fuel rail with power from the battery in series.  This gives about 15 ohms of resistance and keeps the current flow down.  It's the current that would overheat them, they're made for 12 volts.  For precise characterization though, a PWM would be the way to go.  For comparing wide open flow rates to see if they're clogged, just turn on the power and fill six containers.  I've seen up to 20% deficiency in flow rate this way, with old crummy injectors.  You could either add resistance singly or rewire all six at once.  Be careful with vaporized fuel and sparks though.  Once you see an injector spraying well, out in the open, it makes you nervous.

 

Edit - somehow I got a funky font,  WTH.  And I can't change it in the first sentence, it's locked in.

Edited June 8, 2015 by Zed Head

[Redwing]

Reading all I can find on my problem with my '76 - 280 Z. I bought her 3 months ago, my dream of having a Z again.

I had bought an original '71 when they first came out with a 6 month wait, and no choice of color. Luck was with me and she was the Mexican Orange. I drove her for 256,000 miles with no major problems. Just little stuff. My Super car.

Mostly my newer car is hard to restart after being driven for half hour or so. But twice in a cool morning she pulled this, and was hard to start/restart. If I wait for 15 min. or so, she will start and run fine. I cannot check with my tach, as it is not working. Will this fuel filter problem cause low mpg (20 mpg and I expected more)? Another thing that might explain my problems, is a huge whoosh when I open the fuel cap. Only while car is hot, not in the a.m. while cool.

Is this a fix I am able to do myself (I am a 72 yo. Female with some mobility problems.) I do not have an abundance of $, social security does not go far, and I don't have any savings. So I am working with her problems as I can.

Any assistance will be great fully appreciated. Thank you so much.

[siteunseen]

Reading all I can find on my problem with my '76 - 280 Z. I bought her 3 months ago, my dream of having a Z again.

I had bought an original '71 when they first came out with a 6 month wait, and no choice of color. Luck was with me and she was the Mexican Orange. I drove her for 256,000 miles with no major problems. Just little stuff. My Super car.

Mostly my newer car is hard to restart after being driven for half hour or so. But twice in a cool morning she pulled this, and was hard to start/restart. If I wait for 15 min. or so, she will start and run fine. I cannot check with my tach, as it is not working. Will this fuel filter problem cause low mpg (20 mpg and I expected more)? Another thing that might explain my problems, is a huge whoosh when I open the fuel cap. Only while car is hot, not in the a.m. while cool.

Is this a fix I am able to do myself (I am a 72 yo. Female with some mobility problems.) I do not have an abundance of $, social security does not go far, and I don't have any savings. So I am working with her problems as I can.

Any assistance will be great fully appreciated. Thank you so much.

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