1976 280z Fuel Injection Issues

[wright_280z]

Hello fellow Z owners!

After driving my Z the past few weeks, I had noticed the vehicle had a "Hard Start or Stutter" after it had warmed up and was restarted. I put 91 fuel and injection cleaner in the tank for a week. No change... I had also noticed an excessive fuel smell while driving my Z and especially after filing her gas tank. Enough was enough I had a massive headache each time I had taken the Z out for a drive. I decided to check my Air Flow Meter (AFM) was operating just fine, Also checked my Cold Start Valve/Injector that was fine. Lastly I decided to tear the Fuel Injectors out (Stock) and looked at all the tips and hoses. Hoses were fine...The tips were cracked and discolored. I was hoping to clean them and out them back in, but of course that would have been a bad decision down the road. So, I went to NAPA and purchased RE-MAN made by RAM, (Nissan doesn't manufacture them anymore) I know many people on the forums have said, "NO REMANS" but no excuse was given. They went right in just fine. I recommend that you use a little oil on the new O-Rings, Even if you take out your old ones and clean them spend the extra money and buy the new O-Rings. I used a little "Electrical/Conductor Grease" on the tipsTotal job time was about 1 1/2 hours. Plus my drive time...to get the new injectors.

The car now starts better, sounds better. No more excessive fuel smell. Gas mileage has increased (Not really expecting the best)

I just thought I would write this post, due to the lack of people writing about this issue and elaborating on it. If anyone has any questions I will reply!

Best of Luck

Christopher

1976 Datsun 280z (Dottie)

[EuroDat]

Hi Christopher,

Welcome to the club. Yes you are right, not many post their successes on fuel injector issues. Its mostly all the electronics around them that get most of the attention.

"Remanufactured" injectors is not really a good name for them. They are more like "major service" since you can not dismantle them to do any thing with the coil, internal seal, needle and seat. Most shops use an ultrosonic cleaner to clean them, then change the tips and inlet filter screen.

That is why a lot of people don't like using them.

Chas

[FastWoman]

Hey, welcome!

The reman injectors should give you a better spray pattern and more even fuel distribution between cylinders, which is always good. However, I'm very skeptical that was your main issue. If the excessive fuel smell was in the exhaust (perhaps along with a bit of black smoke and fouling plugs), I'd say your Z was running to rich. It's rare for that to be an injector issue. Moreover, injector issues usually surface gradually over a very long time, not suddenly. It's more likely you had a bad connection to your coolant temp sensor, and when you did all your work, you jiggled the connector enough that it made good contact again. All the sensors and connectors in the thermostat housing get a lot of abuse, and rotted/corroded connectors are a common problem.

Either that, or the gassy smell was coming from your fuel tank system. If your filler neck and/or ventilation hoses are split/rotted, you can get gas fumes in the cabin. You can also have a cracked joint in your fuel/air separator or a crack in a ventilation check valve. If this is the case, don't be surprised if you get another wave of gasoline fumes with your next fill-up!

Anyway, you certainly improved your situation with the injectors, but I doubt that's the end of the story.

Edited December 29, 2013 by FastWoman

[wright_280z]

Ah... Yes! You both are correct. The Datsun is continuing to give me a problem.

The issue still remains. Not every time, but on the occasional start-up you will hear and sometimes feel a "Stutter or Hesitation" for approx 30 sec. I also notice that my oil gauge tends to take its sweet time getting to the half way point...

I noticed the fuel filter looked "Abnormally Big" so I replaced it with one that was meant for the vehicle and was a tad smaller, that helped the start-up issue. I also replaced the fuel pump today... started the Datsun multiple times (20 plus) and only once did it have the "Hesitation or Stutter" I can't figure this out for the life of me... I am replacing the Fuel Pressure Regulator and the hose linking it to the manifold in the AM. Still think there is something I am missing.........? Any Suggestions?

I have since refilled the fuel tank at least twice no excessive gas smell. Which is great because I can't keep carrying tylenol with me...haha.

I really am driving my self insane trying to figure it out. I do have one shop that can look at it, but I really enjoy working on my own car...plus saves money to help repaint it!

All comments and experiences are appreciated!

Christopher

[EuroDat]

Hi Christopher,

I would be more inclined to do more trsting than replacing. That way you know you identify the problem then fix. If you change something, itmight improve the situation indirectly and you think you fix it, but it comes back again later.

A simple pressure gauge (0 tp 50psi) in the line after the fuel filter is a great tool to test fuel pressure. Save you the cost of a new FPR.

You can also check if the FPR is holding pressure and giving you the right pressure. Static pressure should be 36psi, but that will drop when the inlet manifold has vacuum.

You can do a lot of testing in the manual.

Do you have a copy of the FSM and thr fuel injection supplement (bible)?

You can downlosd then here XenonS30

Chas

[wright_280z]

CHAS,

I noticed there is a hairline crack in my fuel pressure regulator and the hose linking to the manifold is split... After I replace the regulator I will test from there on forward... Do you still think its a pressure issue? Or sensor?

Have you ever experienced this issue?

Christopher

[FastWoman]

Christopher, on rereading your original post, I'm pretty sure the stutter is "normal" (or at least common) for this car. This is a known issue. When you warm up your engine and shut down, and especially after you wait for 10 min or so, then the engine will run very roughly when you restart it. It will only even out after you run the engine a bit, especially if you put it under load (e.g. pull out). There are many theories about why this happens. You can search the forum for "hot restart issue" and find lots written about it. My own take is that ethanol gasoline is too prone to vaporization at the low operating fuel pressure used by our cars, particularly if it is a winter formulation.

There are a few things to check/correct that will lessen the hot restart problem. First and foremost, your fuel rail needs to hold pressure. There is a check valve on the fuel pump that prevents backflow. If that check valve is worn, the fuel pressure will bleed down fairly rapidly. Also worn injectors will leak down pressure (which might have been part of your original problem). Once fuel pressure has bled down, the engine heat will vaporize it, and thus your injectors become locally vapor locked. It takes a bit of run-time to squirt the fuel vapor out of your injectors and spray liquid fuel again. You should test your fuel rail for leak-down time. It should probably lose no more than 5 psi in a half hour.

There are also two types of insulators at the base of each injector. The old style is aluminum, and the newer style is plastic. The plastic insulates better.

You have the '76, which doesn't have the vented hood. A vented hood from a '77 or '78 helps.

Insulating the fuel rail helps a tiny bit, but I think most of the vaporization problem occurs at the injector tip.

The oil gauge's slow response is normal. It's just the design. It uses a bimetal element to flex the needle.

If your gassy smell is gone, it might have been a leaking injector. That's a common enough issue.

Crack in the FPR -- no good. That could also be a source of the gassy smell. The split in the vacuum hose could cause the engine to run too rich (fuel pressure too high), and that could be a source of "gassy" exhaust.

[EuroDat]

Your problem is not unusual for the 280Z. Fuel pressure loss is a common cause of hesitation shortly after start up.

If you install a new FPR, I still recommend fitting a pressure guage to check the pressure and the leak down rate when its not running.

To find leaks fit the pressure guage betwwen the filter and fuel rail, but leave enough room between the filter and guage so you can clamp the hose shut. This way you can shut the line back to the pump, if it stpos loosing pressure, its the pump or pump check vavle. Otherwise the leak is in the fuel rail hoses, FPR, injectors or cold start injector.

Like Fastwomen said, low pressure allows vapour to form in the fuel system and it takes time to remove. There are ways to help reduce this problem, some people have installed a push button switch which activates the fuel pump to prime the fuel system before starting and I have seen a injector cooling fan from the 280ZX fitted to a 280Z.

Check the heat shield under the inlet manifold is fitted and complete. That can help deflect heat.

Cracks in the FPR are not good and poor leaking vacuum lines wont help your situation either. If the FPR doesn't have the right (enough) vacuum it will provide too much pressure and the ECU can not compensate for this. The engine will run rich, except under full throttle conditions.

Making sure it doesn't leak down too quickly is your first priority. Maintaining pressure will help a lot.

BTW, My system holds pressure for a long time and slowly drops to about 10psi over about 4 weeks. It took me a lot of searching to get it that far. An old hard o-ring in the fuel pump was the last thing I found in my system causing pressure loss.

Chas

[wright_280z]

Thanks for the replies!

So today I replaced the Fuel Pressure Regulator (Simple...) went in easy and restarted just fine. Let it warm up then shut her off. Came outside about 20 minutes later and started it the "Stutter" was back...

Fuel pressure reads fine. So, do you think my Air Flow Meter (AFM) is acting up, or out of adjustment?

Christopher

[240260280z]

Check the hoses and connections in the back quarter above the tank were the evap. system is.

[wright_280z]

Check the hoses and connections in the back quarter above the tank were the evap. system is.

I will look at the FSM, any simple way of accessing those hoses?

Christopher

[Zed Head]

FastWoman's suggestion in Post #7 is most likely the cause. Commonly called the "hot start" or "heat soak" problem (NOT vapor lock). Very aggravating and common. Many people just learn to live with it.

I've done some experimenting and have found that directing cooling air at the injector bodies will stop the problem. Nissan did the same with the 280ZX, but installed a fan and ductwork to cool all of the components of the fuel supply system on top of the manifold. Heat from the engine block and manifolds heats up the injectors and fuel rail causing the problem. Many theories have been proposed but they all boil down to too much heat. 20 minutes seems like the point where things are the hottest. Earlier than 20 and the heat has not transferred to the fuel system, later and everything has cooled down.