One "bad" fuel injector??

[ramsesosirus]

1976 280z, stock system.

Had some bogging at around 3000 rpm, adjusted the TVS.  Checked plugs (which are new, only been run when test firing engine).

I assume the best option will be to "GET A NEW INJECTOR", but I'm trying to avoid that right now... (I know I might have to eventually....)

All the plugs looked the same except one, Cylinder #5 was brand new looking.  Could be no spark, no fuel, or possibly being "steam cleaned" from a water (head gasket) leak.

Checked spark, swapped plugs, wires, etc...  SPARK IS GOOD TO ALL CYLINDERS.  Tested in multiple ways.  

Did the screwdriver test.  Verified all the other injectors have good "tapping" noise, the "bad" one was muffled or no "tap"....

 

Pulled the fuel rail, disconnected coil, turned engine over with rail connected with longer hose and set to spray on cardboard.  Confirmed that #5 fuel injector not spraying.  The others were.

Took bad injector off, and used the 9v method to get it opening/spraying off the car with spare injector connector.  i did this to my "spare" used injectors too.  Off the car, they all clicked and were not clogged.  

Measured resistance on the "bad" injector and the known good ones, about 3 ohms for all.  I've read most injectors should be 10-14 ohms, but maybe these are low impedance ones?  Either way, the ones that were working and the "bad" ones had the same resistance values. 

Anyways, still no fuel from the bad injector.  Swapped injector connectors to make sure it wasn't them.  Same result.  So I know the connectors are good.  

I then swapped the #5 and #6 injector on the rail.  Same issue, the "bad" injector (now in cylinder 6 position) wasn't spraying, the others were.  So this pinpointed the problem to the injector itself (not the fuel rail, not the electrical connections) 

Manually pressed the "pintle" on the bad injector with a dentist-type tool.  Voila, a nicely patterned fuel spray came out!  

Cranked again, no spray from this injector, others are good.

So I know this "bad" injector is not clogged, had same resistance as the other injectors, can spray, and has good power supply/input.  (as verified by switching connectors and position).  (I also moved the clean spark plug to #6 so I can monitor it).  

The other "spare" injectors I have seem to do the same thing (I thought it was odd that not 1 of the 4 spares were good, but will spray manually???)

What voltage does the injector get from the ECU?  I know they always have 12v, but the "pulse" is less?   I can get them to operate fine off of the car with 9 volts.  Maybe less voltage isn't enough?  But then why the same resistance as the others?  (V=IR)

 

What am I missing?  Or is it possible this/these injectors are still dead, despite the successful tests?  

Thanks 

 

[Martzedcars]

I think you need a new or used but good injector.  They don't work on the full 12 volt so.. never put 12 v on them directly.. it will break them!  They are working with serial resistors see your manual..

I believe only the choke injector is 12 volt directly..

Also a good injectorcleaner can't hurt.  When you put all 6 injectors in cans and you crank the engine you will see that every injector delivers a different amount of fuel.. after cleaner it that wil be better..

Succes..

Mart

 

 

[ramsesosirus]

Yeah, I knew going into it that I ran the risk of frying the injector with more voltage, however I'd read that sometimes to get a clogged injector open again, using more voltage (temporarily touching contacts, not constant) will apply more magnetic force to the pintle to lift it.  

My initial thought was that I need a new/different injector.

So I mght as well try to get these "bad" ones going.

It was fun, I learned some stuff, and didn't spend any money... yet  haha 

Thanks 

Does the 12 v that you see at the connectors not actually get applied to the injector?  Trying to visualize this.... 

[Captain Obvious]

Are the part numbers on all of the injectors the same?

 

And as for the resistor/no resistor 9V vs 12V thing without getting too deep into theory... The injector contains a coil (an inductor) and the current through that inductor cannot be described simply by (V=IR). The current through an inductor has a function that is dependent on time. It looks like this:

Which says "The current at a given time equals the maximum current minus an amount that gets smaller as time goes by."

 

So when voltage is first applied to the inductor, no current will flow. But as time goes by, the current will eventually max out at a value of I=V/R where the "R" in that equation is a combination of the injectors internal resistance, the series dropping resistor next to the brake master cylinder, and the internal resistance of the power source which is supplying the current.

 

When you are testing using a 9V battery, you have removed the dropping resistor from the circuit and if the battery were capable of supplying enough current, the injector would burn up. But thankfully the 9V battery has a lot of internal resistance and is not capable of supplying that much current. The injector current is limited by the fact that the little 9V battery just can't supply that much power.

 

If you would be to connect the injector directly to your big 12V car battery for long enough, the injector current would be limited only by it's own resistance and it would likely draw enough current to burn itself open. Your 9V battery can't do that, but your car battery sure can.

[ramsesosirus]

I will check the part numbers.  All of them have the same tip, and the "blue" colored connector.  One had obviously been replaced at some point, since it has 2 hose clamps, the rest had the stock "ferrule" at the injector end.  

The "spares"  that I spoke of were from the donor engine's intake, from a 280zx (can't be sure of the year, but it was an N47 head, non turbo).  These looked the same, but had the "black" colored connectors, and the larger, one piece "spacers"'.  

The one I am trying to salvage IS the blue connector one, from the car originally.   Even when I'm looking online for new or remanned injectors, they don't seem to have the blue connector.  

 

Do you think I burned them up with 9v?  

Ironically, I've seen that exact equation before during my engineering studies.  I should have recalled that, I must be losing my edge.  So you don't have to worry about getting too complex here, I've seen some pretty "deep" equations before... not that I could solve them, but yeah haha..

Surprisingly, the engine is actually running pretty well on 5 cylinders, after adjusting/disconnecting the TVS.  (I reconnected it after adjusting).  I don't plan on being too rough on this engine (since I blew up my stock one), but I would like it to run as good as it can.

Thanks~

 

Edited June 2, 2016 by ramsesosirus

[Zed Head]

I've had the thought that the extra resistance is more for the ECU circuitry than the injectors.  The injector solenoids are covered in fuel.  2.5 ohms gives 4.8 amps at 12 volts.  A few clicks using a 12 volt battery doesn't seem too damaging.  I've done it with some and they seemed fine afterward.  No smoke.

Aren't the resistors 6 ohms?  12 / (6+2.5) = 1.4 vs.  9/2.5 = 3.6 at the asymptote.  So, maybe not enough current to open up a gummy or rusted injector.  You might just let some fuel blow through the "bad" injector to see if it will clear up.

Nissan used tan and light green for it's NA injectors, and purplish brown for turbo.  Black is aftermarket.  The codes will be hard to see, molded or stamped in to the plastic plug portion.  FJ707, A11...., 280 150... are examples.

[Chickenman]

OP.. you are over thinking this. Your definitive test was the screwdriver test where the #5 injector made no noise or tap when engine was running. That's a done deal right there. Injector is defective. Replace it. Period.

Edit: Check electrical connector with a NOID lite of course. But you already swapped injectors and problem injector moved cylinders,  so that eliminates an electrical harness problem

The screwdriver or stethoscope method is a very good test that is often forgotten about. It will immediately show up a bad injector, whether through electrical fault or a mechanical fault. Injectors can test fine electrically, but mechanical faults, such as sticking, will not show up with electrical tests.
 

Edited June 2, 2016 by Chickenman

[Chickenman]

A little story relating to the above post. . A friend of mine ( whom I mentored when we raced together )  now works in the High Performance division of a very large BMW dealership. He was in the " regular " shop one day talking to a Technician who had a problem with a new Bimmer. Engine was direct injection V8 and had a misfire. BMW's specialized engine scanner didn't show any hardware faults, but it was obviously running on only seven cylinders. He suspected a bad injector, but didn't know how to identify it.

My friend Karl, asked if he had a Stethoscope. He did. 30 seconds later bad injector was identified. All the good injectors went Ping Ping Ping. Bad injector went Thunk Thunk Thunk. Easy peasy.

Why didn't the factory trained BMW Technician used this simple method? Because BMW does not train mechanics to " Think " any more. They train them only to read electronic scanners and follow approved factory " Flow Charts " and repair procedures. . Any thinking " outside the box " is discouraged.

BMW will not pay for any warranty work unless their EXACT procedures are followed. And those procedures relied solely on using the BMW electronic scanners and Flow . I fact even after replacing the faulty injector and the engine now running smoothly, BMW would not pay warranty as the Factory scanning tool showed " no faults" with the injector. An Electronic readout of before and after is required with every warranty job. And the scanning tool is used from start to finish of job. It effectively does the " thinking " the Technician just pushes buttons.  About  2 hours of additional paperwork was required, because BMW did not recognize an " Old school " method, such as a Stethoscope as an " Official " testing method.  

Edited June 2, 2016 by Chickenman

[Chickenman]

There's a supplier on E-Bay who sells new sets of six Standard Blue Streak injectors for around $165.. That's the best deal you'll likely find. If it's in the budget that is your best option. Just replace them all.

I'll see if I can find the link.

Edit: Here ya go:

http://www.ebay.com/itm/75-76-77-78-79-80-81-82-83-Datsun-280Z-Fuel-Injectors-FJ707-FJ3-/152062929686?hash=item2367a82b16:i:152062929686

 

 

Edited June 2, 2016 by Chickenman

[Zed Head]

Actually, the screwdriver test will also show a bad electrical connection, the two pins on the injector, maybe.  The OP's is doing and thinking about a lot of stuff, and the fact that the injector worked electrically, off of the car, might have been overlooked.  If the spare injector connector worked it might be worthwhile to clean up the injector pins or even replace that connector, or bend the pins so that better contact is made.  It could just be an electrical contact issue.  The stock EFI connectors are known to be of poor quality after 30 years of heat.  The spare connector might have made better contact than the old corroded ones on the engine now.

" Took bad injector off, and used the 9v method to get it opening/spraying off the car with spare injector connector.  i did this to my "spare" used injectors too.  Off the car, they all clicked and were not clogged.   "

[ramsesosirus]

4 hours ago, Zed Head said:

Actually, the screwdriver test will also show a bad electrical connection, the two pins on the injector, maybe.  The OP's is doing and thinking about a lot of stuff, and the fact that the injector worked electrically, off of the car, might have been overlooked.  If the spare injector connector worked it might be worthwhile to clean up the injector pins or even replace that connector, or bend the pins so that better contact is made.  It could just be an electrical contact issue.  The stock EFI connectors are known to be of poor quality after 30 years of heat.  The spare connector might have made better contact than the old corroded ones on the engine now.

" Took bad injector off, and used the 9v method to get it opening/spraying off the car with spare injector connector.  i did this to my "spare" used injectors too.  Off the car, they all clicked and were not clogged.   "

Thanks for the feedback guys, I really like Chickenman's story about the BMW... so true, that's why I avoid "newer" cars.

This is why I am not sure as to whether or not the injector is bad;  

I swapped the electrical connectors around on the car, so that the connector from the bad injector was on a known good injector, and that injector still fired, while the bad injector still did not.  i also swapped the positions of the injectors, switching #5 (bad) and #6 (good) on the rail, just to make sure fuel was getting there.

So essentially, I verified that:  1) the bad injector will not spray fuel no matter which spot on the rail it is installed to  2) the bad injector will not spray fuel no matter which electrical connector from the car it is connected to  3) the good injector(s) will spray no matter which spot on the rail the are installed to 4) the good injector(s) will spray no matter which electrical connector they are connected to  5)  I can get the bad injector to spray every time off of the car with the 9 volt, or even 3 AAA (4.5 v) batteries and a hose filled with brake cleaner  6) after cranking the car with the bad injector installed, it won't spray, BUT when I push the pintle needle with a tool on the car, it WILL spray gas  7) the good and bad injectors all have (nearly) the same resistance  8)  all electrical connectors have the same voltage at the pins  

So as you can see, I am getting somewhat conflicting info.  If I could, I would gladly just buy 1 (or 6) new injectors, but $$$ is real tight right now.  Even the $40 for 1 injector... I'm looking for work after a few years from hell.  Thank god for the Z, keeps me sane  (or is it zane, maybe inzane ... hmm that's a good license plate idea)

  Working on the Z is not only fun for me, but usually costs me nothing since I have most of the tools, waxes, etc... that I need.  It gives me something "free" to do that I love doing, and am getting pretty decent at (hopefully...).  Also, I know certain items will HAVE to be purchased, such as the wheel cylinder (leaking, gotta have brakes...)brakes, and probably engine mounts (vibration through car) and the key cylinder.  And maybe U-joints and fixing the fuel tank/sender leak, which is still leaking...  So I'm hoping to minimize the costs if there is any hope that existing parts are ok, or usable.  

On a side note, I have a Bachelors Degree in Architectural Engineering, good work history, and good references (and can fix cars...sometimes)  if anyone around Nebraska is looking to hire good people.  Not a whole lot of engineers (or auto technicians, as Chickenman was discussing) can think "outside of the bocks", or even turn wrenches.  I think that is an advantage for me.  And I also make art too.  

Anyhow, I think I might try cleaning the bad one a little more before spending any money.  I can't drive the car yet anyways, need plates and insurance etc...   and brakes   But who needs to stop?   Honestly I'm a little proud of myself for getting this engine this far, to running decently.   A lot of it is due to help, advice, and experience I hear from people here! 

[rossiz]

btw - i have a set of 6 used injectors from my 78 that all worked when i pulled them. pm me if you want 'em to play with for the price of shipping.