Can someone point out which number on the injector is the positive + and which is the negative -

Looks like the 26, 27, 28, and 29 are grounds on the injectors???????????

Click to view attachment

I'm going to try to help with my best guess. I looked at the FI section of the workshop manual and found a figure similar to the one you posted. That figure and yours would lead me to think that the terminals 3,4,5 and 6 are + as on both diagrams, they connect to the ECU and they both also show the other terminals 26-29 being ground connections. So, my best guess is 3-6 + and 26-29 -.

PS, and you can see in your diagram that in the lower right, 26-29 are ground connections. That ground connection is the 3 pronged spade connector on the rear face of the engine case under a case bolt.

SWeeeeeeeet! That is what I thought. I didn't think it mattered on the injector though which is + and which is -

If I understand the Fuel Injector operation, it's like a little solenoid so I would think to "lift the pintel" (pintle?) off the seat to shoot the fuel the solenoid would have a polarity. If it was reversed, it would tend to close the pintle rather than open it. Attached is the diagram from the workshop manual.

Click to view attachment

Whoops, in .doc ..... .gif didn't work and am computer challenged.

Thanks, I will make sure I have them indexed correctly. Thought I was home free but shouldn't be tough to switch, if they are in fact reversed polarity.

THE WIRING ORDER IN THE INJECTOR CONNECTOR HOUSING DOES NOT MATTER. Even the connection is not sexed..the connection can be made inserted either way...

Well, there's 2 hours I'll never get back. Any idea how DC voltage connected with either polarity still make the injector work?

I dunno...ask Robert.....Bosch. Voltage polarity does not matter.

Perhaps all that is going on is you energizing the electromagnet that is attracting the solenoid - doesn't matter what the magnetic polarity is - just that it is magnetized.

My best guess.

It's just a solonoid. Polarity doesn't matter as it's just a coil of wire that acts like a magnet when current is passed through it. Current direction doesn't matter.

The polarity does not matter. I had remembered from my school days many many years ago that if an iron piece was put inside the coil, it would tend to pull into the coil until it centered itself A quick search on google for "does polarity matter on a solenoid?" will give you a few hits with the reason. I cut the answer, but when I pasted it below, it did not show the pictures. The words should be sufficient to explain. JoeO


Why does electrical current polarity not matter
with DC coils?
Below is an excerpt from the book Principles and Practice of Electrical Engineering by Alexander Gray. This excerpt answers the question why solenoid valve coil polarity does not matter.

This book was published by McGraw-Hill in 1917. Although the book is old, the principle in question is still as true today as it was in 1917. (The book has become public domain and we would like to thank Google Book Search for making this book available to all of us to read!)



Principles and Practice of Electrical Engineering

Chapter VIII - Solenoids and Electromagnets
Pull of Solenoids. - A solenoid is a conductor wound in the form of a helix. When an electric current is passed round a solenoid a magnetic field is produced, the direction of which may be determined by the corkscrew law, page 5. This field may be represented by lines of force as shown in diagram A, Fig. 44.





If as in diagram C, Fig. 44, soft iron plungers are used instead of bar magnets, then the lines of force produced by the solenoid will pass through the plungers and cause magnetic poles to be induced; north poles will be formed where the lines of force leave the iron and south poles where they enter... The induced polarity of the plungers shown in diagram C is the same as the polarity of the bar magnets in diagram B so that the plungers are pulled into the solenoid.

If the current in the solenoid is now reversed, the magnetic field of the solenoid will reverse but, since the induced polarity of the plungers will also reverse, the direction of the pull on the plungers will be unchanged.

When current is passed through the injector coil, it produces a magnetic field that attracts the injector pintle. The polarity of the magnetic field is determined by the lead orientation -- if you reverse the leads, the field will reverse. But the steel pintle is attracted no matter the field orientation.

However, if the steel pintle were replaced with a permanent magnet (with its own built-in magnetic field orientation), then the orientation of the coil's field becomes important. By choosing the coil current direction, you determine the coil polarity, and thus you will either attract or repel the permanent magnet.

(By the way, this is exactly the way that a permanent-magnet motor works.)

Summary:
-- steel gets pulled into a magnet regardless of field orientation
-- two magnetic devices will attract or repel based on their field orientation

Thank you for all who helped clarify!!!!!!!!!!!!!!

I was really frustrated as I called Morph and he said it didn't matter but some said it did. I rely heavily on the collective genius that is on the site!

I thought it didn't as PBanders states that if the harness can go in both ways it doesn't matter.

Thank you again!!!!!!!!!!!!!!

I also love the electronic/wiring education detailed explanation.

If someone takes the time to explain why the answer is yes or no then it makes much less room for question.

The more you know the more you can apply to questions that arrise in different areas.

So polarity does not matter. I was just curious if anyone knew why the connector had the angles in the connector to suggest it only goes in one way, but in reality in can plug into the injector either way. Just wondering if anyone knew, no big deal.

Cheers.

It is true, the injector will fire just the same with the polarity either way. The factory engineers want the EMF (Electro Motive Force) to go the same way. If you make the "thumbs up" with both hands and then look straight down at your thumb. You will see one hands figers curling to the left and the other curling to the right. This is an example of EMF direction, clockwise and counterclockwise. There is some speculation that the EMF should all go the same direction to make the circuit more efficient. every time the injector fires it creates the EMF. The EMF then travels on the wire. The injectors usually have a common positive power wire and independent negative trigger signals. CW EMF can counter act CCW EMF and reduce the LC time constant of the injector coil. This will cause the injector to open and close at an unpredictable rate. The actual speed of the solenoid movement. The CW EMF and CCW EMF can also form whats called a "Tank Circuit" which is like an electrical ping pong of energy back and forth on the wire.

In closing

Bottom line, make the polarity the same for all injectors in a given system. It does not matter which connection is positive or negative if they are ALL the same.

Hmm Thank You for your insight.

Ted

while all this google electro babble is interesting, allow me to state clearly:
D-Jet porsche 914 injector does not care which way you plug it in

i did not google it. i did not read it from a book. I did not hear it from a guy on teh internet who's cusin is a google tech writer. I did not calculate field polarity nor did i speculate on teh rotational direction of the earth as it relates to the diection my 914 was pointing while holding the calculator to figure out which way to plug it in. I actually have plugged it in with my own hand. i plugged it into a real d jet injector on a real not virtual 914.
maybe if i lived south of the equator it would not work

This summary says it all. Steel is attracted to both the positive and negative sides of a magnet. Think of a U magnet with positive and negative sides. If polarity mattered to steel, the steel would be attracted to one side and repelled by the other.

Try to put one magnet on another and they will repel or attract depending on orientation.

Solenoid polarity doesn't matter.

This is also why relays powered by AC work.

I agree that the polarity on a simple solenoid SHOULD NOT matter as the core will be pulled into the field either way.
HOWEVER, it is poor design to make it reversible (which Porsche apparently did way back when).

Here is why: When you energize a relay, it is a big inductor and the current in an inductor cannot change instantaneously.
So when you close the switch (Bipolar Junction Transistor {BJT} in the case of the ECU) it takes a while for the current to reach max.

BUT when you attempt to turn OFF the solenoid by opening the switch (BJT), the current cannot stop flowing instantaneously and the voltage on the coil goes to infinity.
(This is how our spark coil works ;-)

As the switch tries to turn off it cannot because the voltage it sees is too high.
In modern circuits, the switch is usually a FET and these high voltages can damage the FET.
SO .... ANY DC inductive load should have a diode right at the coil that allows current to continue to flow until the field collapses. This limits the Reverse Electromotive Force (rev- EMF) at the switch.

Long story short - a lot of newer DC coils (relays, etc.) have these diodes built into the device.

If you reverse the voltage, you will burn out the diode, then the device will continue to work like old-school devices, but you will lose the reverse-EMF protection which means the driver will fail eventually.

Sorry for the long winded explanation ;-)

Stu