What is the voltage to the injectors on a 3.2?

[strikee]

I dont have my Bentley handy, its probably in there but....

I am going to remove mine and clean them using a battery and a suitable cleaner.

I have seen youtube videos using anything from a pair of AA's to a 9v.

Also before I pull them I am going to check with a multimeter the output on the injector cable.

At least one of my injectors is either broken or clogged up.

Thanks very much
Ed

[strikee]

Also will the on / off voltage be detectable on the injector cable (using a multimeter)? As in I would like to see the on off working correctly. I have a feeling with the ignition on, the voltage is present.

Thanks
Ed.

[Tippy]

12+V. You will burn up your injectors using a battery. They have to be cycled on and off in milliseconds which is impossible by hand.

Just read the comments below in these DIY injector cleanings vids from people who tried and lost.

[strikee]

Thanks for the info Tippy.

Looks like a lessened voltage is the go when cleaning. Around 5v 1amp.

A 12v car battery will indeed fry. although I am not really clued up on volts and amps to give a scientific answer.

[ischmitz]

The injectors on the 3.2 are low-impedance versions. Each injector has about 2.6 Ohm DC resistance. As others said connecting them straight to the car battery is not a good idea. The injector will draw ~5 Ampere and produce more ~60 Watts of heat. That will within a fraction of a second lead to thermal overload and permanent damage. A sure way to destroy the thing.

The DME uses a pulse-width modulated peak&hold signal pattern to control the current flow through the injector. The peak current is applied for less than 1/1000 of a second to open the injector and then the reduced hold current is is carefully regulated for the rest of opening duration.

Some use a 9V block battery to "shock" injectors open if they are stuck. These little batteries are not able to supply a high current due to their higher internal resistance. I believe that would be save but have not tried it myself. Others might chime in here.

Ingo

[ischmitz]

Originally Posted by strikee

Also before I pull them I am going to check with a multimeter the output on the injector cable.

At least one of my injectors is either broken or clogged up.

The injectors on the 3.2 are all wired in parallel. Each bank has a separate signal wire that goes back to the DME. The other pin on each injector connector is +12V with the ignition key in RUN. Inside the DME both bank wires are internally connected and the DME produces ONE signal to fire all 6 injectors simultaneously. The "signal" is actually that the wires are connected to GND. This is called a low-side switch.

Measuing the injector signals is not trivial nearly impossible with a DVM. You'd need an oscilloscope and measure the voltage across the injector with the injector connected. And then you still have the issue that all 6 are connected in parallel. If one is bad the measurement would still look O.K. To really check each you'd need an inductive current probe and check the current pattern through each injector.

Alternatively get a NOID light. It plugs into the harness instead of the injector and verifies the correct signals are sent.

Then measure each injector for resistance. It should be between 2 - 3 Ohm depending on the quality of your meter. If one measures open you found the bad one. If an entire bank malfunctions you have a harness issue.

Ingo

[Tippy]

Originally Posted by ischmitz

Some use a 9V block battery to "shock" injectors open if they are stuck. These little batteries are not able to supply a high current due to their higher internal resistance. I believe that would be save but have not tried it myself. Others might chime in here.

Ingo

Ingo, I've read quite a few people burn up their injectors even with the 9V batteries doing this DIY cleaning method. Of course this is not firsthand, but erroring to the safe side.

[strikee]

Thanks for the tip. I can now understand the low-impedance injectors will not be happy with the 12v or 9v battery.

Id be interested to know if it is indeed possible to DIY clean your own injectors and what is a safe power to put through them, if at all.

I appreciate there are some relatively inexpensive places that will do this for you in the US, but down here we pay a premium for this kind of service. As stated on another thread, I was advised $40 per injector.

Thanks
Ed

[T77911S]

on my BMW i just cleaned the screen on the fuel input side with some carb cleaner.
i would also put a bottle of techron in the tanl with it at about 1/2. then i would drive it at hi RPM's so a lot of fuel was going thru the injectors. by that i mean if i was going from stop light to stop light, i would keep it a gear that held it at about 4k- 4500 rpm. i would do a bottle every 3rd or 4th tank for 3 or 4 bottles. cleaned them up nicely. the car now runs very noticeablely better. for an 88 325is, it has very very smooth idle and runs very well.

[E Sully]

I had 2 stuck injectors on my '86 engine. Maybe I was lucky, but I used the 12v car battery with a quick flash and freed them up with no problems.

[ClickClickBoom]

Injectors are like spark plugs, consumable.
Try these:
http://www.ebay.com/itm/Jaguar-XJ6-1990-1992-Fuel-Injector-OEM-Bosch-Free-Shipping-/261536722932?vxp=mtr

3CC per minute difference on the rich side, passed smog with the same numbers as previous years.

[scarceller]

You need a inline ballast resistor to limit current. The coil charges very quickly and then the inline resistor will help limit the current. You could start by using a 25ohm resistor in series with the injector, this will limit current down to .5amps and this should be safe for the injector. Basic calculation for current is:
Voltage / Resistance = Amps
so:
14vdc / (25+3) = 0.5amps
The 25ohms from the resistor + 3 ohms from the injector.

My guess is that the injector would MOST likely open and stay opened at 0.5amps if it does not reduce the resistor size.

[scarceller]

Be aware that 1 shorted injector will cause a no start because all 6 are in parallel and one shorted injector shorts them all out. I've seen this issue a few times in the past.

[ischmitz]

Originally Posted by scarceller

Be aware that 1 shorted injector will cause a no start because all 6 are in parallel and one shorted injector shorts them all out. I've seen this issue a few times in the past.

Sal, it actually can be worse. A partially shorted injector will cause the DME to destroy itself while the engine still runs. It takes about 10 minutes....I know one case were a guy burned up three boxes in short order before the root cause was diagnosed.

[Tippy]

That would be horrible. Were the DME's repairable?

[ischmitz]

Yes - but with expensive NOS Bosch parts. So you really don't want that to happen.