85euro928

Can someone please confirm if the operation voltage of the fuel injectors in my '85 ROW is 12V?

Rich9928p

Simple answer, yes.

Technically more correct it is the system voltage after the Fuel pump relay (that powers the injectors for this model 928). The alternator may provide 13.8 V and there may be some voltage drops along the circuit. So it may be greater than 12 V.

85euro928

That's what I needed to know, thank you.

dr bob

There are voltage drops in diodes and the FET switches used in the injector circuits. When testing in the car, the hot side of the injector sits at about bettery voltage. Tthe other side is pulled low, almost to ground, when the injector is supposed to be open.

If you are thinking about testing the nozzles one by one, use a 9V transistor radio battery. No risk of damage to the coil that way, and nine volts is plenty to open the injector you are testing.

85euro928

Actually my plan is to clean them. They probably don't need it but I figured while I was changing out the fuel lines I mights as well try. I plan to operate them while they sit in a bath in the ultrasonic cleaner, then to clean them again using a cleaning fluid run through a low pressure manifold. I got the idea from YouTube.

dr bob

I was guessing that this was at the root of your question. The 9V transistor radio battery, the little rectangular one, is perfect for this duty.

Normal fuel pressure is in the 45 PSI range. I'm not sure how effective a "low pressure" cleaning might be.

Let us know how the cleaning goes. Maybe some pics of your cleaning fixture too.

85euro928

Here are the pics, hopefully this works.

85euro928

While researching online for information to either replace or have the fuel injectors from my ’85 euro cleaned by Witch Hunter, etc I came across these two videos on YouTube on how to clean your injectors at home.




Since the car ran strong before I started this tear down almost a year ago I decided to go cheap and just clean the injectors myself for good measure prior to reinstallation. This will probably turn out to be one of the better decisions I’ve made during this project as whether from sitting for a year and having the fuel gel, or, maybe the injectors were clogged before I took them apart and didn’t know, what I found was that only three of the injectors actually operated close to how I believe they’re supposed to. Out of the other five, one was stuck completely open, two would operate but were completely clogged, and the other two I couldn’t even get to operate (by operate I mean click or open when voltage was applied). If you’re interested in doing this watch the videos as this will give you the general information on how to perform the cleaning. The information below I’m presenting is the quirky little things I found while performing the cleaning, the YouTube videos will give you most of what you need to know.



After removing the injectors from the intake and wiping them down I ran them several times through the ultrasonic cleaner in a mixture of kerosene and MMM with the heat on. Since they were still quite dirty in the outside I figured this treatment probably did very little to helping clean the inside of the injector.



First thing is to get a 12V power source (YMMV). I have my car battery in the garage on a trickle charger so I knew it would provide the correct voltage. I tried a 9v battery and even went as far as to wire in a 9v plug-in type step-down transformer/charger but neither of these would fire the injectors. A 12v transformer/charger may work but be careful to check the output of the transformer if you go this route! Even though I didn’t use the plug in transformer/charger, after it didn’t work on the first injector I checked the output voltage, and although the transformer said the output was 9v the actual output was 16v! Needless to say this caused some instant anxiety on my part thinking I fried the first injector! Luckily I didn’t.

To get power to the injectors, so I could operate them during the cleaning cycle, I wired the battery in with a momentary switch with two appropriately sized female spade bits. Make sure you tape up or isolate the spade bits from each other as there’s not much room in the injector connector, and check the tape frequently as the carb cleaner will tend to melt the tape (ask me how I know). Alternately you can use an old plug from an actual injector like they did on YouTube.



I didn’t want to go through all the trouble of creating a manifold, like the one guy on YouTube, so instead I decided to use a spray can of carb cleaner, like the other guy on YouTube. And since I didn’t have a 5cc syringe, again, like the guy on YouTube, I instead built a small manifold using old silicone tubing to step up the connection from the spray nozzle on the carb cleaner can to the injector. By fitting a couple size tubes inside each other and sealing with red RTV I created a connector roughly 6” long. Word to the wise, after the RTV or whatever sealant you’re using dries cover the entire silicone adapter in a fair amount of black tape for extra measure as the pressure in the carb cleaner can is significantly higher than you can imagine (again, ask me how I know). Make sure you spray some carb cleaner through the silicone tube before hooking it up to the first injector to insure it’s clean inside the tube.



I then wired the first injector and installed the silicone adapter from the carb cleaner can to the injector. Two words of caution here; make sure you use a small hose clamp on the silicone connector at the injector, AND wear a full face mask as if the connection pops, and it will, the carb cleaner will go everywhere. I’m not sure what chemical make-up was in the card cleaner I used (I’m sure someone will chime in here) but it does burn your face so make sure to protect your eyes.

Phase One - If you’re lucky, and all your injectors operate, just run the carb cleaner through the injector cleaning out the small deposits till you get a nice wide atomized spray pattern in your jar. I didn’t want to keep the injector firing on constant duty as I’m not sure what that would do to the injector so while keeping pressure on from the carb cleaner can we quickly pressed the momentary switch to operate the injector. If that doesn’t work, and you’re like me, you will need to do one of two things to get your injector clean. I found that if the injector operates when you apply voltage with the momentary switch (listen close and you’ll hear it click) but you’re unable to get the carb cleaner to spray through the injector, the best bet is to leave it hooked-up and pressurized for a couple of minutes to let the carb cleaner do its job. After a couple of minutes (3 maybe) try operating the switch again. If it doesn’t work then you’ll need to go to Phase Two (which I’m sure I’ll get some flak for). If the injector does operate, again, just keep pressing the switch spraying through the carb cleaner till you get a nice spray pattern. You may just get a couple of drips at first but after a few seconds of this the carb cleaner should clean the nozzle giving you a nice spray pattern. By the way, this is a two person job unless you go though the trouble to build something to hold or operate both the switch and the carb cleaner nozzle at the same time. You may even want to go as far as having a third person standing by with a fire extinguisher.

Phase Two - Carefully pull the connection to the carb cleaner can. I say carefully because the spray will again go everywhere and it may be atomized and highly flammable! Then, with the plastic handle of a medium sized screw driver (or your instrument of choice) lightly tap (rap) on the metal housing of the injector at the same time someone operates the momentary switch. Sometimes all it took was a light tap; sometimes it took quite a few hard taps to kick start and un-stick the injector. Be careful and make sure you have voltage to the injector while you do this. There’s no sense in beating the injector if there’s no voltage applied. Once you hear the “click”, hook the injector back up to the carb cleaner and have at it until you have a good spray pattern.

The other condition I had was that the injector was actually stuck open and would allow the carb cleaner to run right through without the applied voltage. This injector took the longest to fix and required several applications of both the Phase One and Phase Two processes.



The last thing I did before putting the injectors back was to run compress air through each injector to make sure there was no carb cleaner left inside. Considering how well it dissolved almost anything it touched there’s no reason to leave it inside the injector and tempt fate.



This is what was cleaned from the injectors


I hope this helps.

RFJ

Thanks Thom.

dr bob

Great write-up!