How do you test CIS Injectors? Bosch K-Jetronic

 

I pulled mine out of the bung in the intake and hung it into a plastic cup... Would not recommend doing this with the engine capable of running. Inadvertantly spaying gas would not be good. I pulled the air box off, jumped an on/off switch across 30 & 87 on the fuel pump relay socket, and tested with ingition switch off.
David

 

With a CIS injector pressure stand. What, you don't have one? I haven't seen one in years. some are fancy, with a manifold and 8 spigots to do them all at once. The smart way is to use a graduated cylinder, block the rest of the outlets, and run each one on a single output.

You'll need to turn the CO adjustment screw in to force fuel in at ambient pressure. There is a small hole between the large air inlet and the pump distributor head. That is the 3mm adjustment for CO (enrichment). Or, alternately, you could block the air plate down with a small black of wood. The important thing is to not change anything between tests!

Set it up so you get a modest flow with the pump on. Have a stopwatch and start filling the graduated cylinder for a fixed time. Measure the quantity(or time to a fixed quantity), and swap injectors. Don't move the metering plate, don't adjust the CO screw, just swap injectors and repeat the measurement. Continue until all 8 have been checked. They have a spec which I can find if you want for delta between injectors. Each injector has a PN on the side, and there are many different flow rates for 928s, Mercs, VW, Ferrari, Lamborghini, etc.

The important thing is that they all flow relatively the same, given the same time, and pressure. The CO adjustment is a way to make it richer throughout the range, and there is also an adjustment on the Warm Up Regulator to optimize economy when the car is warm. I don't know how to do that one.

 

Just place injectors into a suitable empty repository...depress air metering plate....measure fuel in repositories...er, yeah fuel pump has to be on (jump terminals) and a buret is great, but...

 

I think I will just have them tested at WitchHunter Performance. They already said they can't clean them because they don't backflush (CIS Injectors), but at least they can tell me which ones are bad. Thanks for all the suggestions!

 

If you don't get a good spray pattern with Docmirrors test (above) they will need cleaned. I've cleared blockages by using compressed air and cleaner. The injectors will need to be removed from the engine but you can leave the holder and rubber seal on them. Spray cleaner into the inlet, let sit then hit it with about 60 psi of compressed air. Wear eye protection when doing this. Repeat until you get a cone shaped spray pattern. BTW just using the aersol cans of spray cleaner won't work due to the high pressure needed to open the injector valve.

Dennis

 

I have never seen one that is adjustable, that is a new one on me.

We used to move the plug on the WUR to adjust the control pressure, but you had to be real careful doing that, it is easy to go in, but very hard to get it back out.

I always wondered why the Volvo's, BMW's and MB's we worked on never had a adjustment on them, good to know some of them do have it.

If the injectors do not spray a good cone shaped pattern, I would just buy a new set.

Greg

 

that's the adjustment, move the plug. I have also put a shim under the spring to change the control pressure. Not really and adjustment per-se. Bosch 0436-140 had a hex drive on the bottom, I think(been a while).

 

This is a great idea. So put some carb cleaner in the injector (out of engine), let it soak for a few minutes, then use my compressor to blow it out and watch the pattern. I didn't even think of this. Thanks for your input guys!

 

You can make a tool to hold them open - 1/8"-5/32" wide thin but stiff steel, cut a slot in the centre ~ 1/16" wide. Blow the injector open with air to lift the 'pintle' off its seat, slip the tool under the head, then you can blow cleaner back from the end to flush the crud out of the filter .
jp 83 Euro S AT 51k

 

JP,

Also, I have seen a braided wire loop used to hold it open. IIRC there was a picture of this setup on www.924board.org recently.

Dennis

 

Dennis,

Can you supply a link to the thread? Did a search with no luck

 

The link is in the first message of this thread.

http://www.924board.org/viewtopic.php?t=24789

Go to the referenced link and scroll down to the end and you'll see a picture of the setup.

Sorry about providing a link to a link.

Dennis

 

Actually Dennis, this is just the method I used to test mine, all 16 of them.

I used brake cleaner fluid (spray can), using the plastic hose that comes with it, placing the hose up inside the injector (from the line end) and turning the whole mess upside down while spraying.

it's not the prescribed way to do it, but it will give you some decent results as to which is really bad to almost good.

I found only 2 out of 16 injectors that sprayed a proper "cone" pattern, and buzzzed as they should.

needless to say, I shopped around, found a set of recently "sonic-ly" cleaned Mercedes Benz brass injectors (see my posts on this) for less than $60 including shipping, and never looked back-----there is place in Arizona that sells this same injector for $27 each new, the best price on new ones that I have found so far.

my broke 4.5L Euro has never run this good.


--Russ

 

you can also shim the pressure relief spring in the fuel distributor to give a little more "go" as well.......

--Russ