Bench checking Bosch injectors

[lurtch]

Hello All

I have been experiencing some rough running on start up along with indications of
a overly rich mixture. After verifying that all the standard mechanical engine settings are satisfactory,
I decided to check out the more difficult one: bad fuel atomization at the tip of the fuel injector. My suspicions were confirmed because three of my injectors had poor dispersion patterns.

 I was able to find a cheap hydro-static tester on Amazon for about US $ 50.00.

I fabricated a holding fixture, silver-soldered a tubing joint, and assembled some fittings and it was ready to start testing
individual injectors.

The book value pressure required to lift the injector pintle is 213 - 256 psi. (15kg/cm2 - 18kg/cm2)   At these pressures a good injector will disburse a very good spray pattern. (see videos) There is an internal filter (not accessible) that can distort the flow of fuel which causes this disruption in the spray pattern. (see videos)     https://vimeo.com/385872636

Regards,

Larry in CA

[mrfatboy]

Great demonstration video.  It should go in the tech manual👍

[kampala]

Very nice video.  Much appreciated.   Agree that this should be inserted into tech manual. 

Thanks

[Garry]

Feel free to put it in there, as a Full Member you have full access and can do so. In fact we rely on you to do so as an ongoing process to assist the Group in populating the Manual.  It is not the Board that have been doing so but dedicated Members doing so when they seen the need.


Practice in the Sand Pit if you don’t feel confident then go for it.


Garry

[bracurrie]

While not mentioned specifically, a leaky injector can also be tested for.

[mdsalemi]

Nice Larry!

At the Pagoda meet in VA in 2017, Jim Villers brought similar home-made device. Tested a lot of injectors, and cleaned a bunch for people there too!

[doitwright]

On a recent forum discussion regarding the cleaning of injectors and referencing the Kent Bergsma videos it was noted that it is possible to back flush the injector with the possibility of cleaning a clogged filter. In one of the Bergsma videos he shows a cutaway view of the internals of a mechanical injector along with the tiny filter within. He uses a tool to pry open the injector tip when back flushing.

[Harry]

Larry,

Can you share the details of your rig, i.e. the specific unit from Amazon and any additional hardware?

Thanks,
Harry

[Pawel66]

Only one comment I would make.

Kent was mentioning it several times in his videos and I found it, actually, relevant: figure out a way not to spray to an open tray as you are exposed to breath in lots of cleaning agent. At least have a fan blowing the spray away from you. In my geography a 1l Coke bottle with neck cut fits perfectly on the injector, supports itself on it (hangs from it) and has the walls transparent enough to see a beautiful spray.

As for backflush - it is very easy to set up a piece of hose and syringe on an injector to blow the other way. The trick is to lift the little closure on the tip of the injector without damaging anything. Or I should say: lift and hold in such a way, that you can put on that piece of hose with the tip of injector open. I was lifting mine with a tool I made (posted picture of it in another thread) and managed to hold it in place with a cut tip of zip tie. But I think the chances of damaging the injector are high (I damaged one).

[ctaylor738]

I was lucky enough to come into a Bosch tester when a Porsche shop quit working on mechanically injected cars.  I use BG44 for testing and cleaning.  If an injector does not have a good pattern, I pump it up to 100 psi or so and let it sit for a few hours.  If that doesn't work, I let it sit pumped-up overnight. If it leaks at lower pressure, I take it off the tester and let it sit overnight filled with the cleaner, then re-test.

I would say this works about 75% of the time.

CT