MFI injector tester and cleaner

[JohnOllen]

For what it's worth I thought I would share a recent success. I built this DIY injector tester and cleaner and it worked great. Putting an old 73 911T back on the road after its been sitting for over a decade so I was concerned about the injectors. All the injectors were partially clogged and would start leaking around 180 psi but after pumping some cleaner through them they all eventually started firing right at 240 psi with a nice mist and whistle. Nice when something actually works out.

[JohnOllen]

[JohnOllen]

[Plays with cars]

Very cool! I bought something similar from MercedesSource.com earlier this year. I wasn't as successful cleaning injectors though. I had 11 that I had collected over time but I was only able to save 5. Five, not being the six I needed for the engine, I ended up buying six new injectors (gulp. But I've been chasing ghosts for a couple of years on this project and needed to ELIMINATE possible failure modes).

Anyway, when I received the new injectors I ran all of them through the tester and found that one of the new ones was no good. It leaked a little bit and the crack pressure was too low. I was able to exchange it for a replacement that tested fine. The tester definitely paid for itself by identifying the bad used injectors and the one bad new one.

[JohnOllen]

Nicely done. The injectors are pricey aren't they. Did you get all the gremlins out in the end? I recall when I put the Targa away so many years ago it was missing or hesitating a bit in the midrange, around the 3000 RPM, rso that is one I expect to have to chase as well. Unless these injectors were contributing to it.

[Olsen911]

Looks good.

Please State the specs. For MFI injectors.?

What kind of pressur are they seing.?

Thanks - Cheers - Olsen911 - Tommy Olsen

[JohnOllen]

They would start leaking at around 180 psi. During cleaning the pressure would spike to close to 300 but eventually try all started popping nicely at 240 psi.

[JohnOllen]

I'm calling them 'MFI' injectors to differentiate them from the Injector type used on the CIS systems which function at a lower pressure, below 100 psi. Those are much easier to test and clean because you use a standard air compressor to blow the cleaning fluids through.

[356RS]

John, What kind of "cleaner" are you using to pump through your tester?

[JohnOllen]

I used a combination of all my favourites mixed together, 1/4 CRC carb cleaner, 1/2 varsol, 1/4 injector cleaner (happened to be Kleen-flo).

[Olsen911]

Thanks.

Inspired by your test rig - I'll give it a try - bought this:



Then one hose connection and a bracket for fixed mounting of the injectors.

Fill it up with cleaner - Pump pressure to 180 PSI and see the injectors start leaking and then a beautiful pattern spray pattern about 240 psi.

Let me know what you guys think.?

Thanks - Cheers - Olsen911 - Tommy Olsen

[JohnOllen]

Now that's a nice looking injector tester/cleaner. Did you get all six injectors working? With the price of new injectors and the peace of mind which comes with knowing your injectors are flowing properly this is almost a 'must have' tool it seems when rebuilding these old engines. Well done.

[Olsen911]

Finally came around to test my injectors on the test bench.

I started modify the test bench, so it would accept the Bosch injectors.



Then a trial run on one all new injector. Building up pressure an then release at 16 Bar - 220 PSI with a nice even pray pattern - all good.



Then i took out the injectors from my running engine, I wasn´t excepting to find anything wrong with these injectors as the car is running good and i had the injectors cleaned and tested all good last year by Bosch workshop.

I was in for a surprise.




Number 1: very uneven spray pattern - only one side is open.
Number 2: didn´t evaporate, only buling up pressure then release in a beam about 20 bar - 290 PSI.
Number 3: Barely opens and when it did it was at 30 bar - 435 PSI.
Number 4: All good.
Number 5: Same as number 2.
Number 6: All good.

I did test it 3 times and with air cleaning every time to be sure and all the test show this result.

I am puzzled about this, can the engine run strong and smooth with these injectors.?

Let me know what you guys are thinking.?

Thanks - Cheers - Olsen911 - Tommy Olsen.

[florio]

Hi, I also like the idea of testing the injectors, can you give us some details on how your system is put together? It looks like you used a jack as a pressure pump?

Thanks!

[Sigurd]

Link to the pump:

ROTHENBERGER RP 30 - Simple and light testing pump for compression testing up to 30 bar

[florio]

Thanks, that's a great idea to use a hydrostatic pump. What liquid did you use? I saw methanol has about the same viscosity as gasoline, wonder if it wouldn't make a safer replacement that didn't eat the o-rings.

great thread!