Don't feel bad. Tony made an engine test stand. I'd love to have one, but I'd only use it every other year at most, and don't have space to store it. Tony loves a challenge, because he wrestles these engines down to his basement and back up!

I keep thinking of using some old brake MCs I have to make an injector pressure tester. Gauges are cheap. But I've not had issues with new injectors, and wouldn't use it often, so it doesn't get done.

I agree there ought not to be raw fuel sitting there on the back of closed valves (and thus probably in the combustion chamber of the open ones). And if I understand things correctly, there ought not to be any significant residual pressure to the injectors with the engine stopped. Because the FD plunger should be down far enough that no fuel can get from the lower to the upper chamber except for the control pressure system, which only gets to the top of the plunger, and also over to the WUR. It shouldn't get to the the injector lines.

I see two protocols for the emissions screw setting system - the one you used involved watching for the injectors to spray, then resetting the screw. The other one involves either removing an injector or - to make things simpler - loosening one of the injector lines at the FD. Adjust until some fuel emerges, then reset the screw. I would expect this second approach would result in a lower position for the plunger, but maybe not. Much easier and quicker than pulling an injector, and not dependent on the injectors. If you get the mixture screw too lean, I'd expect you would see the engine start when cold (on the cold start valve fuel), then stall due to an over lean mixture. Fine tuning of the mixture typically involves an exhaust gas measuring instrument, and checking that at idle when it is running might also be informative.

You can delay the warm up feature of the WUR significantly by pulling the electrical heater plug from the WUR, if that might help.

The fuel pressure specs have a range. You can adjust the fuel pressure with the washers on the pressure setting screw. I wonder if reducing system pressure to Porsche/Bosch's minimum would help, if it is at the higher end of the range? Long shot, as shouldn't matter.

What about the fuel in contact with MC’s seals? Will they handle it?

Maybe a dumb question: your description a couple posts back says “two spark plugs” have fuel. Is it 2 or all 6? So is it 2 injectors that leak or all 6? Did you save all the injectors you bought recently. If only two are misbehaving, you try 2 from your prior set you thought were bad?

“After the 20 minute test, the problem persists! Rough start for a few seconds (flooded again?) and after that runs normal. Waited another 20 minutes and it was even worse, flooding two spark plugs.”

Main reason I am asking is it seems possible to have 2 bad in a new batch of 6 and very unlikely to have all 6 be bad. Somebody may chime in with an “all 6 were bad” experience by it seems worth considering if you have not already, especially if you can’t test their cracking pressure individually.

Answering your question: when I disassembled the air box to repair the crack I noticed that all 6 cylinders had signs of fuel. More evident on those with the valves closed.
Because of this, and because I had already tested Tony’s suggestion about having the fuel pump running with all injectors out in 6 containers, I assumed they were behaving the same. No dripping.
After I drove the car to the running temperature, I stoped and pulled out only two injectors, as a reference, because this engine has hard lines and it is difficult to pull out all 6 injectors without bending the lines. Only two as a reference to stay out over night in the containers to check the amount released.

Today, there were no signs of fuel in the containers.

I am starting to believe that our problem was due to a temporary contamination of the injectors (or the system), and after we recently clean all the components and lines, injectors, fuel tank, pressure accumulator, etc. it is now starting to “stabilize”... (???)...

What is a fact is that many things had improved since starting all the tests and checkings- cold start is much better, running smoothly, etc.

I personally really like have an AFR gauge in my car. You may want to consider if you don’t have easy access to a tailpipe testing unit. It helps ensure your setting, after you have confirmed all your pressures, etc are correct and let’s you know ongoing if things start to go astray. It’s one of the few continuous data providers on these old cars.

yes, you are right! I will consider that

Alex - I wouldn't worry about seal compatibility using a spare brake MC as a pump to test injectors. Brake fluid and gasoline are both hydrocarbons, so that ought to help even if one would use a different seal formulation for a fuel pump. If the seals deteriorate, you'll soon find out with leaks you can easily deal with. I wouldn't expect that to happen in the short time you'd be doing this. If concerned, you could flush the system after you were done with it with brake fluid, or motor oil. Maybe google "seal fluid compatibility" to get some idea of what sources say. But it isn't like this is a part going into your car.

Yes, I will consider that. I have it almost ready. Lack of time is pulling me to other areas...
Meanwhile my mechanic tested the injectors using a different approach.
Please feel free to leave your insight about the conclusion of this test - if there is any!
He connected a fuel pump with a pressure switch, through a gauge, to an injector.
Pressed the switch until the injector opens and right after, release it.

All 6 injectors hold the pressure between 2,4 and 2,5 bar...
Can I assume they open at the same pressure as they hold pressure- close?
Or, closing at this pressure, higher pressure will be needed to open them?

Any ideas?

Fuel injector’s cracking pressure test.......
 

Alex,

You need to test the fuel injectors individually to determine its cracking pressure. All you need is a fuel pump and supply tank to do the test. Or use the CIS in your motor. Below is the picture of my tester for testing the opening pressures of a fuel injector or a oil piston squirter.

http://forums.pelicanparts.com/uploa...1617075155.jpg

You could use air or fluid to do the test. I tend to like to use fluid because you could observe better watching the fluid (water, gasoline, kerosene, etc.) than compressed air.

Tony

Thanks Tony,
I have written “all 6 injectors were holding pressure between 2,4 and 2,5 bar” but when tested individually. This process I described on the previous post, only allows to test one at at time.