73.5 CIS injectors needed

[Rick Cabell]

The 73.5 cars have a unique fuel injectors for that year only. Only source seems to be dealer at almost $300 each! I called and stock in Germany only and a month to get them. Has anyone found away around this expensive problem? Car sat for 25 years. I did ultrasonic cleaning and then a good douching with an injector cleaning pump machine. To far gone. Anyone who has a way around this please speak. (Or type)

[Scott A]

Have you tried the samba

[Jay Laifman]

There is a place that restores them too. Are you sure they can't be saved? I don't recall the place. I'll have to see if I can find it.

I did find this. I have no idea if it is any good: https://rennlist.com/forums/928-foru...injectors.html He uses a tweezers and string to pull the injector open so it can fully clean. I don't know what he does about the screen.

This place seems to have multiple suggestions: https://www.injector.com/cart/pc/home.asp

[Jay Laifman]

I wanted to update this post for this website. I just bought the Mercedes 280, 380 and 450 version of these injectors. They seem to be the same spec, except made of brass on the outside instead of steel. They are also currently $17 each on Pelican, compared to $250 each for the Porsche version. Given how many Mercedes came with them, and only 6 months of Porsches came with them, I'm hoping it's just a question of huge supply and low demand.

Here is the link to them for sale at Pelican: https://www.pelicanparts.com/More_In...56-23-M14&bc=c

Here is the Mercedes ones at $50 each: https://www.pelicanparts.com/More_In...56-23-MBZ&bc=c

Here is the link to a longer thread on Pelican: https://forums.pelicanparts.com/pors...njector-4.html

For what it's worth, I just put these in my 911 because I was chasing a hard start when warm problem. It turned out that a few of my injectors were leaking a little bit after shut off - and that was the problem. I did all the pressure tests and leak down tests, and it was to spec. And someone told me that if an injector is leaking, it's because of the fuel distributor. Well, that turned out to be false since the new FD didn't change anything and the new injectors fixed it. And the spec for testing may be for another issue, but doesn't address 50 year old injectors.

[Rick Cabell]

Jay, do the injectors seems to have the same flow as the Porsche ones? Drivability seem good?

[Jay Laifman]

Drivability is great. But I have to admit I now have a concern about them.

Information online suggests that the Mercedes operate at 60 kpa/8 psi higher fuel pressure than the Porsche. And corresponding with that, online information suggests these Mercedes injectors have an opening pressure that is higher by about exactly the same amount - which makes sense. And in looking at a cut open injector, I realize that the spring never gets fully open - because that would collapse the spring and actually block fuel. So at comparable operating conditions, the Mercedes injector on the Porsche car, will not be as open. That's why some suggest to set the fuel pressure up to the higher end of the Porsche spec, which is actually the bottom end of the Mercedes spec.

So the unknown question is if that extra 8 psi on the spring (approx 10%), allows so much more fuel in that using the Mercedes injectors leaves power on the table. Mercedes: 520-580; Porsche: 450-520. But then the CIS does have the mixture adjustment screw. So it can adjust how rich it is at a given air flow. I would think that would compensate for the difference in injectors. (Update: I've been advised that the adjustment screw will compensate for this)

I wholly realize that this is a CIS T, and not a 2.5 twin spark. But if there is a difference, it would be a reason to spend the extra $1,400 to get the Porsche spec ones. Probably the only way to know is to dyno with both and see. I don't think I'll do that any time soon. I will however pull off one of the Mercedes injectors and measure where it actually opens.

[speedo]

What is the correct part#? I have some CIS injectors and will take a look.

[Jay Laifman]

Mercedes: Part#: 000-078-56-23, Bosch: 0 437 502 047, also listed as 62274

The stock Porsche part Bosch number is 0 437 502 002
Porsche number 911 110 355 01

[karlusmagnus]

I have bought some parts from Carpoint in Germany. With favorable Euro/Dollar rate, exVAT incl shipping was often priced very competitively, and parts arrived in a few days to NY for me. Another resource to keep in mind when shopping.

[speedo]

Yeah sorry...mine are 0437 502 004. Must be for 74-77 2.7 CIS.