Injectors

[dwilli3038]

I took out my injectors and checked them out, using a hand pump. I found they had very poor spray patterns. I pumped some Marvel Mystery oil through them (took 1/2 gallon and a lot of effort) Finaly the spay pattern looks very good. But the pressure when the injectors opened was only around 20 to 30 PSI. I then put some gasoline in the pump. The spay patterns look wonderful but the pressure was even lower.

Should I be concerned about the pressure or take the nice spay patterns and be happy?



Daryl
'64 230 SL
Serial # 508

[Cees Klumper]

In the next Pagoda World (being mailed out almost as we type) there is an article about the Tech Session held at Van Dijk in The Netherlands, where we were shown how these injectors are tested. The (1) minimum pressure at which they open is very important, as well as (2) whether they leak or not and (3) the spray pattern. If either of these three is not up to spec, the injector should be first cleaned (usually this is done ultrasonically) and, if that fails, should be replaced.

Here's relevant information from "Glenn's Mercedes-Benz repair and tune-up guide" (June 1969 print) for the 230 SL:
Bosch number DC 8 C 45R 1
opening pressure: 249-263 PSI / 17.5-18.5 ATM
and - the difference between nozzle pressures must not exceed 42 psi
This good book also says: "CAUTION: Be sure to only use filtered fuel". Maybe your Mystery oil did more harm than good. The spray pattern angle should be 45 degrees. It also says how to measure the fuel flow to check whether it is within spec. etc etc.

This book is quite good and practical, and is sold via Amazon or Ebay from time to time (I think after 1969 its title was changed to "Chilton's Mercedes Benz Repair and Tune-up Guide"). Here's a link to the place where we have listed all books relevant to our cars, that we know of:

http://www.sl113.org/publications.asp

Cees Klumper in Amsterdam
'69 white 280 SL automatic