Fuel Accumulator Old vs New Differences

[Funracer]

Just posting this for anyone interested in these kinds of things.

I have an 83SC with stock CIS. In 2022 I replaced the old greenish Bosch FA with a new silver Bosch FA of the same part number 0438170031. Pelican shows this as correct for my car. I doubt the old green one was original because the PET lists the part number for my 83 as 911 110 197 02 so it was probably replaced at some point before I bought it in 2019.


On both old and new I could hold my thumb over either top port and could not blow air out the bottom overflow port. However the green does not hold vacuum while the silver does.

I have a couple of long threads on this forum looking for the reason my car does not start instantly when cold, as it should and did when new. I started thinking about this new accumulator as a possible cause after rereading this post from Shulisco in one of my old threads:


and decided to put my old green one back in. Now the car cold starts nearly instantly (second or third crank). Fuel distributor plunger is always down even after sitting for several days.

So all good? No. The old green FA will not hold residual pressure. Drops to zero in about 15 seconds after shutdown. So while cold starts are excellent hot starts are now the issue. The newer silver FA will hold residual pressure for about six hours and hot starts perfectly.

They look the same, but there are differences. Note the difference bt the cotton swab height, about 1/3 inch height of whatever is below the center port:


Also the silver inflow port (top center) has a tiny hole visible. I know this hole is open bc when I blew in the outflow port (top side) fuel squirted out this hole several inches.
Green FA has a mark in the same spot but no hole. Even a thin needle would not pass through.



Lastly look in the green outflow side port there looks to be two metal plates joining there. Silver one is flat:



To summarize, same Bosch part numbers, older green will not hold vacuum or residual pressure but cold starts great (FD plunger down) and hot starts poorly. Based on this pretty sure the green one is toast. Newer silver will hold vacuum and residual pressure for hours but cold starts poorly (FD plunger up) and hot starts instantly. But also not sure the silver one is working properly either per Shulisco’s post.

I would like to have a car that starts equally well hot or cold.

[PeteKz]

Thanks for posting that. Interesting observations about the differences. The FD plunger up versus down issue still puzzles me too.