Author Topic: testing early fuel injection pump thermostat  (Read 1464 times)

mnahon

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testing early fuel injection pump thermostat
« on: October 01, 2019, 03:01:11 »
It seems that the (tall) thermostat on the early 230SL fuel injection pump can be tested by placing in boiling water to see if the pin extends. Does anyone know how much it should extend?
Meyer Nahon
Montreal, Canada
1968 MB 280SL Auto Euro LHD Silver
2021 Tesla Model 3

Benz Dr.

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Re: testing early fuel injection pump thermostat
« Reply #1 on: October 01, 2019, 06:35:22 »
It only moves about 1.2 mm on a 230SL but you have a 280SL so it uses a different thermostat. The one on a 280 moves a lot more - maybe 7 -8 mm.
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

Pawel66

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Re: testing early fuel injection pump thermostat
« Reply #2 on: October 01, 2019, 09:19:00 »
The new thermostat (new style) I bought from MB two months ago extended exactly 7mm. The old one I had only 5mm.
Pawel

280SL 1970 automatic 180G Silver
W128 220SE
W121 190SL
G-class

mnahon

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Re: testing early fuel injection pump thermostat
« Reply #3 on: October 01, 2019, 17:55:28 »
Thanks Dan, Pawel,

I've added this information to the Technical Manual on the WRD page:
https://www.sl113.org/wiki/Engine/WarmRunningDevice

I added the following text:
The central pin of the "heat feeler", or thermostat, extends to adjust the mixture as the coolant temperature increases. The thermostat can be tested by placing it in hot water and measuring the pin's extension. The thermostat of the early 230SL looks very different from the one in later Pagodas (picture below shows the later thermostat); and it is much more expensive if you can even find it. The pin on the early thermostat should extend about 2 mm when tested in hot water, while the one on the later thermostat extends by about 7 mm.
Meyer Nahon
Montreal, Canada
1968 MB 280SL Auto Euro LHD Silver
2021 Tesla Model 3