Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help

Go Back   PeachParts Mercedes ShopForum > Technical Information and Support > Vintage Mercedes

LinkBack Thread Tools Display Modes
Old 12-09-2007, 01:02 AM
Registered User
Join Date: Dec 2007
Posts: 2
1979 450sl fuel pressure readings

What are the fuel pressure readings I should get on a 1979 450sl with bosch K-jetronic fuel injector system;
-"Key on", and "running" (taken at the cold start fuel line)?
- Run control pressure on a cold motor and after warm up (taken
between the fuel dist. and the warm-up control valve) ?
My fix-it books only give the volume that the pump should supply and not the pressure. I had a bad pressure control valve, ordered a new one and got a LOT of adjustment spacers. Any help???
I have learned that adding a 2mm shim increases the pressure about 10psi. Is 63psi too low for a 79 450 sl with the fuel pump running and the motor off?
I found a non-MB source for the K-tronic and was given the following info-
System normal operating pressure is aprox 5bar (75psi). This is the point the fuel distributor's primary pressure regulator returns fuel to the tank.
Control pressure (controled by the warm up regulaor) will be aprox 1.0 bar on a cold motor and will increase to aprox 3.5 bar as the motor warms up.

Anyone know if this is the same for my 450 sl???

Last edited by oldone; 12-10-2007 at 04:50 PM.
Reply With Quote
Old 12-10-2007, 05:24 PM
Super Moderator
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,316
Those are good numbers. Here's some more detail (from Alldata, 380SL)


Place valve on pressure gauge in open position.
Disconnect the electrical connector from the control pressure regulator.
Place the fuel supply circuit under pressure by bypassing the fuel pump relay.
Make sure that the cold engine control pressure ranges fall within the specifications shown. NOTE: If the control pressure regulator incorporates a barometric capsule (altitude corrector), take this into account when reading the test pressures. Temperatures given represent ambient air temp.

0C (32F) No Value Given

5C (41F) No Value Given

10C (50F) 1.2-1.6 bar (17-23 psi)

15C (59F) 1.4-1.8 bar (20-26 psi)

20C (68F) 1.6-2.0 bar (23-29 psi)

25C (77F) 1.8-2.2 bar (26-32 psi)

30C (86F) 2.0-2.4 bar (29-35 psi)

35C (95F) 2.2-2.6 bar (32-38 psi)

40C (104F) 2.4-2.8 bar (35-41 psi)

If the pressure tested is incorrect, retest with a new control pressure regulator.


Connect the vehicle harness connector to the control pressure regulator.
Energize the fuel pump by bypassing the fuel pump relay; after 5 minutes, the control pressure should be 3.4-3.8 bar.
If these values are not obtained check the power at connector.
If there is current at the plug, replace the control pressure regulator.
If the rise in pressure occurs too rapidly, replace the control pressure regulator.
Shut off the fuel pump.
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
Reply With Quote
Old 12-10-2007, 08:29 PM
Registered User
Join Date: Dec 2007
Posts: 2

Thanks for the info. I'll give it a try and let you know how I do.

Thanks again for the help!!!
Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

All times are GMT -4. The time now is 01:56 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2011 Pelican Parts - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page