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Old 10-04-2003, 08:40 PM
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Join Date: Sep 2003
Location: Michigan
Posts: 45
help with 74 450sl: electrical and cruise questions

I have a 74 450sl and have a couple things I need help with.
(1) Four of my cylinders cut out on me sporadically (#s 1,4,5,6). They lose power to the fuel injectors and I don't see a common circuit for them on the schematics. If someone can help I would appreciate it. I've tried finding the Electronic Control Unit (ECU) to check connections there but I can't locate it.
(2) On my cruise control, the diagrams show a single vacuum hose attaching to the Servo/actuator unit. Well, I just happen to have 2 vacuum hoses, one of which simply ends and is hanging free between the firewall and the back of the glove box. Any ideas where this goes?
Thanks for helping if you can.

Last edited by OB Joe; 10-04-2003 at 11:05 PM.
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Old 10-04-2003, 11:49 PM
Registered User
Join Date: Jul 2003
Posts: 78
Re fuel injectors cutting out- examine/clean the injection trigger points in the distributor. They are located on a tray that slides in below the ignition control, and these points can eventually become oil fouled.

The ECU is in the passenger side footwell bolted to the firewall.

I don't know where the vacuum actuator for the cruise control is. The hose you describe sounds like vacuum that opens and closes the passenger side damper for the climate control system (for exterior/recirc air).

Hope your cruise amplifier works. I wouldn't know where to begin to get service for those old Philco units. (Anybody know?)

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Old 10-05-2003, 07:15 PM
Registered User
Join Date: Sep 2003
Location: Michigan
Posts: 45
Thanks. I looked at the injector points in the distributor and seemed okay. I found the ECU as well. Now to decide whether to open it or not. As is, still have trouble with the same 4 cylinders. Since the do not appear to be connected on the electrical schematics, I doubt the problem is there but I don't know where to look.
Thanks again.
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