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I am working on my 1980 245 DL B21F, tracking down vacuum leaks, etc. I also have some cold start problems. Yesterday, I pulled the cold start injector - no fuel squirting out when I try to start the car, and I did not feel or hear the solenoid in the injector shift. I disconnected the injector from the engine harness and tested for voltage at the harness connector while cranking the motor. I get a signal between 6-7 VDC when I first start spinning the motor. After about 8-10 seconds, the voltage drops to between 3-4 VDC.
I pulsed the injector with +12 VDC in my hand and could feel and hear the solenoid shift. I hooked the injector back up to the engine harness, tried it again and it still doesn't respond.
I know that the thermal time switch is in the control loop - does it make and break common, or +12 VDC? What minimum potential is required to activate the cold start injector and what is the correct potential?
While I am at it, I intend to pull the auxilliary air valve and test its function. I have the same questions regarding the correct potential for that valve - if I apply that voltage across it, I should be able to see the bimetallic spring force the valve closed as it heats.
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Thermal time switch sounds like the culprit. It switches positive, ground should be constant at the CSI connector. The voltage drop to 3v is indicative of the function of the bimetallic heated element in the switch - but I'd guess the contact points in the switch are burned. The voltage should be battery voltage for the first 8 seconds or so, then drop cleanly to zero. Check resistance across the switch (cold). Should be at or almost zero resistance. Hot engine, the resistance should be infinite as the switch should be fully open. And when open only one pin should have any continuity to ground (via the threaded portion of the switch).
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Chris, Dartmouth NS Canada 70 M-B 280SE, 83 245DL, 84 244 turbo, 90 780 turbo, 92 VW Golf, 90 740 Rex/Regina
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Chris,
I believe it's the the + voltage that is is constant—from starter terminal 16.
The TT switch is in the CS ground side. Time closed depends on ambient temp and how long starter has been cranked (bi-metallic heater switch opens in TT Sw.)
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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
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You're right Bruce - just checked my wiring diagram, the + from starter simultaneously powers the heater in the TTS, and goes directly to the CSI. The ground for the CSI is thru the TTS case to the other side of the heater element and simultaneously through the bimetal contact points, out to the second terminal.
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Chris, Dartmouth NS Canada 70 M-B 280SE, 83 245DL, 84 244 turbo, 90 780 turbo, 92 VW Golf, 90 740 Rex/Regina
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You're right Bruce - just checked my wiring diagram, the + from starter simultaneously powers the heater in the TTS, and goes directly to the CSI. The ground for the CSI is thru the TTS case to the other side of the heater element and simultaneously through the bimetal contact points, out to the second terminal.
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Chris, Dartmouth NS Canada 70 M-B 280SE, 83 245DL, 84 244 turbo, 90 780 turbo, 92 VW Golf, 90 740 Rex/Regina
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Thanks for the information, Bruce and Chris. It looks like I'll be replacing that switch. The connector housing on the switch is broken anyway, a leftover from the previous owner. I have also tested the auxilliary air valve. I started a new thread for that subject; could you guys please take a look at that one and comment?
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Ten Sleep 1980 245DL 1995 850 Turbo
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