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Old 06-10-2003, 04:31 PM
Posts: n/a
87 420 SEL with Cold Start Problem

Hard starting in mornings. I've got no cold start enrichment from the cold start valve. I've narrowed it down to missing TF signal at both Fuel pump relay Pin 2 and Idle Control module Pin 2. My service manual shows a grn/blu wire from Idle control module to Fuel pump relay and another wire (same color) to the CIS module. I exposed the wires going to the CIS module and none are grn/blu and I've used a signal tracer and I'm not picking up any indications of the signal tracer at the CIS connector. I'm assuming the CIS module provides the TF signal to both the Idle control module and the fuel pump relay. Can anyone confirm? I would hate to replace the Idle control module if it really doesn't provide the missing signal. The TF signal should be about 5-6 volts and I'm getting about .5 volt.

I'm using a 10K resistor across the temperature sensor connector and I've tested the start valve, replaced the fuel pump relay and tested the fuel pumps. Anyone got any ideas?

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