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5l32v4c 5l32v4c is offline
1985 Porsche 928s
 
Join Date: Dec 2012
Posts: 315
Garage
Another cold start issue solved

Was having a cold start issue this past weekend. The engine would turn but would not fire. My spidey senses told me it was fuel-related as there was absolutely no smell of gas, as you would expect with a flooded engine that’s not getting a spark.

I had had a cold start issue a week or so ago but it was due to the plug on the temperature sensor being loose.

Here’s how I solved it this time;

Had a helper turn the engine over while I felt the pump to see if it was spinning – there was no sign of life
Disconnected the fuel pump wires and connected a test light to the wires while the engine was being cranked – no power
Replaced cracked wires running to fuel pump – still no power
Checked the fuel pump fuse – looked fine
Checked connecter #30 on relay board where fuel pump relay plugs in (this gets power directly from battery) – was getting constant power
Fuel pump relay and horn relay are the same – checked horn relay and horn worked
Placed horn relay in fuel pump relay socket – engine fired
Placed fuel pump relay in horn socket – no horn

Assessment: faulty fuel pump relay
Old 05-16-2016, 01:19 PM
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