Thread: Cold fuel pump not priming

Recently I have been having issues with my car starting it only happens in the bitter cold.


What I know:
-It occurs only after sitting for a long time in the cold. For example overnight or when I log a 12 hour day at the shop.
-It is temperature related
-I hear the green relay near the ECU (fuel pump relay) click and works like it should.

Sometimes it will take sitting there in the bitter cold and cycling the key back and forth 50-100 times before finally the pump kicks on. It seems when it snows and the car is covered in snow it will start right up.

What I have done to try and fix the problem:
-Replace fuel pump
-Replace green relay
-Replace Ecu
-Replaced Coolant temp sensor (for computer)

Nothing I have replaced has even helped the issue at all. I am normally pretty smart with diagnosising things on the fly but being that it doesn't do it all the time and my shop is heated the car starts each and every time when I pull it inside to look it over.

It wouldn't bother me as it does eventually start but it makes me late for work and appointments. Currently it is the only car I have to drive.

Did you check the wiring and ground for the pump?

Try putting some Heet in your gas

You could wire a push button to the relay and run it for longer manually before starting and see if that helps? Would only require a wire switched to earth as the ecu outputs a earth to trigger the relay.

Interesting, Since you replaced the pump already im sure you looked at the wiring tucked around the corners inside to check for any kind of short or an issue with the wiring itself. Have you checked continuity, grounds etc?
So, next thing im curious about is the ignition switch, is it possible that it is starting to go and when its super cold it isnt making a good connection to send a signal to the ecu for fuel to prime?
The last thing I can think of that relates is my NX started having the same issue awhile back and I did the paperclip in the clutch interlock switch and it fired right up. The paperclip is still in there, haha... its been like 6 mo... lol.
Hope I gave ya a couple ideas, you probably know more about it than me but those have been my experiences with my NX and the 240 I used to have. Stay warm, GL!

*edit, I just had an idea regarding the temps. When you pull into the shop to diagnose, have you used and air can to spray cold air(use ice? idk) on the related components?

So I think I figured it out this morning. Car was slow to crank and it took forever finally I heard clicking and the battery went dead. I jumped it and drove it to my shop. My last battery with regular charging lasted 13.5 years (have the invoice from the original owner). The Interstate battery was bad after only 6 months. I will update everyone tomorrow.

Replaced the battery and the next morning same deal. So I swapped in another ECU I had laying around and my problem is solved. Now I need to find out if it is just the cold start part of my tune or the actual ECU itself.

That's only if it's been sitting a long as time.

Or if he lives in a cold water area where he could have gotten some water/condensation in his tank, which moved into his pump/filter/lines.

probly the part of the ECU that turns the pump on is going bad. i had to hardwire my pump on one of my Calum ecu's after it burned out that part.