I bought a second-hand 2005 Nissan Almera 1.5 just under 6 months ago, and apart from an early issue with the catalytic converter, seemed to be running okay.

However, a month or so ago, I was out running errands and the car refused to start again after my first stop. Battery and starter motor all checked out okay, and after 20 mins or so it started up fine, and drove like normal. However, after returning home I tried to start it again out of curiosity, and had the same issue. Again, it was fine after 20 mins or so.

After some experimentation, it seemed to start okay after short journeys, but not once the engine reaches full temperature.

I have since discovered that the engine fans only come on if I use the AC, so I'm assuming it is a temp sensor or relay somewhere playing up and underreporting engine temp, but I'm not sure where to look for it, or what to look for in a replacement.

Any help would be appreciated. I'm in the UK if that's relevant.

  • Does it crank but not catch? Have you read your OBD codes?
    – GdD
    Commented May 6, 2022 at 12:22
  • @GdD starter motor turns over fine, just doesn't catch until it cools down. Battery levels all check out fine. I might have to buy a gizmo to read the codes, but haven't yet. Nothing shows up on onboard display, unlike my previous Ford, which did give good diagnostics without having to plug in. Commented May 6, 2022 at 12:39
  • It's worth getting an OBD reader and see if you get anything as it could be relevant. Other than not starting are you having any other symptoms? Rough running, bad mileage, etc?
    – GdD
    Commented May 6, 2022 at 13:24
  • Currently around 34mpg, which is lower than I'd like or expect, really. Nothing noticeable regards running issues, though. Commented May 6, 2022 at 13:36
  • Does your coolant temperature stay nailed to the normal operating temperature? If it does, I wouldn't worry about what the fans are doing.
    – BowlOfRed
    Commented May 6, 2022 at 22:06

2 Answers 2


There's a few things that come to mind which match hard starting when hot and a loss of fuel economy:

  1. Bad coolant temperature sensor: if your car's ECU (Engine Computer) doesn't know what temperature the engine is it will not know the correct air-fuel ratio to inject into the cylinders. This is where an OBD reader would com in very handy, you can read the temperatures the ECU is reporting and see if they look accurate. If they stay the same no matter whether the engine is warm or cold, or fluctuate in illogical ways then you probably need to replace the coolant sensor. They cost about 3 beers for the part, and usually are pretty easy to install
  2. Fuel pump: hard starts are one possible sign your fuel pump is on its way out, especially when it's hot. The way to diagnose this is to measure the fuel pressure using a gauge, and replace the pump if it's low. Note that low fuel pressure can also be from a clogged fuel filter, but if that was a problem you'd be getting a loss of power. Your fuel pump is almost certainly electric, and they are usually under £100 for the part, which is in the tank itself, usually accessed though a panel under the rear seat
  3. Faulty Exhaust Gas Recirculation (EGR) valve: The EGR valve is an emissions control measure which should stay closed when starting, if it gets stuck open you can have issues starting, reduced mileage and other performance problems. These valves can get clogged up over time, and in some cases can be cleaned to get them operating again. Given they cost about 35 quid most choose to replace them

This isn't a complete list by any means, just what seems most likely given your description.

  • Thanks GdD, some things I hadn't thought of there. I did consider the EGR valve, as I've experienced that with a prev motor, but I don't get the loss of performance got then while driving. Commented May 6, 2022 at 14:47
  • Next step is to get me an OBD reader gizmo and go from there, I guess.. Commented May 6, 2022 at 14:49
  • 1
    Bluetooth OBD readers are cheap as chips, plus apps like Torque are free to a certain level of functionality, certainly enough for your needs.
    – GdD
    Commented May 6, 2022 at 14:50
  • Add crank position sensor to the list of possibilities. On many cars the tach will register slight rpm readings while cranking. If you see no movement on your tach while cranking CPS could be bad. These are also affected by heat.
    – Jupiter
    Commented May 6, 2022 at 16:15

There were a ton of Hondas that had fuel pump relays on a circuit board that failed after a few years. And they would fail when it warmed up, so the first drive was fine, but a quick stop would leave the car not able to start.

No idea if Nissan had a similar problem, but relay should be relatively easy to test (or replace). Or if you have access to the fuel pump wiring while you start, see if you're getting power to it during the failures.

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