[RedDR]

Fighting my hard start issue when the engine is hot. Cranks fine but takes a while to catch, as if it's flooded (but no smell of gas under the hood or in the oil).

One possibility is that the coolant temp sensor is bad, which tells the ECU the engine is cold, causing it to dump a lot more fuel into the engine. Hence the difficulty starting.

Believe it or not, you can actually get to the coolant temp sensor (unlike almost every other sensor). But there's two... one small and one big.

Anyone know which is the one the ECU uses to control the fuel mix?

 

[kevinjohnson3216]

I think the small one with 1 wire is for the gauge and the one with the harness and plug is for ecu

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[Zero Six LE]

Usually the ECM sensor has 3 wires. One for reference volts, one for return volts and one for ground.

 

[jdtuned]

how do you go about testing these sensors? any info on what electrical values they should have?

 

[Zero Six LE]

how do you go about testing these sensors? any info on what electrical values they should have?

Register here and see if you can find the electrical section for your truck. Nissan Frontier/Truck Service Manuals - Nissanhelp.com

 

[RedDR]

With the connector off, I measured 3.2K ohms across the sensor terminals when cold. With the engine warmed up some, I measured somewhere around 540 ohms. So I don't know if those are the expected values, but they definitely change depending on the temperature of the coolant.

 

[jdtuned]

thank you zero six I will definetely check that out!

Register here and see if you can find the electrical section for your truck. Nissan Frontier/Truck Service Manuals - Nissanhelp.com

when i checked it I was getting somewhere around 680ohms and that was after the engine was warm. I havent checked it cold but I'll check right now and see what it comes up with on a cold motor.

With the connector off, I measured 3.2K ohms across the sensor terminals when cold. With the engine warmed up some, I measured somewhere around 540 ohms. So I don't know if those are the expected values, but they definitely change depending on the temperature of the coolant.

 

[AutoBravado]

You'll need to find a graph for temperature vs resistance to be sure, but those values to seem correct (I haven't needed to test mine, but I've tested many.)

My cheat to not need the spec on the ohms is to check live data against my infrared thermometer. That way, I don't have to look anything up.

 

[jdtuned]

Ok that makes sense, live data as in a obd2 scanner? The one I have doesn't show me temps unfortunately. What I did do was change the gas and temp gauge on the cluster and it looks like I am getting a more accurate temp reading. I bought a thermometer and after letting it idle for over 10 minutes i wasn't any where near 220 or more temp wise. So going off what the thermometer says I think I am in the clear and it was a faulty temp gauge. For good measure in the next few paychecks I'll probably change both sensors.