2001 Tundra Base V6 not turning on in the morning

Hi Everybody, I have a 2001 Tundra that does not turn on in the cold mornings. However, when the weather is hot no problem turning on and off. I already replace the fuel pump, the fuel filter and the coolant sensor. Does anyone had this issue before. Thanks!

 

Stupid question, but logical... are your battery terminals tight?

It's rarely if ever the fuel pump

 

Does the 5vz have an intake air temp sensor?
Any trouble codes? When it does start, does it start strong or does it take it a bit?

clean the throttlebody and MAF sensor.

 

Not turning on: As in;

No dash lights, no radio absolutely nothing as if the key wasn't turned at all.

Dash lights turn on, radio plays and everything else works normally except the starter doesn't turn over the engine. If this is the case do you hear a click when you turn the ignition to the start position?

Finally, everything electrical works normal including the starter, the engine turn over with the starter but does not start running.

Which one?

 

It cranks and everything looks ok. No codes. I does start strong when the weather is hot.

Terminals tight and good battery. I got you, the question is kind of stupid.

Everything electrical works normal including the starter, the engine turn over with the starter but does not start running. Then later when weather gets hot, it turns on. I am in San Diego CA.

Does the 5vz have an intake air temp sensor?
I have no idea. I am going to check on that.

Thank you guys.

 

Sometimes you need to distance yourself from everything that could potentially be wrong and think about the core problem at hand:

Starts when hot
No start when cold
​

So, what what happens when things are hot vs. cold? Contraction & Expansion. Metals espeically expand when hot, and contract when cold. i.e. what may simply appear as a hairline crack when hot, may contract to reveal a 1mm-2mm gap when cold, and 1mm-2mm is enough in some cases to prevent signal/continuity.

For example, in the world of printed circuit boards (PCB)s, if there's a crack in a trace (circuit line) on the board, when it's hot, no problem, the material can expand and can either create or improve the connection. The moment you get it cold again, contraction makes the gap in the crack more pronounced, and you may not get a connection at all. This same kind of thing can be seen with wiring shorts, either mid-wire, or at the connector end. I've seen loose connectors cause issues when cold vs. hot for example. With electronics, if I'm seeing a similar situation, I'm checking all connections, testing continuity on wires and paths when cold to see if I notice any broken connections; if I find one, I'm hunting for the same when hot.

What else is impacted by hot and cold, beyond connectors, circuits, wires? Resistors. Resistors are used all over the place in vehicles. Inside the MAF, temp sensors (coolant, oil, trans), the fuel pump resistor that forces the fuel pump to operate in low-flow mode when engaged at the relay, and some other sender gauges like the fuel level float/slide at the fuel pump.

What would I be checking?

First think I'd want to know: What's been replaced on the truck related to fuel/air/ignition? For example, has anyone replaced the fuel pump or MAF at any point? Spark plugs or coils? If yes, more details would be helpful.

Second thing I'd want to know: Have you checked or cleaned the MAF recently, using (specifically) a name-brand MAF cleaning spray?

Next thing I'd want to know: Have you checked the fuel pressure, to see if there's a clear sign the fuel pump is actually kicking on when the truck is cold, and the fuel pump has power? You may need to forcibly engage the fuel pump by jumpering it at the relay to test.

Last thing I'd want to know: Have you tested for spark when the engine is cold? Just to confirm, at least, you're getting positive spark?

Remember, all you need for an ICE motor to run is air/fuel/spark. For an EFI ICE motor, there are other elements/sensors involved to meter air, spark, and fuel, and verify if the engine is running, but ... Checking for spark and adequate fuel pressure is important, those are two you can semi-easily check ... you'll always be getting air. If you're not getting fuel or spark, that narrows down your focus significantly.

 

Shifty that is so much useful information.

I replaced the fuel pump twice but never checked the pressure so I am going to do that for sure.

Thanks! I will post whatever I find.

Have a great weekend!

 

If you used anything other than Denso brand, that's a huge mistake. The fact you've had to replace it twice should tell you all you need to know. Use Denso brand from a reputable source (i.e. avoid scAmazon, fleaBay, and other similar vendors where the merch isn't authenticated)

 

Hi All,
It was a good help from all of you.
My 2001 Tundra finally did not want to turn on all the time.
Finally a technician found out the computer was the problem.
I replace the ECU and everything works as it should.

Thanks all for your help.

 

Awesome. I'd have loved to see the circuit board inside. We've seen similar over here, and they found water was getting into the ECU, it'd corroded the board.

But ultimately, this is why I spent so much time walking about "PCB"/circuit boards above. It stunk of something PCB related.