No crank when warm?

2005/v6/auto/4x4

I am having a strange issue where I get no crank after the truck has warmed up. Turn key and nothing. If I wait a few hours for everything to cool down it will crank and start right up.
When it refuses to start, there is still signal going to the starter relay (test light). That's about where my ability to trace the issue ends. I was assured that the starter was bad so I replaced it. I have also replaced the starter relay.

Battery is fairly new 12.4v, 14.3v when it is running. Connections are clean. Have also tried with a jump box - no difference. Doesn't seem to be putting any load on the battery when I try to start it.

Is there anything else I should be looking at?

 

Does the big wire at the starter maintain battery voltage when attempting to start?

 

I remember a classmate at the University of Montana, who had a Fiat X1/9 with the same problem. He warmed it up with a trip downtown, and it cooled while we celebrated my last final exam at the Oxford over a couple beers and listening to Norton Buffalo on the stage. Two years later, he still had that sports car, but I don't recall hearing the solution to that problem. Dad figured it was in the ground system. North Dakota winters cool things down pretty fast...

 

What does the battery voltage do when you attempt to start it?

Read voltage at the battery while attempting to start and post the voltage here.

 

Since you found the starter relay, sometimes there’s a few relays exactly the same close by. You could try swapping them and see if anything changes.

 

While you are under there checking the big wire, you could also check the control wire FROM the relay.
It should be a Yellow-Green wire. It needs power when Cranking.

Also, when you say you have “signal” at the relay.
Are you talking about relay control signal?
You should have power to 2 pin at the relay while cranking.

For now, do as others have posted. Start at the starter.
Let us know what you have

 

Check the engine ground wire.

 

Yes, the ground wire. I had a '96 Pontiac Trans Sport SE (added bells and whistles to the Chevy Lumina and Oldsmobile Silhouette so it sold better) that developed a strange habit with the dash voltmeter showing a slow drop in voltage to zero while driving. Late afternoon one day, while checking the TP and paper towel supply in the public restrooms, I heard a guy in one of the stalls talking about a similar problem with a Chevy Lumina, so I asked him about it. Based on his advice, I crawled under the minivan, loosened the wires on the alternator-starter unit, administered spray cleaner, and secured the wires. Sometimes just a little corrosion on a terminal... Check the cable connection at the battery terminal, too.

 

I appreciate the responses!

The battery voltage does not drop when I turn the key and it doesn't crank.

I've created some extensions for the relay to the fuse box so I can probe the wires. When it is working, the relay gets voltage and clicks over. When it is not wanting to crank, there is no voltage to it and no click.

Where could I find the pinout or diagram?

 

Here you go.

 

Start with the easy first. Which would be power to the STA Fuse. (It will probably be fine)
Then go down to the Neutral Safety Switch (NSS) on the transmission and check the Purple wire for power.
If the Purple wire has power, check the Black/Yellow wire for power.
The connector should be plugged in when checking the Black/Yellow wire.

NSS look like this.

 

I've disconnected them and cleaned the contact points up with a bit of sand paper just to be sure. There was a bit of rust.

Thanks!

Pin 2 reads continuity to ground

While it is in this no crank/no start state - and I supply pin 1 with 12v using a momentary switch while turning the key in the start position, it will crank over and start. If I try to crank it without the momentary switch, it does not crank.

If I wait an hour or 2, then it works without the momentary switch to pin 1. I still have to let it run for a while and warm up before it stops wanting to crank/start.

I'm confused.

 

Thanks! I will do this next.

A quick search on the neutral safety switch looks to match my no power to the starter relay issue.

 

No problem, that should help you diagnose the Pin #1 problem.

 

Do 05's have an anti theft system with a flashing red light in the centre console that flashes every 5 seconds or so when there is no key in the ignition (09 and later second gens do)?
If so, make sure the light is goes out when your key is in the ignition. The 09+ models have an issue with the anti theft ecu that disables the main ecu from sparking, although the engine will still crank over.
Third gens have an issue with the ignition barrel heating up and not communicating with the main ecu. This also throws a code.
Both of the above often happen if the key has been left in the ignition and it is hot out. I know you say yours will not crank over, but this is pretty easy to check and rule out.

 

makes sense as a possibility if vehicle can't read the key.

Another option might be a sensor. In general (don't know if this applies to the Taco) vehicles can struggle to start after years/miles when hot if there is an issue with a CPS, whether cam position sensor or crank position sensor; mainly crank position sensor.
Because ECU's can have default values to assume where the cam is at if it's sensor is dead, or calculate that information based on the values of other sensors.
Whereas a crank sensor is more important, to know what position it's at. And can even make the car die while running.

re: grounds yes they can come loose, become corroded, have wires torn or bitten through by rodents, or someone at a body shop forgets to bolt it back up, but it's not common

 

Based on this, my guess is a nss going out. If you have a multimeter, it’s easy to check it. I’ll bet there’s all kinds of resistance in the switch. When mine was giving me the same symptoms, manual transmission so it’s a clutch pedal switch, I bypassed it at the relay. I didn’t like having to stomp the clutch to start it anyhow.

 

One could test it and see?
https://www.tacomaworld.com/threads/p0705-code-and-subsequent-cel-issues.687466/#post-24501335