High rev at start up

[Bill22H]

After driving our Chevy 4500 for around 4 hours and stopping for a rest break, the vehicle will not start after at least 15 minutes of rest time. The dashboard lights appear as normal when the ignition key is turned, but nothing happens beyond that. The battery has a good charge. I have to let it sit until the next morning, and then it starts on the first attempt. This has happened three times now. It has occured the same way and resolved the same way each time. Could there be a defected part in the ignition system that only becomes problematic after long periods of driving and resolves its issues after a long cool down period?

[carriedi]

I don't have wiring for the 4500 but the wiring for the 3500 shows a starter relay in the underhood fuse box. Next time it doesn't want to start try switching the starter relay with another relay that is the same as the starter relay. Look for one that says it's for a non-essential system like a horn or headlight relay. then if the starter does work then you know the relay is going bad. If that isn't the problem then you will need to have the starter circuit checked and find the open in the system when it won't start.

the problem is that when you take it in to be checked it has to not start in order for them to find the problem. if it starts every time they check it, all circuits will show up as good. they can only find the problem when it is happening.

[JimmyO]

2001 chevy silverado hd 8.1l....high rev at start up. New fuel pump...all fuel lines....injectors....fuel pressure regulator....throttle body....tps.

[carriedi]

how high is "high rev"? How long does it stay on high revs? Do you know why the revs come down to normal or does it come down to normal?

Is the check engine light on? Any codes like p1508, p1509 or anything?

Those parts you list, are they parts you already replaced or are they parts your checked and they are all good?

Have you hooked it up to a scanner and graphed what the computer is seeing when the condition exists?

When did the problem first appear? before, during or after you change any parts?

[Guest]

I have a 2016 Chevrolet Silverado v6 work truck. Where is the coolant fan relay?

[carriedi]

they show a cooling fan module relay but the wiring diagram shows the relay built into the fans

[smurray]

2014 Chevy 1500, replace thermostat, and Coolant temperature sensor. Started vehicle, temp cage reads 200, fans don't come on and hoses do not get hot, when driven temp does not rise higher than 204

[carriedi]

are you saying that the gauge reads 200 before the engine gets warmed up? Like, when you key on engine off, on a cold engine? If that is the case you should use a scanner to see what the computer shows as a temperature reading in degrees. See if the gauge matches the computer reading. Also, if the engine has been sitting for over 8 hours, or overnight, check the engine temp. and the intake air temp are close to the same reading. (within 16 degrees)

If you get a 200 degree reading from a warmed engine, that would be okay. Running at 204 would still be okay. The thermostat is set for around 200 degrees before it opens.

Do the fans come on when you turn on the AC? Does the heater have air out of the vent when you put the heater on hot and your gauge says 200? Heater fan on low, you should have 160 degrees out of the vent or hotter.

Do you have an infrared temp gun you can measure the temp on the thermostat housing?

Do you think your engine is running cold or do you think your engine is running hot but the gauge is wrong and the fans aren't cooling the engine?

[bengrate]

At 31-44 mph I hear a faint motor start up for 5-7 seconds and then go off and then repeat again. Checked wheel bearings and jerking steering wheel. A recall at 58k on the power steering was updated. Is this a ghost or is it supposed to do this? Vin 3gcuksec8fg384995 LTZ 4x4 duel cab

[carriedi]

you might have to have someone drive your vehicle so you can listen for the noise to see if you can narrow down where the noise is coming from.

A worn door actuator for the climate control might be moving and adjusting itself.

ABS could be turning on the abs motor to keep the abs pumped up.

It's not the ac compressor turning on is it? Turn the ac off and turn the defroster to the vent position and see if the noise is gone.

Without hearing the noise myself it is really hard to tell you what could be making the noise. You may have to take a mechanic from a shop for a ride and have them listen for the noise and see if they can narrow down where the noise is coming from