No start only when hot

BRUDICUS

MEMBER
1996 CHEVROLET SUBURBAN
0.5L
V8
4WD
AUTOMATIC
20,010 MILES

Hi, I've been having this issue where it will not start back up when it's hot only. The next morning it starts up and runs fine. A shot of starting fluid has worked in the past but not this last time and when it does using starting fluid it doesn't sound good at first "knocking" then smooths out and runs fine. I'm feeling like it's flooding, but why? I did notice that my fuel pressure reads 56 PSI running and after shutdown it jumps to 61 and stays for what seems like way, way, too long. I have no codes. Thank you very much.

Thursday, July 22nd, 2021 AT 5:11 PM

2 Replies

JACOBANDNICKOLAS

MECHANIC
110,176 POSTS

Hi,

I need to know if this is the 5.7 gas engine or the 6.5 diesel.

Also, if it is flooding, you should smell a really rich fuel mixture from the exhaust and even see gray or black smoke from the exhaust.

As far as fuel pressure, normal pressure on the gas engine 5.7L is between 56psi and 62 PSI, so you fall within the manufacturer's specs. See pic 1 below.

Now, I want you to take a look through this link. It describes the most common symptoms related to a failing/bad crankshaft position sensor. When they start going bad, they can fail when they get hot. Keep in mind, when you turn the engine off, for a short period of time, the engine actually gets hotter due to the coolant not circulating. That could be enough to cause the sensor to fail until it cools off.

Take a look and let me know if this seems to mirror your symptoms.

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

Let me know your thoughts after reviewing the link.

Take care,

Joe

See pic below.

Image (Click to make bigger)

Was this

answer

helpful?

Yes

No

Thursday, July 22nd, 2021 AT 8:36 PM

BRUDICUS

MEMBER
2 POSTS

I read the description and I can't say it matches my symptoms though. It has never stalled or ran rough. It just won't start when heat soaked until the next morning and fires right up and runs great.

In that case should I still be looking at the camshaft sensor? So far I've read that the ignition switch module and distributor module will do this along with the absolute manifold pressure sensor.

I've replaced the cap, rotor, plugs, wires, engine coolant temperature sensor so far.

Thanks!

Was this

answer

helpful?

Yes

No

Friday, July 23rd, 2021 AT 6:00 AM