97 k2500 454 hesitates to start when hot

[GMC Guy]

my 97 3/4 ton with 106k sometimes hesitates to start back up after running. it's not the starter, just engine kinda boggs down but then picks back up and starts running fine. i was thinking either injectors, fuel pressure reg, or...?
is there anyway to narrow it down? i'm not exactly excited about spending $300 on a new set of injectors, but i will if that's the problem.

[speedygonzales]

So first start in the morning after sitting all night is not a problem?

Does it have to crank longer than normal when you have the probem?

Does it seem once it starts when you're having the problem, to run slower and possibly rougher than normal and then pick up and run normal after a short time?

[ChevyTech]

It could just be a bad fuel pressure regulator. Test the fuel pressure and see if it drops as soon as the pump stops running with the key on – engine off (KOEO).

[GMC Guy]

Originally Posted by speedygonzales

So first start in the morning after sitting all night is not a problem?

Does it have to crank longer than normal when you have the probem?

Does it seem once it starts when you're having the problem, to run slower and possibly rougher than normal and then pick up and run normal after a short time?

first start in the morning is normal. doesn't crank longer, cranks like normal but putters for a second and then picks back up and comes to life. i don't really notice any difference with the way it runs after the start up.

Originally Posted by ChevyTech

It could just be a bad fuel pressure regulator. Test the fuel pressure and see if it drops as soon as the pump stops running with the key on – engine off (KOEO).

how do i test the FPR?

[speedygonzales]

There are 3 reasons why the pressure drops after start up. You don't have a long cranking issue in the morning so that eliminates the fuel pump check valve.

The other 2 reasons are FPR and injector. So just doing a pressure test to see if it drops after shut off will not tell you conclusively if it's from the FPR or an injector.

You would have to look at the injectors out of the unit to see if they are dripping. If you could get to it, drawing a vacuum on the FPR vacuum line could tell you.

You could also look at the plugs to see if they are sooted up.

[GMC Guy]

so it looks like i'm just going to have to have to replace fuel pressure reg and injectors?

[powerdriver 1958]

I hope I didn't misunderstand but are you saying while the engine is spinning with the starter its slows down or sounds like it grunting extra hard ?

[GMC Guy]

starter spins like normal, but engine acts like its flooded for a second or two, then comes back to life and runs normal

[ChevyTech]

On many of the GM multiport fuel injected systems if the fuel pressure regulator gets a leak in the diaphragm, the fuel leaking to the other side of the diaphragm will drain into the intake through the vacuum hose to the regulator. This makes them flood a bit when started hot. After the vehicle cools down the fuel has evaporated and they start better.

This is a fairly common problem.

On some vehicles the regulator is out in the open and you can easily unplug the vacuum line and see if fuel drips out. On your big block it is on the back and is not easy to see or work on. It would not be impossible for you to get to, but most people can’t do it the first time without removing the upper plenum.

I have a clear container I can put between a hand vacuum pump and the regulator to watch for fuel when testing.

[GMC Guy]

how hard is it to remove the upper intake plenum? will i need to replace any gaskets?

[ChevyTech]

Do it without removing the plenum.

Get the distributor cap out of the way.

Lie on top of a cooled down engine and look at the driver’s side by the distributor. The regulator is there. The photos in the link below should help.

No fuel should come out when the vacuum line is disconnected from the regulator. If it does the regulator is bad. Cycle the key several times with the line off and see if fuel comes out. Put a vacuum on it if you have the equipment.

Here is a link that may help you:
http://www.chevytalk.org/fusionbb/sh...f45815bd7d05b/

[GMC Guy]

just laid on top of the motor and looked down by the distributor, looks like i have to pull a lot of hoses/wires out of the way to even see it?

[GMC Guy]

well i think i'm going to wait and replace the injectors along with the FPR. just do everything at the same time.

http://www.autozone.com/autozone/par...er=221962_0_0_
or
http://www.summitracing.com/parts/SMP-PR217/
&
http://www.fiveomotorsport.com/product-search/?v=10838

[ChevyTech]

I don’t like spending money on parts, unless the old parts are bad.

I would put a fuel pressure gauge on it and see if the pressure holds without the engine running. If the pressure holds you need to look elsewhere for the cause of the starting problem.

Don’t assume you know what the problem is without testing.

It could be something as simple as a coolant temp sensor failure.

Looking at the data and possible codes with a scan tool would be a good idea.