I have an 02 LS for almost two years now, and it runs great. It sat for over two years before I got it. About 3 months ago I started to have a start up issues when the engine is warm. It starts fine(1-2 cranks) first thing in the morning or if it sits for an extended period(6-8 hours). It will start with in 1-2 cranks if I restart it with in 5 minutes of shutting it off. It cranks excessively (3-5 seconds) if I try after more than 5 minutes and sometimes pops back through the intake. It has never not restarted, even with the longer crank time. To date I replaced the fuel pump and filter (10 months ago) and when I test the pressure it is 55-60 psi for prime and when running. it slowly leaks down to about 10 pounds after 30 minutes sitting, but primes back up to 60 psi as soon as I turn the key on. I replaced the distributer, rotor, cap, ignition module and crank sensor within the last two weeks. All part changes have made it rum better, but has not effected the starting issue. I've had no check engine light on, no codes and all monitors are set during this problem. I have run a few data streams and all systems are within their specs. I am starting to draw at straws as to where to check next, all suggestions are welcome.

 

If you pressurize the fuel pump/system, what is the pressure after a 10 min leakdown test?

Have you measured the fuel pressure when it won’t start to compare it to the fuel pressure when it starts and runs normally?

Check the spark at one of the ignition wire plug ends when everything is good. Look at a 1” gap and note the strength, color and cadence of the spark when you crank it or while it’s running. Do the same thing when it won’t start to compare.

Have you done anything with the ignition coil?

What brand of ignition components did you use?


George

 

From what you described, it’s most likely a leaky regulator or poppet valve. What’s happening is it’s flooding the engine after shut-off, and causing your hard start condition. After a period of time the fuel evaporates and the truck starts normally again.

The next time it does it, floor the pedal while trying to start. That will put the engine into flood mode and cut fuel to the injectors, making it (a little) easier to start.

If anything, it’s always a good excuse to upgrade to mpfi.

Going by what you described, I’d bet against ignition component failure.

 

it has 55-60 psi while cranking until it starts. I have checked that it has spark both from the coil and the distributor while cranking, but not the spark’s quality. Other than testing for spark, I have not done anything to the ignition coil. It is one of the things on my list to replace in the future as it looks to be original. I replaced all of the ignition parts with Standard Motor Products parts.

 

We can help you get your truck fixed but you have to answer all of the questions for us to get to the bottom of your problem without just throwing parts at it. I'm not advocating a new coil at this point.

Again, what is the result of the 10 min fuel pressure leak down test. This was my first suggestion because I suspect that you are not holding pressure. This is also Billy1820's theory.

Also, when you get a chance please get a look at spark at a plug end when it wont start.

George

 

Sorry I overlooked that part of the question. It leaks down to about 37-38 psi after 10, about 22-23 after 20 and about 10after 30 minutes.

 

Then forget about ignition for now, you need to fix your fuel pressure problem.

Next do the portion of the fuel pressure sticky test to see if the fuel pump can hold pressure at the fuel filter location. If the fuel pump can hold pressure then Billy is right and you are leaking at the regulator, the "injectors" or in the plenum "plumbing".

George

 

Thank you for the advice George and Billy, I performed the pressure test at the filter and found it held a steady 60psi for over an hour. I replaced the spider and plenum gaskets today. The regulator was bypassing fuel badly. It now starts and runs better then at any point since I’ve owned it.

Thank you again for your assistance.

 

That was an easy fix, glad to hear you got it running again. Something like this would make a great diagnostic ASE test question

 

Good work, glad you diagnosed it properly.

George