No Start!!!

Hey guys I need some help. My 99 has been having starting problems. It always starts but not on the first try and its mostly after it sits for awhile. I just put in a new fuel pump and crank sensor, but the problem is still there. When the jeep has just been driven it starts right up. Any ideas where I should look?

What brand fuel pump did you install? Reason I'm asking is that I have had nothing but trouble with Airtex units. I use Bosch.

If you have an extended crank time, oftentimes it is the check valve on the fuel pump assembly. However, it can also be other things like the injectors, etc. that are leaking down.

What is the fuel pressure while cranking? If you do not have a test gauge you can rent/borrow one from an auto parts store. The schrader fitting on top of the fuel rail is a very common 7/16-20 used on most GM and Chrysler vehicles.

Its a Bosch fuel pump. And alright i will check the pressure when i find my guage.

The pressure comes up to 50work while cranking and stays around 53 while running.

Those pressure numbers sound fine. Spec is 49 plus or minus 5 psi.

You will have to do some fuel pressure testing to help you isolate whether the "leakdown" is coming from the engine side (injectors, etc) or the tank side.

Leave that gauge on there and shut the engine down and watch it. How fast does it leak down in the first 10 minutes? How about after a couple hours? These are all good data points to help you isolate the root cause.

A fuel pressure gauge KIT (with clamps and adapters) and a factory service manual will lead you through the exact isolation procedure.

I left the guage on and it got to just below 40 in a bout 15 min.

I plugged the jeep in at work and got an asd relay code. Replaced the relay jeep starts great.