Long Crank Time but Good fuel pressure

So I've been having this reoccurring problem with my '00 where if my jeep sits for a short period of time (5mins - 12 hrs) it cranks for a while before starting and the only thing that sometimes helps is if i push down the gas pedal as its cranking but it still takes a bit of cranking to start. cycling the ignition 3 times (aka poor mans prime) does not have any affect on the issue.

BUT...

if the jeep sits for a longer amount of time like (15-24hrs) the jeep starts right up great. Originally i thought it was the fuel pump because the check valve was bad and it would leak down below 30psi within 2 minutes but i have since replaced the fuel pump and the fuel pressure no longer drops that significantly. The fuel pressure remains over 50psi after 5 min of sitting and as soon as i turn the ignition 'ON' the fuel pressure goes back up to 56psi before starting.

I was thinking maybe a bad fuel injector but i did swap out the all injectors for a set that i pulled out of a wrecked TJ wrangler that had been sitting a couple months but had previously ran good with no starting problems.

Any insight here guys?

The last person here who had that same problem had it appear when he picked up a cheap set of 4 hole injectors; solved it by putting in quality injectors. My 95 has always acted the same way, the only 2 things under the hood that haven't been replaced are the injectors and the throttle body. One of these days I'm going to get around to replacing my injectors and im sure that will solve it. Yours being a 00, however, could be a weird computer issue; good luck. 00 and 01s do all kinds of weird things.

What you need is the right mixture of fuel, air, and spark. Instead, of mashing the accelerator pedal (too much air) try holding it about 1/8th open. The IAC repositions when you are cranking. If it is sticky and slow to open you get air starved, in a worst-case scenario you are getting fuel but no air which can flood the motor.
Sticky IAC is a common problem, it usually gets better when the motor heats up and the sludge causing the problem liquifies.
I used to take my iAC out periodically and clean it, I don't bother anymore I just fire up the motor and squirt a little brake cleaner into the IAC opening while working the throttle a little to prevent a stall.

Just a guess someplace to start. Common problem.

Unclewolverine said:

The last person here who had that same problem had it appear when he picked up a cheap set of 4 hole injectors; solved it by putting in quality injectors. My 95 has always acted the same way, the only 2 things under the hood that haven't been replaced are the injectors and the throttle body. One of these days I'm going to get around to replacing my injectors and im sure that will solve it. Yours being a 00, however, could be a weird computer issue; good luck. 00 and 01s do all kinds of weird things.

Click to expand...

This is my vote as well. If the injector leaks while the engine is off, it can substantially prolong the crank time to get the engine to start. I've seen the same thing happen on a non-XJ vehicle that I own. I suggest getting your hands on a set of cleaned and tested stock injectors.

Well guys i just wanted to update this in case anyone has the same issues down the road. I pulled the fuel rail and checked for leak down on the injectors and found that the injector on cylinder #1 was leaking so i swapped it out for one that doesn't leak but it did not fix the problem. I also smoke tested the vacuum system to see if there was any vacuum leaks but i did not find any so now i'm leaning towards the IAC valve which i have cleaned in the past. I'll post again when i get a chance to look into that.

Something to add, if your charging system or battery is weak it can mess with IAC function. The starter takes a lot of juice to crank, if it draws the battery down too much the IAC gets sluggish. Either it isn't charging correctly or the battery is weak. You might want to have your battery load tested. It can be a combination of gummed IAC and a battery that falls way low on voltage when it is stressed (starter cranking).

Alright guys, so update here... I took the throttle body off and thoroughly cleaned It and made sure the map sensor port was clear and I replaced the IAC with a “standard motor products” brand and It did not change a thing. I’m still having extended crank times just as before. Could a crank or cam position sensor?

Possibly, but I'm still scratching my head why it gets better if you let it sit longer.

Might want to try some genuine Mopar sensors!

This is my drill, because I'm bad at guessing - get your shop manual. Assuming your air filter is clean, spark plugs, cap & rotor and wires are good, check for dangling wires grounding. The wires coming up from the O2 to the fuel rail wiring harness are a good place to start. Then open your shop manual and test your sensors: the temp sensor, idle solenoid, MAP and TPS. In my experience, the crank position sensor is good - or you stranded by the side of the road - but test it anyway. If they are good and your throttle body is clean, move to the injectors and test the resistance for each one. You can pull them and use a 9v battery should produce a click unless it's defective.