I first thought it was the CSP sensor so I replaced that, I then continued to have the random problem, even when cold sometimes it will not start. When the cranking 5 or more tries with no success I tried starting fluid in the TB, it fires up every time I do that when the failure to start occurs. I did the shade tree method of checking fuel pressure and it felt like it was low on pressure and it would not hold pressure for long after turning it off so I bought a new fuel pump and replaced it with the fuel filter. Now its doing the same thing again, I swapped the fuel pump relay round, bi passed the sand resistor with no luck.


What is next?

I am going to go get a fuel pressure gauge today if I can from harbor freight to actually verify correct pressure.

 

"starting fluid in the TB, it fires up every time"

Will it start if you give it some throttle?

 

Check out you TB like Earl said. You can also try the poor mans prime. Turn the key on for a couple of seconds(Not to start Just to turn on the fuel pump) Do this 2 or 3 times then try to start. If it starts after doing the prime you may have a bad flow back valve.

 

When I cycle the key I can only get the fuel pump to turn on twice for about 3 seconds each time. After 2 cycles I have to crank it a little, then I can cycle the key on/off to run the pump another 2 cycles. Throttle open doesn't help either. I've also tried unplugging the tps sensor with no change.

 

I drove the jeep around yesterday hoping to have the problem occur to demonstrate what it is doing on video, I have 3 short videos combined.



The first clip is in front of my apartment, where of course it starts up fine. The next is in front of burger king after I grab a bite to eat, where it starts acting up. It took two tries of the starter fluid to get it going but ran fine once it got going. I also had decent fuel pressure, I tried running with the FPR vacuum unplugged but it did not change anything. Then later yesterday I was on my way to work when it failed to start... I had to walk around the block and jump into my civic (Almost late to work ). I need to get another can of starting spray, I've used 2 cans so far.

Video was taken by a 3mp iphone 3gs camera so sorry about the quality. My 8mp droid is a pos and the battery always lets me down.

 

I unplugged the IAT sensor, IAC valve and unplugged the fuel pressure regulator vacuum. The problem has not happened in almost 2 days now. Shouldn't it not run without the IAC valve not connected? Maybe it is stuck open or something.

 

Iac gets pulses when starting, not quite a wide open pulse but it opens a fair bit during starting. To test, pull off the intake tube, start it, and cover or uncover the little hole for the iac. Alternitavely, unplug the iac, and twist the pintle out untill the little collar is barely out of the body of the iac. Tighten it back in about 1 1/2 turns, and voila. Manual idle speed, garunteed to not change

 

Day 3 failure to start is happening again. I tried about 6 cranks, I then let it roll down the hill and dropped the clutch in 4th and it fired up after about 10 seconds of turning over. It did it again when I stopped for breakfast, about 6 cranks and no hill so I sprayed some starting fluid in the tb and it fired up. Same as I noted before, IAC, IAT, FPR unplugged. Damn Jeep!

 

After watching your video, it appears that you do not have enough fuel pump pressure @ 31 psi as the gauge indicated while you were cranking the engine. Have you changed the fuel pump yet? change out the fuel filter first unless it is part of the fuel pump assy. inside the fuel tank. This appears to be a fuel starvation problem since the engine wants to start & run after you spray the starting fluid into the throttle body. Not enough fuel pressure (psi) to adequately force fuel through the individual injectors, it appears to be so.

 

Well I replaced the pump with a brand new one. I am not sure if the harbor freight fuel pressure gauge is 100% accurate. Most of the time it starts fine with the 30 psi indicated, even when cold. Most of the time the problem occurs when its hot.

 

fuel pressure regulator replaced with a junkyard unit (I bought 2, they were 3.00 each, autozone wanted 60.00) it starts 70% of the time, when it does have trouble now it will eventually start without fluid, just 3-4 cranks. When I disconnect the idle air it has not failed to start yet.

I had the jeep stall out on me, I had to leave it on the side of the road for a week until I found time to trouble shoot it. Turns out my new fuel pump and my install caused all my trouble. If the fuel pump was like the original, it would not have happened... but if I was a little more careful it would not have happened either.


This picture was taken after I removed the pump from the box.



stock pump/sender wires for the pump go straight up from the pump.




The aftermarket had both the red/black wires laying 90 degrees across the top of the pump, which looked normal to me, but under closer inspection the red terminal was too close to the sending unit frame and shorting.