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Old 07-20-2011, 07:10 PM   #1
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Long Cranking Times on 4.0

I've always thought the cranking times were a little long on my Jeep but lately I have noticed at times that it is much longer. Today I cranked it for probably 20 or more seconds and then cycled the key and it started right up. Any ideas on methods for troubleshooting this kind of a problem?

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Old 07-20-2011, 07:33 PM   #2
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Fuel pressure regulator or fuel injectors bleeding down are two likely causes. It seems to be more common for the regulator to fail however it turned out to be the injectors on my 99 TJ 4.0L. The regulator will cost you about $80.00 if you can drop the fuel tank yourself (it's mounted to the top of the fuel pump). If you need injectors you can buy a reman set for about $140.00. I bought mine here: 1999-2004 Jeep 4.0L Upgrade Fuel Injectors
Very good company to deal with!

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Old 07-20-2011, 07:45 PM   #3
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There is also a check valve in the pump assembly that can fail. I replaced the pump and regulator in mine and still had a long crank time. I wound up replacing both pick up filters and took the check valve out, flipped the rubber disk over and reassembled everything. So far it seems to be working ok, but time will tell.
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Old 07-20-2011, 08:03 PM   #4
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Would bleeding injectors show up on a pressure test?
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Old 07-20-2011, 10:52 PM   #5
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Quote:
Originally Posted by scot68 View Post
Fuel pressure regulator or fuel injectors bleeding down are two likely causes. It seems to be more common for the regulator to fail however it turned out to be the injectors on my 99 TJ 4.0L. The regulator will cost you about $80.00 if you can drop the fuel tank yourself (it's mounted to the top of the fuel pump). If you need injectors you can buy a reman set for about $140.00. I bought mine here: 1999-2004 Jeep 4.0L Upgrade Fuel Injectors
Very good company to deal with!
If fuel pressure regulator or fuel injectors can cause a hard start situation, can they also cause the 4.0L to start like it was flooded? After mine has idled for 10 minutes or so with the air conditioner running in this hot weather and is then restarted within 30 minutes to 3 hours after the next shut-down it runs real rough for the first minute or so then clears up nicely for the rest of the drive. Acts either flooded or missing on one cylinder but the "check engine" light never comes on.
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Old 07-21-2011, 04:57 AM   #6
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If fuel pressure regulator or fuel injectors can cause a hard start situation, can they also cause the 4.0L to start like it was flooded? After mine has idled for 10 minutes or so with the air conditioner running in this hot weather and is then restarted within 30 minutes to 3 hours after the next shut-down it runs real rough for the first minute or so then clears up nicely for the rest of the drive. Acts either flooded or missing on one cylinder but the "check engine" light never comes on.
My Wife's Chrysler has spells where it does this and each time it starts doing it I run fuel injector cleaner through it and it clears it up. I believe an injector is sticking open and dropping fuel in the cylinder. On my Jeep though it doesn't act flooded but rather seems to be lack of fuel.
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Old 07-21-2011, 08:13 AM   #7
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There is a tsb fro Chrysler for the rough start up on a hot soak. Inj #3 vapor locks and takes a min to clear. As far as an inj showing up on a pressure test, yes it would show, but you have to follow a test procedure to see is it's an injector or back at the pump. The most common issues are in the pump assembly. Either the reg or check valve.
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Old 07-21-2011, 10:57 AM   #8
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Quote:
Originally Posted by Gorving3 View Post
If fuel pressure regulator or fuel injectors can cause a hard start situation, can they also cause the 4.0L to start like it was flooded? After mine has idled for 10 minutes or so with the air conditioner running in this hot weather and is then restarted within 30 minutes to 3 hours after the next shut-down it runs real rough for the first minute or so then clears up nicely for the rest of the drive. Acts either flooded or missing on one cylinder but the "check engine" light never comes on.
Yes, that's exactly what mine did. Long crank time, then when it finally started it would run rough for about 20 seconds then smooth out and it ran great. I shot in the dark and replaced the regulator first because I don't have a pressure gauge but it was the injectors that curred the problem.
Like BLEVER said the correct way to diagnose the problem is with a fuel pressure gauge and follow the procedure.
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Old 07-21-2011, 05:37 PM   #9
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try this: turn the key to start but don't push the clutch in. Count to three, then push the clutch in. Does it start right up? If so, you at least know it's probably a fuel delivery issue. Either the fuel rail is draining while it sits, or the pump is not priming fast enough.
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Old 07-21-2011, 05:59 PM   #10
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I posted the FSM test procedure on this thread for anyone interested. Planning on going through it soon.
http://www.wranglerforum.com/f5/how-...tor-90101.html
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Old 07-26-2011, 07:13 PM   #11
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try this: turn the key to start but don't push the clutch in. Count to three, then push the clutch in. Does it start right up? If so, you at least know it's probably a fuel delivery issue. Either the fuel rail is draining while it sits, or the pump is not priming fast enough.
Tried this and it starts right up. So sounds like that check valve is allowing the line to drain down. Can you replace just the check valve or is it part of the pump or some other part?
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Old 07-26-2011, 07:19 PM   #12
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Tried this and it starts right up. So sounds like that check valve is allowing the line to drain down. Can you replace just the check valve or is it part of the pump or some other part?
Its part of the fuel pressure regulator thats sits on top of your tank. Actually quite easy to replace once you get the tank down. Just make sure you have close to an empty tank.
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Old 07-26-2011, 07:20 PM   #13
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The check valve is located inside the fuel pressure regulator, which sits on top of the fuel tank. You can buy a new fuel pressure regulator for around $80 from RockAuto Auto Parts which will fix the problem which is way too common on TJs.

This is what the fuel pressure regulator looks like, I had to replace mine earlier this year for the same problem.
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Old 07-26-2011, 08:12 PM   #14
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Does anyone know what the injector leaking sounds like with a stethoscope?
I checked the pressure and it's within spec. In a second or two it is at spec and still cranks for several seconds. Judging from the sound after she starts, I suspect a leaking injector causing a rich condition in one or more cylinders. Mine must be a leaking injector. I would prefer to know before buying a set of injectors.
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Old 07-27-2011, 04:55 AM   #15
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Thanks guys I'm gonna get a regulator. I don't guess there's any tricks to getting the tank down other than running it way low on fuel is there?
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Old 07-27-2011, 05:53 AM   #16
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You might try looking for gas tank skid plate installs, but I believe you use a jack with a board across it to distribute the weight. You should be able to lower it 6" approx to gain access to the top.
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Old 07-27-2011, 12:11 PM   #17
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Thanks guys I'm gonna get a regulator. I don't guess there's any tricks to getting the tank down other than running it way low on fuel is there?
you could always pull the injectors and put paper towels underneath each one, then turn the key to the on position and see if one leaks. that's how i usually test for a leaky injector.
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Old 07-27-2011, 06:12 PM   #18
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Not to be a pain, but does the rail come off with all the injectors? If so, that sounds like the easiest method.
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Old 07-27-2011, 06:54 PM   #19
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Not to be a pain, but does the rail come off with all the injectors? If so, that sounds like the easiest method.
The fuel rail is only pushed on over the tops of the injectors and held in place with the o-ring at the top of each injector. Same with the injectors, they are only held in with o-rings.

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