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Old 07-22-2010, 03:15 PM   #1
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Post HELP JERRY BRANSFORD! Its driving me crazy!!!

Oh great giver of wisdom please help this lowly back yard mechanic. 97 TJ 4.0 std. It started starting hard about a year and a half ago. I did the turn the key a few times to start it for a while . Now I have decided to fix it. I figured it had to be the anti-drain back valve as there is no black smoke when it starts and it runs fine once it is running. So I replaced the fuel pressure regulator. It starts the same as it did before. Also did a tune up including a new coil. Cleaned the cps. And nothing helped . So I bought a gauge to check the fuel pressure. And sure enough as soon as the pump shuts off from primeing the pressure drops to zero. But running I have 49 psi. So I pulled the fuel rail to try to see a leaking fuel injector . None so much as seeped. I'm getting ready to pull my hair out. Is there somthing I'm missing? I admit I love the opportunity to buy new tools and gauges but I want to make them amout to somthing. Please help. Any suggestions or at this point even a hair brained idea will help. I hate to say this but I long for the days of carburators and points. Thanks in advance.
Chris

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Old 07-22-2010, 03:21 PM   #2
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It's either the fuel prime relay or the pump assembly relief valve. Once it's running, it's fine though?

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Old 07-22-2010, 03:36 PM   #3
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I'm having the same issue flipped73 so I'm going to be no help on this.

I was SHOCKED that replacing the fuel pressure regulator (which contains the pump assembly relief valve as described by AzTJ) didn't fix it. I thought about a leaking fuel injector too but when I pulled them and cycled the fuel pump to build pressure, none were leaking. I cleaned them up and replaced a bunch of fuel injector o-rings but it's still doing the same thing. I even swapped the fuel injectors around which changed nothing.

A friend has suggested it could be a leaky air intake manifold but that doesn't make any sense to me.

Whatever it is, my fuel rail loses pressure too and it misfires for a while after starting it up but then runs ok once fuel is flowing through all the injectors. Even though I replaced that anti-drainback valve via the new fuel pressure regulator, the usual cause of this problem, the problem still exists so I am as confused by it as you are. I have to cycle my fuel pump 8-10 times before the Jeep will even start and it IS aggravating.

So you and I are in the same boat, I hope you find it real soon and tell me what it is.
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Old 07-22-2010, 03:39 PM   #4
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Jerry, you're having the same issue with your new TJ?
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Old 07-22-2010, 03:41 PM   #5
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Leaky air intake manifold doesn't make sense here, either. When mine went bad it whistled. . . LOUD enough to be a PIT ears. good luck
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Old 07-22-2010, 03:49 PM   #6
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Jerry, you're having the same issue with your new TJ?
Yes and it is driving me absolutely nutso.
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Old 07-22-2010, 03:55 PM   #7
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Yes it runs fine after it starts. We just drove it about 250 miles round trip on vacation. Watching the gauge the fuel pressure is there when the pump primes but as soon as it's done with the prime cycle the pressure drops to zero. Also on a side note. In order to get the fuel pressure regulator fast I got it through NAPA. I was chewing out the salesman about the price and he got it out of the box to see if it was made in the USA and found it is a Chrysler oem part with all the Chrysler numbers the pentagram and all on it.
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Old 07-22-2010, 05:09 PM   #8
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I had another vehicle with a similar problem. Everything checked out but something was still wrong. Alas I decided to start in the back and work forward.....First, changed the electric fuel pump...THAT WAS IT. Even though the old one pumped it wasn't enough to keep up. So I say start there, they are relatively inexpensive and somewhat easy to change....Good luck to you all.
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Old 07-22-2010, 09:33 PM   #9
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Obviously if it's not leaking through the injectors, and it's not running out to the outside world, then it's draining back to the tank.

Isn't there a check valve back by the tank?

Try parking it pointing downhill to where the tank is higher than the fuel rail, if it stops doing it, it's draining back to the tank.

Since air is thinner, a small leak in the fuel line can let air in without letting fuel run out, allowing the fuel to run down back to the tank.

I had a Cherokee that did the same thing - but the pump is a little different. It has a 4" rubber hose inside the tank - it got soft and mushy and leaked. That's the difference between a cheapie pump and a quality one - the cheapie (Autozone) didn't have a hose made for fuel - it was a hunk of vacuum line - and dissolved.

As far as I know, TJ's don't have that rubber hose inside the tank.
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Old 07-23-2010, 12:49 AM   #10
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Rich, the TJ's fuel check valve (aka anti-drainback valve) is inside the fuel pressure regulator that sits on top of the fuel pump. That's the first thing I thought of and $90 and a new fuel pressure regulator later, it didn't help at all. Symptoms are the same as before I changed it. The is the only check valve I am aware of in the system and replacing it usually fixes this problem. I'm almost thinking the new fuel pressure regulator might have been bad too. What else could it be? I'm sure it seated all the way down into the fuel pump, the clip snapped into place that holds the regulator down and properly seated into to the fuel pump. I just don't see anything else letting the fuel drain back down into the tank since I already checked the fuel injectors for leakage. And this '04 4.0L engine is new enough to not have the Schraeder valve on the fuel rail so I could attach a fuel pressure gauge to monitor the pressure.
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Old 07-23-2010, 01:00 AM   #11
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I have to prime mine twice to start it. I guess I'll look into replacing the regulator.
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Old 07-23-2010, 03:57 PM   #12
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Ok so I asked my buddy to read this and see what he though. I decided if Jerry needed help it was my mission to help, seeing as he has helped me multiple times. He is a diesel tech at AutoMax and graduated from UTI about 5 years ago. So he is pretty knowledgeable. This is what he told me....... "There is a check ball in the fuel sender and if the fuel pressure is dropping when u turn the key off then for whatever reason the check ball is the problem". I hope this is a fix for u guys or gives u a new idea as to what it could be.
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Old 07-23-2010, 04:23 PM   #13
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That has already been discussed, and the first response that I gave.
But thanks for at least helping.

Like I said though, it could be the fuel prime relay.... or possibly even the auto shutdown relay they both work together.

From my 97 TJ FSM
Quote:
AUTO SHUTDOWN (ASD) RELAY-PCM OUTPUT
The ASD relay is located in the Power Distribution
Center (PDC) (Fig. 2).
The ASD relay supplies battery voltage to the fuel
pump, fuel injector, ignition coil and both oxygen
(02S) sensor heating elements. The ground circuit for
the coil in the ASD relay is controlled by the Powertrain
Control Module (PCM). The PCM operates the
ASD relay by switching the ground circuit on and off.

FUEL PUMP RELAY-PCM OUTPUT
The PCM energizes the electric fuel pump through
the fuel pump relay. Battery voltage is applied to the
fuel pump relay when the ignition key is ON. The
relay is energized when a ground signal is provided
by the PCM.
The fuel pump will operate for approximately one
second unless the engine is operating or the starter
motor is engaged.
The fuel pump relay is located in the Power Distribution
Center (PDC) (Fig. 2).
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Old 07-23-2010, 04:26 PM   #14
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I think my last post this morning didn't get posted.

"Try parking it pointing downhill to where the tank is higher than the fuel rail, if it stops doing it, it's draining back to the tank."

Or use a jack to lift the rear. Jack it up while it's still running, then shut it off. Wait the time it takes to drop pressure, then restart it. It won't fix it, but it will prove or disprove it's flowing back to the tank.

Meanwhile don't fight it and wear out the starter - give it a shot of propane to get it started.

I wonder why they eliminated the Schrader valve, it was useful.
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Old 07-23-2010, 05:12 PM   #15
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Thank you RoSs, the check ball your friend mentioned is a good suggestion but that is the check valve, aka anti-drainback valve, which is located inside the fuel pressure regulator. I already installed a new fuel pressure regulator which contains the check valve and it didn't change the symptom at all. It could still be that since I am now somewhat suspicious that the replacement fuel pressure regulator (which contains th check valve) might have been defective.

AzTJ, the fuel pump and ASD relays are fine, I already tested them and swapped them around anyway just for grins. No changes.

Rich, I can tell it's draining back into the tank just by being familiar with the issue. And I don't need to crank the starter excessively, I prime it with 6-10 cycles with the fuel pump via the ignition switch. PITA but at least it starts ok after that ritual which has become a habit now.

At this point, I'm pretty well nearly convinced the new fuel pressure regulator might have simply been defective or, perhaps, I just didn't get it fully seated properly into the fuel pump so its o-ring seats. It seemed to snap into place ok as expected but...

Once I get my lockers working (the compressors are not yet running) hopefully this weekend, I'll just order and install another fuel pressure regulator from eBay for $50 which is $40 less than what the first replacement cost from RockAuto Auto Parts. It wouldn't be the first time I received a defective replacement part.
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Old 07-23-2010, 05:20 PM   #16
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Worth a shot, was one of the last things I'd think of, unless there is some other electronic wizardry that the newer TJ's have in them.
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Old 07-23-2010, 05:32 PM   #17
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... unless there is some other electronic wizardry that the newer TJ's have in them.
That's what worries me, the new Rubicon and it's new ways of doing a lot of stuff makes me feel like a rank newby amateur. Just like its Rube Goldberg electrical circuit for powering/controlling its two locker compressors that obviously the frigging lawyers designed. I never thought I'd have to wire up my own locker control circuit but it's looking that way now.
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Old 07-23-2010, 05:36 PM   #18
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^

Yeah I know how you feel. Damn XJ is giving me troubles and I think it's the fancy pants AW4.
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Old 07-24-2010, 10:35 AM   #19
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For general FYI, I just learned from the FSM that there is a second fuel check valve at the top of the fuel pump, just below the fuel pressure regulator that also has a check valve. Both are there to maintain fuel pressure at the fuel rail for quick starts.

Since my gas gauge is also extremely far off, showing the tank to be half-full when it is just below full, and empty when it still has a half-tank of gas, I might just replace the whole thing now... fuel pump and fuel pressure regulator. Between both of those, it better fix the slow start and temporary (right after it starts) misfire issue.
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Old 07-24-2010, 02:00 PM   #20
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My old 98 Grand Cherokee 4.0, did the same thing i drove it like that for a year with no issues, then sold it and got my TJ, and the guy who bought my GC said his sons cherokee 4.0 did the same thing for years and they still drive it,go figure
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Old 07-24-2010, 04:57 PM   #21
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While I can understand just how annoying it can be, the up side is, it makes a great theft deterrent!! Jerry, you can leave your rig at work and nobody will be able to start it.
(just kidding of course)

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Old 07-24-2010, 11:32 PM   #22
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For general FYI, I just learned from the FSM that there is a second fuel check valve at the top of the fuel pump, just below the fuel pressure regulator that also has a check valve. Both are there to maintain fuel pressure at the fuel rail for quick starts.

Since my gas gauge is also extremely far off, showing the tank to be half-full when it is just below full, and empty when it still has a half-tank of gas, I might just replace the whole thing now... fuel pump and fuel pressure regulator. Between both of those, it better fix the slow start and temporary (right after it starts) misfire issue.
Is this for '97 or all TJ's Jerry?

Yah know, this got me thinking. Might be the reason I smell gas pretty strongly after a short drive after filling up. Might have to drop the tank and take a peak.
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Old 12-03-2010, 11:55 AM   #23
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Has anyone tried installing an aftermarket check valve in the line right outside the tank between the engine and FPR? My diesel teacher told me that should solve it. I'd like to avoid replacing the whole sending unit for 400$ but I already know my problem is the inner valve. Just a thought.
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Old 12-03-2010, 12:06 PM   #24
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I had the problem similar on one of my yj's...replaced the pump, no more issues
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Old 12-03-2010, 12:21 PM   #25
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Same kinda thing happening here. I just learned to turn the key to run for a couple seconds then crank it. Works everytime. Gonna put in a new module in the spring when the weather is a bit nicer to crawl around under it.
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Old 12-03-2010, 12:34 PM   #26
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Jerry - this was an old thread - revived now.
You last said you were going to replace the entire pump assembly - did that cure it?

I was going to suggest disconnecting the fuel feed line underneath - right about under the driver's seat - I think there's a hard line splice there. Then put a gauge on the tank/pump side blocking it off.
If it still loses pressure there you know it's not a leaking injector.

I recently replaced a Cherokee fuel pump - easy, you don't have to drop the tank. The first new one drained back, (the old one was totally dead.) The 2nd new one drained back too - making me look elsewhere (pressure regulator is on the fuel rail.) But it always came back to the pump. 3rd pump - did the trick!
And they were new NAPA pumps, not Autochina's junk!

Tip: Cherokee's pumps have a short piece of rubber hose on them - inside the tank. The cheapo pumps use vacuum line for it. Gasoline eventually dissolves the rubber and leaks. Whenever the pump is removed, put on real gas hose.

Some TJ's or YJ's may use the same setup - as well as at least one Dodge truck I've seen.
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Old 12-03-2010, 04:22 PM   #27
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my jeep is doing that too and it started only recently. My fuel pump is been replaced and its a mopar one straight from the dealer and then after 2-3weeks the problem started. it only happens when the jeep has been parked for hours like more than 10 because it only happens early in the morning.
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Old 02-14-2011, 02:52 PM   #28
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Was there any resolution to this issue? My '97 Sahara is doing the exact same thing. I have a hunch that it is my ignition switch though. I have to cycle the key a few times while cranking it and then it will finally fire off. Once it's running, it runs great. The reason I think it is my ignition switch is because even sometimes after I get it started, the radio will not come on and the accessories will not work (wipers etc). If I fiddle with the key just a bit, everything powers up.

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Old 02-14-2011, 06:46 PM   #29
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Sorry guys. I never replaced the whole fuel pump , sending unit assembley. But it does work better in the winter. If I get around to affording it this summer I will replace it all.
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Old 02-14-2011, 07:08 PM   #30
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Jerry - this was an old thread - revived now.
You last said you were going to replace the entire pump assembly - did that cure it?
Yes it did but it turns out I didn't need the everything like I ordered (fuel pump, fuel pressure regulator, and gas gauge sender), just the fuel pressure regulator. When I got the old entire fuel pump assembly out, I tested the fuel pressure regulator that I installed a few months ago that I thought should have fixed it but did not. It turns out the new fuel pressure regulator I installed that I bought from Rock Auto months back was frigging DEFECTIVE!!! I was able to blow through it in both directions which meant it was letting the fuel drain out of the engine and back down into the gas tank. It was a bad fuel pressure regulator all along, what I thought the problem was caused by originally. Getting that bad one from Rock Auto was really discouraging since all symptoms pointed to it being bad so it lead me on a wild goose chase checking other parts of the engine like all of the fuel injectors. It was a bad fuel pressure regulator all along... the original and the replacement. As they say, the third time's the charm.

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