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Old 09-23-2009, 03:31 PM   #1
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Starting problem

Howdy folks, I'm David from the Houston area and I'm new to the forum. I bought a new Sahara 8 years ago and I'm having my first issue. This is my second jeep, my first was a '64 Willys Kaiser pickup that I converted to Chevy power.

My problem is starting the engine after it sits for longer than a few minutes. I check the fuel pressure at the schrader valve on the fuel log and find that the pressure goes away pretty quick.

When this first started happening I could just turn the key on and off a time or two and it would start normally. Now I have to spin the engine once and it starts right up on the second spin.

Doing some simple tests I found that the first time I turn the key on and off there is vapor at the schrader valve, same thing the second time, the third time I toggle the key I get fuel and it will start OK. Spinning the engine the first time apparantly purges the vapor through the injectors. Then it starts great but does idle a little rough for a few seconds, probably getting rid of the last bit of vapor. After that it runs perfect as always.

I know it is most likely a check valve and I'm pretty sure the fix requires replacing the whole fuel pump. Just wondering what kind of job it is dropping the fuel tank and replacing the pump?

Thanks
David

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Old 09-23-2009, 04:17 PM   #2
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Dropping tank isn't too bad, people do it all the time to change the tank's skid plate.

Rokmen.com has a basic video about it.

no comment on the problem at hand. I have no idea if replacing the entire FP is required.

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Old 09-24-2009, 10:27 AM   #3
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Thanks for the info, good stuff.

There is one other less likely cause to my starting problem, that is a leaking injector. I think if I pull the injectors but leave them connected to fuel rail I could activate the pump and do a visual to rule out the leaking injector senario.

Thanks again
David
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Old 09-24-2009, 11:35 AM   #4
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I have a 97' and mine is doing the same thing. At first it would start on first crank now it takes the second or third time to start, then runs rough to same thing. I did a tune up plugs and things so I don't think it's that. I really want to get it taken care of now WINTER is right around the corner.
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Old 09-24-2009, 03:02 PM   #5
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Your on the right track, when you turn the key the first time it allows the fuel pump to run a little while longer before the start. Thats why most likely worked for a long time.
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Old 09-24-2009, 03:35 PM   #6
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Quote:
Originally Posted by NWPATJ View Post
I have a 97' and mine is doing the same thing. At first it would start on first crank now it takes the second or third time to start, then runs rough to same thing. I did a tune up plugs and things so I don't think it's that. I really want to get it taken care of now WINTER is right around the corner.
It seems to be a fairly common problem. There are 3 ways fuel can drain from the fuel system that I know of:
  1. Check valve in tank not holding
  2. Pressure regulator valve not holding
  3. Fuel injector not holding

I believe (from what I've read) that the pressure regulator and the check valve are intergral with the pump, fix is to drop the tank and replace the pump.

I also read a thread somewhere that recommended replacing the pump in our situation. Another Jeep guy chimed in that his problem was similar so he took the advice and had the pump replaced (luckily under warranty) but it did not help his problem, replacing the injectors was his fix. The difference was, when he started his Jeep in the garage, he could smell gas, engine was way rich on a cylinder or two from the leaky injector and unburnt fuel was shipped out the exhaust.

I replaced the spark plugs also. I knew plugs would not cause my problem and I thought Jeep used platinum plugs, I was wrong, the plugs were worn out big time, electrodes rounded and gap was big after 75K. It has platinum plugs now. Credit to modern high energy ignition for firing worn out plugs.

I may go ahead and replace the injectors just because that is easier than dropping the tank and my gas milage is not what it used to be. I'm looking at a set of rebuilt Bosch III injectors for $124.95. Jeep Only - Fuel Injector Connection

While I'm rambling, I was out of town last week and the Jeep started cranking slow, I'm thinking "8 years and never put a wrench to it, now everything happens at once". I was hoping it was the battery and not the starter. Battery was Interstate Megatron bought at Sam's 34 monthes ago. Turns out the battery had a bad cell. Warranty covered most of the replacement cost, new $64.95 battery cost me $28. I told you all that to tell you this, when the jeep was running on low voltage, it ran like crap, stalling out, had to keep my foot on the gas to keep it running. New battery and back to normal, voltage has a big effect on the engine management system.

I'll post the fix when I find it, right now I'm waiting on some input to another thread on how to unclip the wires from the injectors, don't want to break anything.

David
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Old 09-24-2009, 09:30 PM   #7
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Battery a year and half old shouldn't be that. At least hope not! Hell I never changed a fuel pump. Really don't want to have to drop the tank, but might have to. How long will it last I wonder? The pump that is.
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Old 09-25-2009, 09:25 AM   #8
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Battery a year and half old shouldn't be that. At least hope not! Hell I never changed a fuel pump. Really don't want to have to drop the tank, but might have to. How long will it last I wonder? The pump that is.
The thing about the battery is not related to our problem, just a little rant.

If your Jeep runs down the highway OK there is nothing wrong with the pump. The problem is most likely a leaking check valve (or in some cases a leaking injector). The check valve should keep the fuel line full but if it leaks, fuel drains back into the tank.

When you turn the key to on, the fuel pump runs for 3 seconds or so then shuts off until the computer receives a rpm signal that the motor is running. The rpm signal allows the pump to restart and run continuously. This is a safety thing, in case you wreck and the fuel line gets severed it won't continue to pump fuel. When the engine stops, fuel pump stops and doesn't run again until you turn the key off and back on, then fuel pump runs 3 more seconds and stops waiting for rpm signal. Each time you turn key off and back on, fuel pump runs 3 seconds.

That is why, when this first started happening, my jeep would start on first crank IF I toggled the key off and on a couple times, now there is too much vapor in the line, check valve leakage must of increased, so I have to spin the engine which fires the injectors and purges the vapor through the injectors. Vapor gets purged but fuel pressure drops to 0, second time I crank the engine, fuel pump runs 3 senonds, there is now fuel and pressure at the injectors, jeep starts.

To answer your question, there is actually nothing wrong with your fuel pump itself, it is most likely the check valve, but far as I know, to replace the check valve you have to replace the pump, all one unit thanks to Jeep engineers and bean counters.
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Old 09-25-2009, 02:10 PM   #9
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had the same problem with my 98 tj, i replaced the fuel pressure regulator and now it start right up.
i used a motorcycle jack to put under the gas tank to hold it and put it back.
the filler neck was a bit of a pain to put back in as i was lifting up the tank...
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Old 09-25-2009, 05:41 PM   #10
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I also had the same problem with my 99 Sahara. Replaced just the fuel pressure regulator and it's been fine for two years. If it runs fine once it's started I wouldn't replace the whole fuel pump. My fix only cost me $118 for the pressure regulator and took me 2-3 hours. Loic is right, the filler neck is a pain to put back in as you're jacking the tank back up. Not nearly as hard a job as everyone makes it sound.
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Old 09-25-2009, 07:13 PM   #11
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As you surmised, this problem is normally caused by a leaky anti-drainback valve inside the fuel pressure regulator that sits on top of the fuel pump. The fuel pressure regulator can be replaced separately and they are normally easy to find on eBay.
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Old 09-26-2009, 10:37 AM   #12
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Quote:
Originally Posted by Jerry Bransford View Post
As you surmised, this problem is normally caused by a leaky anti-drainback valve inside the fuel pressure regulator that sits on top of the fuel pump. The fuel pressure regulator can be replaced separately and they are normally easy to find on eBay.
Jerry said a key word "fuel pressure regulator". I've been looking high and low for the check valve alone not realizing it was part of the regulator assembly. I don't see any pressure regulators on eBay at this time but I did find one at rockauto.com for $100. There are a lot of adjustable aftermarket regulators but so far only found the one in the picture as a direct replacement. I even read a post where a Jeeper bought his regulator from the dealer for only a little more.

Looks like this thing is external to the tank, don't have to pull the pump?

Thanks for the words of wisdom, I'm on a hot trail now and hope to have this critter treed by next weekend!
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Old 09-27-2009, 01:07 PM   #13
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You still have to drop the tank but it's external. Sits right on top of the fuel pump. You don't have to pull the fuel pump.
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Old 09-27-2009, 09:00 PM   #14
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Quote:
Originally Posted by Wind_Rocker View Post
Jerry said a key word "fuel pressure regulator". I've been looking high and low for the check valve alone not realizing it was part of the regulator assembly. I don't see any pressure regulators on eBay at this time but I did find one at rockauto.com for $100. There are a lot of adjustable aftermarket regulators but so far only found the one in the picture as a direct replacement. I even read a post where a Jeeper bought his regulator from the dealer for only a little more.

Looks like this thing is external to the tank, don't have to pull the pump?

Thanks for the words of wisdom, I'm on a hot trail now and hope to have this critter treed by next weekend!
that was me, maybe 2 weeks ago, at local auto store it would take 5 days to come, I called the dealer and they had it in stock, the orice difference was like $5 so I went to the dealer. you dont need to remove the pump, remove the top "clip/ bracket" and the regulator is just pushed in. I had to use 2 svrew drivers as lever to "pop it off" but becarefull not to break the surrounding plastic. again it is just pushed in ( you'll see )
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Old 10-02-2009, 09:30 PM   #15
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Little update, I ordered a new set of Bosch III fuel injectors from the Fuel Injector Connection (Jeep Only - Fuel Injector Connection). They talk 'em up pretty good and only $125, no core charge. Injectors have caused this problem in rare cases. I installed the injectors this morning and it ran very good, gained about 100 rpms on the cold idle, very smooth and power is good. I went out and started it a couple times after it sat an hour or so, normally it would take two cranks but it was starting instantly, first revolution, I had high hopes that I lucked out. Even took it for a drive to the bank, came out and BAM, started instantly and idled incrediably smooth. Drove my wife over to the grocery store and when I came out 1/2 hour later, took two cranks to start

If you think about it, for the fuel line to drain back into the tank, you probably have to have a bad check valve in the tank and a leaking injector or two. If you have an injector leaking but the check valve is good, its business as usual, you wouldn't know it. Its like holding a vertical straw full of liguid, doesn't matter which end you seal with your thumb, the liquid stays in the straw, its when both ends are open the liquid drians from the straw.

At the grocery store the engine up to temperature, middle of the day in Houston, 90+ degrees, heat soak probably vaporized some fuel in the fuel rail pushed some fuel back into the tank. One thing is for sure, when I do replace the fuel regulator (maybe this weekend) I'm going to have the best running Jeep in these parts! Hey, I highly recommend those Bosch 3 injectors!
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Old 10-05-2009, 09:14 PM   #16
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My 2000 tj started doing the same thing about a week ago and now thanks to all this information I know what to do. Thanks for taking the time to help.

Houston, Tx
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Old 10-06-2009, 11:28 AM   #17
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I bought the regulator yesterday and installed it, problem solved. Picked it up at the local Dodge dealer, $117 ($126.66 after tax). Took about an hour to drop the tank and swap out the regulator.

Note: Chyrsler refers to it as a 'Filter'

I didn't have much of a problem with the filler neck, I removed all 8 screws and took off the plastic recessed backer, whatever you call it. Left a big hole that I could reach in.

Putting it back was simple, I laid under the Jeep and guided it up pumping the floor jack with my foot.

New orings came on the new regulator and a new foam donut, but I had to use the blue fuel line clip from the old regulator, just be careful taking it off the old one. Two large screw drivers was the ticket for popping the old regulator out, put one on either side and gave them a littler twist.

I also found a bunch of sand when I lifted up the old foam donut, I very carefully shop vacced that out of there, danger of it falling into the tank.

Thanks for all the tips, sure helped a lot.
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Old 10-06-2009, 11:53 AM   #18
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Note: Chyrsler refers to it as a 'Filter'
Because the main fuel filter is also located inside that cannister.
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Old 08-25-2010, 05:55 PM   #19
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Sorry to revive an old thread, but is this the fuel pressure regulator referred to?

Jeep Fuel Pressure Regulator - Low Price Guarantee

I'm pretty sure I'm having the same problem and would like to take care of it in the near future.

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