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dmw319 07-07-2010 01:39 PM

Fuel Pump problem - help!
Hey everyone. Newbie here. My name is Dave I just bought a 99 wrangler 2.5L. I bought the car from the owner who said the fuel pump needed to be replaced. He had the car sitting for about 2 months, but the day we bought it he went and took it to the gas station to fill it up. When test driving the car, it started up just fine but then when we were driving it it stalled and we couldnt get it to crank back up. However when it got towed to my house this morning the tow truck driver backed it up off the flatbed and drove it right into my garage no problem.

I have searched/read on here that it may be the fuel pressure regulator on top of the pump that needs to be fixed, or maybe i need to replace the whole pump? Any ideas on how to best diagnose the problem before I buy any parts and drop the tank? We really need to get it fixed tonight if possible - I've got plenty of tools and friends to help. haha. Thanks!

Jerry Bransford 07-07-2010 01:59 PM

While that problem COULD be from a bad fuel pump, it may not be and it's definitely not the fuel pressure regulator causing that problem. The engine computer is what turns the fuel pump on and off and if the engine computer is not happy with what all the sensors are telling it, it will shut the fuel pump off via the ASD (auto shutdown) relay.

I'd start looking at the two most likely sensors that can cause this type of problem. First being the Crankshaft Position Sensor that generates the engine's master timing signal. It is mounted up high on the driver's side where the transmission bolts to the engine. When it goes bad, the engine will stall/quit which can happen intermittently. The second sensor is less likely to go bad but when it does, it causes the same problem. This one is the Camshaft Position Sensor which is mounted underneath the distributor cap, under the rotor.

Those two sensors would be high on my list of possiblities. And a big welcome to WF. :)

dmw319 07-07-2010 02:08 PM

thanks Jerry! what makes you think it isnt the regulator? or pump? the guy i bought it from said that he had taken it to a shop and thats what they told him (although, i dont know the validity of the shop)

i had read this post before posting (which is why i was asking):

I will check into those sensors. are those sensors I could buy at any auto parts store and swap out real quick to see if the problem is fixed? could i possibly check the fuel pressure to help diagnose the problem? thanks again in advance.

a little more about the car also.. its intense blue, fresh motor (less than 500 miles on it), 76,000 on body, 33 inch bfgoodrich all-terrains. new exhaust, bestop, PIAA lights, detroit locker front and back, 3.5 inch suspension and body lift. i hope to get pics up soon!

A_Mason 07-07-2010 02:14 PM

Based on your description what you bought defintely is not a "car". You might take it to Autozone if you can get it there and have them check your diagnostic codes. They will do it for free and it might give you some hints about where to start.

Jerry Bransford 07-07-2010 02:23 PM

It's not the fuel pressure regulator because when they go bad, they don't stop the flow of fuel like the fuel pump underneath it can. When the fuel pressure regulator goes bad, it normally just causes very slow starts but once the engine is running, it's fine.

Yes pretty much any auto parts store can get those sensors if they don't have them in stock. BUT where sensors are concerned, I prefer the OE sensors as some of the aftermarket sensors are very poor quality. Some websites like RockAuto Auto Parts often sell OE sensors for a lot less than the dealer will.

dmw319 07-07-2010 02:31 PM

what do you mean when you say "slow starts"? I haven't honestly spent enough time with the car to give an accurate description of the problem, I am just trying to get as much info about what could be wrong while im at work so I can get working on it when I get home.

Jerry Bransford 07-07-2010 02:34 PM

Slow start = it takes a lot of cranking time for the engine to actually start when the fuel pressure regulator has gone bad. They get leaky when they go bad and let the fuel drain down out of the engine and back into the fuel tank... hence the slow start.

dmw319 07-07-2010 02:43 PM

yea, that makes sense. When I get home around 6 I will try and get it going again and post back up. are these cars obd2? I could use a scanner to pull some codes, if it has any. which ones would I be looking for that would point to one of the sensors being bad?

Jerry Bransford 07-07-2010 02:48 PM

Yes our Jeeps are OBDII. I suggest not calling your Jeep a "car" as they (and most Jeep owners) are very sensitive about such things. ;)

dmw319 07-07-2010 02:49 PM

Haha, I can see that. Sorry guys, it won't happen again! Today is my first day owning a Jeep :)

dmw319 07-07-2010 03:50 PM

question - how do you know if you have a 15 or 19 gallon tank?

Jerry Bransford 07-07-2010 03:53 PM


Originally Posted by dmw319 (Post 680095)
question - how do you know if you have a 15 or 19 gallon tank?

That's hard to say but most TJs came with the 19 gallon tank. Only the really stripped down models came with the 15 gallon tank.

dmw319 07-07-2010 03:57 PM

hmm. is there any way to find out?

Jerry Bransford 07-07-2010 04:03 PM

Uh, carry a gallon container of gasoline and then drive it until it runs out? Then you can refill it and know for sure. The gauge will show empty even when there are 1-4 gallons left in the tank so don't use the gauge as the indicator. My way-off gas gauge shows empty now when there are close to ten gallons left in the tank. :eek:

dmw319 07-07-2010 04:06 PM

haha well that would work if the car worked well enough to drive around haha.

dmw319 07-07-2010 04:14 PM

measurement of tank? tell from something else on the vehicle? etc. I have just seen a lot of parts stores online that keep asking for 15 or 19 gallon tank size when looking at fuel pump assemblies and such, just trying to see if there is any other way to find out than the obvious way haha.

dmw319 07-07-2010 11:41 PM

anyway, UPDATE:

We checked the fuel pressure and it was fine.. so we were able to start the car no problem and have it sit in the garage and it would run with no issues other than an occasional hiccup during idle, but kept running. revved it, let it sit, started right back up again, so we took it for a test drive. got about 1 minute down the road and the car died again. We unplugged the IAC and no change. Then unplugged the MAF and the car started right up and ran fine and then we drove it 15 minutes without any issues. Think it could be the MAF? Kinda strange how I don't think it has anything to do with fuel anymore.. I guess tomorrow we can test a MAF once a part store is open..

dmw319 07-08-2010 09:43 AM

here is a picture: Lauren's new jeep! on Twitpic

dmw319 07-08-2010 05:20 PM

also, i mean MAP not MAF, sorry. BUMP!

dmw319 07-28-2010 03:17 PM

bump. car still isnt fixed. anyone with any more ideas?

wyomeeks 07-28-2010 11:27 PM

I think you hurt your "JEEP'S" feelings and won't run because you call it a "CAR''.... Maybe try calling it a jeep and it might run for you???? Just a thought? lol :banghead: :p

dmw319 07-29-2010 08:41 AM

yea yea the JEEP i mean.

soberleaf 12-02-2014 11:13 AM

I am having same issue with 97 wrangler. when you say MAP instead of MAF what are u referring to please. just put new pump on mine 2 years ago and mine is having same symptoms as listed above. gonna pull tank off again and was gonna change fuel pump again but if it could be sensor need to know what to check. thanks

soberleaf 12-02-2014 11:14 PM

understand it now
manifold sensor

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