Time for a fuel pump?

My '96 4.0 has become reluctant to start first time of the day. Today I uncapped the Shraeder valve on the fuel rail before turning the key, and nothing came out. I then primed the pump a few times, and got a good spray out of it. (Our other '96, sitting since Saturday, still had good pressure at the rail). Then, I tried to start it, and it cranked a little, and fired up just fine. It starts and runs fine the rest of the day.
Do these fuel systems have a check valve involved also, and is it replaceable? The pump still sounds strong when primed, but loses pressure overnight.

pretty sure the check valve is internal. might be wrong. it should hold pressure as stated.

It's internal... welcome to '96 hell. 95-down the FPR (and check valve if present, iirc) is on the injector rail, 97 up it's on the pump but external... 96 is the odd year out that got the short end of the stick!

Haven't pulled my old fuel pump assembly apart but it's sitting in one of my jeep parts bins at home. I'm planning on using it on my compressor/generator project so I'll have to take a look at it sometime in the next few days.

You can always just add a second check valve in the line right before/after the external fuel filter.

Seller jbass195 on eBay, 3/8" inline check valve, $14 plus $2 s/h.

joe_peters said:

Seller jbass195 on eBay, 3/8" inline check valve, $14 plus $2 s/h.

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I read a few threads where people have added a check valve and had problems later on with it. Supposedly the replacement check valve wasn't letting fuel drain back into the tank at all. When they turned the jeep off heat soak expanded fuel and burst something at the rail.

Is that a major concern or only with certain years maybe? I have the check valve problem on my 97 and keep putting off a new pump just because of the cost of it. Then I am hesitant to try the check valve after hearing problems around them.

Checked my 96 pump assembly. There is a strange looking white housing inside the tank connected to the pump itself via a short hose. It has a single output line (pressure to fuel rail) and a bypass line that drains back to the tank. Looks like it's a combo check valve / fuel pressure regulator.

Ken-Is your '96 not on the road right now? Did you have to drop the tank to pull the pump? I've only done one XJ pump, and that was because we were putting a new tank in my son's '95. I'm under the impression that I don't have to fix it right away, but I probably will next week.
I looked around online, seems Advance is the cheapest. About $89, for just the motor, although that wouldn't be the check valve, would it? What I should do is pull it first, see what I need, then put together a good 'sending unit'.

It's on the road - actually drove it to work this morning. I installed a 97-up gas tank and pump assembly in it because I didn't feel like paying $300+ for a fuel pump assembly (mine was rusted to oblivion), plus $120 for a tank, when they'd rust out again. What's broken is the AW-4, it occasionally decides it has no gears and just slips till I stop, let it cool down, and start/stop the engine a few times. Hasn't done it recently though, so I think my fluid drain/fill, TV cable adjustment, and TPS replacement helped... pretty sure I have a lurking electrical issue but that's neither here nor there.

I have no idea if I would have to drop the tank to pull the pump - only reason I swapped it out was because I was putting a different tank in, so it was already on the ground when I decided to pull the pump assembly for later use as spare parts. I've heard that you can replace the pump on 96-down without pulling the tank, but I hate working in tight spaces like that so I'd probably pull it anyways. Cut the bolts and buy new (J324 0023 from funjeepsparts.com - $3 each including shipping if you buy a dozen, that's the best price-point I've managed to find, though I'm still selling off the extras.)

My suggestion would be to do exactly what you think you should, it sounds right to me. I don't see a fuel pressure regulator + check valve in the catalog as a serviceable item, hopefully the aftermarket sucks less than Chrysler in this regard because the full assembly will run you 3-400 dollars unless you can find a non-rusty, functional one at the junkyard.

kastein said:

It's on the road - actually drove it to work this morning.

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Work...What a concept! I think I'll dig out the '92, so I'll have something to drive, and just drop the '96s tank and 'rebuild' the whole sending unit. But, in the illustrations for the pump motors, it's just the pump, at around a hundred bucks, but not the check valve, which is my problem. The motor runs fine. It's got about half a tank in it right now, so it's time to go for a ride. How far is Boston?

Boston... about 45-50 miles from me, probably 250 miles from you. I'm presently chained down in a cube in Hudson, MA. Will be heading for an impromptu/unofficial M&G around 9PM tonight in Providence RI though!

Actually, if you want the check valve assembly off my 96, it's all yours for shipping, should cost about 5 bucks for a flat-rate box. The vehicle started and ran great with this pump assembly in it, like I said the rusty tank was the only reason it came out and stayed out. It did sit on my back porch for about 6 months though so it might need a little cleaning up.

I'm kicking around going to Advance to look at the motor. I've been looking at the illustration on their website, and I'm wondering it the check valve is built into the top of the motor. Was your 'poly' tank a dead swap, or did you have to mod anything? I had a '98 ZJ, and it started eating fuel pump motors at 5yrs/60k miles of age. Apparently the detergents in Sunoco gas were dissolving the poly, clogging the screen, and overheating the motor. You could tell it was getting close when the fuel gauge would stop working, as the 'slime' would coat the contacts, and a few weeks later it would become difficult to start, then not start at all. Finally fixed it for good with a cure called 'Subaru Outback'. One dose was all it took!

HDPE tank wasn't quite a dead swap... far from it in fact. I had to bevel the edges on the hose barbs for the fillspout and vent since the plastic ones are a significant bit larger in diameter, then stick the ends of my fill/vent hoses in boiling water. If I'd taken the hoses with the tank this would not have been an issue. I also had to rewire the connector for the harness, the pins were in different spots for the fuel level sender and it still doesn't work quite right (might be the slime issue you mentioned but it's been driving fine for months.) The pump worked great though, just connected the pressure line and vapor line up and away she went! I also had to build a custom heat shield for the exhaust since I couldn't get the bolts loose on the one I was trying to pull at the junkyard.

Haven't had a problem with the gas dissolving the tank... yet. I figure if I do, I'll grab another tank+pump for 50 bucks at the junkyard, throw it in, and forget about it for another year or four.

The plot thickens! Just went to Advance to look at a fuel pump motor. It's not obvious if there's a check valve built in to it, although that may be the case. But, also included in the page on their computer was a listing for a regulator, and when the picture was pulled up, it looks suspiciously like the regulator on the fuel rail on earlier models.The manager (who's a real good guy, takes care of me) suggested I look for some sort of regulator near, or possibly inside the tank, maybe built into the sending unit. And, the kicker is, it costs more than the pump! I have to wait until tomorrow to pull it apart, as there's about half a tank to burn off, and all of a sudden it decides to get excellent MPGs. Go figure.

Well, that's not what I needed to hear. I've been itching to try new hi-po injectors, I guess it may be time. I keep thinking about what a stuck injector did to RichP a few years ago.