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Unread 01-01-2015, 10:08 AM   #1
moggie99
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1996 ZJ 
 
Join Date: Sep 2011
Location: Al Ain, Abu Dhabi
Posts: 665
ZJ Fuel Check Valve Faulty?

I have a 1996 ZJ 4L which doesn't like starting in the morning if parked with the nose up my sloping driveway (it takes a bit of churning and may stall initially or idle slow and rough for a few seconds). However, it is fine when parked nose down. Although a 1996 build, I think it may be a 1997 model year vehicle as it does not have the fuel pressure regulator on the fuel rail. However, the build sheet shows a build date of Jan 1996

Now, having checked the workshop manual and parts manual it seems that the fuel pressure regulator and check valve are part of the fuel filter module on the pump in the tank. My guess is that one or both of these are faulty (I need to check the fuel pressure when/if I can get my hands on a suitable gauge). Given that changing it requires dropping the tank, I was wondering of anyone had experience with fitting an external check valve in the output line from the pump or is it better to just bite the bullet and do the job properly?

Thanks in advance

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'96 ZJ 4L auto, '95 XJ 4L manual, 2003 Landrover Discovery
In the UK: 1969 MGC GT
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Unread 01-01-2015, 11:49 AM   #2
Scrubberguy
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1997 ZJ 
 
Join Date: Jun 2014
Location: Pomona, CA
Posts: 162
I can understand wanting to add a check valve at a different point in the fuel line, however that won't change the problem if your filter / regulator is starting to go bad.

So in this case I'd find the correct tool to check fuel pressure and I'd check it "cold" during a hot re start and I'd let it idle for an hour checking the gauge for fluctuations as it runs.

You did not mention the amount of miles on your 96 but Chrysler's last the life time of the vehicle line is bunk, most makers figure "life time" at about 140K!

You could be experiencing Lazy Capacitor syndrome in your PCM/ECU but usually that shows up as a hard start all the time not at a specifc time of "angle" of the vehicle.

Get a gauge if you can and start with pump pressure, should be about 45 to 49 PSI while running less is not good.

I will also suggest you back track the fuel lines 96 were supposed to have an external fuel filter 97 they went to the top of the pump, you may be "lucky" and be blessed with both, LOL!
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Unread 01-01-2015, 01:22 PM   #3
moggie99
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1996 ZJ 
 
Join Date: Sep 2011
Location: Al Ain, Abu Dhabi
Posts: 665
There is also an external filter which has done 15,000 miles or so. The vehicle has 265,000km (166,000 miles) - but I have no idea what was done to it over the first 80% of that!
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'96 ZJ 4L auto, '95 XJ 4L manual, 2003 Landrover Discovery
In the UK: 1969 MGC GT
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Unread 01-01-2015, 07:54 PM   #4
jeep-pr
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1995 ZJ 
 
Join Date: Jul 2013
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i was thinking of doing an external check valve till i read an article, its just a band aid to the bigger problem, the pump still looses fuel and has to turn dry then gets fuel. the better and permanent solution is just getting a new pump assembly. if you try the external check valve it could at some point fail ( split a line ) and cause a worse situation.

i just bite the bullet and forked over for a delphi pump assembly at rock auto, since they where the cheapest, closer to original and faster shipping.
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Unread 01-02-2015, 12:03 AM   #5
moggie99
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Having just seen the Delphi complete module on Rockauto for $96 I may just do that. I'll have to check out local prices here in Abu Dhabi though, as shipping costs can be high.
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'96 ZJ 4L auto, '95 XJ 4L manual, 2003 Landrover Discovery
In the UK: 1969 MGC GT
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Unread 01-02-2015, 11:06 AM   #6
Uniblurb
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1996 ZJ 
 
Join Date: Jan 2012
Location: Central, Ohio
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Personally I'd go with the Bosch 67646 fuel pump module for your 96 since it's OE and Mopar just repackages them selling them for 2-3 times the price. Runs cool and quiet. Real good deal at $120 from a reputable ebay vendor others here have used although shipping would be $50 to Abu Dhabi. Good luck.

http://www.ebay.com/itm/NEW-BOSCH-67...p=mtr#shpCntId
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-Stalling ZJ? 12 things to check before replacing a sensor; the Dirty Dozen
-Crankshaft position sensor multimeter test. & video of testing.
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Unread 01-02-2015, 03:00 PM   #7
moggie99
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1996 ZJ 
 
Join Date: Sep 2011
Location: Al Ain, Abu Dhabi
Posts: 665
That's all very well, but if mine has the 1997 style one with the integral filter/regulator then that one isn't compatible. Thank, anyway.
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'96 ZJ 4L auto, '95 XJ 4L manual, 2003 Landrover Discovery
In the UK: 1969 MGC GT
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Unread 01-02-2015, 05:13 PM   #8
Uniblurb
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1996 ZJ 
 
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Ahh..I see now. Actually they started installing the fuel pressure regulator in the fuel pump module in 95. Kinda surprised a 97-98 fuel pump module with the external filter/regulator on top of the module works on your 96 since the 96 module was specific to that year only. There was also a TSB issued on the 96 pump for overheating problems so maybe somebody just used what was most available over there? Good luck.
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96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 93 4.0 XJ (spare), 96 4.0 XJ (son's)

-Stalling ZJ? 12 things to check before replacing a sensor; the Dirty Dozen
-Crankshaft position sensor multimeter test. & video of testing.
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