Fuel Issue - JeepForum.com

 
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post #1 of 6 Old 02-12-2011, 08:12 PM Thread Starter
JosHeis
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1998 XJ Cherokee 
 
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Fuel Issue

Ok so heres the problem, first off my 98' takes forever to start and I know that its the pressure regulator because you can here the gas dripping back into the tank "gurgling" when you shut the jeep off. Lately though I can smell gas off and on when starting or getting out after I shut it off. Could the pressure regulator have completely failed? I also am only getting about 200 miles per tank now was getting around 300. How can I be sure of the issue? Can I replace just the regulator? Is it completely necessary to drop the tank? How difficult is it to fix and issues that are known to happen when performing this repair. I haven't ever done a fuel system repair and i'm on a budget so i'll be doing this my self. Thanks in advance you guys are great with advice, Joe.

Note: No fuel leaks can be seen, no injectors are wet no drips under car.

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post #2 of 6 Old 02-12-2011, 10:18 PM
sargergp
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Evap cannister hose

Sounds more like you have a bad evaporator cannister hose. It's a plastic box back by the fuel tank with lines connected to it. There is a couple of places under the jeep where the plastic line has a short section of rubber hose connecting it together. If one of those hoses gets brittle and starts leaking you'll smell fuel right after shut down and it can put your MPGs in the toilet. I think there are some other posts on here about it. Try searching evaporator or emissions canister.
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post #3 of 6 Old 02-14-2011, 06:57 PM Thread Starter
JosHeis
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Alright i'll check that what exactly am I looking for? I'd like to figure this out relatively quickly getting 200 mile per tank sucks lol. Thanks again.
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post #4 of 6 Old 02-14-2011, 07:30 PM
grainofsalt
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It may just be time to replace your fuel pump. How many miles are you showing?


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post #5 of 6 Old 02-15-2011, 06:20 AM
tjwalker
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1. You could have a check valve issue on the fuel pump. Very common. More on it below

2. Best to actually calculate your gas mileage. Miles driven divided by gallons consumed. Doing this is more accurate than trying to figure your mileage by the amount of miles you get per tank of gas.

---------------------------------------------------------------
The check valve is located on top of the gas tank and is part of the fuel pump assembly on 95.5-2001 vintage 4.0 XJs. When the check valve starts to fail, it reduces fuel pressure to a point where an extended crank is needed to start the engine. It is a very common failure. I experienced it on my 99 at around 75K.

A good (and simple) way to troubleshoot this problem is called “the poor mans prime”

1. Turn key to ON position (do not crank the engine!)
2. The fuel pump will energize and run for a couple of seconds
3. Turn key to OFF position
4. Repeat above a two more times
5. NOW crank the engine over

If the engine starts quickly and cleanly after performing this procedure, you may have the check valve issue. If it starts and runs poorly for a few seconds, it could also be a leaky fuel injector resulting in the bleed down and the stumble upon startup is the engine clearing the excess fuel that has leaked into the cylinder because of the faulty injector.

Also be aware that a bad battery can give you this symptom. Sounds strange but it definitely does happen. Have battery load tested if you have any questions; your XJ does NOT like low available battery voltage. Be sure battery connections and posts are CLEAN.

Some troubleshooting tips for extended crank times:

Hook up fuel pressure gauge on the schrader valve on the fuel rail

Start engine and bring to normal operating temperature.

Observe test gauge. Normal operating pressure should be 49.2 psi (plus or minus 5 psi)

Shut engine off.

Pressure should not fall below 30 psi for five minutes.

If pressure falls below 30 psi, it must be determined if a fuel injector, the check valve within the
fuel pump module, or a fuel tube/line is leaking. An adaptor tool/hose included with the fuel pressure gauge can help you with this. Consult gauge manual for more information on this but here is basically how it works:

*Turn the engine off and immediately clamp the fuel line at the adaptor hose. Watch the pressure gauge and see how long it takes to lose pressure.

*If the pressure remains at 49 psi for an extended period of time then the problem is in the tank - possibly the check valve. If the pressure falls below 49 psi fairly rapidly then the problem is probably a leaky fuel injector.

You can limp a check valve problem along indefinitely if you wish as it doesn't mean the fuel pump itself is going bad. Normally, the check valve is replaced as an entire assembly as you have to drop the gas tank to access the assembly. Fuel pump assembly consists of fuel pump, regulator, check valve, filter. If you do replace the fuel pump assembly, purchase a high quality OEM style unit. Some cheap aftermarket assemblies don’t hold up and fail prematurely.

99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!
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post #6 of 6 Old 02-15-2011, 07:44 AM
sargergp
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Quote:
Originally Posted by JosHeis View Post
Alright i'll check that what exactly am I looking for? I'd like to figure this out relatively quickly getting 200 mile per tank sucks lol. Thanks again.
Here is a picture of the cannister. Like I said it's by the tank and rear axle. Just trace the lines and look for sections of rubber hose. You might also want to have your fuel cap checked to make sure it is holding the required pressure. Any place that does vehicle inspections should have the tester for it.
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