Jeep Cherokee Limited 1996 Fuel Problems

Hi

I have a 96 Jeep Cherokee Limited with 160k's on the clock and have
been having some very strange problems recently. The message is long
- so sorry about that but I have included quite a bit of detail...

Many thanks in advance!!!
Jon

1. Heading up a reasonably long (flat) steep winding hill (1-2 hrs of
driving). The car starts to loose power when putting my foot on the
gas pedle, I was able to back of the gas a little but continued to
loose power. I had to stop for 30 minutes as I had no power
whatsoever and then try again - all seemed ok then after 15 minutes on
a flat highway the problem starts again. I took the car back into
town and put it in for a service - the guys replaced a very dirty fuel
filter.

2. Next day - Some as above - 1.5hrs of steep-ish windy roads the car
does exactly the same thing - starts to fail up hill, I turn around
and have the same problems returning to the garage even on the flats.
I am constantly loosing power and getting slower and slower (average
driving speed 110kph down to 10kph).

3. Back to the garage and put a pressure gauge on the schrader valve
on the fuel rail. Take the car out the next day on the same run and
sure enough the same problem. I can see the fuel presure for the
first hour is fine then it starts to drop - the further I go the more
radical the drops in presure (for example 45PSI to 15 PSI on a quick
pump of the gas). At some points the guage reads zero (0) PSI. Also
while the car is failing and the guage is showing 0psi if the gas
pedle is held flat to the floor the car will backfire

4. Back to the garage, we replace the fuel pump (just the motor not
the entire plastic housing) in the petrol tank (the fuel tank is
plastic) and clean the filter in the tank.

5. I drive 3,000k's (about 2200 miles) with no problems, yesterday I
drive up a short steep incline then onto flat highway, about 45
minutes on the highway I start getting the same problems of loosing
power

The mechanic has no idea what the problem could be and I have no ideas
either. So I was hoping someone with a Jeep may have heard of this
problem or may know where I can get further information or technical
expertise. I'm based in Australia if that helps.


My summary for failing is the following :-

- driving up hill, possibly steep and winding
- 1.5 to 2hrs of driving are required before failure
- fuel pressure constantly drops after this
- however driving can continue by watching the fuel pressure and only
accelerating when it has returned to the correct presure
(interestingly when driving at the begining put your foot flat to the
will move the fuel pressure guage down as low as around 20-25psi,
however the pressure recovery is very quick, after having the problems
correct fuel pressure recovery may take between 30seconds to 5
minutes)
- outside temperature are around 27-35 degrees celcius


Cheers!
jON

 

Jon did pass the time by typing:

Do you have the OEM fuel cap or an aftermarket one? Using an
aftermarket cap can cause this because it won't vent the fuel tank
properly.

Think of it this way. As you drive the engine burns petrol, the
petrol leaves the tank and creates a vacuum. If that vacuum
gets too big the system won't work properly and the jeep starves for
fuel.

Next time this happens, hop out and take the cap off and put it back
on again. See what that does.

 

Jon wrote:

Did anyone pump the tank dry to get rid of any water in it? If there is
water in the tank, the fabric fibers in the fuel tank "screen" filter
will swell up as it absorbs that water. It takes some time, depending
on how much water is in the tank, before it starts blocking fuel flow
enough to affect performance. Then when the engine is shut off or the
fuel pump is no longer pushing as much of the water-contaminated fuel
through the fabric, the fibers shrink and pass the fuel again.

That fabric in the filter swells up and reduces flow INTENTIONALLY to
prevent excess water from getting to the fuel system. That's been done
since carburetor days.

Water in the tank may not be from contaminated fuel sources. It could
condense in the tank due to temperature fluctuations.

 

What absolute utter nonsense...

This "fabric" as you call it is Nylon.

Nylon doesn't swell in the presence of water.

If he had water in his fuel, the problem would be there all the
time and would effect the injectors (fuel delivery) long before
it would effect the fuel supply system (as evidenced by his loss
of fuel pressure).

Odds are, since the original repair took the cheap route, he has
another failing fuel pump.

 

: I took the car back into
: town and put it in for a service - the guys replaced a very dirty fuel
: filter.
:
Have you checked the filter since? I'd be willing to bet you have a bunch of
crap in your fuel tank clogging up the screen. When you park, the crap
settles. Drive for a couple hours before it gets clogged up again.

-Brian

 

===================================

But despite commenting about nonsense, your reply didn't answer the
question. Did anyone pump the tank dry, to get rid of any water in it?

Take it from one who found out the hard way. Had similar problems,
which did not go away until the tank was drained. An estimated one inch
of water was in the bottom of the tank.

I do not know what type fiber was used but the "sock" filter in the fuel
tank is designed to block water intrusion. Says so, somewhere in the
pile of Chrysler shop manuals accumulated since my first one in 1968,
for a Slant Six Valiant.

 

It should be pretty obvious that I'm not Grant, and I'm not
posting from the United Kingdom.

What water?
The OPs symptoms do not exhibit characteristics of water
contaminated fuel, i.e., he has to drive 1.5 -2 hours before it
occurs.

That's okay, I'd prefer to not believe someone who claims that a
nylon inlet filter will swell in the presence of water.

Actually, it is not.
Matter of fact, two weeks ago I changed out the original fuel
tank sending unit in a 1967 Coronet 500 for a customer, the inlet
screen used back in the 60s is coarse enough to just about pass
#2 gravel.

Read the subject line....
It's 28 years later and it isn't a slant six Valiant, and
besides, you're wrong anyway as evidenced by the stated fact that
his fuel pressure is dropping to 20-25 PSI during the problem.

 

and later followed it up in another message with more rudeness and
conceit and outright bad manners:

and then:

No, Neil. YOU are wrong to behave this way. The original poster
would not have said what he did, if he didn't have something happen
with his car that backs up what he wrote. If it helped him, it might
help the rest of us, too.

Here we have a group where we are supposed to be helping and
suggesting ways to get our cars to run better, and we have this
Know-It-All blowing his self-centric and self-righteous bovine scats.
If it makes him feel better, he must be a very small person indeed.

I have refrained and will refrain from using profanity, but I do have
to conclude that you must have gotten a batch of bad drugs. Go hide
under a rock.

VF

 

Ah... another product of the outcome based educational system, I
see.
How is it we're so lucky today?

Screw the facts as long as we all feel all warm and fuzzy, right?

Do you believe that nylon will swell when exposed to water?

Ummm, last time I checked, my mother died in 1989.

Yeah, his 1968 Valiant. Not that I have anything against
Valiant's, I've owned two, and a Duster also.

But I digress... If it's water in the fuel tank, why does it not
pose a problem until the vehicle is driven for an hour or so?

Is it 'time delay' water?

To what, follow a wild goose chase?

By pumping out our fuel tanks?
Do you have the slightest idea what a logistical nightmare that
is to accomplish?
'Splain to me how you're going to get any pumping device or
hardware past the roll-over check valves that are incorporated in
the fuel system, and the fuel filler tube to be precise?

Look moron, I've been doing this for a living for over 30 years
and and from Poon's descriptions, can assure you that I have a
lot more working familiarity with this Jeep than he does no
matter how tall of a stack of service manuals he possesses.

Oh, I'm crushed.

Is that the standard explanation for when someone disagrees with
someone else?
Sorry to disappoint, but I do not use drugs, but feel free to
share -your- experiences with them when you have some free time,
m'kay?

I'm guessing that you're posting from the Jeep group.
How prophetic that your closing statement should lend such
credence to the old saying, "when the only tool you have is a
hammer, every problem begins to look like a nail."
Works for both you and Poon.

 

What happened?

Here I go, posting a message in response to Neil the Stuck-Up One and
his self-centric and self-righteous bovine scats. But when I go to
retrieve the day's messages from my mail server, all of Neil's
messages are GONE from the newsgroup. Every one of them.

Darn. His magnetic personality and blatantly overgrown self-image was
such an inspiration to youth gangs and drug dealers and pimps
everywhere.

VF

 

I'm truly sorry.

I've indeed been behaving with rudeness and conceit and outright bad
manners.

I have indeed been self-centric and self-righteous.

I have called people "moron"

I have been inconsiderate of other people on this newsgroup who want
to know and learn and not just listen to me boasting about how great I
am.

Let me explain. I'm really a little weenie. If any of you were to
meet me face to face, and argue with me, I'd run off and go cry in a
corner. On the Internet I can act and behave like the Big Man I so
much want to be. But I let myself get carried away and as I said, I
am truly sorry.

Neil Nelson

 

A forged post, how absolutely original.

What's next?

Paint graffiti on my garage?

Burning dog poop on my front porch?

Ring the bell and run and hide in the bushes?

Prank phone calls asking for Prince Albert in the can?

 

Hi again

I just to say a quick thanks to the replys! I have been bush for the
past month and thus dont have internet access! On the points :-

- OEM fuel cap - good point and yes I have an aftermarket fuel cap
on, and did think of the pressue issue, on the second ocassion I did
stop and undo the cap. There seemed to be not pressue build up in the
tank

- Rechecking the fuel filter, I will do this next service and let you
know what they find!

BTW I have completed a further 10,000kms since this last message and
haven't had any problems at all - and I've been on some nasty
tracks...


Thanks
jON