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

Re: Jeep Cherokee Limited 1996 Fuel Problems
 

Jon did pass the time by typing:
> Hi

Hello.

> I have a 96 Jeep Cherokee Limited with 160k's

<snippie>

> 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

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.

--
DougW

Re: Jeep Cherokee Limited 1996 Fuel Problems
 

Jon did pass the time by typing:
> Hi

Hello.

> I have a 96 Jeep Cherokee Limited with 160k's

<snippie>

> 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

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.

--
DougW

Re: Jeep Cherokee Limited 1996 Fuel Problems
 

Jon did pass the time by typing:
> Hi

Hello.

> I have a 96 Jeep Cherokee Limited with 160k's

<snippie>

> 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

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.

--
DougW

Re: Jeep Cherokee Limited 1996 Fuel Problems
 

Jon did pass the time by typing:
> Hi

Hello.

> I have a 96 Jeep Cherokee Limited with 160k's

<snippie>

> 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

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.

--
DougW

Re: Jeep Cherokee Limited 1996 Fuel Problems
 

Jon wrote:


> 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


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.

Re: Jeep Cherokee Limited 1996 Fuel Problems
 

Jon wrote:


> 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


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.

Re: Jeep Cherokee Limited 1996 Fuel Problems
 

Jon wrote:


> 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


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.

Re: Jeep Cherokee Limited 1996 Fuel Problems
 

Jon wrote:


> 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


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.

Re: Jeep Cherokee Limited 1996 Fuel Problems
 

In article <wMDnc.104$Bs1.69804@news.uswest.net>,
Gene Poon <sheehans@ap.net> 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.