I have 110,000 miles on my TJ and am losing what I assume to be fuel
rail pressure when parked for a few hours. Before starting the
engine, I leave the ignition in the on position for a few seconds
before cranking the starter. The engine always starts promptly when I
do this.

Before running up the maintenance bills, cleaning the injectors,
replacing o-rings, etc., I thought it might be better to simply
replace the injectors.

I guess what I'm asking is if fuel injectors 'wear out'. That is, how
long will a set of injectors last?


-- msosborn at msosborn dot com

 

While I am also interested in the expected life expectancy of the injectors
is it worthwhile to incur the expense of changing them before failure?

There was a post several days ago where someone was unable to find the
grounds in his engine compartment. While I was down photographing them I
decided, for some reason, to check the pressure in my fuel rail. As I
hooked up the gauge I got no leakage so I am assuming that all the pressure
had leaked down. I turned on the key for a few seconds and then turned the
ignition off and removed the key. The pressure gauge was now set on 50 psi
and stayed there for the duration of the photography and removal of
leaves/needles from the cowling and inspection of the wiper blades. When I
removed the gauge, still at 50 psi, I did get fuel spillage.

How long will the fuel rail hold pressure? I know for sure I drove the
Cherokee Sunday but I think it may have sat several days since then.


<Matt Osborn> wrote in message
news:s02vo1l5vvslisolap1ah490l8048fv8kq@4ax.com...
>I have 110,000 miles on my TJ and am losing what I assume to be fuel
> rail pressure when parked for a few hours. Before starting the
> engine, I leave the ignition in the on position for a few seconds
> before cranking the starter. The engine always starts promptly when I
> do this.
>
> Before running up the maintenance bills, cleaning the injectors,
> replacing o-rings, etc., I thought it might be better to simply
> replace the injectors.
>
> I guess what I'm asking is if fuel injectors 'wear out'. That is, how
> long will a set of injectors last?
>
>
> -- msosborn at msosborn dot com

 

While I am also interested in the expected life expectancy of the injectors
is it worthwhile to incur the expense of changing them before failure?

There was a post several days ago where someone was unable to find the
grounds in his engine compartment. While I was down photographing them I
decided, for some reason, to check the pressure in my fuel rail. As I
hooked up the gauge I got no leakage so I am assuming that all the pressure
had leaked down. I turned on the key for a few seconds and then turned the
ignition off and removed the key. The pressure gauge was now set on 50 psi
and stayed there for the duration of the photography and removal of
leaves/needles from the cowling and inspection of the wiper blades. When I
removed the gauge, still at 50 psi, I did get fuel spillage.

How long will the fuel rail hold pressure? I know for sure I drove the
Cherokee Sunday but I think it may have sat several days since then.


<Matt Osborn> wrote in message
news:s02vo1l5vvslisolap1ah490l8048fv8kq@4ax.com...
>I have 110,000 miles on my TJ and am losing what I assume to be fuel
> rail pressure when parked for a few hours. Before starting the
> engine, I leave the ignition in the on position for a few seconds
> before cranking the starter. The engine always starts promptly when I
> do this.
>
> Before running up the maintenance bills, cleaning the injectors,
> replacing o-rings, etc., I thought it might be better to simply
> replace the injectors.
>
> I guess what I'm asking is if fuel injectors 'wear out'. That is, how
> long will a set of injectors last?
>
>
> -- msosborn at msosborn dot com

 

While I am also interested in the expected life expectancy of the injectors
is it worthwhile to incur the expense of changing them before failure?

There was a post several days ago where someone was unable to find the
grounds in his engine compartment. While I was down photographing them I
decided, for some reason, to check the pressure in my fuel rail. As I
hooked up the gauge I got no leakage so I am assuming that all the pressure
had leaked down. I turned on the key for a few seconds and then turned the
ignition off and removed the key. The pressure gauge was now set on 50 psi
and stayed there for the duration of the photography and removal of
leaves/needles from the cowling and inspection of the wiper blades. When I
removed the gauge, still at 50 psi, I did get fuel spillage.

How long will the fuel rail hold pressure? I know for sure I drove the
Cherokee Sunday but I think it may have sat several days since then.


<Matt Osborn> wrote in message
news:s02vo1l5vvslisolap1ah490l8048fv8kq@4ax.com...
>I have 110,000 miles on my TJ and am losing what I assume to be fuel
> rail pressure when parked for a few hours. Before starting the
> engine, I leave the ignition in the on position for a few seconds
> before cranking the starter. The engine always starts promptly when I
> do this.
>
> Before running up the maintenance bills, cleaning the injectors,
> replacing o-rings, etc., I thought it might be better to simply
> replace the injectors.
>
> I guess what I'm asking is if fuel injectors 'wear out'. That is, how
> long will a set of injectors last?
>
>
> -- msosborn at msosborn dot com

 

Matt Osborn did pass the time by typing:
> I have 110,000 miles on my TJ and am losing what I assume to be fuel
> rail pressure when parked for a few hours. Before starting the
> engine, I leave the ignition in the on position for a few seconds
> before cranking the starter. The engine always starts promptly when I
> do this.
>
> Before running up the maintenance bills, cleaning the injectors,
> replacing o-rings, etc., I thought it might be better to simply
> replace the injectors.
>
> I guess what I'm asking is if fuel injectors 'wear out'. That is, how
> long will a set of injectors last?

A set of injectors will last as long as the engine if you maintain the
filter and use good fuel.

Pressure drop in the fuel rail is one of three things.
- fuel pressure regulator
- fuel pump backflow valve
- fuel injectors

And injectors are bloody expensive.
A system called MotorVac can be used to clean the whole thing
from intake to cat. about $100.

First thing to get is a fuel rail pressure gauge. The good ones
have a little hose for dumping fuel. Measure the rail then measure
how fast it drains. Failed check valve in the pump will drop pressure
very quick, failed regulator will give you a low 20-30psi reading rather
than the stock 32 (double check with the dealer to make sure 32 is standard
it was in 93) and your pressure gauge will also drop quickly.

A leaky injector will drop pressure very slowly.

If you want to, you can remove the rail, leave the injectors attached.
Let the pump run and the rail pressurise, then look for drips.

If you do remove/clean/replace the injectors, use new O rings and lube
them with a bit of motor oil so they slide in easily and don't tear.
(and don't loose the clips)

--
-- DougW -- 93 ZJ 4.0 http://revbeergoggles.com
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!

 

Matt Osborn did pass the time by typing:
> I have 110,000 miles on my TJ and am losing what I assume to be fuel
> rail pressure when parked for a few hours. Before starting the
> engine, I leave the ignition in the on position for a few seconds
> before cranking the starter. The engine always starts promptly when I
> do this.
>
> Before running up the maintenance bills, cleaning the injectors,
> replacing o-rings, etc., I thought it might be better to simply
> replace the injectors.
>
> I guess what I'm asking is if fuel injectors 'wear out'. That is, how
> long will a set of injectors last?

A set of injectors will last as long as the engine if you maintain the
filter and use good fuel.

Pressure drop in the fuel rail is one of three things.
- fuel pressure regulator
- fuel pump backflow valve
- fuel injectors

And injectors are bloody expensive.
A system called MotorVac can be used to clean the whole thing
from intake to cat. about $100.

First thing to get is a fuel rail pressure gauge. The good ones
have a little hose for dumping fuel. Measure the rail then measure
how fast it drains. Failed check valve in the pump will drop pressure
very quick, failed regulator will give you a low 20-30psi reading rather
than the stock 32 (double check with the dealer to make sure 32 is standard
it was in 93) and your pressure gauge will also drop quickly.

A leaky injector will drop pressure very slowly.

If you want to, you can remove the rail, leave the injectors attached.
Let the pump run and the rail pressurise, then look for drips.

If you do remove/clean/replace the injectors, use new O rings and lube
them with a bit of motor oil so they slide in easily and don't tear.
(and don't loose the clips)

--
-- DougW -- 93 ZJ 4.0 http://revbeergoggles.com
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!

 

Matt Osborn did pass the time by typing:
> I have 110,000 miles on my TJ and am losing what I assume to be fuel
> rail pressure when parked for a few hours. Before starting the
> engine, I leave the ignition in the on position for a few seconds
> before cranking the starter. The engine always starts promptly when I
> do this.
>
> Before running up the maintenance bills, cleaning the injectors,
> replacing o-rings, etc., I thought it might be better to simply
> replace the injectors.
>
> I guess what I'm asking is if fuel injectors 'wear out'. That is, how
> long will a set of injectors last?

A set of injectors will last as long as the engine if you maintain the
filter and use good fuel.

Pressure drop in the fuel rail is one of three things.
- fuel pressure regulator
- fuel pump backflow valve
- fuel injectors

And injectors are bloody expensive.
A system called MotorVac can be used to clean the whole thing
from intake to cat. about $100.

First thing to get is a fuel rail pressure gauge. The good ones
have a little hose for dumping fuel. Measure the rail then measure
how fast it drains. Failed check valve in the pump will drop pressure
very quick, failed regulator will give you a low 20-30psi reading rather
than the stock 32 (double check with the dealer to make sure 32 is standard
it was in 93) and your pressure gauge will also drop quickly.

A leaky injector will drop pressure very slowly.

If you want to, you can remove the rail, leave the injectors attached.
Let the pump run and the rail pressurise, then look for drips.

If you do remove/clean/replace the injectors, use new O rings and lube
them with a bit of motor oil so they slide in easily and don't tear.
(and don't loose the clips)

--
-- DougW -- 93 ZJ 4.0 http://revbeergoggles.com
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!

 

Billy Ray did pass the time by typing:

> How long will the fuel rail hold pressure? I know for sure I drove the
> Cherokee Sunday but I think it may have sat several days since then.

On a new engine, days.
Test threshold is less than a 20psi drop in 30min.
Mine still has about 10psi in it after sitting all night
and that's a 93

--
DougW

 

Billy Ray did pass the time by typing:

> How long will the fuel rail hold pressure? I know for sure I drove the
> Cherokee Sunday but I think it may have sat several days since then.

On a new engine, days.
Test threshold is less than a 20psi drop in 30min.
Mine still has about 10psi in it after sitting all night
and that's a 93

--
DougW

 

Billy Ray did pass the time by typing:

> How long will the fuel rail hold pressure? I know for sure I drove the
> Cherokee Sunday but I think it may have sat several days since then.

On a new engine, days.
Test threshold is less than a 20psi drop in 30min.
Mine still has about 10psi in it after sitting all night
and that's a 93

--
DougW