Casper

One other thought... I'm not very familiar with the security system, so
is it possible it is shutting off the voltage to the fuel pump? So far
as I can tell, the SS seems to be working fine but now that I have more
test info on that, I can test that too if it is tied to the problem. I
was told the only way to turn the SS off is a trip to the dealer and
$$. I would prefer avoiding turning it off/on and keep it on for the
neighborhoods I must frequent. This problem started a few months after
I was rear-ended. Since then the rear (door, bumper and associated) has
been repaired/replaced. Although the damage did not really look bad, I
could not open the rear hatch and there was a small wrinkle in the
frame that was straightened. I am not familiar with the wiring to know
if the SS is connected to anything in the rear that could cause the
voltage to not reach the pump.

DougW

Casper did pass the time by typing:
> (Optima) Battery(s), either old (fully charged) or new, the system
> cranks. All cables, ground, etc., have been cleaned, checked and appear
> fine.
>
> You can hear the relays clicking when you turn the ignition to the RUN
> position, but not the fuel pump, at least not all the time (hearing is
> not as it used to be). Connected fuel pressure guage and no pressure
> when key is in the RUN position. This should read at least 20 on the
> guage. Checked the relays in the engine compartment and they get
> voltage(click). Checked relay/fuse compartment and it has voltage.
> Checked rear power feed line to the fuel pump (near tank) and no
> voltage. My understanding is that 12v should be going to the fuel pump.
> If there is 12v at the relay box, but not at the rear junction, then
> where else can I check where the power in not passing through? Since
> the jeep sometimes starts, then I suspect a short or "open" somewhere
> between those two points?? (your input here).

12V is not always sent to the pump.

Long story short.

- turn the key on
- pump runs for a few seconds to pressurize the system
- pump then shuts off

- engine starts
- pump turns on

Swap the AC/or/Fog and fuel pump relays and see what happens.

Here are the schematics.

http://www.revbeergoggles.com/temp/zj-13.jpg
http://www.revbeergoggles.com/temp/zj-54.jpg


--
DougW

DougW

Casper did pass the time by typing:
> (Optima) Battery(s), either old (fully charged) or new, the system
> cranks. All cables, ground, etc., have been cleaned, checked and appear
> fine.
>
> You can hear the relays clicking when you turn the ignition to the RUN
> position, but not the fuel pump, at least not all the time (hearing is
> not as it used to be). Connected fuel pressure guage and no pressure
> when key is in the RUN position. This should read at least 20 on the
> guage. Checked the relays in the engine compartment and they get
> voltage(click). Checked relay/fuse compartment and it has voltage.
> Checked rear power feed line to the fuel pump (near tank) and no
> voltage. My understanding is that 12v should be going to the fuel pump.
> If there is 12v at the relay box, but not at the rear junction, then
> where else can I check where the power in not passing through? Since
> the jeep sometimes starts, then I suspect a short or "open" somewhere
> between those two points?? (your input here).

12V is not always sent to the pump.

Long story short.

- turn the key on
- pump runs for a few seconds to pressurize the system
- pump then shuts off

- engine starts
- pump turns on

Swap the AC/or/Fog and fuel pump relays and see what happens.

Here are the schematics.

http://www.revbeergoggles.com/temp/zj-13.jpg
http://www.revbeergoggles.com/temp/zj-54.jpg


--
DougW

DougW

Casper did pass the time by typing:
> (Optima) Battery(s), either old (fully charged) or new, the system
> cranks. All cables, ground, etc., have been cleaned, checked and appear
> fine.
>
> You can hear the relays clicking when you turn the ignition to the RUN
> position, but not the fuel pump, at least not all the time (hearing is
> not as it used to be). Connected fuel pressure guage and no pressure
> when key is in the RUN position. This should read at least 20 on the
> guage. Checked the relays in the engine compartment and they get
> voltage(click). Checked relay/fuse compartment and it has voltage.
> Checked rear power feed line to the fuel pump (near tank) and no
> voltage. My understanding is that 12v should be going to the fuel pump.
> If there is 12v at the relay box, but not at the rear junction, then
> where else can I check where the power in not passing through? Since
> the jeep sometimes starts, then I suspect a short or "open" somewhere
> between those two points?? (your input here).

12V is not always sent to the pump.

Long story short.

- turn the key on
- pump runs for a few seconds to pressurize the system
- pump then shuts off

- engine starts
- pump turns on

Swap the AC/or/Fog and fuel pump relays and see what happens.

Here are the schematics.

http://www.revbeergoggles.com/temp/zj-13.jpg
http://www.revbeergoggles.com/temp/zj-54.jpg


--
DougW

DougW

Casper did pass the time by typing:
> (Optima) Battery(s), either old (fully charged) or new, the system
> cranks. All cables, ground, etc., have been cleaned, checked and appear
> fine.
>
> You can hear the relays clicking when you turn the ignition to the RUN
> position, but not the fuel pump, at least not all the time (hearing is
> not as it used to be). Connected fuel pressure guage and no pressure
> when key is in the RUN position. This should read at least 20 on the
> guage. Checked the relays in the engine compartment and they get
> voltage(click). Checked relay/fuse compartment and it has voltage.
> Checked rear power feed line to the fuel pump (near tank) and no
> voltage. My understanding is that 12v should be going to the fuel pump.
> If there is 12v at the relay box, but not at the rear junction, then
> where else can I check where the power in not passing through? Since
> the jeep sometimes starts, then I suspect a short or "open" somewhere
> between those two points?? (your input here).

12V is not always sent to the pump.

Long story short.

- turn the key on
- pump runs for a few seconds to pressurize the system
- pump then shuts off

- engine starts
- pump turns on

Swap the AC/or/Fog and fuel pump relays and see what happens.

Here are the schematics.

http://www.revbeergoggles.com/temp/zj-13.jpg
http://www.revbeergoggles.com/temp/zj-54.jpg


--
DougW

Casper

Already swapped Fuel/ABS and Start/AutoShutdown (All four) relays.
Problem perisists.
Tested rear junction with OHM meter while turning ignition to RUN
position and no voltage.

Casper

Already swapped Fuel/ABS and Start/AutoShutdown (All four) relays.
Problem perisists.
Tested rear junction with OHM meter while turning ignition to RUN
position and no voltage.

Casper

Already swapped Fuel/ABS and Start/AutoShutdown (All four) relays.
Problem perisists.
Tested rear junction with OHM meter while turning ignition to RUN
position and no voltage.

Casper

Already swapped Fuel/ABS and Start/AutoShutdown (All four) relays.
Problem perisists.
Tested rear junction with OHM meter while turning ignition to RUN
position and no voltage.

Mike Romain

'Something' is shutting down the fuel pump. Alarms can have that
feature....

You should for sure see a voltage spike at the rear junction when the
key hits run.

I would next check right at the relay. I would look for the trigger
signal when the key hits run. If I have that, then I would be thinking
the contact in the relay box might be bad.

Could you have a bad ignition switch?

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
Jan/06 http://www.imagestation.com/album/pi...?id=2115147590
(More Off Road album links at bottom of the view page)

Casper wrote:
>
> Already swapped Fuel/ABS and Start/AutoShutdown (All four) relays.
> Problem perisists.
> Tested rear junction with OHM meter while turning ignition to RUN
> position and no voltage.