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Unread 03-04-2010, 01:55 PM   #1
acc1
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1997 TJ Wrangler 
 
Join Date: Jul 2008
Location: ar
Posts: 16
long start time - not fuel pressure regulator

When I go to start my jeep, it takes a while to start. It starts fine, just takes longer than you would expect. I can kill the jeep and it restarts in a normal amount of time. Eventually, after sitting a while, it gets back to where it takes a long time to start. I thought it was bleeding off at the the fuel pressure regulator, so I replaced it, but that has made no difference. Anyone have an idea what to try next? I have a 1997 TJ with 4.0 liter.

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Unread 03-04-2010, 02:02 PM   #2
mdm
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2000 TJ Wrangler 
 
Join Date: Apr 2005
Location: Elkmont, AL
Posts: 9,723
You are describing the classic anti-drain back valve problem. If you turn the key on and let it sit for a moment it should start right up.
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Unread 03-04-2010, 02:06 PM   #3
acc1
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1997 TJ Wrangler 
 
Join Date: Jul 2008
Location: ar
Posts: 16
Yes, I know...the fix is to replace the fuel pressure regulator, which I did. It didn't fix it, so that got me to wondering what it might be
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Unread 03-04-2010, 02:21 PM   #4
Dean O
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1997 TJ Wrangler 
 
Join Date: Sep 2004
Location: Durham, NC
Posts: 473
Leaky fuel injector maybe? I've got the same problem with my '97 and I just picked up a fuel system pressure tester from ebay for pretty cheap. It has enough fittings to allow me to isolate both sides of the system so I can tell if the leak is coming from the injector side or the tank/pump side. I'm waiting for warmer weather before tackling the job though.

Edit: here's a link to the kit.
http://cgi.ebay.com/ebaymotors/ws/eB...6480&viewitem=
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Unread 03-04-2010, 02:32 PM   #5
mdm
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2000 TJ Wrangler 
 
Join Date: Apr 2005
Location: Elkmont, AL
Posts: 9,723
Quote:
Originally Posted by acc1 View Post
Yes, I know...the fix is to replace the fuel pressure regulator, which I did. It didn't fix it, so that got me to wondering what it might be
From the '00 FSM -
FUEL PRESSURE LEAK DOWN TEST
Use this test in conjunction with the Fuel Pump
Pressure Test and Fuel Pump Capacity Test.
Check Valve Operation: The electric fuel pump
outlet contains a one-way check valve to prevent fuel
flow back into the tank and to maintain fuel supply
line pressure (engine warm) when pump is not operational.
It is also used to keep the fuel supply line
full of gasoline when pump is not operational. After
the vehicle has cooled down, fuel pressure may drop
to 0 psi (cold fluid contracts), but liquid gasoline will
remain in fuel supply line between the check valve
and fuel injectors. Fuel pressure that has
dropped to 0 psi on a cooled down vehicle
(engine off) is a normal condition. When the electric
fuel pump is activated, fuel pressure should
immediately (12 seconds) rise to specification.
Abnormally long periods of cranking to restart a
hot engine that has been shut down for a short
period of time may be caused by:
Fuel pressure bleeding past a fuel injector(s).
Fuel pressure bleeding past the check valve in
the fuel pump module.


...


(13) Testing for fuel pump check valve, filter/
regulator check valve or fuel tube/line leakage:
Clamp off the rubber hose portion of Adaptor Tool
between the vehicle fuel line and test port T on
Adapter Tool. If pressure now holds at or above 30
psi, a leak may be found at a fuel tube/line. If no
leaks are found at fuel tubes or lines, one of the
check valves in either the electric fuel pump or filter/
regulator may be leaking.
Note: A quick loss of pressure usually indicates a
defective check valve in the filter/regulator. A slow
loss of pressure usually indicates a defective check
valve in the electric fuel pump.
The electric fuel pump is not serviced separately.
Replace the fuel pump module assembly. The filter/
regulator may be replaced separately on certain
applications. Refer to Fuel Filter/Fuel Pressure Regulator
Removal/Installation for additional information.


It would appear there is a check valve in the pressure regulator and another in the pump itself. Another possible source of the problem is a leaking fuel injector.
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