Is it possible to replace just the fuel pump without replacing the entire unit?

dvibbert

dvibbert

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Maysville, KY, USA
I searched and could not find an answer. Is it possible to just replace just the fuel pump without replacing the entire unit on a 99 TJ 4.0? I would rather just replace the pump by itself and the FPR and that’s it. If anyone has done just that let me know the steps and challenges
 
Hello. I remplaced recently my fuel pump.
I remplaced only the pump without replacing the entire unit... I have a 2002 tj 4.0 . ..
The problem that I have the same startup problem... The car always starts on the second attempt... I think it's a filter problem. I regret not having bought the whole unit (pump with filter with sealing) ... I advise you not to make the same mistake as me.

IMG_20180709_091151.jpg


IMG_20180709_091157.jpg
 
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You might have a problem with the pressure regulator. If it sits for a while and its hard to start it MIGHT be that fuel is draining back into your tank.
 
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So by replacing your fuel pump, will it and did it solve the hard to start problem? My 97 tj 4.0 does that. I usually cycle/prime the pump 3 times before I try and start the jeep, and then it cranks.
 
This is a picture of the fuel pressure regulator. I have yet to replace mine. Because i am lazy and after cycling the key a couple times before i start my jeep it usually starts.
FuelPressureRegulator1.jpg
 
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I just don't want to be on the trail and in an awkward position and my jeep go dead, and then have to go through all that to start my jeep. It could cause a problem
 
Eddie Greenlee said:
I just don't want to be on the trail and in an awkward position and my jeep go dead, and then have to go through all that to start my jeep. It could cause a problem
Click to expand...

I agree with you. If you buy the entire fuel pump unit it should comes with the new pressure regulator. Its also upwards of $250. Vs $70+ for the regulator.

There is a way to test both at the same time. If you hook up a fuel pressure tester (free loan a tool) and start the engine check the pressure. Leave it attached to the fuel rail and turn off the jeep and let it sit for a while ( a couple hours) If you see a huge drop in pressure you know that is the hard start problem.
Now the problem is it could be coming from a couple places. You could have a leaky injector (possibly) or the pressure regulator is leeking back into the tank ( also a possibility)
If you have low pressure to start off with then you can assume that the fuel pump is weak. And change it.
Its a lot of trouble shooting but i hate throwing money at problems that dont need to be fixed. Its better spent on upgrades or flowers so i can buy more upgrades
 
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Boinked said:
This is a picture of the fuel pressure regulator. I have yet to replace mine. Because i am lazy and after cycling the key a couple times before i start my jeep it usually starts. View attachment 47369
Click to expand...

That one won't fix the hard to start issue. Trust me...I tried. I believe that is the Filter/pressure regulator. It is the reason that TJ's don't have a return line from the fuel rail. What fails on the TJ's famous "hard to start" issue is a check valve on the pump outlet, which by the service manual, is non-replaceable.

Here...From the service manual.
FUEL PUMP
DESCRIPTION
The electric fuel pump is located inside of the fuel
pump module. A 12 volt, permanent magnet, electric
motor powers the fuel pump. The electric fuel pump
is not a separate, serviceable component.
OPERATION
Voltage to operate the electric pump is supplied
through the fuel pump relay.
Fuel is drawn in through a filter at the bottom of
the module and pushed through the electric motor
gearset to the pump outlet.
Check Valve Operation: The pump outlet con-
tains a one-way check valve to prevent fuel flow back
into the tank and to maintain fuel supply line pres-
sure (engine warm) when pump is not operational. It
is also used to keep the fuel supply line full of gaso-
line 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. Refer to the Fuel Pressure Leak
Down Test for more information.
The electric fuel pump is not a separate, service-
able component.
FUEL PUMP MODULE
DESCRIPTION
The fuel pump module on all models is installed
into the top of the fuel tank (Fig. 6). The fuel pump
module contains the following components (Fig. 6) or
(Fig. 7):
• A combination fuel filter/fuel pressure regulator
• A separate fuel pick-up filter (strainer)
• An electric fuel pump
• A threaded locknut to retain module to tank
• A gasket between tank flange and module
• Fuel gauge sending unit (fuel level sensor)
• Fuel supply tube (line) connection
The fuel gauge sending unit, pick-up filter and fuel
filter/fuel pressure regulator may be serviced sepa-
rately. If the electrical fuel pump requires service,
the entire fuel pump module must be replaced.
 
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I guess I am more confused. The kit I bought was the Bosch fuel pump (pump and filters only) and it came with a new fuel presssure regulator. But some say the pump alone can be changed without replacing the entire unit. I know the FPR can be replaced easily. Just don’t know whether the pump alone can be replaced for sure. Hate to drop it all to replace and find out that I have to have the entire assembly
 
They do sell just the pump/filter and many people have just replaced it. Jeep says it is not serviceable but that it their book. They say a lot of things that cant be done and we do it anyway.
 
Remember that the assembly might be as much as 20 years old ( assuming 1998) plastic does get brittle. I would watch a few YouTube videos and see if you want to attempt it or replace the whole assembly
 
dvibbert said:
Hate to drop it all to replace and find out that I have to have the entire assembly
Click to expand...

Here's what I just did and you may try it if you haven't already. I cranked the jeep pulled it into the carport, opened the hood, took the cap off of the bleeder valve, and when I depressed the bleeder valve (after just pulling into the carport) absolutely NO gas came out of the valve. So i think i will be needing a new fuel pump also .
 
Boinked said:
This is a picture of the fuel pressure regulator. I have yet to replace mine. Because i am lazy and after cycling the key a couple times before i start my jeep it usually starts. View attachment 47369
Click to expand...
I took that photo 15-18 years ago, that's my hand holding the FPR.

The problem is the slow start problem that happens after the Jeep has been sitting a while is not fixed by replacing the fuel pressure regulator. I tried that a few times after someone told me it was the cause of the problem and it never helped. My experience confirms what I later confirmed in the Jeep Factory Service Manual, that it's the check valve in the fuel pump outlet, not the fuel pressure regulator, that causes the usual slow start problem that happens after sitting a while or overnight.

The FSM says this:
"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."
 
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Eddie Greenlee said:
Hey Chris the fuel pumps at O'Reilly's by the name precision 96.00 are prob not the quality the Bosch are right?
Click to expand...

Definitely not. It seems all the stories I've read, people have issues using fuel pumps that aren't Bosch. I'm fairly sure Bosch was (and probably still is) the OE supplier to Mopar.

It's another one of those cases where are TJs are finicky with aftermarket sensors and such.
 
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