ZJ 5.9, still not starting - JeepForum.com
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post #1 of 58 Old 03-14-2020, 10:23 AM Thread Starter
Rotheeno
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ZJ 5.9, still not starting - IT RUNS!

1 week ownership, I drove it home -long 8 hours trip- without turning off the engine. Parked in garage and since than it was not starting. Cranking free and happy til the battery dies.

I was told by the PO that there was a problem with the passenger door module, than the immobilizer.
With a friend and a diagnose we checked everything, without finding a single issue with the immobilizer. Checked crank PS, coils, sparks and so on. The only issue seems to be with the fuel pressure, way too low, close to zero. Ignition on, pump relais works, but the pressure in the line is barely enough to spill few drops. Filter? Pump? Regulator? What are your guess guys?

I have ordered a complete fuel pump assembly, now I'm lowering the tank. I wonder if -just to clear my mind- the immobilizer/alarm does work on the fuel line, regulator or pump itself.

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post #2 of 58 Old 03-14-2020, 10:50 AM
jtec
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Ther should be a schraider valve on fuel rail to check fuel pressure with a gauge, post PSI.

Be advised the fuel pump only has power to run for @2seconds if engine does not start. Butt would not drop off quickly.

Did yu check for codes?

Immobilizer does not work on pump, regulator, or fuel line, If the systems wants to disable vehicle the injector pulsing is disabled.
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post #3 of 58 Old 03-14-2020, 12:02 PM
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You need to have the specified fuel pressure on the rail, can be checked from the scharder valve like JTEC mentioned. When my pump started to fail I started getting weird running issues, and the pressure test verified only a fairly minor drop in fuel pressure.

If fuel pressure is really low, you definitely must replace the fuel pump. The whole assembly includes the pressure regulator, if the vehicle still has the original it is most likely about to fail anyway. I hope you bought a Bosch or Mopar, most others are pretty crappy.
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1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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post #4 of 58 Old 03-15-2020, 09:06 AM Thread Starter
Rotheeno
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Thanks for the replies. We have tested the pressure at the valve (actually, my friend did, but I have no doubts about him). It feels strange that the pump fails so quickly, as I drove the car long way till it was parked in my garage, without a single issue. When I first parked the car, turned off, started and died in 1 second (immobilizer I guess), let it alone one night and since the day after it would not start, just cranking. Anyway, I dropped the tank yesterday (what a pita) and removed the pump assembly. The lower filter is nasty. I'll take some pictures later today. How is it called the valve in front of the tank (not on top), need to replace as it's completely rusted.
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post #5 of 58 Old 03-15-2020, 09:34 AM
RedRiverT
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When you say "immobilizer" I assume you mean the security system. Does it have the factory security system? That sounds like the problem, the security is not turning the pump on. Could you hear the pump whine when you turned the key ON?

Since the lower filter was nasty, you didn't waste your time by changing the pump now. Hopefully the pump is the problem. It could have been over worked during your 8 hour drive because of the nasty filters, then when you turned it OFF, it stuck and can't re-start.

I don't know what you mean by "valve in front of the tank". Maybe the PO added an in-line filter or pressure regulator. Or maybe a zg (export model) is different and has the in-line style like the '93-'96 instead of the combined unit on top of the pump module.
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post #6 of 58 Old 03-15-2020, 09:59 AM Thread Starter
Rotheeno
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Quote:
Originally Posted by RedRiverT View Post
When you say "immobilizer" I assume you mean the security system. Does it have the factory security system? That sounds like the problem, the security is not turning the pump on. Could you hear the pump whine when you turned the key ON?

Since the lower filter was nasty, you didn't waste your time by changing the pump now. Hopefully the pump is the problem. It could have been over worked during your 8 hour drive because of the nasty filters, then when you turned it OFF, it stuck and can't re-start.

I don't know what you mean by "valve in front of the tank". Maybe the PO added an in-line filter or pressure regulator. Or maybe a zg (export model) is different and has the in-line style like the '93-'96 instead of the combined unit on top of the pump module.


I can hear the pump, but I'm going to test it now that is out of the tank. I'll take some pictures of the tank and under the car as well. There's a second regulator under the body

1994 ZJ 4.0, 200k miles
1998 ZJ 5.9, 120k miles. Project - restoration
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post #7 of 58 Old 03-15-2020, 11:43 AM
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Quote:
Originally Posted by RedRiverT View Post
When you say "immobilizer" I assume you mean the security system. Does it have the factory security system? That sounds like the problem, the security is not turning the pump on. Could you hear the pump whine when you turned the key ON?

That is not how the VTSS system works; immobilizer and the alarm system are both built into the security system; of these immobilizer cannot be deactivated, security alarm can be deactivated with a DRB.
Immobilizer disables the vehicle after about two seconds of running; it does not turn off the fuel pump, it kills the injectors.

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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post #8 of 58 Old 03-15-2020, 11:45 AM
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Quote:
Originally Posted by Rotheeno View Post
I can hear the pump, but I'm going to test it now that is out of the tank. I'll take some pictures of the tank and under the car as well. There's a second regulator under the body
Stock ZJ/ZG fuel system on a '98 has the regulator and filter with the pump assembly, no external filters or regulators in the fuel line. So someone has done something to the fuel system at some point. IIRC the '97- '98 regulator and filter is inside the tank, not outside on top of the module. It's been a while when I replaced my fuel pump.

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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post #9 of 58 Old 03-15-2020, 12:14 PM Thread Starter
Rotheeno
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Quote:
Originally Posted by Timo_90xj View Post
Stock ZJ/ZG fuel system on a '98 has the regulator and filter with the pump assembly, no external filters or regulators in the fuel line. So someone has done something to the fuel system at some point. IIRC the '97- '98 regulator and filter is inside the tank, not outside on top of the module. It's been a while when I replaced my fuel pump.


Thre you go: The tank, the rusty-crusty valve (?) in front of the tank and the regulator (?) which is bolted to the underbody in front of the rear axle. A rubber fuel line connects the rusty vale to that regulator.
Attached Thumbnails
20200315_174831.jpg   20200315_174838.jpg   20200315_174909.jpg  

1994 ZJ 4.0, 200k miles
1998 ZJ 5.9, 120k miles. Project - restoration
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post #10 of 58 Old 03-15-2020, 12:21 PM Thread Starter
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And other pictures, fuel pump assembly (tested pump, works nicely), filter, regulator...
Attached Thumbnails
20200315_181434.jpg   20200315_181443.jpg   20200315_182832.jpg  

1994 ZJ 4.0, 200k miles
1998 ZJ 5.9, 120k miles. Project - restoration
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post #11 of 58 Old 03-15-2020, 12:25 PM Thread Starter
Rotheeno
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Quote:
Originally Posted by Timo_90xj View Post
That is not how the VTSS system works; immobilizer and the alarm system are both built into the security system; of these immobilizer cannot be deactivated, security alarm can be deactivated with a DRB.
Immobilizer disables the vehicle after about two seconds of running; it does not turn off the fuel pump, it kills the injectors.

Than I think it's safe to say that the immobilizer is not the problem of my jeep not starting. Alarm, I have no idea how it works. It was probably disabled on my car, as there's no intermittent horn or headlight blinking.

1994 ZJ 4.0, 200k miles
1998 ZJ 5.9, 120k miles. Project - restoration
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post #12 of 58 Old 03-15-2020, 12:38 PM
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That is a fuel tank from an older ZJ with a fuel return system - your '98 has a returnless system, so a single fuel supply line with no inline filter, and a fuel vapor hose that connects at the top of fuel tank.
Stock fuel lines are plastic with SAE quick disconnects, not rubber with hose clamps.

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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post #13 of 58 Old 03-15-2020, 12:59 PM Thread Starter
Rotheeno
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Quote:
Originally Posted by Timo_90xj View Post
That is a fuel tank from an older ZJ with a fuel return system - your '98 has a returnless system, so a single fuel supply line with no inline filter, and a fuel vapor hose that connects at the top of fuel tank.
Stock fuel lines are plastic with SAE quick disconnects, not rubber with hose clamps.

Found the build sheet and my zj has the extended range tank (21 gallons). Fuel lines are plastic and they have quick disconnects

1994 ZJ 4.0, 200k miles
1998 ZJ 5.9, 120k miles. Project - restoration
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post #14 of 58 Old 03-15-2020, 02:20 PM
RedRiverT
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Rotheeno, in post #10, the metal canister is the regulator/filter combination unit. I guess you can call it the "pump outlet filter", then the flat rectangular screen on the bottom of the module could be called the "pump inlet screen". There is another one inside the module that filters the fuel again before it gets in the pump.

Here is the regulator/filter :
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Mopar 5210053 Filter & Regulator.jpg  
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post #15 of 58 Old 03-15-2020, 02:32 PM
RedRiverT
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Perhaps the added regulator has a problem now and is stopping the fuel.
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