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Old 12-08-2006, 08:28 AM   #1
biplanepilot
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2001 Trooper starting problem

In the last 6 months my Trooper has begun failing to start upon the first crank. Engine cranks fine, just fails to fire up. This generally happens when the engine is warm. It usually starts on the second try. A little pressure on the gas pedal during starting seems to help.

I serviced the throttle body but that had no effect. I then waited a few months before doing anything else, since the car was coming up on a 60,000 mile service.

Well, I just had the service done and the problem still hasn't been cured.

Any ideas anyone?

Thanks in advance.
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Old 12-08-2006, 01:06 PM   #2
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Re: 2001 Trooper starting problem

I have a 2000 Trooper and am now having the same problem. If the engine is cold in the morning, it starts right up. When it's warm, it takes 2-3 tries. I've got about 40k miles. I was wondering if it was a fuel delivery issue? Maybe a fuel pump?
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Old 12-08-2006, 01:11 PM   #3
amigo-2k
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Re: 2001 Trooper starting problem

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FAQ 98-04 Isuzu Rodeo, Rodeo Sport, Amigo, Trooper

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Old 12-21-2006, 08:45 PM   #4
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Re: 2001 Trooper starting problem

amigo-2k,

Thanks for the link. I haven't been able to solve the problem yet unfortunately. I have no check engine light on, which is unlike what others have described having this problem. Cold start is generally good. Hot start can be good, but more than likely is not. Cranks fine, but fires weakly until the rpms stabilize. After that everything is fine.

Anyone else have these symptoms?

Thanks.
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Old 12-21-2006, 10:17 PM   #5
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Re: 2001 Trooper starting problem

Ironically it just started to happen to me this last weekend ... same thing.

I'm trying to determine if it is a warranty thing or not before I try to fix it.
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Old 12-21-2006, 10:21 PM   #6
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Re: 2001 Trooper starting problem

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Old 12-22-2006, 08:29 AM   #7
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Re: 2001 Trooper starting problem

Hi, I guess I will weigh in on this one. I wondered if you had checked the fuel pressure at the fuel rail on your vehicle? There is a fitting to do this on the rail somewhere. The factory has a bulletin out that describes the behavior of a faulty fuel pressure regulator that fits what you describe pretty well. The link supplied by amigo is a good one, but for clarification sake, a leaking regulator will not leak where you can see it. It means that it will not hold pressure after the fuel pump is off and allows bleed down of the fuel system. When you turn on the key, the fuel pump only turns on for a couple seconds, at which time you crank the engine. If it fails to start right away, the fuel pump will NOT turn on unless it sees the engine oil pressure rise over a few pounds which tell the pump it is OK to run because the engine is running (based on oil pressure being dependent on the engine running, a safety precaution in the event of rollover or accident). Problem is that you have to crank for a while to get the oil pressure up. An alternative is to turn the key off after trying, wait a while, then turn key back on to let the pump run again for a couple seconds. Of course, this is not fool proof, as the regulator may not hold pressure even for the brief pause, the fuel filter state can impede pressure build up, etc.
The bottom line here is diagnostics, ie: On the normal operating temp engine, when you know you have a hot start condition, you can jumper the fuel pump at the relay to be on, and then crank it to see if the engine catches right away ,and see if that cures the problem. If the pressure checks out OK, and the vehicle starts better, then chances are good that the regulator is the culprit. Changing the fuel filter and checking the pressure of the gas at the fuel rail with the pump jumpered on and then off can also tell you about the state of the pump, regulator, check valves, etc. My thinking is that the regulator is likely to be the cause based on probability once you are sure the rest of the fuel system is OK. Hope this helps, one owners non professional opinion.
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Old 01-30-2007, 09:46 AM   #8
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Re: 2001 Trooper starting problem

Guys,

Thanks for your posts and help. Sorry for not replying earlier but I've been away working for a few weeks. Anyway based on the information you've supplied I think I am just going to go ahead and replace the fuel regulator. The problem is not getting any better and I need to to something. I know on some other posts that you referenced, someone mentions that it's a 20 minute job to do this, implying it's a relatively easy job. Not having done it before can anyone give me any pointers on how to do this? Is there anything I should be aware of before I launch in? I hate getting half way through a job only to find out I need some special custom tool.

Thanks,

Biplane
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Old 01-30-2007, 11:26 AM   #9
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Re: 2001 Trooper starting problem

<H3>hi, Never done it, but does not look too bad. Do not try to unhook fuel rail from fuel supply to do this. Release fuel pressure first as described below. It looks like you should be able to do it.

good luck

2001 Isuzu Truck Trooper S 4WD V6-3.5L

Vehicle Level Engine, Cooling and Exhaust Engine Fuel Pressure Release Service and Repair Service and RepairFuel Pressure Relief Procedure

CAUTION: To reduce the risk of fire and personal injury, there are necessary to relieve the fuel system pressure filler and gauge unit before servicing the fuel system components.

CAUTION: After relieving the system pressure, a small amount of fuel may be released when servicing fuel lines or connections. Reduce the chance of personal injury by covering the fuel line fittings with a shop towel before you disconnect the fittings. The towels will absorb any fuel that may leak out. When the disconnect is completed, place the towel in an approved container.

  1. Remove the fuel cap.

  1. Remove the fuel pump relay from the underhood relay box.
  2. Start the engine and allow it to stall.
  3. Crank the engine for 30 seconds.
  4. Disconnect the negative battery cable.

</H3>



2001 Isuzu Truck Trooper S 4WD V6-3.5L

Vehicle Level Powertrain Management Fuel Delivery and Air Induction Fuel Pressure Regulator Description and Operation Description and Operation

Fuel Pressure Regulator
The fuel pressure regulator is a diaphragm-operated relief valve mounted on the fuel rail with fuel pump pressure on one side and manifold pressure on the other side. The fuel pressure regulator maintains the fuel pressure available to the injector at three times barometric pressure adjusted for engine load. It may be serviced separate.

If the pressure is too low, poor performance and a DTC P0131, DTC P0151, DTC P0171 or DTC P1171 will be the result. If the pressure is too high, excessive odor and/or a DTC P0132, DTC P0152, DTC P0172 will be the result. Refer to Fuel System Diagnosis for information on diagnosing fuel pressure conditions.


2001 Isuzu Truck Trooper S 4WD V6-3.5L

Vehicle Level Powertrain Management Computers and Control Systems Testing and Inspection Non-Trouble Code Procedures Fuel System Diagnosis Fuel System DiagnosisFuel System Diagnosis

Fuel System Diagnosis
Circuit Description
When the ignition switch is turned "ON", the powertrain control module (PCM) will turn "ON" the in-tank fuel pump. The in-tank fuel pump will remain "ON" as long as the engine is cranking or running and the PCM is receiving 58X crankshaft position pulses. If there are no 58X crankshaft position pulses, the PCM will turn the in-tank fuel pump "OFF" 2 seconds after the ignition switch is turned "ON" or 2 seconds after the engine stops running.
The in-tank fuel pump is an electric pump within an integral reservoir. The in-tank fuel pump supplies fuel through an in-line fuel filter to the fuel rail assembly. The fuel pump is designed to provide fuel at a pressure above the pressure needed by the fuel injectors. A fuel pressure regulator, attached to the fuel rail, keeps the fuel available to the fuel injectors at a regulated pressure. Unused fuel is returned to the fuel tank by a separate fuel return line.

Step 1
Steps 2 - 12
Steps 13 - 23
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart:

  1. Connect the fuel pressure gauge to the fuel feed line as shown in the fuel system illustration. Wrap a shop towel around the fuel pressure connection in order to absorb any fuel leakage that may occur when installing the fuel pressure gauge. With the ignition switch "ON" and the fuel pump running, the fuel pressure indicated by the fuel pressure gauge should be 333 - 376 kPa (48 - 55 psi) . This pressure is controlled by the amount of pressure the spring inside the fuel pressure regulator can provide.
  2. A fuel system that cannot maintain a constant fuel pressure has a leak in one or more of the following areas:
    • The fuel pump check valve.
    • The fuel pump flex line.
    • The valve or valve seat within the fuel pressure regulator.
    • The fuel injector(s).
  1. Fuel pressure that drops off during acceleration, cruise, or hard cornering may case a lean condition. A lean condition can cause a loss of power, surging, or misfire. A lean condition can be diagnosed using a Tech 2. If an extremely lean condition occurs, the oxygen sensor(s) will stop toggling. The oxygen sensor output voltage(s) will drop below 500 mV . Also, the fuel injector pulse width will increase.
IMPORTANT:</B> Make sure the fuel system is not operating in the "Fuel Cut-Off Mode".When the engine is at idle, the manifold pressure is low (high vacuum). This low pressure (high vacuum) is applied to the fuel pressure regulator diaphragm. The low pressure (high vacuum) will offset the pressure being applied to the fuel pressure regulator diaphragm by the spring inside the fuel pressure regulator. When this happens, the result is lower fuel pressure. The fuel pressure at idle will vary slightly as the barometric pressure changes, but the fuel pressure at idle should always be less than the fuel pressure noted in step 2 with the engine "OFF".
  1. Check the spark plug associated with a particular fuel injector for fouling or saturation in order to determine if that particular fuel injector is leaking. If checking the spark plug associated with a particular fuel injector for fouling or saturation does not determine that a particular fuel injector is leaking, use the following procedure:
    • Remove the fuel rail, but leave the fuel lines and injectors connected to the fuel rail. Refer to Fuel Rail Assembly in On-Vehicle Service.
    • Lift the fuel rail just enough to leave the fuel injector nozzles in the fuel injector ports.
CAUTION:</B> In order to reduce the risk of fire and personal injury that may result from fuel spraying on the engine, verify that the fuel rail is positioned over the fuel injector ports and verify that the fuel injector retaining clips are intact.
  • Pressurize the fuel system by connecting a 10 amp fused jumper between B+ and the fuel pump relay connector.
  • Visually and physically inspect the fuel injector nozzles for leaks.
  1. A rich condition may result from the fuel pressure being above 376 kPa (55 psi) . A rich condition may cause a DTC P0132 or a DTC P0172 to set. Driveability conditions associated with rich conditions can include hard starting (followed by black smoke) and a strong sulfur smell in the exhaust.
  1. This test determines if the high fuel pressure is due to a restricted fuel return line or if the high fuel pressure is due to a faulty fuel pressure regulator.
  2. A lean condition may result from fuel pressure below 333 kPa (48 psi) . A lean condition may cause a DTC P0131 or a DTC P0171 to set. Driveability conditions associated with lean conditions can include hard starting (when the engine is cold), hesitation, poor driveability, lack of power, surging , and misfiring.
  3. Restricting the fuel return line causes the fuel pressure to rise above the regulated fuel pressure. Command the fuel pump "ON" with the Tech 2. The fuel pressure should rise above 376 kPa (55 psi) as the fuel return line becomes partially closed.
NOTE:</B> Do not allow the fuel pressure to exceed 414 kPa (60 psi) . Fuel pressure in excess of414 kPa (60 psi) may damage the fuel pressure regulator.CAUTION:</B> To reduce the risk of fire and personal injury:
  • It is necessary to relieve fuel system pressure before connecting a fuel pressure gauge. Refer to Fuel Pressure Relief Procedure.
  • A small amount of fuel may be released when disconnecting the fuel lines. Cover fuel line fittings with a shop towel before disconnecting, to catch any fuel that may leak out. Place the towel in an approved container when the procedure is completed.
Fuel Pressure Relief Procedure
  1. Remove the fuel cap.
  2. Remove the fuel pump relay from the underhood relay center.
  3. Start the engine and allow it to stall.
  4. Crank the engine for an additional 3 seconds .
Fuel Gauge Installation
  1. Remove the shoulder fitting cap.
  2. Install fuel gauge J 34730-1 to the fuel feed line located in front of and above the right side valve train cover.
  3. Reinstall the fuel pump relay.
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Old 01-30-2007, 09:20 PM   #10
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Re: 2001 Trooper starting problem

atfdmike,

Thanks for the detailed post. I was inspecting my fuel pressure regulator, mainly to ensure I could remove it easily, and I noticed that when I removed the vacuum line, fuel leaked out of the vacuum fitting on the top of the regulator housing. This surely is not right and may indicate that the regulator has indeed failed.

One thing I still cannot figure is how the regulator attaches to fuel rail. The regulator apparently sits in a receptacle which is part of the fuel rail, but how it is retained in the receptacle is not clear to me yet. Not sure if it just pushes in or what. I went to the Isuzu parts dept at my local dealership today to see if I could look at a regulator, but they didn't have the right one it stock. They had one for 1998 and prior engines which looks like it pushes in to the end of the fuel rail and is retained by a flange and two screws. This is not the arrangement that I have on my 2001 model.

If anyone has any insight I would sure appreciate it.

Thanks again,

Biplane
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Old 01-30-2007, 10:21 PM   #11
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Re: 2001 Trooper starting problem

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Old 01-31-2007, 05:22 AM   #12
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Re: 2001 Trooper starting problem

Well, I would have to say that the fuel pressure regulator is definitely not supposed to have fuel in the vacuum line, so the diaphragm or whatever inside is definitely not right. I know some GM vehicles have exhibited the same failure, and it is difficult to diagnose unless you have some experience. This extra fuel has been known to compromise the catalytic converters due to the over rich fuel mixture, so fixing it will have far greater benefits.
Sorry I don't know how it attaches, but Amigo gave a good illustration, so hopefully that will help.
Good luck
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Old 01-31-2007, 10:12 PM   #13
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Re: 2001 Trooper starting problem

amigo-2k,

Thanks for the graphic. Unfortunately this is not the one I have. However I have found another local Isuzu parts dept and they had my type of Pressure Regulator in stock. Upon inspection it appears the regulator is retained in it's receptacle by a snap ring. One just has to remove the snap ring pull the regulator out and replace. The only complication is the 'Pressure regulator protector', a plastic piece that shrouds the regulator which I think I will have to remove in order to take out the snap ring. This will be tricky as one if the screws is in a tight spot at the rear of the engine compartment. Might have to cut down an allen wrench to fit in the space available.

I will let you know how it works out.

Thanks for all the help.

Bipe
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Old 01-31-2007, 11:32 PM   #14
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Re: 2001 Trooper starting problem

easy way to check the rgulator is use a clear hose to a vacuum port and regulator if it is leaking you should get fuel in the line
another one is if you have a fuel pressure guage
connect get pliers on fuel return hose behind the regulatorwhile there have someone turn the key to the on position as soon as fuel pressure rises pinch the return line so it cant leak back to the tank if pressure still drops yo could have either a leak back at the pump in the tank or you will have fuel in your clear hose indicating leaking regulator
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Old 02-01-2007, 01:57 PM   #15
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Re: 2001 Trooper starting problem

Fixed the problem,

Well, I just replaced the fuel pressure regulator and that seems to have solved my starting problem. As I anticipated, the hardest part was removing the FPR Protector, but I never did have to cut an allen wrench to fit. Just a bit a patience required to remove that rear bolt. Fortunately it wasn't too tight! Once I had moved the protector out of the way it was just a matter of removing the snap ring and lifting the regulator out. The main body of the regulator came out all in one piece but it left a couple of O rings and a fuel strainer in the bowl. The new regulator came with a seal kit and a new strainer all assembled so I simply removed the old seals and the strainer and popped the new assembly in. Replaced the snap ring (also came in the bag), reattached the protector and that was it. Works like a charm... and no more fuel in the vacuum line!

Thanks for all your advice,

Bipe.
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