How to bleed fuel system and change fuel filters?

Tiny
ANONYMOUS
  • MEMBER
  • 2011 ISUZU NPR
  • 45,000 MILES
How do I bleed the fuel system after replacing the fuel filter cartridge? I have the bleeder open and pumping primer on top of water separator does not seem to be doing anything.
Monday, December 10th, 2012 AT 8:21 PM

18 Replies

Tiny
KHLOW2008
  • EXPERT
Open the air bleed screw and there should be a manual pump near the engine fuel distributor. Here are diagrams and instructions below on how to replace the fuel filters below

If you are not able to do it, remove the filter, fill it up with clean diesel and reinstall. Start the engine and let it self bleed. Try keeping the throttle open slightly or revving it to keep engine from stalling until it stabilizes.

Check out the diagrams (Below). Please let us know if you need anything else to get the problem fixed.

Cheers
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Monday, December 10th, 2012 AT 8:43 PM
Tiny
JTQUILICI
  • MEMBER
  • 2010 ISUZU NPR
  • 20,000 MILES
I have a 2010 isuzu npr, I replaced the fuel filter and the light is still on. How do I reset the light?
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Thursday, August 23rd, 2018 AT 11:59 AM (Merged)
Tiny
DOCFIXIT
  • EXPERT
A check engine light or maintance reminder light?
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Thursday, August 23rd, 2018 AT 11:59 AM (Merged)
Tiny
JTQUILICI
  • MEMBER
Yes, now I need to re-set the light
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)
Tiny
DOCFIXIT
  • EXPERT
That was an or question so which light?
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)
Tiny
JTQUILICI
  • MEMBER
The fuel filter replacement light
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)
Tiny
DOCFIXIT
  • EXPERT
Getting conflicting info is there a service rest button left of speedo? Or is there a button marked M? And is there controls in steering wheel?
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)
Tiny
JTQUILICI
  • MEMBER
There are two buttons left of the spedo, no buttons on the steering wheel
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)
Tiny
JAGERRULER
  • MEMBER
  • 2007 ISUZU NPR
I have a 2007 isuzu npr with the fuel filter light on, on the dash. I have replaced the filter. What are some possible causes that the light is still on?
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)
Tiny
SATURNTECH9
  • EXPERT
This is all I can find on your problem hope it help's.
Fuel Sedimenter Switch

Fuel System

Inspection

1. Check that there is continuity between the switch connector terminals when the float in the fuel sedimenter is above the water drain line.
2. Turn on the ignition switch, remove the fuel sedimenter connector, and connect the terminals of the connectors on the harness side. Confirm that the sedimenter warning lamp lights up.

If abnormalities are detected during the check, replace the switch parts and carry out repairs in case of defective connection between circuits or short circuits.
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)
Tiny
DOCFIXIT
  • EXPERT
Can you post a pic?
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)
Tiny
MGARRARD
  • MEMBER
  • 1999 ISUZU NPR
  • 78,000 MILES
This morning I purchased a 1999 Isuzu NPR V8 350 in Ontario, CA for $6000.00. I test drove the vehicle and everything seemed just fine. I began my 6 hour drive back to Phoenix. As I increased speed upwards of 70-75mph the acceleration started to struggle. So, I kept my speed around 70-75 mph. My gas gauge was showing less than a quarter of a tank so I stopped to get fuel. As I pulled into the gas station the truck shut off! I coasted up to the gas pump but was just short. I tried starting the engine but it wouldn't start. It just gurgled and had some engine knock. After a 5 min wait I was able to start he truck and pull up to the pump. I filled the tank and got back on the highway. Things seemed to be the same as mentioned above until I was back down to about a quarter tank of fuel. My acceleration/power decreased and the engine shut off again as I exited the highway! I tried to start the truck again but no luck. After another 5 min wait I was able to start the truck again so I could pull up to the pump. I filled the tank and did some calculations. I only got 7.75 miles per gallon on one tank! That's horrible. As I began to drive again I could only get up to 50mph on the highway. Then after a short drive I began to loose acceleration/power again so I pulled over. I waited 10 minutes and tried to drive again. I only was able to drive about 8 miles at 50mph so I pulled over again and decided to have some dinner. Now I am going to go and try to drive it again after a 40 min wait. I will let you know what happens.

Could it be the fuel filter? The ERG valve? Clogged fuel lines? Exhaust flap getting stuck?

Any help you could provide would be greatly appreciated. Thank you. Marc
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)
Tiny
KHLOW2008
  • EXPERT
There are a few possibilities and the fuel filter is might be partially clogged as the engine is struggling when you increae the speed.

Reduce the driving speed to see if there are any changes.
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)
Tiny
MGARRARD
  • MEMBER
After waiting 40 min last night I was able to drive the truck 50 miles back to my house without any problems. I didn't try any rapid accelerations or try to top out the speed for fear of having any problems. I just wanted to get home.

This morning I drove the truck to my job site and did not have the same problems I experienced last night. The only thing I noticed this morning was a knocking noise upon acceleration. It was coming from the driver side and sounded like it was coming from the exhaust/muffler area. This only happened one time.

Now I am sitting in the truck idling with the AC on and I can smell the fumes. The AC is on recycle so I shouldn't be smellin the gas fumes.

Hopefully this provides you with the information you are needing. Where should I begin with the trouble shooting process? Thank you again for your assistance as I just spent my hard earned $6000.00 and can't afford to spend another $1,000-3,000.00 on repairs.
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)
Tiny
MGARRARD
  • MEMBER
Let me add that just now when I got out of the truck I heard that knocking noise coming from the catalytic converter. Could this be my dilemma?
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)
Tiny
KHLOW2008
  • EXPERT
It is possible the catalytic converter is bad and this can result in the knocking noise you are hearing. It can also cause the inability of high speed driving as knocking noise form the catalytic converter can mean it is dislodged internally and cause partial blockage of the exhaust system.

You would need to remove it to check. A viausl inspection might tell you something.

When the catalytic converter fails, it would usually throw a code. Is the MIL indicating and have you checked for trouble codes?
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)
Tiny
MGARRARD
  • MEMBER
Yesterday (Tuesday) I drove the truck for the first time since arriving in Phoenix. The check engine light kicked on and stayed on the entire time I drove the truck. At stop lights the truck would go from idling as if the engine wasnt even running (which is great) to choking every 10 seconds or so. The choking made it feel like the truck was going stall. It had me in a panic everytime I came up to a light.

So, I stopped by O'Reilleys and had them check for a code. It said it was an issue related to the catalytic converter. I took the truck in to a muffler shop and they installed two new cats. The one cat was completely wasted inside and definitely needed to be replaced. After an hours wait. Voila. Two new cats and I was back on the road. I thought my problems were resolved! NOPE! Read on.

Once again the truck acted as if it wanted to stall at lights! Then as I was exiting the freeway, the truck decided to stall completely as I pulled up to the light. I couldnt restart the truck so I exited the truck and gave it 5 minutes. I went back to the truck and started it up. I drove straight to an Auto Zone. I spoke with one of the guys and described my problem. He said it could be a fuel filter, fuel pump, a sensor, a vacuum issue, etc. I purchased a fuel filter and I am going to start with that. While I am in there I am going to check the spark plugs as well.

Does anyone have any other suggestions or recommendations? Thank you for your help!
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)
Tiny
KHLOW2008
  • EXPERT
Check the fuel pressure and if the idling was too low, have the throttle body and IAC cleaned.

Other than that your planned course of action should be sufficient for now.
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Thursday, August 23rd, 2018 AT 12:00 PM (Merged)

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