Runs but shuts off alot

Tiny
MCS4574
  • MEMBER
  • 2006 ISUZU NPR
  • 105,000 MILES
The truck was shutting off so I changed fuel filter and then I bled the lines. I got it to run thinking I fixed the problem but it started shutting off even more frequitly. I need help this truck needs to be on the road.
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Thursday, October 24th, 2013 AT 6:27 AM

15 Replies

Tiny
KEN
  • ADMIN
Hello,

These trucks (Diesels) had a problem with the secondary fuel pump going out causing the engine to stall out. Here are diagrams to help you remove the pump and get back going again.

Check out the diagrams (Below)

Please let us know if you need anything else to get the problem fixed.

Cheers, Ken
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Sunday, January 7th, 2018 AT 7:54 PM
Tiny
DCMEZA
  • MEMBER
  • 2001 ISUZU NPR
  • 50,000 MILES
Rebuilt the engine, runs well but stalls in drive or reverse when you take your foot off the brake. 2001 Izuzu diesel NPR 4he1t
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Tuesday, October 30th, 2018 AT 5:34 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Idle is controlled through the injector pump. Was there any issue prior to the re build?

Roy
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Tuesday, October 30th, 2018 AT 5:34 PM (Merged)
Tiny
DCMEZA
  • MEMBER
The guy bought it broken so we do not know. I guess that is the best place to start?
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Tuesday, October 30th, 2018 AT 5:34 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Most likely a failure in the injector pump.

Roy
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Tuesday, October 30th, 2018 AT 5:34 PM (Merged)
Tiny
DCMEZA
  • MEMBER
Oh, and thank you!
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Tuesday, October 30th, 2018 AT 5:34 PM (Merged)
Tiny
BENNETTSAUTO@COMCAST.NET
  • MEMBER
  • 2005 ISUZU NPR
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 75,000 MILES
2005 isuzu npr if you take off full throttle before you reach high gear the engine will cut back to just an idle you have to turn key off wait a couple minutes then you can go again now if you take off up to half throttle you have no trouble at all it has a diesel turbo intercooled engine 5.2 vin # JALBUB16557012203 the throttle pedal is all fly by wire theres no codes we have changed fuel filters we dropped the tank cleaned it out we blew air back threw the fuel system
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Tuesday, October 30th, 2018 AT 5:34 PM (Merged)
Tiny
DOCFIXIT
  • EXPERT
Was fuel pressure checked? Was accelerator pedal OHM checked for dead spot?
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Tuesday, October 30th, 2018 AT 5:34 PM (Merged)
Tiny
GGALLIFANT
  • MEMBER
  • 1999 ISUZU NPR
  • V8
  • 2WD
  • AUTOMATIC
  • 100,000 MILES
We have paid for several tow trucks. Sometimes it starts back up after a few minutes of Embarrassment with a Trailer full of Equipment and a Four Man Crew standing on the side of the road, that pushed the rig out of a busy intersection only to Leave them Stranded again later and possibly farther from home.
We were charged for Tow Trucks and replacement of Fuel Pumps four or five times, Fuel Filters Etc.

I have had many Mechanics point out the Stupidity of the "Spider Fuel Delivery System" under the Intake Manifold, This is a very expensive system and not a SOLUTION, GM Designed for only two years.
No Recalls - WEIRD! However, no one has admitted to the True Issue and Owners can't afford to be their Test Program! This is a WORK TRUCK! Men are stranded on their way to work!

I have two of these 1999 Sweet Trucks and they have under 100K on them because no employees are willing to be stranded in them any longer! I wish GM would answer for this issue!

Any Ideas how to keep them running would be greatly appreciated. I hear this is Wide Spread, so I hope there is a solution other than towing and fuel pumps.
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Tuesday, October 30th, 2018 AT 5:34 PM (Merged)
Tiny
CARADIODOC
  • EXPERT
Why so many fuel pumps? At some point you have to figure out that isn't the cause of the stalling. Has anyone actually diagnosed anything yet? Has anyone checked for spark when it won't start? By far the most common causes of engine stalling on any brand of vehicle causes a loss of fuel AND spark but too many people get hung up on the first thing they find missing, and don't look for any additional clues. Has anyone read the diagnostic fault codes yet?

I'm definitely not a fan of GM's customer-unfriendly business practices, but what you're describing happens all the time on all brands of vehicles. That's no reason to expect a recall or special action on their part. What you need is a proper diagnosis.

When you have an engine running problem, you need to list the engine size. In this case the only V-8 is a 5.7L so there's no mystery there. Your engine uses a crankshaft position sensor, a camshaft position sensor inside the distributor, and an ignition module. It is real common for any of those to fail by becoming heat-sensitive, then they work again after they cool down for about an hour. When the signal is lost from either sensor, the Engine Computer will shut down the ignition coil, injectors, and the fuel pump because it thinks the engine stopped rotating. That is a safety measure done on all vehicles in case a fuel line gets ruptured in a crash. The fuel pump could keep running and dump raw fuel on the ground creating a major fire hazard. With no fuel pressure, the engine can't run. When it stalls, the Engine Computer sees that engine rotation stopped by the lack of signals from those sensors, so it shuts everything down, including the fuel pump. A lot of people only see the stopped fuel pump and they assume it is defective.

If you're lucky, there will be a diagnostic fault code stored in the Engine Computer. Don't disconnect the battery or let it run dead because that will erase that valuable information. Many auto parts stores will read those codes for you for free. Be aware that fault codes never say to replace a part or that one is defective. They only indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition. Many auto parts salespeople don't understand that. When a sensor is referenced in a fault code, it is actually the cause of that code about 50 percent of the time. You also have to rule out broken wires, corroded splices, stretched and corroded connector terminals, and things like that.

Sometimes a code doesn't set because the engine stops running too quickly. In that case you need a scanner to view live data. During the no-start condition, most scanners will list those two sensors with some indication of whether signals are being received from them during cranking.
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Tuesday, October 30th, 2018 AT 5:34 PM (Merged)
Tiny
GGALLIFANT
  • MEMBER
Thank You for Your Interest and Answering,

I have been out on a limb for sometime.

I understand what you are saying and some of these things / theories open new avenues of thinking.

If your up, please call me on my cell phone and let me explain what we have considered and tried. It might save my poor typing and your breathe.

Respectfully,

Grant
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Tuesday, October 30th, 2018 AT 5:34 PM (Merged)
Tiny
CARADIODOC
  • EXPERT
Actually, I had a major house fire so I have to drive ten miles each night to sit in the public library parking lot to use their wireless internet. I'm fixin' to head home pretty soon because I'm falling asleep. On top of that, I'm not as knowledgeable about your vehicle as I'd like to be. I have to treat it like all the other systems that work the same way, other than the injectors.

From what you've said so far, this problem isn't related to the unusual injector system. It sounds identical to what happens on every other brand of vehicle. The two things you can do are to check for spark the next time it won't start, and get the fault codes read. If there's a code related to one of those sensors, we'll be half done with the diagnosis.

Your truck may be different, but in general, stalling is related to the fuel pump and supply system only about one or two percent of the time, and it's related to the ignition coil, or ignition module, when one is used, like on your truck, about one or two percent of the time. Well over 95 percent of the time stalling is caused by something that affects both systems, and that's the cam and crank sensors.
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Tuesday, October 30th, 2018 AT 5:34 PM (Merged)
Tiny
GGALLIFANT
  • MEMBER
Fuel Delivery Pressure has been the Theory.

I have heard a little of the Crank and Cam Sensors, however I have had this on more than one of these trucks from brand new to now.

It seems to be a repeat situation. I have heard or read others struggling. What are the chances I Bought more than 1 of these.

I wish the Chevrolet Fleet / Commercial Dealerships that have towed these while still under Warranty and After would have supplied me with a Code from the Computer or just handled the Issue. I do have a ton of paperwork to sort through for their repairs. I will review that again.

I don't think they were too concerned then as the Truck restarts after time and they send it back to me only to have it repeat this days or weeks later.

Respectfully,

g
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Tuesday, October 30th, 2018 AT 5:34 PM (Merged)
Tiny
GGALLIFANT
  • MEMBER
Thank You,

Sorry for your House Scenario!

I will follow the Sensor lead which seems more practical then fuel pressures which all have focused on.

Thx,

g
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Tuesday, October 30th, 2018 AT 5:34 PM (Merged)
Tiny
CARADIODOC
  • EXPERT
Thank you. The insurance company has been real good to me so far.

Stop by an auto parts store and ask them to read the codes. They do that for free and it just takes a couple of minutes. The only thing is they often self-erase after around 50 starts if the problem doesn't act up again within that time. If there's no code related to this, check for spark as soon as it quits again.

As a point of interest, I chased an intermittent problem on my '88 Grand Caravan daily driver for a year and a half. I drove it all that time with a fuel pressure gauge tied to the radio antenna, and I learned that 50 pounds of fuel pressure is normal, and it would still run with no symptoms down to 20 pounds. At 15 pounds it started to sputter. That surprised me.

From some of the high-level classes I attended, I've heard on multiple occasions that a lot of GM truck engines will not start or run right if the fuel pressure is as little as two pounds low. I can't verify that from experience, but with all the pumps you've gone through, I doubt fuel pressure is the problem.
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Tuesday, October 30th, 2018 AT 5:34 PM (Merged)

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