ISUZU NPR PROBELM

[mathura]

Hello Friends

Hope someone can help, ISUZU truck with 4HK1 engine, engine does not start unless you unplug the FRP(Fuel Rail Pressure) regulator or use starting fluid.

After engine starts it idles only no acceleration, I do not have the scan tool for ISUZU. I need some help here please

Thanks

[Juanincho]

Hello Friends

Hope someone can help, ISUZU truck with 4HK1 engine, engine does not start unless you unplug the FRP(Fuel Rail Pressure) regulator or use starting fluid.

After engine starts it idles only no acceleration, I do not have the scan tool for ISUZU. I need some help here please

Thanks

OK, did you disconected the mechanical regulator or the pressure sensor?

If you disconnect the rail pressure sensor, and there aren't any other problems, the engine will start but it won't accelerate. (it enters in backup mode) When you use starting fluid, it makes the engine to gain speed, check the starting system (batteries, starter, and so on).

Try to scan using the check engine light, look at the ecm, there are a group of connectors, look for the blue ones, and join them while ignition is on. It should begin flashing codes. Each code will be shown three times.

Look at the engine crank speed sensor, check its resistance, or other damage on it.

Did you do some kind of repair, or overhaul? Check for incorrrect assembly (specially on the timing, and camshaft, sometimes it is 180~ advanced or retarded)

Good luck !!

:thrasher:

[mathura]

OK, did you disconected the mechanical regulator or the pressure sensor?

If you disconnect the rail pressure sensor, and there aren't any other problems, the engine will start but it won't accelerate. (it enters in backup mode) When you use starting fluid, it makes the engine to gain speed, check the starting system (batteries, starter, and so on).

Try to scan using the check engine light, look at the ecm, there are a group of connectors, look for the blue ones, and join them while ignition is on. It should begin flashing codes. Each code will be shown three times.

Look at the engine crank speed sensor, check its resistance, or other damage on it.

Did you do some kind of repair, or overhaul? Check for incorrrect assembly (specially on the timing, and camshaft, sometimes it is 180~ advanced or retarded)

Good luck !!

:thrasher:
Thanks for the response
Can you give me some more details about the connector location that I can use to flash the codes.
No mechanical repairs was done to this engine

[Juanincho]

Usually the ecm is located behind the seat, may be at the drivers or the other, just pull the seat up. There will be the ecm and 2 or 3 relays. Near the relays, there will be a group of connectors, may be taped, look for the connectors, they are yellow and blue, male and female. Turn ignition on, join the blue connectors and the check light will flash the codes, 3 times each, the yellow connectors are for deleting the codes.

[mathura]

Usually the ecm is located behind the seat, may be at the drivers or the other, just pull the seat up. There will be the ecm and 2 or 3 relays. Near the relays, there will be a group of connectors, may be taped, look for the connectors, they are yellow and blue, male and female. Turn ignition on, join the blue connectors and the check light will flash the codes, 3 times each, the yellow connectors are for deleting the codes.


Appreciate your time

This is a 2005 model and the ECM is mounted under the truck near the transmission, I do not see any connector except 1 blue connector, I tried jumping across the pins but the light will not flash.
I have gotten hold of the manual but it does not say anyting about flashing the codes it only speaks about using the diagonistic tool.

[eric486]

Check out this bulletin that isuzu has for the 4hk1. I've seen a few come in our shop that needed the SCV for a no throttle response complaint.

[mathura]

Check out this bulletin that isuzu has for the 4hk1. I've seen a few come in our shop that needed the SCV for a no throttle response complaint.

Thanks for the information

Do you know how this engine flash codes can be done, without using the Tech 2 software.

[bekamon]

I had the same problem a couple of days ago and the problem was that the ecm was bad

[mathura]

I had the same problem a couple of days ago and the problem was that the ecm was bad

Thanks for letting me know, however I have the manual for this engine but it does not describe how to use the flash code method only describes using tech 2

[Poptest]

Hello Mathura,

Put a jumper across pins 4 and 6 on obd socket. I hope this helps.

[mathura]

Now I need some additional help with this ISUZU engine(4HK1-TC).

I replaced the fuel rail pressure sensor and the engine is now starting but it is not delivering any fuel to the #4 injector.
When you start all four cylinders are working but when you accelerate the engine to maximum it starts to miss on #4, if you loose the injection line on #4 no fuel.

I removed the common rail accumulator and check to see if any thing is blocking the #4 but found nothing, interchanged #4 delivery unit with another but no fuel when accelerate to max engine RPM, and even when back to idle no fuel.

Any suggestions

[peter21]

Now I need some additional help with this ISUZU engine(4HK1-TC).

I replaced the fuel rail pressure sensor and the engine is now starting but it is not delivering any fuel to the #4 injector.
When you start all four cylinders are working but when you accelerate the engine to maximum it starts to miss on #4, if you loose the injection line on #4 no fuel.

I removed the common rail accumulator and check to see if any thing is blocking the #4 but found nothing, interchanged #4 delivery unit with another but no fuel when accelerate to max engine RPM, and even when back to idle no fuel.

Any suggestions

maybe the injector is bad, I haved same problem on 6HK1 I change the injector and the problem was resolved... Test by switching injectors....

[mathura]

maybe the injector is bad, I haved same problem on 6HK1 I change the injector and the problem was resolved... Test by switching injectors....

Iwill give it a try and let you know the results

[mathura]

maybe the injector is bad, I haved same problem on 6HK1 I change the injector and the problem was resolved... Test by switching injectors....

You seems to be right, I switched injectors and the probelm follows the injector.
I have placed an order for new injector, will let you know how it goes

Thanks for your help

[mathura]

UPDATE

Changed injector for #4 cylinder, job succesful work great now.

Many thanks Peter

[eric486]

UPDATE

Changed injector for #4 cylinder, job succesful work great now.

Many thanks Peter

More people should update when they found the problem, it makes this forum much more informative!

[mathura]

The truck encountered the same probelm after in use for about three weeks, this time the issue was with the #3 injector, I replaced the injector and it woks fine once more.

Question: What can possibly cause these injectors to fail, I am afraid that #1&2 may fail soon.

Another thing that the owner brought to my attention, when you start the truck in the morning it sounds as though it is missing and if you attempt to drive it the engine vibrates a lot. If you allow it to warm up for about 5 minutes it works fine.

Any ideas, no codes thrown, check lamp off.

Thanks

[Solomio]

Those engines have a reputation for making noises when you start then cold. That's just the way it is. Bad or cheap fuel, oil or even the wrong fuel filter will cause injector failure.

[mathura]

Those engines have a reputation for making noises when you start then cold. That's just the way it is. Bad or cheap fuel, oil or even the wrong fuel filter will cause injector failure.

I think we dont get the best quality of fuel here, is there an additive that I can use to improve fuel quality

[rp1210a]

its very common for the hi-pres pump to fail and send metal particles to the injectors. maybe the pump is starting to fail and clogging the injectors.

[4hillbilly]

hi i have a 4hk1 with a dpf filter here in Australia and want to know if you bloke over there have by passed the dpf filter if so how... and does any one know what oms are coming out of the pressure switch on the chassie near the exhaust burner
thank