4HE1 problem

[bibabo]

Hello,

I am French, and I hope you will understand the translation and help me.

I have a problem with my Isuzu NPR 4.8L 4HE1-XN 2003 engine.
Here’s the situation:

The truck was running perfectly, starting well and having power. However, there was overpressure in the cooling system, and exhaust gases were escaping through the expansion tank.
Diagnosis: blown head gasket.

I had the cylinder head checked and resurfaced (by 0.3mm) and installed a new Chinese head gasket (1.8mm inside and on the edges) to prevent the gears from getting blocked. (The Isuzu head gasket is 1.8mm inside but 1.5mm on the edges, which causes blockage). My original head gasket was an Isuzu 1.8mm.

I installed the new gasket and the resurfaced head, aligned the white mark on the camshaft with the TDC mark on the crankshaft, and torqued the lifters correctly.

When I tried turning the engine by hand, it was blocked! I forced it a little (thinking it was the engine’s compression), and then "KLAC", the crankshaft freed up but got stuck again a little further.

It turns out the white mark on the camshaft was incorrect, and I should have used the "B" mark instead. When I torqued the lifters, a valve crushed piston 1 or 4.

I then properly aligned the camshaft and reassembled everything.

When I started the engine, it ran with some difficulty. It ran almost correctly but emitted a bit of white/blue smoke. However, as soon as the automatic choke stopped, the engine ran very poorly, shook violently, and emitted a huge amount of white/blue smoke, making it impossible to drive. The smoke burns my eyes and throat.

I disassembled everything to check if I had broken a valve or punctured a piston, but everything looked perfect, no visible damage.
I then replaced the valve stem seals and lapped the valves.

I reassembled everything but had exactly the same smoke issue.

I disassembled again to check for cracks or any other damage, but everything looked perfect.
I reassembled everything (new Chinese gasket, new bolts, etc.) and replaced the turbo (thinking I might have damaged it by removing the hoses when taking off the cylinder head).

Before installing the new turbo, I started the engine without the turbo and without coolant for better visibility. The result:

• Smoke comes out of all 4 combustion chambers.
• The smoke is mainly white.
• Unburned diesel is dripping from the exhaust ports.

I had my injectors checked, and they are all fine.
I replaced the fuel, fuel filter, and water separator—everything is OK.
I reinstalled the turbo and everything else.

I started the engine, and the same problem persisted!

I disassembled everything again and installed a brand-new cylinder head with my old valves and components (everything was checked and confirmed OK).
I used a new Isuzu 1.8mm head gasket, new bolts, and reassembled everything.

STILL THE SAME PROBLEM! I'M GOING CRAZY!

So, I checked the fuel injection pump timing, and it was set at 6 degrees BTDC. Is this normal?

In the workshop manual, the injection pump for the 4HE1-TC (which is similar to my 4HE1-XN) should be set at 8 degrees BTDC.
In online videos, 9 times out of 10, it is 8 degrees BTDC for the 4HE1, sometimes 7 or 9 degrees.

I went to an ISUZU garage, but they don’t know—my truck is too old, and they refused to help me.

Is it normal that my timing is set at 6 degrees BTDC?

Could the "KLAC" from the incorrect camshaft timing have shifted a gear tooth? That seems impossible to me…

Would it be possible to adjust it to 8 degrees? That seems impossible because moving one tooth on the injection pump gear would shift it too far, by 10 or 11 degrees, since the teeth are too wide.

Or maybe the timing slipped on the crankshaft gear (which has finer teeth), but in that case, wouldn’t I be unable to properly time the camshaft?

I managed, by removing the intake manifold, to adjust the ignition timing by pivoting the pump toward the engine (moving it outward was impossible because the injector pipes were too tight), but the problem remains the same.

Maybe the "KLAC" cracked the engine block or broke something else, causing low compression and poor combustion. But across all four cylinders—is that even possible?

I'm waiting to receive a compression tester to check.

Do you have any other ideas? Camshaft position sensor? Another sensor? Where are they located? I haven’t found anything.

I have videos of the startup and smoke if needed. I can send them to you on WhatsApp.

Thank you.

 

[mekanik]

A compression test is a good start. When you refer to the automatic choke, what is that? Does this engine have an electronically controlled injection pump?
Low compression and incorrect injection timing can cause white smoke.
I wouldn't expect the injection timing being 2 degrees retarded would cause your problem.
Does your engine have EGR? Exhaust Gas Recirculation?

 

[bibabo]

Thank you for your feedback.
I don't know if it's an automatic choke, when the engine reaches a certain temperature, the engine speed drops. And then, there's a lot of smoke. It seems to me that this reduces injection thanks to the aneroid compensator. The injection pump is mechanical, with no electronics... I believe . There is no EGR valve.
I really need to know if the 6-degree mark is normal (meaning it was like that before I disassembled it) or if I somehow skipped a tooth (though that seems impossible to me). Because if 6 degrees is normal, it would mean that I’ve damaged one or more rod bearings or cracked something else... That would be really unlucky, all because of the false mark.

I'm waiting for the compression tester to check. If you have any other ideas regarding the injection pump or a hidden sensor, I’m all ears. Thanks!

 

[mekanik]

Could you send me a picture of the pump? I doubt you did any serious damage to the engine with the cam not timed right. If a valve hit a piston it will usually bend the valve and leave a mark in the piston.
The valve would need to be replaced.

 

[bibabo]

I also doubt I broke something. But that's the only thing that went wrong. I did not touch the injection pump and with the new original cylinder head and gasket I thought I would solve the smoke problem. I don't understand why the pump would be out of order. I'll take the photo tomorrow

 

[heymccall]

4he1 pump
Busbee's is a great source for NPR parts, at least in my experience.

 

[heymccall]

R&R

 

[bibabo]

Hello, I have watched all the videos possible, I have had my problem for 3 months. I contacted "busbee's" but so far no response.

 

[bibabo]

Attached are some photos:

• Photo of the engine
• Photos of the pump and identification
• Photos of the only two electrical components: the 24V on the pump, and the other, which appears to be a sensor near the pump’s gear but is not attached to it.
• Photo of the aneroid choke: In the cold position, the engine smokes moderately and runs well at 80/100. But in the hot position, the engine smokes heavily and runs at 50/100. The engine starts more or less correctly when cold (it's currently around 0 degrees), and when hot, it starts instantly despite its malfunction.
• Photo of the injector outlet: It is dry, and there is no fuel return to the tank (except for the pump’s lubrication fuel, which I had to block). Is this normal?

 

[bibabo]

suite

 

[bibabo]

If that's not normal, would it mean that my injectors are leaking into the combustion chamber? (Even though they were checked by a diesel specialist.) Or is the pump not sending enough pressure to the injectors, causing poor atomization and thus excessive smoke?

 

[mekanik]

Your engine appears to have a throttle valve on the inlet manifold. If its not opening it could be causing your problem.

 

[bibabo]

Your engine appears to have a throttle valve on the inlet manifold. If its not opening it could be causing your problem.

That's not it, I already checked. Even having dismantled the entire intake and exhaust to see what goes in and what comes out of the engine, the problem is the same.

 

[mekanik]

There is a two bolt flange with a hole in the centre on the intake manifold just behind the #3 injector line to the head. What connects there?

 

[bibabo]

It's clogged, probably for a different engine model. My problem doesn't come from the intake; everything is fine.

I also took a closer look at the aneroid, but it's not causing the drop in RPM when hot with increased smoke. In fact, it only acts on the throttle cable. If I manually force it to reduce the smoke, nothing changes. It must be controlled by the same thing that causes the drop in RPM and the increase in smoke.

 

[bibabo]

I absolutely need to know if my 6 degrees before TDC is normal, if it was set like that from the factory (maybe only for the European market?). But who can give me this information? In France, no one can answer me.
And is it normal that no fuel return to the tank after injectors? (last photo)

 

[mekanik]

I believe there should be a very small amount of fuel return to the tank from the injectors.
When do you get the tools for doing the compression test?
The fuel pump on your engine if very complex it adjusts the injection timing internally. If the engine passes the compression test it might be a good idea to remove the pump and have a fuel system shop make sure it is working properly.

 

[Birken Vogt]

I do not think very much fuel comes from the fuel injector returns. Just a tiny amount. It is not a useful thing to look at for diagnosis.

 

[bibabo]

Okay, the absence of fuel at the injector outlet has nothing to do with my problem. Thanks.

For my compression tester, I hope to receive it tomorrow; otherwise, it will be Monday. I can't wait to test the compression to see if I’ve broken something—or if, by some improbable coincidence, my pump just happened to fail on its own while I was working on the cylinder head!

 

[mekanik]

Keep us posted!
When you do the compression test make sure the throttle plate is open.