Familiar with Isuzu NPR cab/chassis with 4HE1 engine? No start

[fastline]

Nah, she is far from rusted up but of course thr business side of that turbo is. Just not sure if I heat those bolts or what just yet. ? Never had luck with any spray until something moves.

You understand my plan which is to leave down pipe on the turbo. Every bolt brings risk.

 

[OzDozer]

How many miles on the engine? That's the primary measure of whether you replace the turbo or re-use it.

 

[fastline]

How many miles on the engine? That's the primary measure of whether you replace the turbo or re-use it.

175k. Otherwise solid as a rock.

 

[OzDozer]

That turbo should be just fine to put back, at those miles. Just check to see there's no excessive movement in the bearings, and that the housings on compressor and turbine are unmarked by the wheels.

The bearings normally have a surprising degree of sloppiness, they tighten up with high temperatures.

These engines will do over 400,000 miles before they develop any signs of wear.
Isuzu engines are built like the old Allentown Macks - "robust" is the best description of them that I've heard.

 

[fastline]

Thanks! With a LOT of careful operating, I was able to get the nuts off the turbo flange. I will be replacing them to ensure the best chance of success here. The little bolt on the turbine side that bolts into the manifold was not so fortunate. Appears it has about 8 threads of engagement in which 4 on the end were galled when I finally got it out. My hope is to carefully chase the threads once the turbo is lifted up.

But all this does bring the question of why the gasket failed. I noted the rubber waste gate actuator hose was rotted off so it was previously not able to relieve. But I have since replaced that hose. Then I tested the truck exhaust brake. I am wondering if that blew the gasket? Like if the gasket was weak or broke and my bump of the exhaust brake sent it to full failure? I am not sure how much exhaust pressure they can build.

 

[heymccall]

That gasket and flange area can handle more pressure than you can throw at it. The gasket simply failed due to thermal cycling over its lifetime. Even the broken wastegate cannot create enough pressure to be an issue. The wastegate is there to A) allow faster spool up, 2) keep boost pressure limited for engine longevity, and iii) to maintain emissions standards.

 

[fastline]

That gasket and flange area can handle more pressure than you can throw at it. The gasket simply failed due to thermal cycling over its lifetime. Even the broken wastegate cannot create enough pressure to be an issue. The wastegate is there to A) allow faster spool up, 2) keep boost pressure limited for engine longevity, and iii) to maintain emissions standards.

Speaking of emissions.....lol What emissions? That's one thing I love about that truck! So much easier to work on, and less to worry about.

When that that muffler flange finally gives up (she close), I just want to know what these sound like on the straight pipe.

 

[heymccall]

"Maintain emissions standards" also means operate cleanly, which also translates to operate efficiently.

 

[fastline]

"Maintain emissions standards" also means operate cleanly, which also translates to operate efficiently.

Yeah, that is one thing I had concerns about with a turbo leak but it at least appears the injection pump does have a manifold pressure input? To compensate injection events based on boost?

 

[OzDozer]

All the Japanese diesel truck and 4WD engines have utilised an aneroid-controlled rack for many years.

The aneroid can be used to compensate for altitude, and to limit rack travel under full throttle application at low revs to prevent excessive black exhaust smoke.
An aneroid can also be used in conjunction with a turbo to control rack movement according to boost levels. Some injection pumps have two aneroids.

However, the 4HE-1 utilises a Zexel injection pump with a modern design, and it contains electronics to produce variable injection rates and variable fuel injection timing, from an old-style jerk type pump.
Zexel called it TICS technology - (Timing and Injection rate Control System).
This pump also contains electronic circuitry to provide self-diagnosis and back-up.

This design was the final frontier in jerk-type pump design, before fully electronic common rail injection took over fuel injection design - because CR injection provided a massive boost in injection pressure that the old jerk-type pumps could never produce in a million years.

These Zexel TICS pumps are pretty high-tech, and you don't fool with them, they require attention from an experienced injection pump repairer if they're displaying faulty operation, and if you want them fixed properly. They need specialised test and repair equipment.

Here's the TICS outline from Zexel -

"TICS is a sophisticated system that detects engine conditions, vehicle speed, coolant temperature, accelerator angle, etc to control the fuel-injection engine and vehicle to the highest efficiency at all times.
To control the volume and timing of injection, TICS has an electronic governor with a linear DC motor, and an electromagnetic rotary actuator.
In addition, it has a movable timing sleeve for prestroke control to realize a variable injection rate (pressure).
At low speed, the prestroke is increased to raise the injection pressure so that smoke emissions and improved while increasing the torque.
At high speed, the prestroke is reduced to advance the injection timing, while suppressing an excessive increase of the injection pressure to decrease NOx emissions."

Zexel was taken over at a corporate level by Robert Bosch GmbH in 1997 and on
July 1, 2000, Zexel Corporation changed its name to Bosch Automotive Systems Corporation.

The company then went from Zexel-branded pumps, to the Zexel-Bosch brand name.
Not sure if the Zexel name is still on any injection systems any more, the company got broken up by Bosch, who sold off various Zexel divisions.

Zexel - Wikipedia

en.wikipedia.org

 

[Delmer]

As far as I know, that injection pump system rotates the cylinder as well as the plunger to control the beginning and end timing of the injection stroke. It is very much electronically controlled, but will also run surprisingly well with none of the electronics working, with certain increased emissions.

 

[fastline]

Thanks for the deep dive on the injection system!!! I am eager to learn more about that system before I ever have to deal with issues with it. I did note that system is far from simple, with a bank of vacuum and pressure valves. One matter that I am investigating is if that injection system has any limits set on it because that truck is a former rental truck and we have experienced these types of trucks with speed or power limits on them. I have not had to truck running fast enough to see if I hit a wall yet.

I did note the lack of power past about 40mph which would make sense as it appears the aneroid system would not be able to achieve proper pressure for increased fuel. It still hit highway speed without too much issue and I have to realize it is a 175hp 4cyl, so I am not expecting to burn up the roads!

But if the rack is partially controlled with electronic means, that could complicate bringing the truck up to full power/speed.

 

[fastline]

Well this turd seems to run like a dream! Been out burning up the roads and it has brought some new questions for you NPR guys. This truck is a HAND FULL on the road! Id like to know any tricks with them? I have already pulled some of the backlash out of the steering box but I intend to do more and better inspect all the links.

I notice I take quite a ride sitting right on top of the front wheels. Somewhat a pogo stick so I'd like to try some new shocks. I checked tire pressure at 70psi which I would think would be spot on the decent ride and loading.

It does have a sway bar but not real well designed, or at least it would not have much torsional stiffness. Just trying to spot some ways to help me drive this thing! In a 20mph cross wind, it is a 2 hand, white knuckle driver. Maybe tighter steering will help manage it? Almost like the back needs a sway link! That is a lot of wind loading on that box.

 

[OzDozer]

Check your front wheel alignment, and especially the front wheel caster angle. If the box is light, there may not be enough weight to keep the back end down. A back end sitting high reduces caster angle. Big boxes have a lot of wall area that is badly affected by crosswind, more so if they're tall.
The smaller Japanese trucks tend to be a bit narrow in the track, so that doesn't help.

 

[Truck Shop]

It's a truck acting, driving like a truck in 20 mph winds.

 

[fastline]

So we have some miles on this truck now. Been running like a top! However, I have a couple simmple questions.
1. I detect an audible 'tick' sound of the engine once warm, which I suspect might be valve lash? Do these engine normally just have a slight valve noise? Nothing alarming but might be something we should look at?

2. Finally got a chance to do cold weather start testing. She will start in 30s for sure, but little slow to start and smokes a bit. Curious if these have a factory block heater? I can't find one anywhere. Sure would help ensure we can run it when cold out. I noticed the glow plug indicator does not stay on near long enough to actually do much so wondering if they have the same BS as the old GM 6.5s where you need to manually glow them or something? Even at 30F, the glow lamp was on for like 2sec. That should be more like 10s IMO

 

[Truck Shop]

IIRC I installed lower radiator hose heaters in 7 of those for food distributor vendor
because none had block heaters.

 

[OzDozer]

It doesn't hurt to do valve clearances every 100,000 miles. You will often be surprised how a valve clearance adjustment will improve the power level - particularly if they were all out of spec.

A light tick is bound to be valve lash, a heavier knock is wrist pin bushing wear, the Isuzus tend to get this type of wear with age.
I have an '89 Isuzu FSR500 with the 6BG-1 engine, it's done 720,000 kms (450,000 miles) and while it runs sweetly, it has a steady but light wrist pin knock from worn little end bushings.

It doesn't use much oil, but the exhaust smells of oil upon startup, and the oil gets black quite quickly, so there's a moderate level of ring wear in it.
It doesn't breathe all that badly, and most operators around here tell me they get well over 1,000,000 kms out of their 6BG-1 engines. Isuzu make good engines.

 

[fastline]

The truck has like 175k on the clock. I know I can see a touch of blowby from the vent tube, but I recall putting my finger on it with nothing I would be concerned about. I do know it is not a race truck! It is a 14ft box truck with 14.5k gvw and I typically am close to floored when accelerating but it will do 70mph if I need it to. I guess I would have to drive another one to know how well it runs. Certainly no stumbles, glitches, or smoke. But sitting right on that engine, I can hear that slight tick and being a wrench head, I am pretty certain it is valve noise. Probably safe to say those valves have never been touched in its life.

But I will have to evaluate the cold starts. Like to be able to fire it at 15-20F if needed. I'm sure I could get it to light but I don't like clumsy cold starts. Would be nice to just get some intake air heat. That is what CAT and my Duramax like to use. They seem to work really well rather than glows alone.

 

[fastline]

I did an oil change on it to get a clean baseline and if memory serves, it was a 14qt capacity and I think I got about 10qt out of it.

Now that dip stick!!???? Who TF designed that! It is a nightmare to use and causes me to not check oil like I should because I know it is a 5min affair! The cable that the Duramax uses seems to work well but I have heard of the bulb on the end coming off!