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4JX1- 3.0DT Essential reading (part 1)

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Twister
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PostPosted: Tue Jul 26, 2005 22:53    Post subject: 4JX1- 3.0DT Essential reading (part 1) Reply with quote

Hello everyone

Welcome to the first in my series of understanding the 4JX1 Engine, and what to do if you own one.

Like many of you 3.0DT Trooper owners, I only discovered after buying the car that this engine had problems. I then spent months trying to get as much information about the 4JX1 as I could.

If I were to put it all into one post it would take me hours, and at the moment time is precious, so I intend to share what I know in small bite size chunks.

DISCLAIMER NOTICE

I am aware that this engine may be the subject of legal disputes in some parts of the world, and possibly in the UK. This post, and following posts by the author regarding the 4JX1 engine are not intended to be factual, but are merely friendly advice from one owner to another. No responsibility shall be accepted by the author for any loss or damage caused by any action taken by any persons acting upon the advice / information herewith. No legal arguments shall be entered into by the author.

Right, thats that bit done.

The following information regarding the 4JX1 engine ( in this and subsequent posts) has been gleamed from several sources. These include various web sites, ex Isuzu employees, International Motors, and good old hands on experience. All figures and dates are approximate.

THE 4JX1

There are many myths in circulation regarding this engine, and these are caused by a lack of proper information. By writing these posts I intend to rectify this, and put some of your minds at ease.

In the mid to late 90s there was a lot of pressure on vehicle manufacturers, mainly self imposed, to develop new more efficient and more powerful diesel engines. It was considered that the diesel engine would one day out perform and out sell the petrol engine.
To this end it was considered that the rotary or mechanical injector pump system was the limiting factor to the development of diesels.

Along came common rail injection systems, direct injection, and catalytic converters, never before seen on diesels.

Isuzu in their bid to make the greatest leap forward turned to one of the largest manufacturers of commercial diesel engines, Caterpillar.

Caterpillar had been using a high pressure injection system on some of their larger engines for some time. This system is known as the HEUI system ( Hydraulically activated, Electronically controlled Unit Injector )

http://www.cat.com/cda/components/securedFile/displaySecuredFileServletJSP?fileId=87775&languageId=7 ( Adobe Format )

http://hometown.aol.com/jzettel73/Injector/Injector_Operation.html

Together Isuzu and Caterpillar created the 4JX1.

Ever wondered why your car has 2 oil filters ? now you know.
Not only does it have 2 filters, it has 2 oil pumps, a primary and a secondary. The primary pump does the job of a normal oil pump, and circulates oil around the engine for lubrication. The secondary pump however is responsible for feeding extremely high pressure oil ( up to 20000 psi !!) to the top half of the injectors. Meanwhile, the bottom half of the injectors are fed with high pressure diesel. The injection process is controlled electronically. This creates a very fast, precise spray of fuel into the cylinder. Hence the superb power and torque.

The common myth about this engine is that it self destructs by burning its own oil from the sump.

This is not strictly true.

Within 12 months of the launch of this engine reports started coming in that 4JX1s were "running away" and self destructing. The reason this was happening was down to the failure of the seals within the injectors that seperate the high pressure oil from the high pressure diesel.

This is why if a 4JX1 has this problem you will find the oil level rising on the dipstick due to diesel entering the oil via the injectors. However, this is usually a slow process, and symptoms will include blue smoke from the exhaust as the engine burns oil. Also if the engine is faulty, you will find traces of oil in the fuel filter.

By 2000 Isuzu had relised that there was a problem with the injectors, and modified them on new production models.

There has never been a recall on Isuzu Troopers regarding this problem, there has however been a "Service Campaign" within the UK. ( I do not know about other countries ) . Therefore, if your motor has a full Isuzu service history, the work should have been done. If not, my advice to you is to ring International Motors, quoting your Chassis number, and ask them whether your car is subject to this campaign, whether or not the work has been done, and by whom and when.

I hope this answers some of your doubts regarding this engine.

Further posts will cover other problems commonly associated with the 4JX1, and the relevant fixes for them.

Cheers.
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PostPosted: Tue Jul 26, 2005 22:53    Post subject: Google Ads keep this community free to join!


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PostPosted: Wed Jul 27, 2005 0:15    Post subject: Reply with quote

ummm nice post but some of that isn't quite true.
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PostPosted: Wed Jul 27, 2005 3:48    Post subject: Share the knowledge Reply with quote

That's really good thanks Mr Twister Exclamation This will come in handy if I or anybody else I know for that matter looks at a 4JX1 in the future. 8)

Sorry for the dumb question, but the term 4JX1, is this the first part of the chassis number or? For example, mine is UBS17.
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PostPosted: Wed Jul 27, 2005 7:04    Post subject: Reply with quote

Keep going Mr Twister, something along these lines is much needed! If others have different opinions or corrections it would be great if you could add them.
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PostPosted: Wed Jul 27, 2005 10:08    Post subject: Reply with quote

What is the purpose of feeding high pressure oil (20000 psi must be a mistake?) to the top half of the injectors?
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PostPosted: Wed Jul 27, 2005 13:53    Post subject: Reply with quote

Steve, really enjoyed the write up even though I don't have a 4jx1 motor.
The more I read the happier I am with my 4jg2,( mbw13, these numbers are the Isuzu engine model number, ie the 2.8 Diesel is a 4jb1, the 3.1 is a 4jg2 & the 3.0 litre DOHC from the 1998 & on Troopers / Bighorns / Jackaroos / Monterays etc is the 4jx1, the new 3.0 as found in the new Rodeos & similar is the 4jh1)
From my inderstanding of the links, the 4jx1 is not a common rail engine as I understand them to be, ie those that use the fuel supplied at a very high pressure (30,000psi ?) to the injectors, which are then activated electronically to admit this high pressure fuel to the cylinder. In the Isuzu/Caterpiller HEUI injectors the fuel is suppied at moderate pressure & the engine oil at very high pressure, energises the injector to admit fuel to the cylinder, & its this oil which is causing the grief, right?, Looking forward to the next episode Smile Cheers, Steve.
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Twister
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PostPosted: Wed Jul 27, 2005 18:51    Post subject: Reply with quote

Sorry, 20,000 psi is a typo, should read 2000 psi Embarassed
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Twister
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PostPosted: Wed Jul 27, 2005 19:02    Post subject: Reply with quote

Check the link to the Caterpillar site, this explains it much better than I ever could.

You might also want to try putting "HEUI" into Google or any search engine and seeing what comes back. The information is out there, its just a case of finding it.

I am not an Isuzu expert by any means, but this is intended as a general explanation of the 4JX1 engines injector system. Things your local isuzu dealer would probably not tell you.
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PostPosted: Wed Jul 27, 2005 19:56    Post subject: Reply with quote

technically there are 3 oil pumps one does do the normal oil pump job of lubricating the engine the 2 is a low pressure pump (85psi) that pushes oil through the secondary oil filter up to a reservoir on top of the third oil pump the high pressure pump. this pumps oil at high pressure about 6 mpa or 60 bar or 882 psi on idle to the gallery that the injectors are bolted to. even the test reading of 27.9mpa would only be 279 bar or just over 4000 psi the pressure of the diesel in the tip is achieved by a 7:1 ratio of the oil pressure so at idle diesel in the tip is pressurised to about 6174 psi hence why they some times explode!
the diesel is fed to the bottom of the injectors by no more than a lift pump really in the bottom of the high pressure oil pump the injectors then sit in a constant flow of diesel in the head and the diesel enters through a hole in the side of them. when the ecu fires the poppet valve the oil rushes in and pushes on the top of a plunger which pushes on the diesel which then works the needle inside the injector like a normal diesel injector would this type fires twice the first is a pilot spray then the second is the normal spray.

this engine does run on it's own oil and is not a myth.

the seals are not the ones inside the injector that fail they are the ones on the out side that over time with constant changing temperature and pressure of diesel albeit not great pressure they just give up and start to leak.

if it's smoking it's got a problem i've never seen one yet give out blue smoke due to worn injector seals black,grey and white but not blue.
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PostPosted: Wed Jul 27, 2005 20:42    Post subject: Reply with quote

Thanks for that suzu.

I knew there would be somebody out there who would understand this engine better than I do.

I have learnt more from that one post than I have from months of internet surfing and talking to technicians.

My intentions when I started this string were to get some info out into the general arena so that all, including myself could learn a bit more about the 4JX1.

Would you know whether there is a non return valve anywhere in the oil system that keeps the second oil pump primed ?

I know this engine takes some time to fire on a cold start due to the fact it has to build up the oil pressure before the injectors will fire, but mine then takes a further 5-7 seconds to register any oil pressure on the guage, which presumably takes its reading between the 2nd and 3rd pumps.

I've been told this is an oil pressure switch fault, but am not convinced, because it only happens on cold start up following a hot shut down.

If I were to run the engine for a minute the night before from cold ( ie the oil is circulated but not warmed ) then the following morning it will register oil pressure immediately. Its as if when the oil is thinner it is seeping back into the sump.

Any ideas ?

regards
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PostPosted: Wed Jul 27, 2005 22:16    Post subject: Reply with quote

Mr Twister wrote:

I know this engine takes some time to fire on a cold start due to the fact it has to build up the oil pressure before the injectors will fire, but mine then takes a further 5-7 seconds to register any oil pressure on the guage, which presumably takes its reading between the 2nd and 3rd pumps. That is why the engine can start without there being pressure in the primary circuit.

I've been told this is an oil pressure switch fault, but am not convinced, because it only happens on cold start up following a hot shut down.

If I were to run the engine for a minute the night before from cold ( ie the oil is circulated but not warmed ) then the following morning it will register oil pressure immediately. Its as if when the oil is thinner it is seeping back into the sump.


My oil pressure behaves exactly the same way as yours does.

The oil pressure switch is located in the primary oil circuit (immediately above the main oil filter) so is not dependent on the second or third pumps.

I do not believe in my case that the oil switch is faulty as I have taken it out and tested it twice and I can also hear a difference in the engine noise when the oil pressure comes up.

I did once have a problem with one oil filter (main not secondary) which had a faulty non return valve which made the oil pressure take much longer to come up, the length of time being dependent on how long since last start up. I fixed that by replacing the oil filter with a genuine Isuzu one. As a result of this experience I don't think that the oil pressure delay you speak of is a result of an oil filter fault.

One possibility is a fault on the seal of the oil strainer/pick up on the primary circuit. This is something I am going to look at.

A while ago someone posted on this forum that the oil pressure took a few seconds to come up and the length of time depended on whether their truck was facing uphill or downhill when cold started. I haven't yet conducted an experiment on mine to see if this is the case.
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suzu
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PostPosted: Wed Jul 27, 2005 22:20    Post subject: Reply with quote

if you mean the gauge on the dash that is reading the pressure for the engine lubrication not the injector side from the top of the oil filter housing.

there is no non return valve for the low pressure oil pump

there is a relief valve in the filter housing and if using genuine filters there will be one in the filter as well. it may be creating a syphon effect due to the 5/30 oil being very runny when hot and just emptying the filter a bit, best bet would be to connect a separate gauge and see if that reads pressure straight away which would then point to a pressure switch problem.
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PostPosted: Wed Jul 27, 2005 22:25    Post subject: Reply with quote

suzu wrote:

the seals are not the ones inside the injector that fail they are the ones on the out side that over time with constant changing temperature and pressure of diesel albeit not great pressure they just give up and start to leak.


Two questions arising from this:

1/ Should the injector seals be replaced regularly, say every 80,000km / 50,000 miles, or are the latest ones good for the (unshortened Smile) life of the engine.

2/ How rapid is the flow of diesel into the oil when an injector seal starts failing and is a weekly oil check enough to pick up the problem before it becomes destructive.
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PostPosted: Wed Jul 27, 2005 23:05    Post subject: As posted Reply with quote

Hi All.

Many thanks to SteveG. Suzu and all others contributing. Keep it coming lads, the more we all learn the better we may be able to care for/nurse our 4JX1s to old age. The interest in this thread is self evident, I can’t recall seeing 12 replies to one subject in one day since I joined!

Every chip in is worthwhile, since each prompts a further response.

As I’ve said many times, whilst running they are a SUPERB motor. The best performer I’ve experienced.

Incidentally, although I understand the Trooper manufacture ceased in 2003? are there still new vehicles being brought into the country (not Japanese imports) does anybody know?

Dafydd W.W.
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Twister
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PostPosted: Wed Jul 27, 2005 23:57    Post subject: Reply with quote

Scrooge wrote

Quote:
One possibility is a fault on the seal of the oil strainer/pick up on the primary circuit. This is something I am going to look at.


This is actually one of the "service campaign" items I was going to talk about.

I too notice a slight change in the engine as the oil pressure registers, and very occasionaly a slight stall, as if the injectors are being momentarily starved.

Apparently on some but not all of these engines ( dependent on production dates) the oil pick up pipes had a habit of coming loose from their mounts. Potentially catastrophic ?.

So shortly after I discovered this I had my local trusted garage remove the sump and check both strainers.

My trusted mechanic ( he gets to do the dirty jobs like oil changes or something that I dont possess the right tools for) and I summised that if an oil pick up pipe was loose, then surely this would cause a frothing of the oil ( bubbles ) as the air from above the oil in the sump would be pulled in through the resulting leak.

However, both strainers were on solid. As I said above, Isuzu have issued a "service campaign" regarding this problem, again dependent on prod. dates, so a word with International Motors may save you getting your hands dirty.

Having read a copy of Blueprints ( The filter & parts people) trade mag, which stated that a problem sometimes occured in the pressure relief valve wherein the ballbearing in the valve would become scored and therefore not seat properly (dont quite know why), and taking into account all that is in this thread, I think I'm going to replace the valve in the oil filter housing and see what happens. It makes a bit more sense now.

It goes without saying that only original oil filters should be used on this motor. And for me only Isuzu supplied oil.

I shall let you know the results, although it may be a while before I actually get to do it. No rush, the engine has been like this since I bought it 2 1/2 years ago, and has shown no sign of any deterioration, unlike myself !

Regards
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