Engine intermittent cut out

[sands]

1999 3.0TD Trooper Citation. 85,000 faultless miles until....intermittent difficulty starting, loss of power/compete engine cut-out when travelling, restarting very difficult and sometimes only half the engine works. No fault found at Isuzu dealers. Replaced injectors, alternator, checked immobilsers and fuel systems and sensors. It goes really well apart from this intermittent engine problem. Any suggestions - we're tearing our hair out now!

[geeves]

first very ugly thought "computer" My father in law had a similar thing in a Disco took over a year to track down
Only other thoughts are wiring fault or bad earth on the engine. It might be the secondary oil pump but unlikly.
When it dies get it towed to the dealer so they can read the diagnostic record It might help

[Roscoe]

Gday SandS, First of all, does the engine cut out instantly or does it slowly loose power first or run rough?
Have you changed your grade of oil recently or even brand of oil?
When it does start normally, is the starter wind over time the same as its always been?
The times that it has cut out, has there been a common scenario, ie, under load etc?
Does the engine blow any smoke at all, at any time?
Have you altered anything at all on the engine or anything to do with the engine, eg, fitted an alarm system, imobiliser or anything electrical that did not come from the factory?

Im a Diesel Mechanic by trade but still learning about these engines ( hard to keep up with all the modern technolagy) I also own a vehicle with one of these engines in it.

geeves is on to it with the earth problem, Computors will not tolerate even the slightest resistance to earth, although, normally you will see all sorts of weid things happening in this case, ie, multiple fault codes showing for no reason etc.
If you can answer the above questions then maybe we can narrow it down a bit.

Cheers

[Benzev]

Sounds like a commencement of injection problem!! Is it a diesel EFI? If so look for the cranksignal(poor connection on the sensor perhaps) Also called the TDC sensor sometimes! Where are you at? US of A by any chance(going by the trooper citation name and reference to miles instead of kilometers).

[geeves]

3.0 TD is the 4jz1 engine with the very complicated heui injection developed by Catipilar and also used on Ford power stroke diesels. You cant do anything to these engines without a degree in computing.

[DavidM]

Friend of mine had similar symptoms on a petrol engine Mitsubishi. Several weeks of frustration and about $700 worth of replacement parts and the problem was finally traced to an insecure negative connection on the battery!! Sometimes the most frustrating problems turn out to have the simplest of causes.

David.

[Benzev]

geeves said:

3.0 TD is the 4jz1 engine with the very complicated heui injection developed by Catipilar and also used on Ford power stroke diesels. You cant do anything to these engines without a degree in computing.

Hydraulically actuated Electronically controlled Unit Injectors(HEUI) has also been used on Volkswagen diesels for some time and was developed by Oded Sturman from sturman industries but worked on a project with Caterpillar to develop what they called MEUI the project was ditched and Sturman later moved on and worked for Navistar where he developed the HEUI system from his original drawings which Caterpillar had "stolen"! Sturman had already applied for the patent but at the same time Caterpillar lodged their application taken from the drawings of Sturman while was still working with them! There's been a major courtcase in the States over this one! Needless to say Sturman was the inventor! And Navistar(now International truck and engine design) came out first with the system integrated in their engines!
With emission laws tightening up everywhere most manufacturers are going to have to make similar systems anyway! Volkswagen already has for a while! I know this because I work for a VW dealer!
To expand on the intermittent cut out problem I think it also possible you have a dodgy cam speed sensor! As the HEUI system would cease to function without this signal! Or could be just a bad connection on the plug of this sensor!