Outer Limits 4x4 Board

I have a question for any diesel guru's reading this.
Recently had a compression test on the 2.8 ltr 4JB1T in the rodeo.
It appears #2 cylinder is 40 psi lower than the other 3.
It doesnt appear to have a great deal of blowby, no obvious hissing sounds in either inlet or exhaust manifolds.
So my question is how do you check for leakage in the rings and valves on a diesel?
On a spark ignition engine you usually put in a squirt of oil and watch the difference in compression.
What do you do with a diesel?, as I assume you would then have a problem with the possible ignition of the oil you've dropped into the cylinder as it compresses and shoots your compression guage somewhere at a great rate of knots.
Over to you the necromancers of the compression engine...................

pete

Guzzi,

Sensitive topic for me at the moment as my engine packed it in 6 weeks ago. Now in for a total rebuild. Problem turned out to be bad fuel that stuffed the injectors and ended up cracking the piston crowns due to the bad combustion. When measured my compression was down to around 200PSI. I now have a $jb1t.

But not the reason for the reply. I do not have an answer as to how to test and am keen to know myself, but with regards to the figures you have, the compression spec on the 4jbit is 441PSI with a limit of 313PSI at 200RPM. Your 40 PSI drop in one cylinder may still be in spec if it meets the lower figure above.

Cheers

Rainsey

Can you get a leakdown test?
Hook that up and listen for air escaping. Especially crankcase breaker, inlet and exhaust manifolds.

There will be a factory comp spec, a service limit, and a variation percentage.
The factory spec is what the motor is designed for.
The service limit is where the motor is rooted.
The variation percentage is the allowable variation between highest and lowest.

I will call my old workplace and see waht i can dig up for you.

Layto....

Folks

On topic .. sort of..

I have finally got my truck back from the mechanic after 2 months.. ( sore point). I managed to keep the old pistons and every one of them is cracked.

The engine is a 4JB1T with only 205000 KM on the clock. In Theory only just run in. for a diesel... I will scan in the pistons later and post but each piston has cracks radiating out from the valve inserts to the edge of the piston.

The mechanic has indicated that the cause of the failure was bad fuel. The original use of the truck was in the mines and the mechanic inidated that this may have casued the prob but, on learning that I have been running biodiesel, indicated that this could also be the cause of my engine failure.
Due to the fact that he had 2 other vehicles in ( a Merc ML and a Kia) both running Bio and both with engine probs.

Any ideas?????

Cheers

rainsey

Rainsey,
How much boost were you running and how many KM's had the injectors done? and had they ever been serviced?
Any idea on exhaust temps?

Guzzi,

The boost pegs out at about 9PSI according to the guage in my truck. I bought the truck second hand years back and it has only 205,000K on the clock when the engine packed it in. I have done about 90,000K in it since I have had it. A diesel is only run in at this milage.

I have to assume that the speedo and the real milage are the same. Re the history.. I have had the truck for 5 years and the injectors have not been serviced since I have had it, but the oil, and filter changes have been religiously done as per the perscribed service intervals.

Have had no way of measuring exhaust temps. Always wanted to get a pyrometer mut could never quite get around to faulking out the bucks.

Another thing I have noticed was the big end bearings. I retreived the originals from the mechanic and one half out of each conrod has extensive pitting like in the realms of 2-3 mm in diameter in some spots. Almost like they have been extensively corroded.

If i did not know any better I would swear that the oil had never been changed and it had gone acidic and started eating away the metal.

Does anyone know if one can back track the history of a vehicle through the RTA, i.e. speedo readings on pink slips and the likes. I am curious as to how many K's the engine had actually done prior to packing it in.

Cheers

Rainsey

mate,
Ex mine truck eh...........
its quite possible that the KM's are original, and it has been neglected.
If you've found corrosion you may well have an engine that didnt have any oil changes at all, also highly possible the injectors have never been done at all either.
Mines will basically drive it for a year and then sell, why service when you only have it for a year? and will get more than 1/2 your money back when you sell it.
Mine has 225,000km and lowish compression on #2, have also found a shedload of red dirt in strange places, like yours mines had TLC and regular servicing, while I've had it.

You may be able to track it by the VIN number, holden may know who they sold it to originally or you can ask the RTA and see if you can find someone there with an IQ slightly higher than idiot to speak to about it.(don't hold your breath though).
Diesels arent much fun when they crap out are they $$$$$$.
How much for the rebuild?

Guzzi,

$6K. I have done nearly a 1000K in the last week sense getting it back so it goes back in for is 1K km tighten up. This was 4 new pistons, all new bearings, new seals, referbed fuel injectors, replacement glow plugs, head job ( lucky bugger ) radiator refurb and replacement of any hoses that looked crap. Did not include any fuel pump servicing. This turned out to be my cheapest option. Over $2,500 of this was labour!!

Scary though, $6k got me basically a new engine. I have already had the gearbox rebuild 12 months ago. All I need now is the turbo to pack it in for the trifecta.

What you have said about the mines vehicles pretty well matches the sentiments of the mechanic. Anyone out there listening... don't touch ex mines vehicles. Re chasing up the history of the truck, over the last week I have tried ringing the RTA twice just to enquire as to if it can be done. Twice I had to give up as ther was only so many times that I could handle the message that ' my call has progressed in the queue'. This is one way to not have to answer any questions... put people in a voice mail loop.

Say, now I have a new engine and can start afresh.. what engine oil do we all recommend. I am current running what the mechanic indicated as running in oil... all I know is that my oil pressure is way low, most probably to the very viscious nature of it. Do people recommend synthetic from day one?? I have to date been running Penrite HPR 20W-60. I might drop a trhead in the general section.

Cheers
Rainsey

$6K!!!???
Well at least youve now got a known engine.

Oh goody its turned into an oil thread, life doesnt get much better does it....

IMO unless you go to the trouble of fitting a bypass oil filtration system synthetic is a bit of a waste as you'll change it every 5,000 km.
Check this out https://www.amsoil.com/storefront/bf.aspx

Otherwise just run any of the known brand diesel oils that suit the 4jb1t and change it regularly.

The RTA is the current cause of greenhouse gasses, they suck in vast amounts of oxygen and produce nothing therefore changing the oxygen/co2 ratios in the atmosphere, a bit like anti 4x4 greenies really.

Did the leakdown test and compression test on mine done the other day, looks like the head will have to come off as #2 inlet is pissing out air quite loudly. Thats $250.00 worth of gaskets and bolts before you even look at fixing the head

Guzzi,

The line item on my invoice for the head was $560. They sent it off to an engineer to get it cleaned up, a though or so taken off it, the valves reseated and new seals on the valve stems.

Not a cheap task! The reseating and the seals you can probly do your self. If air is really pissing out though, it shoulds like more than a badly seated valve!!

Rainsey

For future reference - you can pick up a NEW 4JB1T off ebay for around $2500 - 3500.... why spend $6K on repairs..... ?

(link valid @ 30/10/07)
http://cgi.ebay.com.au/Brand-New-Isuzu- ... dZViewItem

Just my 2c worth

Crazy

crazy,
It may have had something to do with this in small print 1/2 way down page

*Please note:- These products are Non Genuine, fully imported*

Which to me = chinese copy.

I havent heard of anyone actually buying one, has anyone?
If so how are they?

Still haven't got around to pulling the head.
Ive also found that if you skull drag a 1000kg camper trailer for 1200 km it fixes the oil consumption nicely, didnt use a drop.
Last trip used 500ml in 500km, same oil.
Nice to have a win occasionally.

My Bad - I did think that had to be a *little* too good to be true.... Just hadn't had reason yet to pay too much more attention.

Crazy