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Smokey and Slow

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Smokey and Slow

Postby HornimusPrime » Mon Nov 28, 2016 6:10 pm

Hey crew, 1st post. Decided to join the ranks after lurking for far to long reading many helpful posts from you guys, figured i would get involved

I have a 96' LWB bighorn with electric fuel pump, standard engine/turbo (for now) owned it for 25000k and has 300km on clock now. I service every 5000k with what ever she needs.
Under previous ownership has had reconditioned injectors at approx 270k

my problem is that over time its become very boggy and smokey below roughly 2300ish rpm . pretty much every time I take off from a stand still I leave the car behind me in a lovely cloud of black smoke in addition I'm very slow until I hit 2300rpm then its all go as usual.

Things I have done to try remedy
-new fuel filter
-ran a high dose of injector cleaner

after extensive research on clubisuzu.com and elsewhere I'm left with these possibilities and want to sound them out with you guys, I have listed them in the order that I think is most likely.

1. faulty turbo - as far as I know / can tell its the original unit (has had the death whine on shut down in all my ownership so its on the way out slowly) removed air intake today and has some play but spins ok to the hand, hard to know what condition its in without having a new one to compare. would like to replace with a new RHF5 VICC when time and budget allows.

2. Faulty EGR valves - I am planning on removing these regardless, just ordered a blanking kit off ebay. the vac houses are pretty knacked, I have done my best to tidy them up in case one was leaking.

3. injectors - either becoming fouled again in 30000k or they were not done when I was told (no receipt)

4. ???? the great mystery of engines, could be something I have not thought of?????

if anyone has any ideas / feedback on the above that would be great, thanks alot in advance.
HornimusPrime
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Re: Smokey and Slow

Postby HornimusPrime » Mon Nov 28, 2016 6:12 pm

forgot to add that I have ordered a boost gauge to hook up this week to get an idea of what the turbo is doing and confirm / deny a fault with that.
HornimusPrime
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Re: Smokey and Slow

Postby Jacktragic » Tue Nov 29, 2016 1:34 pm

Hi
Is your engine a 4JG2T with EFI pump and ECU controller, not sure if it has a throttle body senor also? These might need checking as well. The ECU has a life cycle. Turbo boost a good start and one or more injector nozzles might partly stuck open as it sound like it is over fuelling.
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Re: Smokey and Slow

Postby HornimusPrime » Tue Nov 29, 2016 2:22 pm

Yes I have a electronic fuel pump, and i reckon your right about the over fuelling its a matter of why.

So have installed boost gauge today and found the following.

It hits full boost (12psi) at about 2500rpm which seams very late in the piece for a diesel. this coincides with the power I have (and dont have).
this is leading me to think the turbo is the problem unless something like the injectors or egr can affect when you boost comes on? from my knowledge this seams unlikely but I come from a turbo petrol background.

This all leaves me thinking that the smoke is all the fuel it would normally need going out the exhaust, if the turbo was providing the boost correctly. From what I have researched this would mean it would be running hotter combustion temps with the air/fuel mix being wrong? is this likely to be harmful in the mean time to drive it?
HornimusPrime
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Vehicle: 1996 Isuzu Bighorn LWB - Factory for now

Re: Smokey and Slow

Postby turnturn » Tue Nov 29, 2016 4:19 pm

A bit of a long shot but maybe your Manifold Pressure Compensator is faulty or badly adjusted?
I am of course assuming that the Computer Controlled Injector Pump runs one?

Edit: I have just re-read your original post and what I have suggested above is probably unlikely as you are running rich before the boost comes on.....
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Re: Smokey and Slow

Postby geeves » Tue Nov 29, 2016 6:28 pm

could be low compression but its more likely a fuel issue. Leaky injectors would cause problems at all revs but a faulty fuel pump could play up more at low revs. Low fuel pressure causing injection timing to slow or the injector timing is retarded although this should also cause overheating.
Diesels dont have a mixture as such. They always take as much air as they can and only adjust fuel
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: Smokey and Slow

Postby HornimusPrime » Wed Nov 30, 2016 7:37 am

Thank you for you replies. just to confirm, these possible issues with fuel pump / injectors can have a direct affect on the boost of turbo? I'm not fully versed on what in involved with having an electric pump. I would have though the turbo would still spool up as usual with a fuelling issue?

surely only achieving 12psi by 2500rpm is a problem on its own? when should I expect full boost on a factory engine?
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Re: Smokey and Slow

Postby geeves » Wed Nov 30, 2016 8:23 am

It is low. You should hit 12 just below 2000 at full throttle. However this is affected by other engine issues as well. If your engine isnt producing full power the turbo doesnt get spun as well. Also issues with intake and exhaust flow will slow the turbo
Sanding your knuckles before starting work can help. That way you cant skin them
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Re: Smokey and Slow

Postby HornimusPrime » Mon May 08, 2017 6:55 pm

I thought I would post a conclusion to this to help someone with a similar problem. Turns out it was the EGR valves, I had mine blocked off and just like that no more black smoke and a much more responsive engine, a very easy cheap fix compared to replacing entire turbo. I was away for the whole summer and only just now got it sorted. Would definitely advise removing EGR on the 4jg2 even as a pre emptive measure based on my experience with this problem, the less things you have the less that can go wrong. back to happy 4x4ing and not pouring black smoke everywhere!
HornimusPrime
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Re: Smokey and Slow

Postby turnturn » Mon May 08, 2017 9:50 pm

Good result and thanks for remembering to post it. This could help somebody else in the furure.
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Snorkle, Intercooled
1993 Isuzu Mu 2.8 Manual (UCS55)
Spare Parts/Donor
1994 Isuzu Mu 3.1 Manual (UCS69)
Snorkle, Intercooled
1996 Isuzu Mu 3.1 Manual (UCS69)
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