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Old 10-31-2013, 08:51 PM   #1
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Is my turbo working?

ok, this may be another stupid question to some but here goes. since ive never owned a turbo charged vehicle before, my isuzu turbo engine is all new to me. my question is, without having a point of reference, how do i know if my turbo is functioning properly or at all. i was bound and determined to get our maiden voyage in this fall and indeed a couple weeks ago we ventured about 100 miles to raccoon lake SRA in central indiana. we had an absolute blast and the 310 ran very well i must say. ive been working my way through her like so many others and i was pleased. i didnt keep track of our miles per gallon. she did seem to have a little problem with the inclines in the central indiana area which i consider to be rather mild. i never had to down shift but if i didnt get a running start at a long incline she would slow down a bit and seemed to have a bit of trouble maintaining a consistant speed. since i really dont know what the performance should be im just wondering if my turbo is functioning properly. is there a way for me to tell or do i just need a qualified mechanic to look at it. on relatively flat interstate i was running at about 2850 rpm at 60 mph. any thoughts folks.
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Old 10-31-2013, 09:23 PM   #2
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You should have a boost meter on the dash. It should indicate an increase in pressure as the turbo kicks in.
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Old 10-31-2013, 09:34 PM   #3
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Hi, your turbo should also make a high pitched whine noise; This doesn't mean that it is working correctly.
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Old 10-31-2013, 11:22 PM   #4
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If your rig does not have them, both a boost and an exhaust temperature meter are very helpful. The exhaust temp is quite critical on a diesel, especially a turbo one. A friend had a diesel 280 and the exhaust temp would go up to dangerous temps on any grade. He finally found that some PO idiot had put the mufflers on backwards. After that he could run rings around me in my 454 equipped 310. He could hill climb fantastically well. Now, the brakes on his 280 were terrible and mine were much better so he went uphill fast and downhill slow, I went slow up, but never had any stopping issues so could come down faster than he did.
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Old 11-01-2013, 03:17 AM   #5
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thanks folks. now does the boost gauge work off a vacuum line? i was up under the dash the other day replacing the heater control cable and found what appeared to be a vacuum line just hanging free. i didnt know where it should be connected and its still hanging there. could this be the line going to the boost gauge? is there any other vacuum powered gauge or control up under the dash?
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Old 11-01-2013, 04:57 AM   #6
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When the turbo spins-up the manifold vacuum becomes pressure.

The gauge indicates both and is connected to the intake plenum.

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Old 11-01-2013, 08:47 AM   #7
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thanks folks. now does the boost gauge work off a vacuum line? i was up under the dash the other day replacing the heater control cable and found what appeared to be a vacuum line just hanging free. i didnt know where it should be connected and its still hanging there. could this be the line going to the boost gauge? is there any other vacuum powered gauge or control up under the dash?
All of the heater and dash air conditioning controls are vacuum operated. The lines are all under the dash.
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Old 11-01-2013, 02:15 PM   #8
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its sure a mess under that dash
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Old 11-01-2013, 02:18 PM   #9
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im not getting a reading on either of the turbo gauges so i got to trace down whats up. so, there should be a vacuum line to the pressure gauge?
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Old 11-01-2013, 03:12 PM   #10
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im not getting a reading on either of the turbo gauges so i got to trace down whats up. so, there should be a vacuum line to the pressure gauge?
Can't speak specifically of the Isuzu but the Cummins doesn't supply vacuum for the heater. There is a separate electric vacuum pump for that. You should see at least a few pounds of boost under load. If not I would expect a gauge problem or turbo problem.
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Old 11-01-2013, 03:50 PM   #11
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When you open the doghouse you will see a cast aluminum tube going from left to right across the top of the engine. It's 3" to 4" in diameter. Right in the center on top of the tube is a small elbow fitting with about a 1/16" I.D. rubber tube, it looks like a vacuum tube. That is the tube that goes to your boost gauge. If you remove the tube and rev up the engine you will feel the turbo pressure. The original BAE turbo was a low pressure aftermarket add on turbo and will provide a maximum boost of about 10 psi.

The Isuzu has a vacuum pump on the rear of the alternator. The original step is vacuum operated as well as the cruise control. Some years have vacuum operated A/C and heater controls, some do not. My 1982 has no vacuum to the A/C and heater control.
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Old 11-01-2013, 06:07 PM   #12
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[QUOTE=mayco;1374281 i was running at about 2850 rpm at 60 mph. any thoughts folks.[/QUOTE]

Unless you're smoking, your Turbo/Isuzu should be close to it's factory specs .Around 3200 rpm is max from GM specs with the turbo.If you're going to keep the the old dear, think about a overdrive unit, we have one.
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Old 11-02-2013, 07:27 AM   #13
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as always folks, thanks so much for all the valuable info. im going to check into the overdrive units but its gonna have to wait till the budget allows. thanks for all the good info on the turbo, ive been reading quite a bit on how the unit works and i think ive got a better understanding on whats going on. sure appreciate all you folks for your experience and willingness to share. good on ya!!
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Old 11-20-2013, 07:59 PM   #14
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When I bought my 310 TD the turbo boost gauge didn't work. Not hearing any turbo noise/whine I thought there was a possibility that my turbo didn't work. I talked to a diesel friend who told me that if the coach is accelerating fairly well and not spewing black smoke everywhere, the turbo works. It turned out that the vacuum line was disconected from the intake plenum.

If your turbo doesn't work it's like stuffing a sock into the intake. Without sufficient air intake the diesel fuel doesn't burn completely and is ejected from the cylinder in the form of black smoke. Without complete burn the engine doesn't make peak horsepower.

Of note…….Shepherd57 found his turbo sandblasted to a point that the intake fins were worn down and the turbo wasn't pushing air as efficiently. Make sure your air filter is clean using a filter cleaner or soap and water and re oil the pleat material (there should be no holes in the pleat material). It is critical that the filter is good especially in dusty conditions.
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Old 11-21-2013, 05:58 AM   #15
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thanks again. i continue the work on the 310 and have been able to determine that the turbo is indeed working. now if its working at peak efficiency is another story. i did track down the vacuum line that goes to the boost gauge and everything seems to be in order. i think the gauge was just stuck and wasnt reading any boost, it now is showing up to 10lbs boost under load. i continue to find idiotic decisions that were made by previous owners though. the latest was that someone had glued carpet over the front doghouse access panel that covered the bolts to remove it. i had read and read on these forums about removing the "entire" doghouse to access the engine and since i could not see how that front panel was connected i didnt realize it comes off. duh! well, i was able to expose the mounting bolts and remove it so i could get to the upper fuel filter, which abviously had not been changed at least as far back as when the carpet was installed. i changed both fuel filters yesterday and took it out for a run on the highway to get her up to temp. big difference in her performance and now...........all the sudden......the BOOST GAUGE IS WORKING!! this is really a process! trying to get this baby ready for hitting the road on a more consistent long term basis. ive got plenty of time, my wife has another couple years before she retires and thats when we plan to spend winters in the south somewhere in the 310. i love the vehicle, but at times get a bit discouraged as every time i turn around there seems to be something else to repair. but, i realize, thats the name of the game with these classics. got to slow down on the expense side for a few months though. i must say, she is to a point right now that i feel pretty confident we could take off for a long road trip and be in pretty good shape. my next big ticket items will be to start laying in critical spare parts ie; alternator, starter, etc. for the isuzu. so far i have done front airbags, front shocks, new harmonic balancer, radiator repair and boilout with coolant flush, flush power steering, flush brake system, new fuel filters, new coolant hoses, new water pump, new belts alt., various electrical repairs, new trumpet horns, new heater control cables, new brake pads, boy i know im forgetting a few things here but i think ive got a good start on getting this rig up to spec. of course these are only the chassis repairs, ive done a great deal on the "coach side" also but those have been more wants than needs. ITS A PROCESS for sure. i am eternally greatful for this forum and those of you with such incredible experience and knowledge to help us rookies get out and enjoy these beautiful machines.
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Old 11-21-2013, 06:34 AM   #16
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I am a bit jealous, but I believe if I were to buy a Classic motorhome, I would seek an early turbo diesel. The mechanically injected Isuzu engines are very stable.

I am not a diesel tech, but I have played around with several.

As mentioned before, diesel engines create very little vacuum. This is because, unlike gasoline engines, the air intake is not a factor in controlling engine speed. The fuel flow is.

The throttle of a diesel engine does not control an air restricting throttle plate as in a carburetor or even a fuel injected gasoline engine. It controls the metering valve at the injector pump. As such, no vacuum can be created because air flow is not being restricted.

Without a turbo charger, the engine power output is limited by the volume of air the cylinder can draw in under almost atmospheric pressure. The fuel charge supplied by the injector pump must be limited to match the air available for ignition/combustion.

A turbo charger blows air into the engine under pressure. This increases the volume of air available for combustion. So, the fuel charge can be increase substantially to take advantage increased amount of air.

More fuel+more air = better combustion and MORE power.

If the turbo charger fails, the fuel charge will be too rich and the under burned fuel will exit the tailpipe as black smoke.

So, the line from the pressurized side of the after-turbo side of the air system to the gauge on the dash is not measuring vacuum, it is measuring the positive pressure created by the turbo charger.

But, all this boost and added fuel can create a monster under high output conditions like pulling a long grade. The engine is working hard and temps can rise quickly.

These older diesels don't like water temps above about 180 degrees or exhaust temps above 1000 degrees. They will fail quickly when pushed to hard.

I would make sure my water temp gauge was working and add a pyrometer if there isn't one. When the temps start to climb, back off the throttle and enjoy the ride.

Keep fuel and air filters changed. Diesel is more oily and dirty then gasoline, and the filters begin restricting flow much more quickly then gasoline.

The Isuzu will last a long last a long time with a little care.

Sorry to get lengthy. I hope it helps.

Regards,

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Old 11-21-2013, 08:11 AM   #17
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Good info!

I'm not familiar with the Isuzu but a handy addition to the Cummins is a fuel pressure gauge. They connect to the output line of the final filter that feeds the injector pump. It will let you know if you have any issues with the fuel system suck as clogged filters or a failed lift pump. On the Cummins, the P1700 injector pump can be damaged by low supply pressure or suction feeding. Air bubbled in the pump can form under low feed pressure which are very abrasive and can take out the pump in a short time. Its about a $3000 repair. Mine runs about 15 to 28 psi depending on engine load.

Another consideration is the massive air flow of these engines. The filters tend to clog quicker that you would expect. Especially in a rear engine configuration (dusty end) like mine. A filter minder is cheap and easy to install.

I've got almost 3 years of digging into mine and feel pretty comfortable knowing that there is very little that I couldn't repair on the road other that a major engine or transmission failure. Good preventative maintenance and operating practices should reduce the chance of problems.

Good luck and have fun with it.

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Old 11-21-2013, 08:30 AM   #18
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oh please, i appreciate your input. i dont know much about these diesels at all. i grew up working on my own vehicles like so many out of necessity. so ive spent a fair amount of time under the hood of various old classics but they have always been gas powered. also, im an novice at best but have managed. some of the folks on this forum just blow me away with their expertise in mechanics. it scares me a bit because ill never know that much, dont know if i want to. hehe. but, my main goal is to make sure i have done ALL that i can to make the vehicle safe and reliable as i can and then let things happen as they will, enjoy the ride where ever and what ever the situation. we have found in our travels, mainly in various areas of mexico and central america, that some of the best of times have been had when things dont go exactly as planned and we are faced with making the best of the situation at hand. soooooooo, i guess i want to know enough about this monster to not be completely vulnerable when it breaks down out in some strange place, yet at the same time i dont want to constantly worry about whats gonna break next! there is some balance there...................i hope. all in due time, next up is the master cylinder and then the steering stabilizer. ahhhhhhhhhhhhhh......it will end....wont it? hehehehe, maybe not, and maybe thats the beauty of the whole experience.
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Old 11-21-2013, 08:54 AM   #19
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hey dakota, i just noticed that youre out in boulder. my son and daughter are both up in fort collins. we get out there from time to time, i did my internship many moons ago in longmont. we hope that our next trip out will be in the 310 next spring.
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Old 11-21-2013, 09:08 AM   #20
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hey dakota, i just noticed that youre out in boulder. my son and daughter are both up in fort collins. we get out there from time to time, i did my internship many moons ago in longmont. we hope that our next trip out will be in the 310 next spring.
Definitely get in touch when you come through!
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