Boost difference between OK and CO - what's happening?
07-21-2005, 07:36 PM
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Boost difference between OK and CO - what's happening?
Hi all,
Well after spending about a year in Oklahoma and experiencing first hand the dead economy, at least in the IT field, my wife and I are in full swing mode to get relocated again in Colorado. We lived there about 20 years then moved to OK last year to help her aging parents (health issues) but now realize there are more opportunities in CO.
Anyway, about 2 weeks ago I drove to Colorado on a job and house search and my initial impression of my truck's performance was that it seemed like it was hardly affected by the mile difference in elevation between OK and CO. It climbed Raton, La Veta and Wolf Creek passes very nicely. In fact, I had a litle fun with a few other vehicles while going up these passes - just push the go pedal and it started to accelerating nicely as expected, w/o hesitation, leaving them all behind rather quickly.
Now, however in the past week or so, since I've been in Colorado Springs, it seems to have lost a very noticable amount of quickness getting away from traffic lights as well as when trying to accelerate out on the hi-ways. I also noticed it doesn't build boost nearly as quick nor as high. Boost used to build pretty quick in Tulsa and get up to 32-34 psi easily. Now it comes up much slower and about the highest I've seen is 20 psi.
I also noticed about this same time that the truck wasn't starting as reliably as it did before too. I used to just bump the starter and it was up and running. Now, some times it won't do that. Several times I've bumped it like before and no fire. Then I'd try letting the starter spin the motor for several seconds and still no fire. Lastly, I'd wait a few seconds and bump it and finally it will start. Another thing too is it seems, by fuel gauge indication, to be using more fuel than before, for the amount and type of driving I'm doing.
I've checked the after-cooler boots and clamps - the boots appear to be OK (no visible tears or holes) and the clamps are tight. I also checked and tightened the clamps on the rubber fuel feed and return lines (installed new LarryB hoses last fall). The most recent thing I've done is put some diesel fuel system cleaner & lube in the tank and ran in out on the hi-way about 30 miles to get it going through the system and maybe do some good.
I don't have or have access to a fuel pressure gauge to see what it's like but I have my doubts this is the problem. I suspect, because the truck has a little over 128K miles, the overflow valve may be starting to fail so I placed an order today for a new overflow valve which I'll install when I return to Tulsa this weekend to see my wife and take care of a few other things. My thinking there is it may be by-passing too much fuel and not letting enough get to the injection pump and engine, hence the lower boost and sluggish performance. I'm also going to order a new Fleetguard fuel filter just in case I got a bad tank of fuel here too. I'll also check and clean the pre-filter screen when I change the fuel filter.
So, after my long-winded description, doesn anyone have any experience with regard to changes in performance related to elevation like I described? Or do you think it really is something amiss with the truck? I'll have more knowledge when I get back to OK this weekend as to whether its an elevation related phenomonon or a real mechanical problem that needs to be fixed. I'm hoping it's the latter so when we get relocated I can still enjoy the perky performance I've had since upgrading the truck.
As always, any and all suggestions or comments are welcome and appreciated.
Steve
Well after spending about a year in Oklahoma and experiencing first hand the dead economy, at least in the IT field, my wife and I are in full swing mode to get relocated again in Colorado. We lived there about 20 years then moved to OK last year to help her aging parents (health issues) but now realize there are more opportunities in CO.
Anyway, about 2 weeks ago I drove to Colorado on a job and house search and my initial impression of my truck's performance was that it seemed like it was hardly affected by the mile difference in elevation between OK and CO. It climbed Raton, La Veta and Wolf Creek passes very nicely. In fact, I had a litle fun with a few other vehicles while going up these passes - just push the go pedal and it started to accelerating nicely as expected, w/o hesitation, leaving them all behind rather quickly.
Now, however in the past week or so, since I've been in Colorado Springs, it seems to have lost a very noticable amount of quickness getting away from traffic lights as well as when trying to accelerate out on the hi-ways. I also noticed it doesn't build boost nearly as quick nor as high. Boost used to build pretty quick in Tulsa and get up to 32-34 psi easily. Now it comes up much slower and about the highest I've seen is 20 psi.
I also noticed about this same time that the truck wasn't starting as reliably as it did before too. I used to just bump the starter and it was up and running. Now, some times it won't do that. Several times I've bumped it like before and no fire. Then I'd try letting the starter spin the motor for several seconds and still no fire. Lastly, I'd wait a few seconds and bump it and finally it will start. Another thing too is it seems, by fuel gauge indication, to be using more fuel than before, for the amount and type of driving I'm doing.
I've checked the after-cooler boots and clamps - the boots appear to be OK (no visible tears or holes) and the clamps are tight. I also checked and tightened the clamps on the rubber fuel feed and return lines (installed new LarryB hoses last fall). The most recent thing I've done is put some diesel fuel system cleaner & lube in the tank and ran in out on the hi-way about 30 miles to get it going through the system and maybe do some good.
I don't have or have access to a fuel pressure gauge to see what it's like but I have my doubts this is the problem. I suspect, because the truck has a little over 128K miles, the overflow valve may be starting to fail so I placed an order today for a new overflow valve which I'll install when I return to Tulsa this weekend to see my wife and take care of a few other things. My thinking there is it may be by-passing too much fuel and not letting enough get to the injection pump and engine, hence the lower boost and sluggish performance. I'm also going to order a new Fleetguard fuel filter just in case I got a bad tank of fuel here too. I'll also check and clean the pre-filter screen when I change the fuel filter.
So, after my long-winded description, doesn anyone have any experience with regard to changes in performance related to elevation like I described? Or do you think it really is something amiss with the truck? I'll have more knowledge when I get back to OK this weekend as to whether its an elevation related phenomonon or a real mechanical problem that needs to be fixed. I'm hoping it's the latter so when we get relocated I can still enjoy the perky performance I've had since upgrading the truck.
As always, any and all suggestions or comments are welcome and appreciated.
Steve
07-21-2005, 08:54 PM
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Well, a turbocharger is an centrifugal compressor driven by a gas turbine. A centifugal compressor performace is greatly affected by the density of air. As you know, the density is greatly reduced at altitudes of that magnitude. So compressor performance can be substantially reduced at high altitudes, and also at high temperatures.
Than being said, your reduction seems more drastic than that alone. But if it was also quite hot, that could be the case... Were you smoking at all??? Where EGT's high???
KP
Than being said, your reduction seems more drastic than that alone. But if it was also quite hot, that could be the case... Were you smoking at all??? Where EGT's high???
KP
07-21-2005, 10:30 PM
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No, the symptoms you describe are -not- normal for the elevation change. I drive at sea level to 3000 feet for part of the year (east coast), and 5000 to 11,000 feet for part of the year (Rockies).
You will have a drop in performance and mileage at high altitudes. And you will make higher EGT's, have more smoke, and suffer a loss in boost and more time for boost build-up. The differences are enough to notice, but they are not excessive. However, you will -not- suffer hard starting issues, and you will be able to generate well in excess of 20 lbs. boost.
I've never had a hard starting issue, even when parking the truck overnight at 10,500 feet. And I've built 30 lbs. boost just below the Eisenhower Tunnel on I-70.
I think you've got something else going on there, a fuel or boost problem. Maybe both, but with the hard start, sounds like fuel.
You will have a drop in performance and mileage at high altitudes. And you will make higher EGT's, have more smoke, and suffer a loss in boost and more time for boost build-up. The differences are enough to notice, but they are not excessive. However, you will -not- suffer hard starting issues, and you will be able to generate well in excess of 20 lbs. boost.
I've never had a hard starting issue, even when parking the truck overnight at 10,500 feet. And I've built 30 lbs. boost just below the Eisenhower Tunnel on I-70.
I think you've got something else going on there, a fuel or boost problem. Maybe both, but with the hard start, sounds like fuel.
07-22-2005, 01:35 AM
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Thanks for the feedback guys. I tend to agree with JP and Gear Poet that there's something other than higher elevation happening here. I'll keep a close eye on the performance as I travel back to Tulsa this weekend to see if there's any increase in power as the elevation drops back down. If it's still the same as here I'll know there's definitely something wrong, which I'm really hoping is the case. Regardless, I'm changing the overflow valve and fuel filter after I get back to Tulsa in hopes that will take care of it.
Another thought was presented to me when I visited a diesel emissions testing station here and that was I might have had a rock impact the aftercooler causing a small leak, thus bleeding off boost. The only thing that can't be explained with that is the starting problem, which again leads me to think bad fuel/clogged filter and/or bad overflow valve.
I'll post my findings after I get back to hot and steamy Oklahoma. Thanks again for all your feedback.
Steve
Another thought was presented to me when I visited a diesel emissions testing station here and that was I might have had a rock impact the aftercooler causing a small leak, thus bleeding off boost. The only thing that can't be explained with that is the starting problem, which again leads me to think bad fuel/clogged filter and/or bad overflow valve.
I'll post my findings after I get back to hot and steamy Oklahoma. Thanks again for all your feedback.
Steve
07-22-2005, 12:38 PM
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EXTREMELY high altitude when combined with cold temps can cause hard starting.
I'm talking 12K-13K feet and temps near or below zero. But in your case, you should NOT have a hard start problem just from the altitude.
Also, while you WILL lose boost, it will only be a couple PSI. Maybe 3 or 4.
Oh, and btw-- you really ought to REMOVE the boots to inspect them. They can crack on the inside and leak to where it's almost undetectable from the outside.
Let us know once you check/change the FF and the other things.
JLH
I'm talking 12K-13K feet and temps near or below zero. But in your case, you should NOT have a hard start problem just from the altitude.
Also, while you WILL lose boost, it will only be a couple PSI. Maybe 3 or 4.
Oh, and btw-- you really ought to REMOVE the boots to inspect them. They can crack on the inside and leak to where it's almost undetectable from the outside.
Let us know once you check/change the FF and the other things.
JLH
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07-22-2005, 01:16 PM
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temps near or below zero will cause hard starting regardless of altitude.
Boost should really only drop 3 to 4 psi at altitude. I'm at 6000ft and when I go up over the passes at 10-12k ft I still boost what I normally do down here. might loose 1psi of boost.
Boost should really only drop 3 to 4 psi at altitude. I'm at 6000ft and when I go up over the passes at 10-12k ft I still boost what I normally do down here. might loose 1psi of boost.
07-22-2005, 01:24 PM
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heh, believe it or not, the temperature is not -always- at or near zero, nor even below freezing, at 10,500 or 12,000 or even 13,000 feet. Not in summer in the Rockies, anyway, when Steve noticed the problem. Not even at night, and I speak from long experience. 
I'll reiterate - parking my truck overnight at between 8000 and 10,500 feet, in June through August and in December and January, I've never had a hard start issue. Of course, in December and January, having the block heater plugged in and a heating pad on the oil pan may have had something to do with it....
I'll reiterate - parking my truck overnight at between 8000 and 10,500 feet, in June through August and in December and January, I've never had a hard start issue. Of course, in December and January, having the block heater plugged in and a heating pad on the oil pan may have had something to do with it....
07-22-2005, 01:38 PM
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last year I was parking every night at about 8000ft and the only time I ever had it start hard was when it was below 10deg F a couple times. Never plugged in the block heater either. It still started but it didn't like it.
07-22-2005, 02:01 PM
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Originally posted by Gear Poet
heh, believe it or not, the temperature is not -always- at or near zero, nor even below freezing, at 10,500 or 12,000 or even 13,000 feet. Not in summer in the Rockies, anyway, when Steve noticed the problem. Not even at night, and I speak from long experience.
heh, believe it or not, the temperature is not -always- at or near zero, nor even below freezing, at 10,500 or 12,000 or even 13,000 feet. Not in summer in the Rockies, anyway, when Steve noticed the problem. Not even at night, and I speak from long experience.
I stated also that it wasn't really relevant to his case, as he's obviously not high enough or cold enough to meet the circumstances I outlined.
07-22-2005, 06:00 PM
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Hohn,
Thanks for the tip on removing the boots to check for signs of leaks on the inside of them. I thought I'd be able to see anything from the outside, but when I stop to think about it, it wouldn't take a very large tear or hole to bleed off enough boost to make a difference.
Like I've said before, this is the greatest site for CTD owners. The feedback from the braintrust here is the best. It sure keeps me coming back for ideas, assistance when needed and to help when I can be on the giving end.
Steve
Thanks for the tip on removing the boots to check for signs of leaks on the inside of them. I thought I'd be able to see anything from the outside, but when I stop to think about it, it wouldn't take a very large tear or hole to bleed off enough boost to make a difference.
Like I've said before, this is the greatest site for CTD owners. The feedback from the braintrust here is the best. It sure keeps me coming back for ideas, assistance when needed and to help when I can be on the giving end.
Steve
07-22-2005, 10:26 PM
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ok...this has a lot of the same problems im having with my truck im trying to get a second boost gauge to check boost because ive not seen over 20psi except when i was doing like 88mph on the freeway and it went to 25psi
07-22-2005, 10:29 PM
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see i tought the boost gauge was broken because a while ago the boost slowly started getting lower and lower over tim eso i want to check with another gauge but to think about it....it might be right.....i use to spike 41psi with lvl 5 on the edge comp a few months ago.. and yet to see it since....