1995 DT466e AT545 experiencing loss of power at most any speed

[wood-duck]

Hello,

I’ve got a 1995 DT466E with an AT545 transmission, and I’m taking it on its first long-ish trip yet. Drove around 4 hours today.

For the last 20 minutes of the drive, it felt as though the engine power would cut in and out, even with the gas pedal pressed down the same amount. Pressing the pedal further usually resulted in a slight uptick in RPMs and power for a second, and then cut back out. Water temp and oil pressure gauges looked normal.

The governer is set at 55, and with this weirdness I was able to maintain around 45-50. Driving on slower roads the engine still seemed to cut in and out even at 35 or so mph.

It seemed to improve slightly when I took my foot off the gas and then back on.

I’m not sure what to look at or check! Air filter? Fuel filters? In the meantime I am in a church parking lot outside of Memphis TN.

Any ideas would be welcome! I have a video showing the gauges while this was happening if I can figure out how to post it.

Thank you for your time!
Noah

 

[ewo1]

Hello,

I’ve got a 1995 DT466E with an AT545 transmission, and I’m taking it on its first long-ish trip yet. Drove around 4 hours today.

For the last 20 minutes of the drive, it felt as though the engine power would cut in and out, even with the gas pedal pressed down the same amount. Pressing the pedal further usually resulted in a slight uptick in RPMs and power for a second, and then cut back out. Water temp and oil pressure gauges looked normal.

The governer is set at 55, and with this weirdness I was able to maintain around 45-50. Driving on slower roads the engine still seemed to cut in and out even at 35 or so mph.

It seemed to improve slightly when I took my foot off the gas and then back on.

I’m not sure what to look at or check! Air filter? Fuel filters? In the meantime I am in a church parking lot outside of Memphis TN.

Any ideas would be welcome! I have a video showing the gauges while this was happening if I can figure out how to post it.

Thank you for your time!
Noah

How old is your fuel filter? If you don't know then start by replacing it and see if anything changes.

 

[wood-duck]

I’ll check on the fuel filter age. I believe I have the documents for it somewhere, but it is NOT brand new.

I did some poking around in the engine compartment and it looks like a part related to the “throttle return” (if I’m right about that name) may have come loose?

I took a video of the part that seems loose, link here:

It looks like a probable issue to me, would you agree? And if so do you know what this part might be called and whether I could replace it myself?

 

[wood-duck]

(It looks like my replies need to be approved before they are made visible, but I have some new information that I’ll add before either reply gets published)

It looks to me like the housing for this accelerator pedal cable transfer piece is somehow loose. I didn’t look at it for too long but I didn’t see any obvious way that it was broken or any obvious bolt to tighten, and I’m not sure how it is supposed to look all put together properly.

Here is another video of the assembly while the gas pedal is being pressed

 

[cadillackid]

definitely sounds fuel related,, if the HPOP were not keeping up it should set a 333 code and turn on the 'WARN ENGINE' light.. fuel flow is not monitored by the computer.



is the fuel level low in the tank? navistar fuel gauges are notorious for being inaccurate.. just wondered if you have shined a light into the tank or tried to measure fuel level with a stick to make sure you arent low.

 

[wood-duck]

Thank you both for your advice!

I think I have a few replies queued at the moment, and I’m not sure how to view my previous replies before they get approved, so I might repeat a couple things. But I have new information!

First, I couldn’t figure out how to tighten that accelerator pedal cable linkage (video in previous message) back to what it seemed it should be in the little bit of time I spent working on it. Perhaps if I took it all the way off it would have become more obvious. But I ended up being right next to an International garage and so I zip tied it up best I could and then (gently) drove to the garage. I had them do a few things: fix linkage piece, change oil, oil filter, fuel filter, grease joints. I don’t see anything visible on the outside done to the linkage piece but it is somehow quite sturdy now.

Then I attempted to drive it about 3 hours down the road. I made it! The engine power was there for the first part of the trip. The power no longer “gave out” like it had before. But then:

I think I ran into the low fuel issue mentioned by Cadillackid about halfway through - the power would cut out (more subtly than when the cable was giving) when the gauge read somewhere between 30% and 50%. After refueling and resting about 30 minutes this seemed to go away.

Another hour down the road, the same thing seemed to be happening again. My max speed would seem to slowly decrease from 55 to 52 to 48, and when I approached these speeds the rpm’s would drop a bit, then come back, then drop, then come back. At this point I was almost to my destination so I made it and now I am still wondering what is really going on.

Someone on the street mentioned checking the turbo for a small oil leak. It looks possible that some components under the turbo are a bit oily, but I don’t see anything visible actively leaking to help narrow down where it is coming from.

It seems like a trend is that this loss of power only happens after the bus has been driving an hour or so, but I am not sure what to take from that.

 

[PorchDog]

Yo may have a lot of crud in the fuel tank. You might try changing the fuel filters again and see if that provides an immediate improvement. If that turns out to be the case-- maybe the fuel tank needs cleaned. Algae formation in old diesel fuel is a problem nowadays since we went to low Sulphur fuel, and can be very detrimental to the fuel system. Just a guess.

 

[cadillackid]

Another possibility is what about tank not venting .. if it starts acting up and you stop while it’s idling open the gas cap and see if you get a whoosh if suction then the tank pressure would be going negative making it harder for the lift pump to do its job

 

[wood-duck]

Hmm — I was wondering if that was normal! When I take the gas cap off it does have a suction! Even at gas stations with the vehicle off. It has been happening about the whole time I’ve had the bus so I thought it was just a quirk of diesel tanks. I’ll look around for something that looks like a clogged vent on the tank.

It looks like I am close to an auto parts store now so I’ll probably go see if they have some kind of diesel fuel test kit there to carry around with me too

 

[wood-duck]

I’m not sure if/when my original replies will ever make it through, so I’ll add this here to help clear up the original problem.

Some cable linkage near the accelerator pedal return spring had come loose, and here is a video of it:

But this is now fixed by an International mechanic, and I’m not sure how as from the outside it looks the same as it did before but now it no longer wobbles.

I’m still experiencing a more minor loss of power after driving for 1+ hours and, as mentioned, my fuel tank seems to not be venting properly. I’ve traced the two big hoses going in and out of the tank and don’t see any obvious kinking. Should I look at getting a new gas cap that handles the venting?

 

[Omnibot2000]

Pretty much every tank I come across has a dedicated vent, not one through the cap(that I can remember)

On the vent line there is a little check valve, it allows air to go in, nothing to come out. The check valve for the most part is there in case of a rollover accident, fuel does not pour out of the vent line.

So, the fix. Located your vent line and remove it, make sure it's not plugged up and clean it out or replace it. Check the vent valve itself.

I've replaced them in pairs when trucks with dual tanks are only drawing fuel from one tank after back flushing all the lines for possible blockages.

With all that said, you can crack your tank cap loose for now and confirm your rig is running good allowing it to vent. Just don't loose the cap.

FYI, I may have used a regular diff vent on a fuel tank to get a truck running down the road in the past. What that driver did after for the proper fix was on him.

 

[BamaBus]

I’ve got a 1995 DT466E...

I believe this is a mechanical (with P-pump?) engine. If so lose the E on the 466 like you did in the registry to avoid issues with advise.

The vent for the tank may be on the top of the tank or routed by rubber hosing to a higher location. Most likely plugged at the end with dirt.

 

[sportyrick]

I agree with bamabus a 1995 DT466 is most likely a mechanical pump engine, especially since I have a 1995 DT466 which is mechanical. In that vein of thought at the entrance to the fuel filter on the rear of the pump is a small removable container with a screen for larger particles that could be in the tank, that should be definitely be checked. I have seen this problem in the field on many larger diesel machines in that they will run for a while and then get starved out of fuel, shut them off and wait a while and they will run fine.....for a while....and then starve out again. The problem was trash in the tank clogging up the screen on the pick up tube hence starvation of the fuel system.

 

[cadillackid]

I agree with bamabus a 1995 DT466 is most likely a mechanical pump engine, especially since I have a 1995 DT466 which is mechanical. In that vein of thought at the entrance to the fuel filter on the rear of the pump is a small removable container with a screen for larger particles that could be in the tank, that should be definitely be checked. I have seen this problem in the field on many larger diesel machines in that they will run for a while and then get starved out of fuel, shut them off and wait a while and they will run fine.....for a while....and then starve out again. The problem was trash in the tank clogging up the screen on the pick up tube hence starvation of the fuel system.

both the NGD 466 and the DT466E existed in 1995..

the flat nose AmTran Genesis equipped with a DT were mechanical through 97 (early 98)...


the 3800 chassis was heavily switching over in 95 to the DT466E. as was the 4700 truck which the 3800 chassis is derived..


so this bus in fact can be a DT466E.. its also possible that its mechanical 466.. obviously a pic of the engine tells us for sure..

 

[Omnibot2000]

both the NGD 466 and the DT466E existed in 1995..

the flat nose AmTran Genesis equipped with a DT were mechanical through 97 (early 98)...


the 3800 chassis was heavily switching over in 95 to the DT466E. as was the 4700 truck which the 3800 chassis is derived..


so this bus in fact can be a DT466E.. its also possible that its mechanical 466.. obviously a pic of the engine tells us for sure..

It looked mechanical to me seeing the YouTube video.

 

[sportyrick]

Obviously there is throttle linkage and is the E model fly by wire?

 

[cadillackid]

I totally missed the youtube link!! yes this is definitely a mechanical engine.. the throttle in an 'E' is 100% by wire and theres no fuel pump on the engine like this..

 

[Mr P]

Woodduck, you might want to fix your first post, delete the E from your engine description. That "E" changes the diagnostic ballgame drastically. I totally ignored this topic because of the E label. But now I'm interested (as I have an engine like yours).

Were both fuel filters replaced? Or only one?

 

[wood-duck]

Thank you all! I’m not sure why I had it in my head that this was an e engine. Thank you for the correction! I’ve fixed the tags and I’ll keep looking around for a way to edit the original post/title.

Re: workaround for air not venting
I ended up unscrewing and rescrewing the cap every time I stopped, and it seemed to be okay. If I went more than 2 hours of driving without unscrewing the cap and relieving the vacuum I would start to experience the loss of power, but it was fine enough for this trip (and I have now, as of last night, made it to my destination for at least the next couple months! A 1,500 mile trip in too few of days! Arriving felt miraculous.)

Re: how to fix the air vent
I am not at the bus at the moment but will be able to get back in a couple days to take a closer look and see if I can clear some dirt out. If I recall correctly the sensor wires for the fuel tank were easily accessible in an access panel through the bus floor, but the two larger (maybe 0.5”) hoses coming out of the tank did not seem to be so easily accessed. But hopefully it is the other end of the hose with the issue, so I’ll try to trace it and see what I find. I’ll try to remember to take pictures too.

Re: cleaning the fuel filter particle screen
I have not done that but I should probably take a look there either way

Re: which fuel filters did they replace
I believe they only replaced one. They also said pretty specifically that they did NOT replace the fuel/water separator.

Thank you again for all of your help!

 

[Omnibot2000]

Thank you all! I’m not sure why I had it in my head that this was an e engine. Thank you for the correction! I’ve fixed the tags and I’ll keep looking around for a way to edit the original post/title.

Re: workaround for air not venting
I ended up unscrewing and rescrewing the cap every time I stopped, and it seemed to be okay. If I went more than 2 hours of driving without unscrewing the cap and relieving the vacuum I would start to experience the loss of power, but it was fine enough for this trip (and I have now, as of last night, made it to my destination for at least the next couple months! A 1,500 mile trip in too few of days! Arriving felt miraculous.)

Re: how to fix the air vent
I am not at the bus at the moment but will be able to get back in a couple days to take a closer look and see if I can clear some dirt out. If I recall correctly the sensor wires for the fuel tank were easily accessible in an access panel through the bus floor, but the two larger (maybe 0.5”) hoses coming out of the tank did not seem to be so easily accessed. But hopefully it is the other end of the hose with the issue, so I’ll try to trace it and see what I find. I’ll try to remember to take pictures too.

Re: cleaning the fuel filter particle screen
I have not done that but I should probably take a look there either way

Re: which fuel filters did they replace
I believe they only replaced one. They also said pretty specifically that they did NOT replace the fuel/water separator.

Thank you again for all of your help!

Your going to look for a 3rd line. Coming out of the tank and just hanging down not attached to anything.