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Old 11-16-2022, 06:11 PM   #1
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Has anyone replaced their HEUI?

I've been troubleshooting some surging behavior when my C7 is cold, and a noticeable knocking in specific scenarios - usually when the engine is under heavy load. I got a *totally legitimate* copy of Cat ET and ran some diagnostics and collected some logs and finally determined that my injection actuation pressure (basically, the high pressure oil) was really erratic, swinging +/- 200 to 300 PSI from what the ECM wanted when the engine was cold. I didn't get to collect any data while driving with the knocking occurring, but all of this has led me to an unfortunate conclusion: I probably need a new HEUI pump.

I'm guessing what actually happened is the HEUI solenoid is just clogged up from use and possibly the wrong oil weight (I'm running 15w40 now, Cat recommends 10w30, no idea what it had before I owned it). However, the C7 HEUI is not serviceable at all, unlike the 3126 HEUI. (Had I known all of this I may have looked more closely for a bus with a 3126...or just a Cummins.)

I've watched lots of Adept Ape's videos on YouTube, some several times, emailed back and forth with him directly, found Cat service manuals and read them online, the whole gamut, so I'm fairly confident that my diagnosis is correct; I'm out of culprits basically. Fuel pressure is solid, injector cutout tests didn't reveal a bad injector...I can't even remember what else I tried. The problem is while I understand conceptually how to replace the HEUI, I'm not a confident or experienced mechanic, and I don't want to get into a tight spot and not have anyone to come bail me out.

All that being said, I was wondering if anyone here has had their HEUI replaced, and if they DIY'd it or if they had Cat do it. I tried calling my local Cat dealer to get a ballpark price and they basically said "we don't do that, you have to bring it in first". I understand why they might not want to give estimates over the phone, but it's still annoying. I know it's easily a $2000 part, and I don't think it looks like it would take more than 8 hours of labor to replace (probably less realistically), but I'm still worried about being raked over the coals. I don't think I need an injector kit and I know they're going to try to push me into buying one. Just trying to get myself prepared for what's to come.

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Old 11-16-2022, 06:25 PM   #2
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it sounds more like the ICP or IPR is going bad.. if the HPOP goes bad it just wont make pressure.. when the HPOP in my T444E was going.. I could see under heavy load.. (I set my software to do a trip report where it recorded selected parameters that I could playbaclk)..


mine would be where the desired was well above the actual and id see the IPR % command out at max duty cycle for the calibration (87% in my case).. so I knew the HPOP just couldnt supply enough oil pressure...



a fuel knock is often the case with a bad injector that is drizzling fuel into a cylinder when it shouldnt be.. the result is the cylinder fires early and creates a Knock...



I would run a trip report and monitopr your TPS, HPOP, ICP actual and ICP desired, as well as IPR duty cycle...



in the end my HPOP was weak and the PSI problem was solved after a new HPOP and also new ICP / IPR.. then I installed new injectors just because I wanted bigger spray for bigger GO....
-Christopher
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Old 11-16-2022, 06:30 PM   #3
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Quote:
Originally Posted by cadillackid View Post
it sounds more like the ICP or IPR is going bad.. if the HPOP goes bad it just wont make pressure.. when the HPOP in my T444E was going.. I could see under heavy load.. (I set my software to do a trip report where it recorded selected parameters that I could playbaclk)..


mine would be where the desired was well above the actual and id see the IPR % command out at max duty cycle for the calibration (87% in my case).. so I knew the HPOP just couldnt supply enough oil pressure...



a fuel knock is often the case with a bad injector that is drizzling fuel into a cylinder when it shouldnt be.. the result is the cylinder fires early and creates a Knock...



I would run a trip report and monitopr your TPS, HPOP, ICP actual and ICP desired, as well as IPR duty cycle...



in the end my HPOP was weak and the PSI problem was solved after a new HPOP and also new ICP / IPR.. then I installed new injectors just because I wanted bigger spray for bigger GO....
-Christopher
You speak international and I speak caterpillar, but I think weíre on the same page. Since the fuel pressure is steady Iím not inclined to believe I have a leaky injector but itís definitely a possibility. In the C7, the HPOP contains the solenoid that controls it as well as the actual oil pump, and you canít take it apart and put it back together. On a 3126 you can just replace the solenoid, but the C7 has a non replaceable gasket that gets broken when you open the top to get to the solenoid. Iím inclined to believe the solenoid fails far more than the pump but you have to replace the whole thing no matter what.

If money was no object Iíd be fine with doing all the injectors plus the HEUI but thatís like $10k easily from what Iím hearing.
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Old 11-16-2022, 06:56 PM   #4
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Quote:
Originally Posted by cadillackid View Post
it sounds more like the ICP or IPR is going bad.. if the HPOP goes bad it just wont make pressure.. when the HPOP in my T444E was going.. I could see under heavy load.. (I set my software to do a trip report where it recorded selected parameters that I could playbaclk)..


mine would be where the desired was well above the actual and id see the IPR % command out at max duty cycle for the calibration (87% in my case).. so I knew the HPOP just couldnt supply enough oil pressure...



a fuel knock is often the case with a bad injector that is drizzling fuel into a cylinder when it shouldnt be.. the result is the cylinder fires early and creates a Knock...



I would run a trip report and monitopr your TPS, HPOP, ICP actual and ICP desired, as well as IPR duty cycle...



in the end my HPOP was weak and the PSI problem was solved after a new HPOP and also new ICP / IPR.. then I installed new injectors just because I wanted bigger spray for bigger GO....
-Christopher
Reading this again and doing some googling, here's a translation table first:

Cat HEUI = International HPOP + IPR
Cat IAP sensor = International ICP sensor

I had definitely considered changing my IAP sensor, but first I'll try to leave ET running in log mode while I drive up to my in-laws place for our Thanksgiving weekend trip next week and see what happens. I get a lot of the knocking when I'm trying to maintain 65 MPH and I'm going up an overpass (there are no natural hills here in NW Ohio). That way I can see what the IAP (injection actuation pressure) desired (from the ECM) vs actual (from the IAP sensor) looks like. The only thing I know right now is on a cold start when the engine is still cold the IAP reports actual pressure bouncing around the desired IAP, to the order of like +150 and -150 in a short period of time (hence total swing of 300).

In the image below, the yellow line is the desired pressure from the ECM, the purple line is the actual pressure measured by the IAP sensor. This is at idle RPMs (~700) on a cold start.

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Old 11-17-2022, 06:27 AM   #5
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yeah that bounce looks a little inconsistent but mine bounces around quite a bit too..



yeah I speak international.. and honestly I figured the systems were similar enough to be relevant. I had no idea that CAT had put the HPOP and IPR solenoid in one non serviceable package.. GRRR! on the IH, the IPR screws into the back of the HPOP.. (a bit of a PITA to change since its UNDER the powered steering pump) but nevertheless replaceable..
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Old 11-17-2022, 09:28 AM   #6
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I received confirmation last night, the HEUI solenoid should read about 10 ohms, so if mine is coming back with 30 then it's wayyy out of spec. I'm going to get a better multimeter and check again this weekend. Nevertheless, I feel that I should also check my fuel lines to make sure I'm not sucking in air somewhere, I have a feeling I may be due for a fuel filter base at the very least as mine is very rusty and the fittings on it are probably going to break off instead of unscrewing.

I found a really interesting document on Scribd describing the theory of operation for the C7, here's a link from my cloud site for those that are interested:
https://cloud.tastefordanger.xyz/ind...4gr5g2L2PpHkiN

In that document (which is, of course, protected by DRM so I can't copy paste), it does explicitly say that the HEUI should not be disassembled.
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Old 11-17-2022, 10:17 AM   #7
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Have a read here. https://www.skoolie.net/forums/f33/c...ter-32393.html This thread has a couple bullet points you should know. My post 7 has how the HPOP functions. It's variable displacement, unlike IH using fixed displacement with a regulator valve.

I fixed a dump truck with a c7 that had a surging/misfire issue under load. A new HPOP fixed it. I saw the same data that you did, and verified the surging pressure with a mechanical gauge. CAT ET has a function where you can control HPOP pressure. So I commanded it high, and then test drove it and seen that the pressure fluctuation was worse with higher pressure, and was absent with lower pressure. Which coincided with the surge/misfire being worse and also absent. A new HPOP and the pressure was a lot steadier with no surging under load.

That one did it all the time, though. Yours only doing it when cold leads me to believe it might be an oil supply issue. Some of those have a service screen after the HPOP. See if yours does and see if it caught any metal. If metal is found, clean the screen, change the oil and filter, and replace the HPOP. If it isn't, still clean the screen, change the oil and filter to 5w40, and test it again.

Also throw an appropriate amount of hotshot's stiction eliminator in it, as that might help as well. 5w40 and hot shots does wonders on a lot of heui engines.

You can replace an HPOP yourself. It's not hard and doesn't require a calibration or anything. Adept ape has a video on it. He also shows how to check for metal in the system, as if metal is found, you'll have to flush the rail and replace the injectors too.

Replacing injectors requires their respective trim files to be uploaded. I believe it will still run without doing so, but I've never tried it. If you have CAT ET, you can do it yourself, as most injectors will include a CD with the correct trim file.
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Old 11-17-2022, 10:24 AM   #8
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Quote:
Originally Posted by Booyah45828 View Post
Have a read here. https://www.skoolie.net/forums/f33/c...ter-32393.html This thread has a couple bullet points you should know. My post 7 has how the HPOP functions. It's variable displacement, unlike IH using fixed displacement with a regulator valve.

I fixed a dump truck with a c7 that had a surging/misfire issue under load. A new HPOP fixed it. I saw the same data that you did, and verified the surging pressure with a mechanical gauge. CAT ET has a function where you can control HPOP pressure. So I commanded it high, and then test drove it and seen that the pressure fluctuation was worse with higher pressure, and was absent with lower pressure. Which coincided with the surge/misfire being worse and also absent. A new HPOP and the pressure was a lot steadier with no surging under load.

That one did it all the time, though. Yours only doing it when cold leads me to believe it might be an oil supply issue. Some of those have a service screen after the HPOP. See if yours does and see if it caught any metal. If metal is found, clean the screen, change the oil and filter, and replace the HPOP. If it isn't, still clean the screen, change the oil and filter to 5w40, and test it again.

Also throw an appropriate amount of hotshot's stiction eliminator in it, as that might help as well. 5w40 and hot shots does wonders on a lot of heui engines.

You can replace an HPOP yourself. It's not hard and doesn't require a calibration or anything. Adept ape has a video on it. He also shows how to check for metal in the system, as if metal is found, you'll have to flush the rail and replace the injectors too.

Replacing injectors requires their respective trim files to be uploaded. I believe it will still run without doing so, but I've never tried it. If you have CAT ET, you can do it yourself, as most injectors will include a CD with the correct trim file.
Mine surges when it's cold, and ONLY when it's cold. It knocks (misfires?) when under heavy load at any temperature. Not so bad that I can't get up and going, but there is a slight loss of power.

You're recommending 5w40? Cat recommends 10w30. I need to re-learn what oil weights really mean to figure out the difference. I had considered using some Hot Shots in there too. Ideally I'd like to do an oil change soon myself since it has 15w40 in there right now, but I need to find the info on how much oil I should expect to drain/add so I can make sure my drain pan is big enough!

I have watched the video on HEUI replacement several times, my concern is just getting to a point where I'm stuck/beyond my abilities or available tools. With a small child at home and two adults with busy work schedules I have a really hard time being able to say "I need a full weekend to work on this project without time constraints". The cost of having Cat do it definitely motivates me to DIY though!

Only other problem is I still haven't looked to figure out if my bus has a primer knob, and if not, how I get it primed once I lose prime from disconnecting the hoses. It seems there's not one unified answer there so that one I have to figure out myself.
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Old 11-17-2022, 10:57 AM   #9
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The expense is in the components. Replacing the pump and/or injectors is fairly simple to do and doesn't require much time.

Diesels have an inherent knock, it's part of the injection/combustion process. If it's got like a skip to it, that'd be only one cylinder knocking, and I'd be inclined to believe that's more along the lines of an injector issue. But, it's pretty difficult for me to diagnose anything over the internet.

Oil weights: They group oils based off their viscosity, which is a number assigned to a certain thickness/ability to flow. Smaller the number, the thinner the oil. Larger is thicker. Thin oil flows better, but protects worse, Thick oil flows worse, but protects better.

First number is the weight at 0įF, second number is a 212įF.

An SAE 40 is a 40 weight at 0 and 212.
A 15w40 is 15 at 0 and 40 at 212.
A 10w30 is a 10 at 0 and 30 at 212.
A 5w40 is a 5 at 0 and a 40 at 212.

There are youtube videos out there that show people pouring various weights of oils at freezing temperatures to give you an idea of how they act. The difference is pretty substantial visually, and can give you an idea as to why thinner oils handle cold climates better.

A 40 weight below freezing is nearly a solid, where as a 5w40 will flow like a liquid. Yet they're the same thickness at 212.

For years, diesels ran 40 weight, because they operate at higher temps and pressures then gasoline counterparts, and require thicker oil to compensate for protection. IN the 80's they switched to multi-grade 15w40, because it allowed better cold starts and operation. Recently, manufacturers have been pushing 30 weight and thinner because of fuel efficiency desires. I'm not saying efficiency is a bad thing, but I'm not sold on the idea of sacrificing engine protection for it.

A 15w40 in a c7 isn't bad. Requires a little warm up when freezing out, but we ran them for years that way. It's thicker at 0 and 212 then a 10w30. A 5w40 vs 10w30 would be thinner at 0, and thicker at 212, which is what you're after. A 5w40 will give you cold temp flow, and high temp protection, and that's why I recommended it.

Having a rough running heui engine while cold isn't unheard of when they're using 15w40. It's part of the reason why you see diesels idling all the time when it's cold out. Partly because the cold makes them hard to start, and partly because the oil is too thick to run right, so they're trying to warm it up.
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Old 11-17-2022, 11:01 AM   #10
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Buses run oil capacities in the gallons. So most drain pans at your local parts store won't be near big enough. I'd recommend at least 8 gallon/40 quart. Much less mess with too much capacity then not enough.

The big pans you'll often times see on wheels as well. Because that much oil isn't easy to scoot around without wheels.
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Old 11-17-2022, 11:27 AM   #11
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RE: the knocking I'm hearing, this video from the day I drove it home captures it pretty well. It only does this under certain loads, like when you're getting to the top of the RPMs in a certain gear while accelerating, or in this case, trying to keep 65 MPH going up a very slight hill on US 33.

https://youtu.be/4mCHMME9N0A

Your oil weight explanation was a perfect refresher, thanks; it's been a while since I went down that rabbit hole, now I want to find those videos of people pouring oil in freezing temps! My general theory is that perhaps the HEUI is sensitive enough that it really doesn't "appreciate" the heavier oil weight overall (even at 212 40 is thicker than 30), but it could also just be a temperamental part.

I'll be taking a closer look at my particular HEUI this weekend to see how difficult it will be to reach some of the fittings, and formulate my decision from there.
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Old 11-17-2022, 11:28 AM   #12
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Originally Posted by Booyah45828 View Post
Buses run oil capacities in the gallons. So most drain pans at your local parts store won't be near big enough. I'd recommend at least 8 gallon/40 quart. Much less mess with too much capacity then not enough.

The big pans you'll often times see on wheels as well. Because that much oil isn't easy to scoot around without wheels.
Yeah, I bought a drain pan at Tractor Supply but I think it's only like 16 quart, it was the biggest they had... still need to see if I can fit a bucket down there!
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Old 11-17-2022, 02:10 PM   #13
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I have a nice square Hyper-tough pan.. you can put plugs and caps on it to carry it.. plus the vent and drain holes are small enough ther oil plug wont fit down them... it says 23 quart but I teested it actually holds about 28 quarts.. my busses hold 13,19, and 20 quarts so no worries..
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Old 11-18-2022, 08:30 AM   #14
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I'd do an overhead on that, and then check all around the engine for something loose/rattling.

To me, your rattle doesn't seem to follow engine firing or anything, It's just an extraneous rattle under the dog house.
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Old 11-18-2022, 09:38 AM   #15
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Originally Posted by Booyah45828 View Post
I'd do an overhead on that, and then check all around the engine for something loose/rattling.

To me, your rattle doesn't seem to follow engine firing or anything, It's just an extraneous rattle under the dog house.
I had an overhead done the month after I got it, didn't make a difference. It rattles toward the top end of the engine speed so it is hard for me to tell if it's really affecting the power - it feels like there's *slightly* less power when it's rattling, but again, the engine is getting upwards of 2k+ RPMs so it could just be getting out of its power band. This would be a lot easier if I could drive another identical bus that doesn't have issues...

I think my next drive with ET logging data will tell me more about what's happening during the rattle so I can determine if there's really an issue. Either way, I think my HEUI is not happy, but again collecting data over the span of a 40 minute drive on the highway should tell me a lot more.
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Old 11-18-2022, 02:28 PM   #16
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dbsoundman: open that dog house while going down the highway so you can get a good fix on where that rattle is coming from while someone else is driving. It (the noise) coming in and out like that makes me think it's not the engine. As far as when it's cold the oil has a hard time going through the screen on the oil pump pickup if there is stuff stuck to the screen but gets better with warm up. That may account for low pressure. I have had that happen to me before so you might want to drop the pan and see how the screen looks.
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Old 11-18-2022, 02:57 PM   #17
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dbsoundman: open that dog house while going down the highway so you can get a good fix on where that rattle is coming from while someone else is driving. It (the noise) coming in and out like that makes me think it's not the engine. As far as when it's cold the oil has a hard time going through the screen on the oil pump pickup if there is stuff stuck to the screen but gets better with warm up. That may account for low pressure. I have had that happen to me before so you might want to drop the pan and see how the screen looks.
I'll add that to "things you can't do with a dog nose bus"

I'm the primary/sole driver currently but my wife is going to try it soon hopefully. In the meantime hopefully I can take a closer look at the pulleys/idlers...
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