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Old 01-14-2021, 02:23 PM   #21
Skoolie
 
Join Date: Jan 2017
Location: USA
Posts: 106
Year: 1995
Coachwork: Thomas
Engine: Cat 3116
Rated Cap: 84
Broken Spring!

I may have finally found my root issue!
.
I was starting to check the fuel pressure and the first thing I found was a broken spring in the last check valve before the fuel goes back to the tank.
.
My Internet searches tells me that is a dual purpose item. It is supposed to maintain fuel pressure after the engine shuts down (for easier starting). And it is the low RPM fuel pressure check valve!
.
I’m heading into town tomorrow to see what I can find.
Not knowing the medium duty lingo and having intermittent internet is making it fun to find stuff. Also having issues because everyone wants the serial number of my engine but the info plate is missing from the valve cover.
The serial number has to be somewhere else on this thing!!!

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Old 01-18-2021, 07:39 PM   #22
Skoolie
 
Join Date: Jan 2017
Location: USA
Posts: 106
Year: 1995
Coachwork: Thomas
Engine: Cat 3116
Rated Cap: 84
Okay, so I found out that the broken spring was not my issue. That’s basically only to keep fuel in the rail after you shut the engine down.

I was also able to get some clear line and Guess What??? Lots of air in the fuel lines!
Not so much at an idle, but the second you rev it up big huge bubbles.
I moved the clear line to before the primary filter and still getting air bubbles in the line.
So, I pulled the line off the tank. Thanks Thomas Built for putting an easy access panel inside the Bus!
Not 100% sure what I’m seeing here.
It looks like the pickup tube is attached to the bung that is welded to the tank??? The elbow fitting is either 3/4 or 1/2 NPT fitting that seems to securely fit into the welded bung.
I’ll attach a pic shortly.

Am I missing something obvious as to how the pickup tube is removed?
Thanks all, hopefully we get this sorted out soon!
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Old 01-18-2021, 08:23 PM   #23
Skoolie
 
Join Date: Jan 2017
Location: USA
Posts: 106
Year: 1995
Coachwork: Thomas
Engine: Cat 3116
Rated Cap: 84
The threads in the tank side are there and are good, pic is just at a weird angle.
Attached Thumbnails
Fuel pickup fittings.png  
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Old 01-18-2021, 08:43 PM   #24
Bus Crazy
 
Join Date: Oct 2020
Location: Near Flagstaff AZ
Posts: 1,951
Year: 1974
Coachwork: Crown
Chassis: "Atomic"
Engine: DD 8V71
Excellent diagnostic troubleshooting! A cracked pick-up tube is better than a bad turbo...or the other options. If you can't get that pick-up tube out, you can replace it using one of those threaded ports. Nicely done.
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Old 01-18-2021, 09:48 PM   #25
Skoolie
 
Join Date: Jan 2017
Location: USA
Posts: 106
Year: 1995
Coachwork: Thomas
Engine: Cat 3116
Rated Cap: 84
I’m going to go through every fitting first.
Hopefully it’s an easy fix!
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Old 01-19-2021, 02:21 AM   #26
Bus Crazy
 
Join Date: May 2018
Location: topeka kansas
Posts: 1,815
Year: 1954
Coachwork: wayne
Chassis: old f500- new 2005 f-450
Engine: cummins 12 valve
Rated Cap: 20? five rows of 4?
Air in the fuel

I have had more than one vehicle with 20-plus year old fuel lines, suck air right through the walls of the rubber lines.

William
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Old 01-19-2021, 08:26 AM   #27
Skoolie
 
Join Date: Jan 2017
Location: USA
Posts: 106
Year: 1995
Coachwork: Thomas
Engine: Cat 3116
Rated Cap: 84
Side story! A long time ago I had a customer’s car that would idle just fine and you could rev it up in neutral all day long. It would sputter and die shortly after putting it in gear and trying to drive.
Many hours of diagnostic testing later, it turns out that the fuel line had a small tear inside. When the fuel flowed enough it pushed on the tear , creating its own check valve.
Crazy thing almost scrapped the car.
...

I picked up some extra fittings, hopefully the weather cooperates today and I can put some regulated pressurized air in the lines and do a bleed down on the individual lines.
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Old 01-23-2021, 11:02 AM   #28
Skoolie
 
Join Date: Jan 2017
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Posts: 106
Year: 1995
Coachwork: Thomas
Engine: Cat 3116
Rated Cap: 84
Well.
I’ve checked every connection and hose.

No leak or holes, etc...

I have some serious froth coming out of the return line.

Local mechanic says probably a bad o-ring on an injector.

Heading out to pull the valve cover.

I’m definitely learning a lot about diesels and this one in particular!!!

I’m anxious to get it fixed soon though. Hopefully this is the real problem.
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Old 01-23-2021, 11:16 AM   #29
Bus Geek
 
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Location: Eustis FLORIDA
Posts: 23,829
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
Quote:
Originally Posted by KlingonFiero View Post
Well.
I’ve checked every connection and hose.

No leak or holes, etc...

I have some serious froth coming out of the return line.

Local mechanic says probably a bad o-ring on an injector.

Heading out to pull the valve cover.

I’m definitely learning a lot about diesels and this one in particular!!!

I’m anxious to get it fixed soon though. Hopefully this is the real problem.

You may want to enlist the help of a serious Cat mechanic if messing with the injection system.
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Old 01-23-2021, 01:37 PM   #30
Skoolie
 
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Posts: 106
Year: 1995
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Engine: Cat 3116
Rated Cap: 84
I have been getting information from a 40 year diesel mechanic that knows these engines inside and out. Unfortunately he’s about 2 hours away, so it’s a bit of work then wait for him to get back to me, then the next step, then wait some more. Good thing I got nothing else to do! lol
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Old 01-23-2021, 02:00 PM   #31
Bus Crazy
 
Join Date: May 2018
Location: topeka kansas
Posts: 1,815
Year: 1954
Coachwork: wayne
Chassis: old f500- new 2005 f-450
Engine: cummins 12 valve
Rated Cap: 20? five rows of 4?
problems

Think of the problem you have as a stack of paper. Each paper is a separate problem. All of these papers added up to your problem you see and hear. Each paper by itself does not kill or stop the engine. Together all the papers manifest in an easy to see problem. You fix the problem on the top of the stack and you throw that paper in the trash. Then you can see the problem under the first sheet. Work through the entire stack.

This is similar to checking a bus for it's first trip out. Really should pull all the wheel off, go all the down to the wheel bearing and wheel seals. Inspecting brakes, hubs, bearings, lines, bushings, kinpins, draglinks, tie rods, steering box, yadda yadda yadda. A single drip of coolant from a water pump can be like a rattle on a rattle snake, a warning before you get bit. You have to listen to the warning to do you any good. If you get used to drips under the engine all the time, you will never know when you get a "new" leak that is a forewarning to impending failure.

I started with a 200,000+ mile bus. It is getting all the bearings, brakes, steering and suspension new, before we ever hit the road. I have found very little that was not worn that I have not replaced. Even two of the rims have been replaced because of out of round condition.

william
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Old 01-23-2021, 02:22 PM   #32
Skoolie
 
Join Date: Jan 2017
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Posts: 106
Year: 1995
Coachwork: Thomas
Engine: Cat 3116
Rated Cap: 84
I agree. Lots of little stuff that stacks up to make Bus life difficult.
Also being a diesel novice doesn’t help much!
.
I’m pretty sure that I did have a small air leak or two in the fuel lines. Taking them apart and resealing the NPT fittings with new sealant and reseating the JIC fittings helped with that.


I got the valve cover off.
No major gushing or spraying of anything like the mechanic said I might see.

Manually pushing the injector rail at each injector did make the rpm go up a bit, except #2. No rpm response unless you hold the pin in and then the engine will kinda stutter a bit.

I’m now waiting on the mechanic to get back to me, and waiting till Monday for the local Cat place to open up.
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Old 01-25-2021, 06:31 PM   #33
Skoolie
 
Join Date: Jan 2017
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Posts: 106
Year: 1995
Coachwork: Thomas
Engine: Cat 3116
Rated Cap: 84
After conferring with the local Cat 3116 Guru, he says it’s almost guaranteed to be the injector.
I have a reman unit on its way to the Cat Shop.

Hopefully this is finally it.
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Old 01-25-2021, 08:05 PM   #34
Bus Geek
 
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Location: Eustis FLORIDA
Posts: 23,829
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
Quote:
Originally Posted by KlingonFiero View Post
After conferring with the local Cat 3116 Guru, he says it’s almost guaranteed to be the injector.
I have a reman unit on its way to the Cat Shop.

Hopefully this is finally it.
Sounds like its in good hands. Reaming those injector cups doesn't sound fun, idk.
Keep us posted, sounds like you've got it!
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Old 01-28-2021, 09:27 AM   #35
Skoolie
 
Join Date: Jan 2017
Location: USA
Posts: 106
Year: 1995
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Engine: Cat 3116
Rated Cap: 84
It’s running better after the injector replacement!
But still not right...

I’ve decided I’ve hit a wall with my limited diesel knowledge and lack of the special cat tools.
It’s going to the Cat mechanic as soon as I can get it in.

I’ll update this post with the final determination of the mechanic!

Thanks to all of you for your support and help!
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Old 01-28-2021, 09:32 AM   #36
Bus Geek
 
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Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 23,829
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
Quote:
Originally Posted by KlingonFiero View Post
It’s running better after the injector replacement!
But still not right...

I’ve decided I’ve hit a wall with my limited diesel knowledge and lack of the special cat tools.
It’s going to the Cat mechanic as soon as I can get it in.

I’ll update this post with the final determination of the mechanic!

Thanks to all of you for your support and help!
did you ream the injector cup?
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Old 01-28-2021, 09:35 AM   #37
Skoolie
 
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Posts: 106
Year: 1995
Coachwork: Thomas
Engine: Cat 3116
Rated Cap: 84
I did not.
I listened to a well respected Bus Guru that’s kinda local to me.
I was advised that it wasn’t needed in my case.

I’m guessing it really is needed!

I’m looking at getting all 6 cups recoined and having them sync injectors and the rack.

Hopefully it’s not overly expensive!!!
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Old 01-28-2021, 09:42 AM   #38
Bus Geek
 
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Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 23,829
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
Quote:
Originally Posted by KlingonFiero View Post
I did not.
I listened to a well respected Bus Guru that’s kinda local to me.
I was advised that it wasn’t needed in my case.

I’m guessing it really is needed!

I’m looking at getting all 6 cups recoined and having them sync injectors and the rack.

Hopefully it’s not overly expensive!!!
Its a multi-step, multi-tool job that a lot of guys aren't even familiar with. I'd expect to spend a bit.
Getting a shop that knows the 3116 is crucial if owning one. Just for the mechanical injection system.
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Old 01-28-2021, 10:30 PM   #39
Skoolie
 
Join Date: Jan 2017
Location: USA
Posts: 106
Year: 1995
Coachwork: Thomas
Engine: Cat 3116
Rated Cap: 84
The Cat shop in Yuma seems to have a 3116 guy.
He was actually referred to me as The Truck Engine Guru...
I guess we’ll see what happens!

I’m waiting on a callback to get the bus in to them.
Really hope it isn’t a long wait...
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Old 02-11-2021, 06:19 PM   #40
Skoolie
 
Join Date: Jan 2017
Location: USA
Posts: 106
Year: 1995
Coachwork: Thomas
Engine: Cat 3116
Rated Cap: 84
Finally got news!

It seems my shade tree (cactus???) replacement of the #2 injector was on the right track, it turns out that the #3 injector was letting combustion gases into the fuel rail too.

The #2 and #3 cups need replaced and the #3 injector is being replaced as well.

The Cat place in Yuma ( can I say the name on this site???)
Is also doing the complete overhead job. Setting everything to best running condition as well as bumping everything up about 10% while making sure it’s still reliable.


It’s taking pretty much all of my current build budget to get it running well again, but it’s gonna be good for my stress level knowing the engine is

I’ll be starting a build thread soon, I do have a fair chunk of demo done already. Next step after we get it back is too start the excess wire removal, my bailiwick!
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