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Old 04-12-2022, 02:40 PM   #1
Mini-Skoolie
 
Join Date: Jul 2021
Location: Tulsa, OK
Posts: 23
Year: 2004
Engine: CAT 3126E
How can I prime the fuel/Get my baby to start

First off I only recently learned I'm working with a 3126. Was told it was a C7 but apparently that's not the case. If someone could confirm that for me from these pictures that would be great. Cause I don't know if it's a 3126B.

Bus is a 2004 Thomas Saf-T-Liner MVP

Anyway, been sitting a long time and it cranks but doesn't start. So pretty sure it's not an electrical problem.
Father in law suggested purging air from the fuel line. From watching Adept Ape videos, looks like the best way is to use a Brakes Bleeder and connect it to the return fuel line. Great, sounds simple. Well now I'm struggling to figure out where the return line ends. I believe it's connected to the fuel filter I have a picture of. If this is the case, how on earth do I access this line? Thought it was going to be near the engine but it seems to run back under the bus.
Doe anyone have experience with this?
Is this the line I need to draw the fuel from?
Is this actually a 3126?
Am I even going in the right direction?

Any info helps. Just very ready to here my baby vroom vroom again HAHA

https://imgur.com/a/ViGwHpA

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Old 04-13-2022, 08:49 AM   #2
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Engine model is on the engine data tag. Upper right hand corner of tag. 3216

I don't have any experience with that family of engine. I am not much help.
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Old 04-13-2022, 09:43 AM   #3
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Yes, its a 3126.

I have a 3126 in my bucket truck, and mine has no manual primer. When I lost prime, I just filled my fuel filters and cranked it.
Start with new, clean filters, and CLEAN fuel. Fill the filter through the small holes, NOT down the center. After fitting the new filter in place, there is a fill plug on top of the filter housing. Clean it off before removing the plug. I used a squeeze bottle full of fuel to top it off. Then crank it. No ether. It may take a while, so you'll need a good battery. Don't overheat your starter!
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Old 04-16-2022, 07:55 AM   #4
Mini-Skoolie
 
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Engine: CAT 3126E
You said to remove the filter plug, but then what do I do with it?
And are you describing the component that the filter goes into? Cause that is where I'm not sure about accessing.

From my pictures there you can see where the return fuel line connects and it's above the filter and very high up. Am I doing anything with that fuel line?

Also if my engine isn't getting any fuel in, how is adding fuel to the filter on the back end of the system going to help get fuel into the engine? Or am I completely off as far as to where these filters are in the workflow of the whole system?
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Old 04-16-2022, 09:02 AM   #5
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Quote:
Originally Posted by TheBryceIsRight View Post
You said to remove the filter plug, but then what do I do with it?
And are you describing the component that the filter goes into? Cause that is where I'm not sure about accessing.

From my pictures there you can see where the return fuel line connects and it's above the filter and very high up. Am I doing anything with that fuel line?

Also if my engine isn't getting any fuel in, how is adding fuel to the filter on the back end of the system going to help get fuel into the engine? Or am I completely off as far as to where these filters are in the workflow of the whole system?
I apologize for the confusion I caused you Bryce

Upon closer review of your photos, I now recognize that all of the filters shown were placed by the vehicle manufacturer, not by Caterpillar. My comment about the filter housing plug is therefor irrelevant.


If you choose to draw a vacuum on the fuel return line as described by AdeptApe, doing so at any point after the engine is fine. Why not do so where the line is easily accessible, such as that point at which you took the photo?


The fuel filters are located before the engine, not after.


My now amended suggestion is to open the valve at the bottom of the fuel/water separator (the one with the valve at the bottom) and catch what comes out in a clear container. Look at it to see if it is fuel, water, or a mixture of the two. If there is more than a few tablespoons worth of water, you'll have to deal with the water first.

Next, clean all the filth off of the filter housings that the filters screw into. (perhaps using compressed air) Then, carefully remove the filter and see that it is brim full of fuel. If any fuel filter is not completely full, fill it with clean fuel as described above and screw it back on. Crank the engine. If it sputters and bucks but wont run, re-check and re-fill the filters as needed until it will run. Expect it to run poorly until all of the air bubbles are pumped out of the supply side of the fuel circuit.
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Old 04-16-2022, 09:50 AM   #6
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Ah no need to apologize! haha Sorry if I came across strong. You're definitely sending me in the right direction. Except now there's more questions haha

So correct me if I'm wrong, that white canister is the fuel filter, correct?
And the fuel return line is after fuel has gone through the engine?
So why would that line then go to a fuel filter if the filter is supposed to be before the engine?
Or is that not even the fuel return line and I'm just really backwards?

Definitely seen plenty of people mention the separator, so I'll give that a go.

I'm very very new to working with engines so this is a huge learning process and it didn't help that up till this point I thought I was working with a C7 haha
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Old 04-16-2022, 04:52 PM   #7
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Yes, the white canisters are filters and or separators. My 3126 has three filters, and the fuel flows in this order:
Fuel tank --> fuel/water separator --> fuel filter --> fuel pump (inside engine) --> fuel filter --> engine --> return to fuel tank.
Follow both the lines from the fuel tank to the engine. The return should go directly to the back of the cylinder head, and the supply should pass through various filters before entering the fuel pump near the front of the engine on the driver side.
Any filter that you did not install is suspect. Over time, Diesel fuel can grow bacterial slime that plugs up filters. Go through each of them and make sure each one is clean, full, and leak-free. Remember that any place on the supply side that fuel leaks out of, air will leak into.
Give it a whirl and let us know what happens


Rich
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Old 04-16-2022, 05:50 PM   #8
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Just tried and did accomplish the task of getting a diesel engine started that hadn't run since 2003. I used a spray bottle with diesel and just a shot of gasoline in it and sprayed like crazy into the intake and it started well. Now we had been trying to start it for 30 minutes with only some sputtering on either but with the fuel being sprayed into the intake manifold it got very happy and started right up. I never liked either because of the damage it does to cylinders by drying up the lubricating oil and hammering the pistons.
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Old 04-18-2022, 06:31 PM   #9
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I had a crank / no start on my Cat 3126 a few months back. Replaced weak starter batteries, fuel filter, fuel water separator filter, and then manually primed it with the hand pump (located right next to fuel filter on the right side of the engine bay - I have a 2003 Thomas Saf-T-Liner HDX). I wish I hadn't primed it, because I didn't know my own strength and then broke it and had to replace the hand pump. Started right up after that. Turns out my filters were filthy (especially the fuel water separator filter) and my tank needed biocide additive from sitting around too much on a near empty tank. Apparently I never even needed to prime with the hand pump at all, but back then the engine wouldn't start and I didn't know that it was simply because the engine compartment door was open and I had to press down on the sensor.

Check and make sure you don't have a hand pump. We have almost the same bus/engine.
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Old 04-20-2022, 07:38 AM   #10
Mini-Skoolie
 
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Year: 2004
Engine: CAT 3126E
I am almost certain there is no hand pump, which is quite unfortunate. And I have a feeling it's the fuel that has just got nasty. Going to check the filters and the water separator.
Any suggestions on removing them? I was out there the other day and boy that filter was on tight. I have strap wrenches, figure that might do the trick.
Also, probably will want to do the additive to the fuel. Is that only for if the fuel has gellified? Again bus hasn't started since December, it's at half a tank of fuel and it dropped well below freezing during that time. I know that the filter will be nasty if it's turn to gel but are there other signs that the fuel has gone bad?

And on the priming part. How would I prime it without the hand pump?
As I've mentioned earlier I've seen using a brake bleeder to suck the fuel through the return fuel line but the way mine is set up I have no idea how I can even get to that line, if it's what's attached to my filter. Are there other suggestions on how to prime this engine?

Definitely feeling the drain of this. I know that if I can get it started I'll really be able to get going on other stuff. This has just turned in to a far more frustrating situation that I had predicted. I'll definitely make sure to prepare a bit more come next winter. haha
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Old 04-20-2022, 09:02 AM   #11
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If you can't find a hand pump, and have no good location for one, a cheap facet cube pump primed parallel to a check valve can work wonders at getting it primed and also at filter change time.

Put it on a toggle switch located in the side access door, let it run for a minute or so, and then fire it up. Might not hurt to crack the line before the lift pump to let the air out as well.

PS. The hose in your 3rd pic is the fuel return. Don't mess with it. Your lift pump should be under the black air intake hose to the left of your first pic. It will be attached to the back of the injection oil pump.
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Old 04-20-2022, 05:51 PM   #12
Mini-Skoolie
 
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Quote:
Originally Posted by TheBryceIsRight View Post
I am almost certain there is no hand pump, which is quite unfortunate.
The hand pump on my CAT 3126 looks like this:
Click image for larger version

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Quote:
Originally Posted by TheBryceIsRight View Post
And I have a feeling it's the fuel that has just got nasty. Going to check the filters and the water separator.
Any suggestions on removing them? I was out there the other day and boy that filter was on tight. I have strap wrenches, figure that might do the trick.
I agree and suspect you just need to change your filter(s) like I did, and it will probably fire right up without even needing prime (if you pre-fill the filters with diesel before putting them on - outer holes). Use a strap wrench.

Quote:
Originally Posted by TheBryceIsRight View Post
Also, probably will want to do the additive to the fuel. Is that only for if the fuel has gellified? Again bus hasn't started since December, it's at half a tank of fuel and it dropped well below freezing during that time. I know that the filter will be nasty if it's turn to gel but are there other signs that the fuel has gone bad?
I didn't have a gel problem, but I use anti-gel anyway. I had an "algae" problem, which is when you don't keep the tank full for so long and it grows on the empty tank. I use three additives religiously now at every fill-up and keep the tank full: a stabilizer, anti-gel, and biocide (anti-gel not necessary when temps rise). One sign you may have an "algae" problem is if you ever smell a strong rotten egg smell. You can also tell by the debris in the filters once you pull them, it's different from gel.

Quote:
Originally Posted by TheBryceIsRight View Post
And on the priming part. How would I prime it without the hand pump?
As I've mentioned earlier I've seen using a brake bleeder to suck the fuel through the return fuel line but the way mine is set up I have no idea how I can even get to that line, if it's what's attached to my filter. Are there other suggestions on how to prime this engine?
This I don't know, but I'm betting you just need to change filters and pre-fill them. Most people don't prime from what I understand.

Quote:
Originally Posted by TheBryceIsRight View Post
Definitely feeling the drain of this. I know that if I can get it started I'll really be able to get going on other stuff. This has just turned in to a far more frustrating situation that I had predicted. I'll definitely make sure to prepare a bit more come next winter. haha
Feel free to PM me if you need help with your bus in the future.
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Old 04-22-2022, 12:39 PM   #13
Mini-Skoolie
 
Join Date: Jul 2021
Location: Tulsa, OK
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Year: 2004
Engine: CAT 3126E
Tried to remove the fuel filter. Are they supposed to be screwed on so tight?

Bought an oil filter removal tool cause my strap wrenches were slipping. But now I'm just causing dents to form on the filter, don't think that's supposed to happen.

Of course I'm not sure which way I'm supposed to rotate it. I was going clockwise because that was the only direction it was turning, but was I supposed to be going counter clockwise and I've actually just been tightening it more?

Also if I need to remove the water/fuel separator should I just get a larger sized oil filter wrench or is there a better tool for the job?
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Old 04-22-2022, 01:51 PM   #14
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Quote:
Originally Posted by TheBryceIsRight View Post
Tried to remove the fuel filter. Are they supposed to be screwed on so tight?

Bought an oil filter removal tool cause my strap wrenches were slipping. But now I'm just causing dents to form on the filter, don't think that's supposed to happen.

Of course I'm not sure which way I'm supposed to rotate it. I was going clockwise because that was the only direction it was turning, but was I supposed to be going counter clockwise and I've actually just been tightening it more?

Also if I need to remove the water/fuel separator should I just get a larger sized oil filter wrench or is there a better tool for the job?

Hi Bryce

The filters can seem quite tight while trying to remove them. Usually the dirty oily film on them is pretty slick. Since you are disposing of the old filters, dents wont matter. Dents happen.

Looking at the smooth, domed end of the filter, turn it COUNTER-CLOCKWISE to remove. The old saying "Righty tighty, lefty loosey" comes to mind.
Any tool that will turn the filter can be used. Big slip-joint pliers (channel locks), A strap wrench, an old fan belt and a bar, or a chain wrench can all be helpful. The filters are a maintenance item; if you're going to be doing your own service going forward, get the tools you need.

Once you get the filters off, the new ones are typically tightened hand-tight plus one quarter to one half turn.

Remember to make sure that all of the old gasket is removed from the filter housing, and to put some clean fuel on the new rubber gasket and the threads before installing the new filter.
Once you get things running smoothly, wipe the new filters CLEAN, and write the date and mileage on them, and in your maintenance log.
Good luck!
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Old 04-22-2022, 02:56 PM   #15
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Hi Bryce

The filters can seem quite tight while trying to remove them. Usually the dirty oily film on them is pretty slick. Since you are disposing of the old filters, dents wont matter. Dents happen.

Looking at the smooth, domed end of the filter, turn it COUNTER-CLOCKWISE to remove. The old saying "Righty tighty, lefty loosey" comes to mind.
Any tool that will turn the filter can be used. Big slip-joint pliers (channel locks), A strap wrench, an old fan belt and a bar, or a chain wrench can all be helpful. The filters are a maintenance item; if you're going to be doing your own service going forward, get the tools you need.

Once you get the filters off, the new ones are typically tightened hand-tight plus one quarter to one half turn.

Remember to make sure that all of the old gasket is removed from the filter housing, and to put some clean fuel on the new rubber gasket and the threads before installing the new filter.
Once you get things running smoothly, wipe the new filters CLEAN, and write the date and mileage on them, and in your maintenance log.
Good luck!
Couldn't say it better myself ^. Mine also were tight when I tried to remove them, which is probably another sign they haven't been replaced in a while (or someone just over-tightened them). I went through the same thought process though, like "am I turning these the right way??" because it's kind of upside down when you're doing it, and they weren't budging. Eventually I got the fuel filter off with a strap wrench, but I couldn't get the angle for the fuel water separator filter and had to buy some filter pliers. Something like these. A lot of people apparently rave about the vise grip ones too: https://www.harborfreight.com/lockin...nch-63696.html. All depends on how you have to get your hands in there I guess.

Oh and I *destroyed* the filter to get it off, it's no issue. Just don't destroy the new one when you put it on.
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Old 04-22-2022, 04:25 PM   #16
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Quote:
Originally Posted by TheBryceIsRight View Post
Tried to remove the fuel filter. Are they supposed to be screwed on so tight?

Bought an oil filter removal tool cause my strap wrenches were slipping. But now I'm just causing dents to form on the filter, don't think that's supposed to happen.

Of course I'm not sure which way I'm supposed to rotate it. I was going clockwise because that was the only direction it was turning, but was I supposed to be going counter clockwise and I've actually just been tightening it more?

Also if I need to remove the water/fuel separator should I just get a larger sized oil filter wrench or is there a better tool for the job?

Yeah. Get the vice grip kind. I recently bought every kind they make. I finally got my oil filter off with the vice grips and a cheater bar.

Dave
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Old 04-23-2022, 10:17 AM   #17
Mini-Skoolie
 
Join Date: Jul 2021
Location: Tulsa, OK
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Year: 2004
Engine: CAT 3126E
Alright so just to clarify.

Current plan should ne
A) Remove and change fuel filter
B) Loosen valve on water/fuel separator
- if more water than fuel replace saparator?
- if even mix leave be?

Sound about right?

You guys have been such help. Definitely going to be fun to learn more about how whoever built the bus configured the engine. Is it common in FE flatnose to reconfigure the engine or did someone just think, "hey this'll be fun to do differently!" haha
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Old 04-23-2022, 10:28 AM   #18
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Quote:
Originally Posted by TheBryceIsRight View Post
Alright so just to clarify.

Current plan should ne
A) Remove and change fuel filter
B) Loosen valve on water/fuel separator
- if more water than fuel replace saparator?
- if even mix leave be?

Sound about right?

You guys have been such help. Definitely going to be fun to learn more about how whoever built the bus configured the engine. Is it common in FE flatnose to reconfigure the engine or did someone just think, "hey this'll be fun to do differently!" haha
Huh?

If you don't know the age or mileage of them, replace all filters. And if it doesn't come off with a strap wrench, hammer the longest flat blade screw driver you have through both sides of it and twist it off counterclockwise. It doesn't matter if it gets ruined upon removal, it's trash anyways.

There should be ZERO water in the water separator. The water separator is also a filter, albeit higher micron, and should be replaced along with the fuel filter every time.

God only knows what's been done to your bus in the last 20 years. Stuff might be missing, stuff might be added, stuff might not have been there from the get go. You'll find that even amongst a group of experts, there probably isn't one "right" way to do things.
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Old 04-23-2022, 10:59 AM   #19
Mini-Skoolie
 
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Quote:
Originally Posted by TheBryceIsRight View Post
Alright so just to clarify.

Current plan should ne
A) Remove and change fuel filter
B) Loosen valve on water/fuel separator
- if more water than fuel replace saparator?
- if even mix leave be?

Sound about right?

You guys have been such help. Definitely going to be fun to learn more about how whoever built the bus configured the engine. Is it common in FE flatnose to reconfigure the engine or did someone just think, "hey this'll be fun to do differently!" haha
Actually the fuel water separator filter was the worst filthiest one for me, after I replaced it that's when the bus started. The bowl is simply there for periodic draining of water, that's what the filter does it separates the water. Just drain it periodically when you see water in there. Check eBay and Amazon for your filter after getting the p/n off the old one. If not call your closest CAT dealer.
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Old 04-23-2022, 03:05 PM   #20
Mini-Skoolie
 
Join Date: Jul 2021
Location: Tulsa, OK
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Year: 2004
Engine: CAT 3126E
Ok so then I should just replace both the fuel filter and the water/fuel separator.

Once the new ones are installed do I need to do anything, or just try to start her up?

I don't have a manual primer pump so I'm not sure what I would need to do to prime it. Or is adding the fuel into the fuel filter "priming"?
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