The other day I took it out for a spin.
Though normally starting right up with no issues, this time it started up very slowly.
With the pedal to the floorboard, acceleration was slower than normal.
Top speed was 50 mph, when I've hit 70 mph in the past.
My fuel filters were changed less than 5000 miles (less than 2 years) ago.
Regardless, I called MCI to ask what might cause problems with the fuel pressure. Though he referred me almost instantly to Detroit Diesel for any questions about the engine's fuel system, he did also suggest that I check the color of the diesel fuel in my filters. If it was greenish, he suggested, then the problem could be algae in my fuel tank.
Upon following his suggestion, the diesel fuel in my filters looked like the normal yellowish color.
Since that last outing, I've replaced the air intake filter (dry kind, not the oily kind), and I've started her up a few times.
She starts up fine, but I haven't taken her out for a spin yet.
Each time I've started her up, I've taken readings from the fuel pressure gauge inside the engine compartment.
At start up, the pressure gauge reads 50 psi. After idling for a while, with a few manual accelerations at the engine, the pressure gradually drops down to 25 psi or below.
Anyone know what the fuel pressure should be while idling?
Has anyone experienced anything similar?
Any ideas what could be causing this weaker performance?
Fuel pressure gauge in the back?
sounds more like oil pressure behaviour?
Trace that line...
What condition did you find the air filter in that you changed out?
happy coaching!
buswarrior
The fuel filters can get blocked up quick with one load of contaminated fuel, and there is always the possibility of the fuel pump giving up. Check the air filter just to be sure, but the fuel filters are a good bet.
You can have good fuel pressure and a filter be plugged it all depends on which side of the filter the gauge is reading from, change both filters and you can roll again
If your exhaust is smoking black under load, it is a plugged up air filter (bird nest?), If not, it probably is plugged fuel filters.
could be a linkage problem, getting full travel ?
5000 miles and two years on a set of fuel filters? That would be my number 1 place to look for the problem.
When I brought my bus home from NJ last fall, it had recently had new filters put in. By the end of the 1300-mile trip home, I was noticing a reduction of power on the hills. Sure enough, the primary was pretty dirty and the secondary starting to get there. Changed them out and all was good again. Doesn't take much to plug them up enough to affect performance.
Check the shut down cylinder too and be sure it is retracting all the way and not hanging
Let's see.....1981 coach with the build up of crap, dirt, algae and moisture in fuel in fuel tank over the years, which settles to bottom of tank, only to be stirred up at every refill, and sloshing fuel going down the road.....change, at least primary fuel filter. Pre fill it with fuel, install, start and run engine immediately at 1500 to 1700 for 15 to 20 seconds, before dropping to idle so you don't allow the little bit of air introduced when changing filter/s to cause engine to stall out.
The majority of older conversions should have fuel tanks pulled and thoroughly cleaned. Will save many fuel filter replacements over the years. But most won't do it.
Thanks for the quick replies, everyone!
I will change out the fuel filters and let you know how she performs.
I will also plan on pulling out the diesel tank and washing it out.
What's the best way to wash out the fuel tank? Just hose it out?
QuoteQuote from: buswarrior on November 01, 2018, 01:01:37 PM
Fuel pressure gauge in the back?
sounds more like oil pressure behaviour?
Trace that line...
What condition did you find the air filter in that you changed out?
happy coaching!
buswarrior
I have an oil pressure gauge on the dash (shown in attached photo with master switch in "off"), and there's a different gauge in the engine compartment that's connected to what I think is the fuel pump, but I'm not sure (i'm totally a newbie).
When the bus is running they show different pressures, so they can't both be gauging the oil pressure (unless my dash board gauge is innacurate)
The other pictures show the fuel(?) gauge in the engine compartment and what it's connected to ("blue component").
I'm assuming it's the fuel pump as it's also connected to what I think are fuel lines.
But, I'm going to download the Detroit Diesel 8V71 manual to start reading up on my engine anatomy.
As for the air filter, it was pretty gray though not crazy dusty. But, I know it hadn't been changed in several years. Looking on the inside of it, no light was permeating through the filter walls (like the new one that I ordered).
The "blue" component in your last photo is the air compressor that supplies air pressure for your brakes, suspension and wipers. If the hose from the manifold that that gauge is attached to is the small one attached to the compressor, it is supplying engine oil to the compressor crankcase, so that gauge is oil pressure, as well. It's not unusual for the 2 gauges to disagree.
Bob
Fuel filters reduce flow by gallons thru not hours or miles or time.
Yes I know I'm full of XYZX.
Fuel tanks don't make water.
I know, more BullXYZX.
And fuel doesn't wear out..well ok maybe after years, more than 5...
been around stored equipment, mothballed between contracts for years and never found algae or water in a tank that just sat in storage.
And I've owned and serviced equipment that had 4-5 year old fuel filters.
They ran fine.
If it ran fine last week, it probably isn't the filter.
I had a similar issue. I had someone push the pedal all the way down and noticed I only got 2/3 to 3/4 travel.
The linkage was bent. I think it happened when I tried pushing the pedal down with the high idle on.
When I cleaned the tank in the 4104, I used pea clean gravel, about a coffee can worth, and a gallon of lacquer thinner. Rocked tank back and forth like a see saw. When done, removed solvent and gravel, left tank air out till lacquer thinner evaporated. Reinstalled. I was amazed at the layer of crud in bottom of tank. Keep any flame or sparks away while doing it. Some tanks have baffles that don't al!ow solvent and gravel to pass back and forth, and might need steam cleaning instead. I've just shortened a 4905 tank and had the ability to look closely at the baffle system. The baffles are about every 20 inches, go from top clear to the bottom. About 2 inches up from bottom there is an approx 2" hole to allow fuel to pass. Some fuel can get by at bottom of baffles. Looks like it may have been designed to avoid dirt and debris from moving through whole tank, but be contained to first compartment which has the fuel drain , and big removable fuel filler. Sort of how septic tanks are designed today.lol
Btw, with fuel filler removed, you can see the slot in baffle for fuel gage float clearance, whether it has the fuel gage or not. This tank had some crud in first compartment, but not like in the 4104.
I think it's safe to say this issue has been resolved.
I followed the suggestion most of you made to change out the fuel filters.
First, I tried flushing the fuel system with a can of Sea Foam. Then, I changed the filters out and added some fresh diesel with a new can of Sea Foam (1 oz per gallon of diesel).
She revved up beautifully in neutral and when we took her out, acceleration was back to normal and we hit a top speed of 65.
I made an effort to remove the entire tank for cleaning, hoping to avoid having to change the filters again too soon.
But, I was not successful in detaching the fuel lines without potentially damaging them. I will try again some day, but for the time being, I'll continue administering Sea Foam when the tank gets low. Hopefully, that will keep everything cleaner.
The one downside to this procedure is that I may have let a bit of air get into the fuel lines while I was changing out the filters. Immediately after changing the filters, the ignition button struggled to get the engine to turn over. I had to press down on the gas to get it to push through to full ignition and then a normal idle.
I ran it until the air pressure was full, revving it once and a while. The next time I started it (to take it for a spin), I had the same issue. I haven't tried starting it since our little spin, but hopefully that several mile circuit pushed any air bubbles out.
I'd like to avoid having to prime the fuel system, if possible.
If not, any advice on how best to prime?
An electric fuel pump in line between the tank and the primary filter primes the system really easily.
JC
The filter base has a plug to remove for priming that is where I prime the system from
Well, it sounds like you still have issues. It is normal to have to hold the throttle high to keep the engine running after changing the fuel filters even after putting clean fuel in them.
It is not normal to get air in the fuel system after being parked. So either your fuel filters are loose, or the fuel line(s) are loose or damaged letting air get in the system.
You shouldn't have to prime the system if everything is right. However, a permanently mounted electric fuel pump with a bypass is the easiest back-up system to have.
For now, make sure the filters aren't loose (don't overtighen!), and the fuel lines are tight.
Well, it turns out this issue may not yet be resolved after all.
Took the bus out yesterday to head to a nearby state park, and it was slow to accelerate, again. Absolute top speed was 60 on flat parts, though I had to "pedal to the metal" to get her there.
On slight inclines, it wouldn't do more than 40, and it had to down shift to do that, even.
Looking back on the performance improvement a month ago, the only change that was made was a new set of fuel filters and some Sea Foam in a quarter tank of diesel. I assume this provided a general cleaning to the fuel lines/tank/injectors, etc, that could have been partially clogged by gunk from the fuel tank.
Is it possible that having sat unused for 1 month that the fuel system components gunked up again?
Would a few more cans of Sea Foam fix this up?
Could the fuel injectors be dirty/malfunctioning? The fuel pump?
I look forward to your troubleshooting ideas!
Your muffler could be plugged up (falling apart inside or full of oil), and creating so much back pressure the engine can't get full power.
No more shotgun parts changing, snake oil drinking...
Methodically confirm the proper mechanical operation of the throttle linkage.
That the injectors go to full fuel when the accelerator is pushed to the floor. Bent rods, rusted attachment points that bend when you push the pedal up front, "adjustments" inadvertently made to external connections on the governor...
Check under the driver's floor, with an assistant, every rod, crank, linkage, attachment point, bracket, hanger... same down the back...
If a cable install, a split shield somewhere will allow movement at the pedal, without pushing the throttle down the back.
The busnut who plumbs a pair of fuel pressure gauges into the filter heads doesn't guess about plugged filters EVER again, he just looks at the gauges and compares to spec/each other.
And KNOW, not guess.
Make the coach work FOR you, not against you.
Seafoam isn't fixing what's wrong here...
Happy coaching!
Buswarrior
Was it cold? Could fuel starting to gel slow fuel filter flow? I know parts of TX can get in the 30s or lower. I took mine out a few weeks ago, and I felt like before enough fuel ran through the engine to warm it up I wasn't going as fast as I'd like.
So, I'm finding this is an inconsistent issue, which is perplexing.
The latest theory is that the drastic temperature changes here in SE Texas are causing water to build up in the fuel tank.
For example, when I run the engine on a cold day, there may be some water created during diesel circulation.
Has anyone else ever dealt with water in their fuel tank before?
What's an effective way to remedy?
Install a diesel/water separator?
Thanks y'all!
You already have a diesel/water fuel separater-- your primary fuel filter. Sorry, but maybe you need an honest to God Detroit Diesel mechanic to get you through this.
If you keep your fuel tank full you won't have a problem of water condensation. :)
Ditto, get help.
Water condensation is the biggest piece of bullshit mythology ever perpetrated on vehicle and boat owners.
Nothing but a lie to cover up the water in the fuel from the pumps.
Since all the advances in fuel storage regulations, decades ago, we don't often get water delivered into our tanks via the pump like the old days. And when we do, someone introduced the water, it didn't "grow" there.
Believe in whichever false prophets you want, if you are really committed, I would love to see a test done to "create" water in a proper vehicle fuel system. Some decent measure of scientific method and the ability to reproduce the results please.
Happy coaching!
Buswarrior
So i guess that when i get in my car and the windows are all fogged up on the inside that means that somebody has sprayed water on them? :)
No Ed, the moisture is in the carpet and seating materials. Not the same at all.
Happy coaching!
Buswarrior
Ummmm......what about the moisture in the air?
Day late and a dollar short on the picture of the engine compartment gauge - it's screwed into the end of the oil pressure manifold on the side engine cradle of an MCI. Definitely not the fuel pressure, you can see the oil pressure sender and the oil pressure switch on the manifold also.
Re: moisture in the air.
I think you're both right.
1) yes air condensing will precipitate water, how much?
2) how much enough to matter?
There is roughly 1 pint of water in 1000 cubic feet of air at 100% humidity at 70 degrees.
Using 7.48 gallons per cubic foot and let's assume an empty 150 gal fuel tank for worst case scenario, we get 20 cubic feet of air.
If my math is right , and we condense all the moisture out of the air we get .32 oz of water.
This is assuming no air is ever exchanged.
Now if you're a working charter bus and you full up in the morning, .32 ounces is now 10 ounces after 30 days.
I don't think a few moves of water is enough in a tank. However using this math and you have all the hot moist air coming into a holding tank at a filling station, water can quickly build up there, but I hope they are separating it.
If you get fogged up windows on the inside of your car, either the carpet is wet or the heater core is seeping coolant at a seam. If it is hard to evaporate with defroster, it's coolant. If the carpet is dry and heater core isn't seeping, then pull the carpet; the padding is wet. Leave it that way and car will smell musty eventually. Have seen that several times over the years.
I think water in the fuel systems is pretty remote anymore. Since they required fuel tanks across the country to be replaced, water and dirt is mostly a thing of the past. However conversions with water and crap in the fuel tanks is common. Owners of older coaches should thoroughly clean their tanks. The lower cost ohf fuel filters will more than pay for it.
You can easily rule out water in the bottom of the tank. Either crack the drain valve is there is one and take a sample, or put some of this on the end of a long stick and insert till you hit bottom. The paste will let you know instantly if you've got water in the tank.
https://www.amazon.com/Kolor-Kut-Ounce-Water-Finding/dp/B00905UC5E/ref=sr_1_1?hvadid=241900463166&hvdev=c&hvlocphy=9018822&hvnetw=g&hvpos=1t1&hvqmt=b&hvrand=1119095459885555116&hvtargid=kwd-10010660&keywords=water+finding+paste&qid=1552252009&s=gateway&sr=8-1&tag=googhydr-20
I wish they had a gizmo on our tanks like small planes have to quickly take a fuel sample in a glass jar to check for contaminants.
They do Richard. It's called a drain plug. Just unthread it and quickly reinstall it. If you drop the pkug, there won't be any water in the tank.🤣
I'm expecting that my diesel tank is dirty and possibly coated with a healthy layer of microbes.
However, I don't have the proper facility/equipment to remove the 130 gallon tank and clean the inside of it.
Any ideas on where I might be able to take it to have it done professionally?
Quote from: chessie4905 on March 10, 2019, 03:38:56 PM
They do Richard. It's called a drain plug. Just unthread it and quickly reinstall it. If you drop the pkug, there won't be any water in the tank.🤣
I guess a drain plug would qualify as a gizmo. I should have been more specific - a
handy gizmo.
Since the tank's drain plug is not that handy, what I usually do is drain a little from the primary fuel filter into a class jar to check the fuel.
Condensation needs a sufficient change and/or differential of temperature, along with air laden with an appropriate amount of water.
The air, fuel and the tank are all the same temperature when they are sitting, any change, they change together.
And in a sitting fuel tank, very little if any meaningful air exchange.
A very slick lie was told to us, repeated over and over, a lie that "makes sense"... we believe it because it sounds good, and we can't be bothered to test the theory... Someone who "knew what he was talking about"... someone who had a vested interest in blaming the water on imaginary sources, or blaming the owner for "not keeping the tank full" to cover their own tracks...
And any water found in the fuel tank immediately becomes the proof, no matter where it really came from.
A fuel tank rigged up in the storage shed for the winter, the summer, whatever, extend the fuel filler pipe to a sheltered outside location to confirm outdoor air, and be amazed that it stays dry for as long as you try.
Same as the one in your coach.
happy coaching!
buswarrior
Quote from: richard5933 on March 10, 2019, 03:51:37 PM
I guess a drain plug would qualify as a gizmo. I should have been more specific - a handy gizmo.
Since the tank's drain plug is not that handy, what I usually do is drain a little from the primary fuel filter into a class jar to check the fuel.
Trouble with that, you are only checking the fuel at the height of the fuel pick-up...
Water and crud lies on the bottom.
Pull your drain plug and know the truth.
It is a fun adventure the first time, especially if the plug gets away from you.. you'll be fine, expect to get splashed, expect to fumble the plug, have a big enough pan, don't let the plug bounce under the coach...
happy coaching!
buswarrior
HenryTX,
Look up the marine folks.
Fuel polishing / fuel tank cleaning service is what you need.
Negotiate and shop around. Go to them, come to you.
happy coaching!
buswarrior
I have a 400 gal. diesel farm fuel tank that sits outside under a roof and posts . It goes from full to almost empty and full again . I check it a couple times a year with the water grease stuff to see if there is any water in it and in the 20 years I have been using it there has never been water in it . I guess my bulk diesel guys give me the good stuff ?
we get lots of temperature changes and snow and ice and rain
I agree if you have water in your fuel someone put it there
dave
There is no plug on my 5C. I have looked and asked on all boards but no responses, does not show one in any manual I have or parts book etc. :)
there is water finding paste.
I fueled a Gulf-Stream jet once. <OK more than once>
They took a fuel sample in a Waterford crystal bar glass. They gave me the glass.
Point, water in fuel is easy to determine.
Filters contain it.
Quote from: buswarrior on March 10, 2019, 07:21:55 AM
Ditto, get help.
Water condensation is the biggest piece of bullshit mythology ever perpetrated on vehicle and boat owners.
Nothing but a lie to cover up the water in the fuel from the pumps.
Since all the advances in fuel storage regulations, decades ago, we don't often get water delivered into our tanks via the pump like the old days. And when we do, someone introduced the water, it didn't "grow" there.
Believe in whichever false prophets you want, if you are really committed, I would love to see a test done to "create" water in a proper vehicle fuel system. Some decent measure of scientific method and the ability to reproduce the results please.
Happy coaching!
Buswarrior
Quote from: Dave5Cs on March 11, 2019, 08:35:52 AM
There is no plug on my 5C. I have looked and asked on all boards but no responses, does not show one in any manual I have or parts book etc. :)
Interesting... on the bottom of the face of the tank, with the body panel in front of the tank removed?
Maybe Brian Evans has an answer?
Happy coaching!
Buswarrior
Dave on my 5A it was behind a little door/flap just behind the entry door down low.
If the problem is sporadic, it could be something floating in the fuel tank that only plugs up the fuel pick up at random times.
Had that happen on our 4104. Couple large chunks of solder would come up and partially block fuel flow. Solder probably came from a previous tank repair in it's life. Acted like fuel filters were plugging up. Randomly. Last time, it did it again shortly after changing them. While I had tank out, I noticed the crud build up on bottom of tank from years of accumulation. Thoroughly cleaned tank while I was at it. After installed, I put fuel back in in 5 gallon at a time to record when reached movement on gauge, then when It read 1/4 tank. Never had the problem again.
Had that happen on our 4104. Couple large chunks of solder would come up and partially block fuel flow. Solder probably came from a previous tank repair in it's life. Acted like fuel filters were plugging up. Randomly. Last time, it did it again shortly after changing them. While I had tank out, I noticed the crud build up on bottom of tank from years of accumulation. Thoroughly cleaned tank while I was at it. After installed, I put fuel back in in 5 gallon at a time to record when reached movement on gauge, then when It read 1/4 tank. Never had the problem again.
Quote from: Geoff on March 09, 2019, 04:37:53 PM
You already have a diesel/water fuel separater-- your primary fuel filter. Sorry, but maybe you need an honest to God Detroit Diesel mechanic to get you through this.
PROBLEM SOLVED.
In the end, I took it to one of the few Detroit Diesel mechanics here in the city.
There was nothing wrong with the fuel pressure.
His diagnosis was a malfunctioning fuel valve inside the governor.
Upon taking apart the governor housing, they found a buildup of gunk preventing an emergency air valve from pushing completely open the fuel line into the left side injector panel.
The issue was inconsistent, however, with the fuel line opening more or less depending on the day.
After cleaning out the gunk and clearing the motion inside the governor, acceleration and performance were back to normal, actually with a mild increase in horsepower.
The mechanic was very complimentary of the condition of the engine, saying it sounds GREAT :)
We took her out driving on a camping trip the past four days, and, apart from strong head winds, it was a beautiful trip and the bus behaved admirably.
Thanks to everyone who participated in helping me get this fixed!
Translated, your air shut down cylinder was sticking, not allowing full rack travel for full power. I would be worried about the gunk inside your governor-- that is usually from water/antifreeze leaking into the oil.
I would have a lab analysis of your oil done.
Geoff
so I guess all the water I find in my aircraft fuel tanks don't come out of the air?? I guess if you don't live in Florida or SE Texas you wouldn't know. condensation in the fuel tanks have killed thousands of people in airplanes, and what is it in the mornings when I go out to my bus and it is wet?? is that something else??
In high humidity there is condensation , and guess what, not a lie
Don't leave the fuel filler cap off, allowing moisture in. Sounds like those planes need a better fuel mangement system.
A couple of good reads about condensation in fuel tanks:
http://www.mycleandiesel.com/pages/SolutionWater.aspx
https://www.yachtsurvey.com/myth_of_condensation_in_fuel_tanks.htm