The charging problem I HAD is NOW gone! That's a plus and to boot, the batteries don't continually drain while sitting over night. In fact, they have stay pretty charged since replacing the R3 Relay. I have read everyone's opinion on what the charge rate should be set at and re-read the charts everyone supplied and came to the conclusion that I needed to adjust the regulator to bump the rate up just a tad! Well, to do this the coach needed to be started so today I had time and went out to start the bus. It cranked a little longer than normal but started. It just didn't sound quite right so I shut it off. I raised the engine door and looked around to make sure a squirrel or SOMETHING hasn't done damage. None found so, I restarted and the same result but this time I tried to accelerate and there was NO throttle response. Looking at the tach, it showed only 300 rpm and stepping on the pedal made no difference. Now I'm stumped. I tried the high idle and nothing. OK, now I'm thinking electronic since that is what started all the trouble. I start checking relays, breakers, wires, and anything else I could think of. I got the book out and read up on fuel delivery. Didn't tell me much more than what I already knew but I DID learn that the throttle won't work IF the ddec test switch is in the ON position, which it wasn't so back to the drawing board. I called my friend Brian Joy who is the regional service guy from Prevost. I call him a friend since he has heard my voice so much he knows me by name although we have never met. I explain my woes and he says that there is nothing electronic tied to the coach that relates to the fuel delivery and says to start with the filters. If I still have a problem it could be the fuel pump OR since I have had the voltage problem it COULD be the ECM going bad. Uhh, not what I wanted to hear but none the less, I had to start somewhere so changing the filters was the thing to do. After siphoning (yuck) fresh fuel from the generator tank into a can to fill the new filters that I installed, my friend Niles from Tampa who also owns a Prevost H model gave me a surprise visit along with a VERY LARGE Pizza. The Pizza had to wait as I just had to see if the filters did the trick. It started, It idled at the normal idle and it accelerated by the pedal. Next was to see if the high idle worked and it did too! All is now good but don't you find it peculiar that this happened in my driveway with absolutely no warning? I do but for now, it's charging like it should and running like it should, for NOW!
I DID learn a lesson from all of this. Just because you have one problem fixed and another pops up soon after, don't think they are always related! In this case they weren't but I'm sure they could have been! One way to keep the mind working for sure!
Ace... ready to roll!!!
I don't know what it was but obviously you did SOMETHING to piss off the gremlins.
Yes tell me about it! Now get this. I just came in from outside and I dumped the fuel from the filters into a glass jar and the scary thing is, it's pretty darn clean! No trash, no water, nada!
Does anyone know a good way to cut the filters open besides using the filter cutting tool? I'm just curious as to why and IF this actually fixed my problem?
Ace
I use a large tubing cutter just like the small ones you would use on copper tubing, Ive had it for years and even then was a pricey $90.00, but it works great by holding the closed end in a vice and cutting off the end at the threaded end. The whole filter falls out of the tube and can be seperated and looked at in the sun, its amazing what youll find>>>Dan
Ace, the fuel we get now days is pretty good stuff. A few years ago the filters would plug about every 8 months if you operate every day. Now they go over a year and what the catch is very small in size. We used to pour a mix of stuff that you could see out when we looked at the old fuel, but now its not unusual to have a plugged filter and pour out clean looking fuel.
I still use a hack saw to cut mine, I know what the metal from a saw looks like and I just discard that when I look at the paper and most of it falls outside anyway.
I have heard talk of biocide use especially with a biofuel mix but I don't know that anything is growing in your tanks. Last winter I used a biocide in my tanks and was concerned that if it killed something I would plug the filters anyway. No plugged filters so I guess nothing was growing in my tanks. My local fuel dealer told me that they are putting the biocode in their bulk tanks anyway.
I only buy non biodiesel and I only fuel at high volume truck stops and have not had a problem yet. Hope that filter was just used up and not plugged by recent contamination.
Hopefully the filter was full to the top and you don't have a sucking air situation.
I never go anywhere without spare filters just in case.
Well to update, I went out and cut open the smaller filter and found nothing weird inside other than black or very dark colored wet paper. I couldn't see any light thru it as I held it up to a bright light so not sure what this tells me if anything! I want to believe that the filters were just clogged to the point that they wouldn't pass fuel enough to run but that still doesn't explain why I had no peddal response!
Does anyone know what the fuel pressure spec is supposed to be on a 8v92? If I were to install a fuel pressure gauge, first is this a good idea and would it mount directly to the fuel filter housing? I see a fitting on top that is plugged. Would this be a good place? I also carry extra filters on my trips! I guess you just never know!
Ace
look for a gremlin named susan. she's probably lhao about paybacks for bucket heads ;D
LMAO but that reminds me Tom, bobofthenorth sent me a pm inviting us to meet him at Wally World. Seems his wife needs a new "bucket" and he needs help finding the right size! Are you still in Florida or are you in Texas now? Did you go by the service place I told you about? If so, how was it?
Ace
did, good, more to follow.
we're in polk city overnight, then on to Bushnell and Texas.
fran wants a couple miles on her bus first before posting results.
Ace,
I recall a fellow told me that the fuel pressure on the 8V92 and the 6V92 are the same. I recently learned that the fuel pressure on my 6V92 is supposed to be 15-20 PSI at idle and somewhere between 50 and 70 PSI at the high RPM. I placed a pressure gauge on the top of my secondary filter where the plug is located that you mention and verified my pressure at various rpm. There is a very distinct pressure profile on a unit with a good pump and no air mixed with the fuel. On my unit I had both a weak pump and a air coming into the line from the fuel tank. My engine would idle low and high just fine but would not run up to 2100 rpm. The pressure at idle was 15-20 and it would rise up some when the throttle was pressed but would fall back as rpm increased. This fall back was from the air in the fuel. the pressure should rise as rpm rises and not fall back except when under heavy load. The gauge installed at this location is invaluable and I would suggest everyone do a run up now and then as a preventive test to verify good pump and a tight fuel system. Of course you will want to make sure you have fresh filters when you do this check. Hope this helps. - Greg
Quote from: Blacksheep on January 08, 2009, 06:38:24 PM
Well to update, I went out and cut open the smaller filter and found nothing weird inside other than black or very dark colored wet paper. I couldn't see any light thru it as I held it up to a bright light so not sure what this tells me if anything! I want to believe that the filters were just clogged to the point that they wouldn't pass fuel enough to run but that still doesn't explain why I had no peddal response!
Does anyone know what the fuel pressure spec is supposed to be on a 8v92? If I were to install a fuel pressure gauge, first is this a good idea and would it mount directly to the fuel filter housing? I see a fitting on top that is plugged. Would this be a good place? I also carry extra filters on my trips! I guess you just never know!
Ace
Greg thanks for the info. What type gauge did you use?
Ace
My suggestion is not necessary a must have but because of the unknown fuel condition from algae or bad fuel or collapse hoses...the following installed gauges will guarantee to pin point the problem from the fuel pickup, hoses, filters, broken injector's line and fuel pump.
See if you have restricted filter or not or partial...even collapse hose.
1) Install a tee between primary filter to gear pump.
2) Install a tee between gear pump to secondary filter.
3) Install a tee between secondary to cylinder head (fuel manifold to injectors).
4) Install a mechanical 0-30 HG vacuum gauge in # 1 tee.
5) Install 2 electric 100 psi oil/fuel pressure gauge. One for each...# 2 & # 3 tee.
While in driving in accelerating mode and hill climbing mode...you must watch the gauge in the order of sequence 1- 2 - 3:
1) For higher vacuum of more than 5% than baseline. Primary or tank inlet or collapse hose is restricted.
2) For # 2...higher psi of more than 10% at warm temperature and # 3 is lower psi than # 2. Secondary filter or collapse hose is restricted.
3) For # 2 & # 3 lower then spec psi is one of two things...broken injector's line or weak fuel pump.
Caution: The % figure is only my suggestion...it can be higher due to very cold fuel ...you need to do the road test and reports your finding.
About the source for gauge...Marine supply and auto parts store.
FWIW
Sojourn for Christ, Gerald
BTW...I start this 3 hours ago but didn't finish till now and learn of Robert's good information about air in fuel system.
Ace,
There is a DDEC sensor mounted at the filters. No flow/fuel, no throttle. It has given me fits when trying to prime the DDEC system until I unhooked it, then I was able to bring the RPM up enough to burp the air out of it. Probably not smart, I think its probably there to protect those spendy electronic injectors!
Ace,
We installed 2 fuel pressure gauges on our 8V71. We have a mechanical gauge in the engine compartment and an electrical fuel pressure gauge in the dash. Both are connected to the output side of the secondary filter(after the fuel pump). As was mentioned we run about 15-20 at idle and about 65 at higher RPM. Although we have not had any fuel issues since the delaminated supply line to the primary filter, the gauges are a great diagnostic tool Wish I had the gauges when we had the fuel line problem, it would have made trouble shooting much easier.
The Wet Black sounds like algae. Jack
Just out of curiosity, what fuel pressure would you expect at cranking speed? Might help diagnose a no start condition.
Thanks as always for the info.
Jack, I never thought about the black wet look being algae. I just figured it was the paper element in the can that was soaked with diesel.
Does anyone know WHY, (IF) the filters were in deed clogged with algae or whatever other substance, did I get NO response from the fuel pedal? This REALLY boggles me and scares me to think that the filters were really not the problem. I have an air throttle and am leaning towards there is an air problem or similar associated with the throttle.
How come things happen at the same time rather than by themselves? :) At least that way, you would know they aren't related!
Ace
Quote from: Blacksheep on January 09, 2009, 05:54:58 AM
Jack, I never thought about the black wet look being algae. I just figured it was the paper element in the can that was soaked with diesel.
I have an air throttle and am leaning towards there is an air problem or similar associated with the throttle.
Ace
Algae usually looks & feels like snot. Did you have air pressure when you tried the throttle? Jack
Nope no snot! Just wet looking, normal to me, paper!
As for air, yes and no! A little at the start as it was airing up but remember, it was only idling at 300 rpm and would NOT accelerate. Even after letting it idle enough to air up to 75 lbs, there was still no throttle. Only after I changed the filters and it ran faster, did I get throttle!
Ace
???????? Hmmmm, that does sound weird. Jack
Gremlins.... ;)
The part I don't understand here is the air throttle on the DDEC I never saw one on a DDEC before in a Prevost but all things are possible
good luck and hope you find the trouble
Ace...do you have a air schematic of your H-40?
I am not a DDEC man...so with a link or photo of the schematic, we can find the so call "Gremlin" problem.
Right off hand I believe 75# is a the border point of moving the throttle? ? ?
If any one has the air schematic and don't mind post it or e-mail to silverclip1 at AOL dot com. I would greatly appreciate it to add to to my file for future project. Thank you so much.
Keep us updated as to your findings!
Sojourn for Christ, Gerald
Update:
This is what I found so far!
I was wrong in assuming it was an air throttle. It is electronic so that eliminates my theory of low air not allowing the throttle to respond! This brings me BACK to my original problem, electronic! It could have been a coincidence with the fuel filters, maybe not but going back and tracing my steps, I found that I started the bus with the battery tray slid "OUT". I know this shouldn't make a difference BUT, remembering back when I was purchasing the bus, the mechanic had the bus idling and at that time was showing me all the different compartments. When he slid the battery tray OUT, the bus stumbled, coughed, spit, and sputtered. When he quickly slid it back in, it cleared up! I had forgotten this until laying in bed last night trying to make myself believe the filters COULD make the throttle to quit working. I just couldn't come to that conclusion! Yesterday, before the Pizza arrived, I remembered sliding the tray partially back IN. Could this be the reason why everything started working as usual? Now I have to start the bus and TRY to get it to repeat the problem by sliding the tray IN and OUT just to ease my mind! Not exactly sure what I'm looking for but it sounds fishy and definitely something that needs attention!
By the way, the batteries are staying charged and while running, the volt meters are where they need to be not to mention all lights are brighter than they have ever been!
Also the 1 gallon pickle jar that I emptied the filter fuel into showed nothing this morning after sitting all night that would cause me to believe they were the problem. They may have needed to be changed but I am not comfortable thinking they were keeping the engine from running!
Ace
Ace - I was surprised when you said air throttle as mine is fly by wire - I think when we were jiggling components we might have fixed it - It might just have been my "magic" touch - I think the problem is at the electric buss - FWIW
Well were still scratching our heads down here because just when I thought everything was fine, my late night thoughts about them filters came true. It wasn't the filters after all because today when I went out to start the bus, the same thing happened. Very low idle (300 rpm) and no pedal, then after about 3-4 minutes of this very low idle, I had a little pedal. Very Little and when I tried to accelerate, it would act as if it were starving! Only thing I didn't consider was a clogged or dirty air filter. Taking it out made no difference so it was back to the electronics!af
Talked to a bus mechanic today and he agrees that the throttle is electronic and not air so that eliminated the air causing the problem. He says, after hearing my step by step diagnosis that it must be a faulty relay that is not being energized to operate the throttle. Well since I already had ONE faulty relay for the charging system, which is now definitely fixed, I'm thinking (scary huh) that now the system is getting full voltage and causing the old (1992) relays to go bad, one being the relay to the throttle which I still can't find! So what is the next best thing? Order all new 24v relays from Prevost. At 5 dollars plus each, it aint gonna break me but when I ordered in quantity, the price dropped and they will go out Monday so next week this coach will have all new 24v relays whether it needs them or not and we'll go from there!
Geeze, what a hassle!
Ace
Ace,
DDEC does NOT have an air operated throttle.
DDEC DOES have a TPS - Throttle Position Sensor. It's an electronic device attached to your throttle pedal and has a small three wire connector on it. This sends throttle info to the DDEC computer (ECM) for engine speed. Check this connector. Much more detail to explain but not necessary right now.
Check all the DDEC power and ground connections - fuses,breakers,chassis and battery grounds.
Sounds like you have an intermittent connection.Look real good at all connectors in that battery tray, yes it's a pain in the you know where - been there, done it too. :)
Put a ProLink scan tool on it and check TPS operation. Again, much more detail to explain but not necessary right now.
Make SURE you put proper relay (24v) in R3 position.
Buying 2 or 3 relays is fine, not all of them. Don't just change parts, save your money for fuel :).
Sammy I wasn't aware of the TPS electronic device on the pedal but will go look for it when I'm done here. I DID see a plug that would accept a relay for the TPS but it is and always has been empty. R11 I think but not sure until I look at it again! Is the TPS device behind the pedal?
Your right when you say intermittent! Do you think having a good charge rate now is doing something to the relays that are old where as before the charge rate was very low to none at all which would not affect the relays?
Ace
Sammy I found the device connected to the pedal. Its on the right side, has a connector with 3 wires in wire loom coming off it and going down thru the floor into darkness. Like I said, I found the receptacle that would hold a relay for the TPS but its empty! It is R73 and says 24v throt pos sensor cut-in (aut. Only)
Does this need a relay in it?
Ace
Ace, your bus does NOT use R73.
I had a similar problem where my DDEC engine went to idle, but I was traveling 60 MPH! This occurred many times on a trip, until I had a Detroit Diesel dealer check it. They could not find a problem in the wiring, TPS, or ECM. The likely problem was the TPS, so they changed it. That fixed the problem.
The interesting point was that even with a computer graphing the TPS output, no problem could be found or duplicated.
Ed Roelle
I dunno from TPS on a Prevost but on a Powersmoke they are a regular maintenance item.
Blacksheep:with all that was going on with the battery charging on your Prevost you may have to much voltage.DDEC's are sensitive to voltage and the manufactures know this and that is why I follow their recommendations not the battery manufactures
David
Ace,
You said that you had voltage issues. The TPS is a self calibrating unit. When you had low voltage the TPS probably ran out of spec. It is re-calibrated by repeatedly turning the main power switch off and on 10 times.
Still not sure you are not getting air into the filters and the DDEC sensor at the filter is not cutting the power as replacing the filters with full filters would stop the problem until it sat awhile and bled some more air into the line. Were the filters full to the top when you pulled them? If not you have a leak in a hose or fitting.
DDEC allows you to unhook the sender on the fuel filter that senses air and clear the air through the injectors by picking up the RPM. Like I said before though, I think its there to stop you from running the electronic injectors without fuel (if you run the tank dry for instance) and seizing a plunger. (Spendy). So the sensor just shuts the injectors down. (300 RPM)
The other problem I have had with the DDEC relays is moisture related. They don't handle a large load and are sensitive enough that they will stop working and simply taking them out and polishing the terminals with some fine sandpaper and replacing them brings them back up.
I'm about 5 years into my DEEC and ATEC learning curve and was not to long ago going to look for a older coach and give up on the damn stuff, but the more I study it the more comfortable I get with it. I still don't like it much though and like the mechanical engines that will always bring me home with no issues and without $1000 issues or more related to computers. Sure wish it was easy to stuff a Big Cam 3 Cummins in an Eagle.
David, I appreciate that and yes I have thought that as well BUT, this happened right before I set the charge rate up to what the Prevost book calls for so with that I would have to rule that option out.
I am a little confused with the R73 relay socket that is empty. The schematic calls for it but my bus and my friends H3 both do not have it installed. I guess there is a good reason.
I'm still studying electronics trying to learn!
Ace
NJT thanks! I wasn't aware that the tps could be re-set. When you say turn the main power switch on and off 10 times are you talking about the key switch or the battery disconnect? Is that a fix fix or a temporary fix? At this point, I will try anything!
As for the filters? They both were full to the top yesterday and today when I checked them for that exact reason!
I know what you mean about looking for an older coach with a mechanical engine. Been there a few times but when you fix the gremlins that the electronics give you, it's a really good feeling! It's times like this though that cause you to go fill a can of gas at the station. The good thing about that is, it gives you just enough time to come to your senses! I sure hope they don't build a station closer to me than what is already here! That might mean trouble!
Ace
Ace,
If it is out of calibration, its a fix, fix. Its the battery disconnect. The DDEC copys a signal over 20,000 times a minute so this could be an issue with low batterys although DDEC is supposed to operate down to about 10 volts. My experience with DDEC has been if its bad it won't work at all. If it has a hickup it just likes to be reset and may go for months before that issue repeats. The more you ask the DDEC to do the more attention it pays to hickups and shuts down. Its works best with the full shutdown mode turned off. It will then for some reason overlook hickups and keep running when it gets a code where it will shut down at the smallest loss of the 20,000 times a minute signal.
Ace,
I kicked the DDEC Motherload, (Bible) back to the top for you to spend some time with. Hours of information for free and online. Scroll down about halfway to start when you have some free time, its worth the effort.
R73 was for buses made previously to yours - as per schematic.
Don't worry about it. Check all power and ground conections.
Sammy thanks! I have checked and rechecked. I must be just overlooking something. I will not mess with it tomorrow as I have to pop corn from 8am to 3 pm but when I get home I will go at it again!
NJT, thanks! Not sure I understand what you mean when you say you kicked it back to the top for me to read! I looked everywhere for whatever it is and just like this problem, it isn't to be found! Are you playing with me? ???
Ace
Ace,
It's the 6th post down, DDEC Motherload For Free, it was down to page 6, I first posted it on Jan 1. Sorry, Didn't mean to confuse.
Yea I found it after I posted and have been reading ever since!
Thanks... hope I can learn something from it! ::)
Ace
Quote from: Blacksheep on January 09, 2009, 06:55:54 PM
Yea I found it after I posted and have been reading ever since!
Thanks... hope I can learn something from it! ::)
Ace
we all do too :D :D :D :D
How's basket head, the pampered babe?
Hey Tom, that story must have made a mark on you guys! Bob wants to get together and get his wife one of those buckets (not baskets)!
I'm not sure I want to be around for the sizing though! You know how women can get when things like that happen but if you guys want to venture out on your own (you really don't need me) make sure you shop without a buggy and remember to keep her hands full! Then then mosey on around until you find the right one/s and just GO FOR IT ;D
Ace
Ace,
If the fuel sensor that plugs in by the filters was bad it could stop the fuel flow (DDEC). I think you can unplug it and its no longer reads as a bad code to the DDEC.
Ace,
Ace,
Check the plug on the DDEC that goes to the injectors. If not all you injectors fire all the time it acts like a loss of power from dirty fuel filters. Also, the turbo boast pressure sensor controls how much fuel can go to your injectors to prevent smoke on take offs from stoplights.
Art
Time to plug the pro-link in ACE and let it do it's job good luck
Hello:
Check the wiring at the batteries . Sammys advice is backed up with many years working on Prevost buses.. One of those wires and fuses supplies the power to the DDEC. You have changed all the batteries and disturbed the system and it does act like a loose connection or a broken wire so that the voltage drops off and the computer goes into safe mode. Computers do not like loose grounds because at the speeds the computer runs at milliseconds.. thats one or two thousanths of a second a loose ground could drop the voltage off to below the safe point for enough cycles so that the computer thinks the voltage is low and diverts to safe mode..
We looked ot the batteries when you were at Jacks rally. One of those cables may be loose or has a bad connection. The wiring diagram will tell you which one is the power and ground to the DDEC system.
just another opinion thats all... get it done so you can go to the bluegrass rally..
regards and happy bussin....
mike