The "Problems" continue

[Blacksheep]

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

[JackConrad]

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

[Blacksheep]

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

[JackConrad]

??  Hmmmm, that does sound weird.    Jack

[Hartley]

Gremlins....

[luvrbus]

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

[Sojourner]

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

[Blacksheep]

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

[niles500]

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

[Blacksheep]

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

[Sammy]

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  .

[Blacksheep]

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

[Blacksheep]

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

[Sammy]

Ace, your bus does NOT use R73.

[edroelle]

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