Love my Bus but...

[Sammy]

Pull relay 56 in Front electrical compartment - jake brake .
See if it makes a difference.........

[Ace]

Sammy I will do that but is it possible this is the problem? I don't exactly undersatnd jakes, so that's the reason for the question!
It sounds like it has back pressure or something holding the engine back from running. Sounds flat and dull. Could they be activated even at idle somehow?
Thanks again...

Ace

[mikelutestanski]

Hello
Maybe a stupid question but is there a switch on the dash to shut the jakes off   ...?   
    Regards and   you will conquer this thing..     Just think about how much you are learning about your bus....
     Mike
   

[gus]

With a clutch, full Jakes turned on will shut down the engine if the clutch is disengaged. Don't know how it works with an AT.

I don't see how you could even get the engine to run with Jakes on except if you have a selector switch which normally will select 2-4-6-8 cyl and you have 2 or 4 selected. If you have this switch and it is "Off" it might be faulty.

[JohnEd]

Ace,

I read long ago that the throttle is disabled when the jake is on.  That discussion said that ANY throttle applied when the Jake was activated was a VERY bad thing so the throttle was disabled.  I don't remember whether it was 2 strokes or 4 but maybe both would be the same.  Looks like you are on to something.

Looks like Lin and I both were a little confused by the OIL or FUEL question.

If there is "no throttle response" then why would the fuel pressure drop from 40PSI to 35PSI when you depress the throttle?  Lower pressure means more fuel flow, right?  What am I missing?

John

[Blacksheep]

Ok to make things just a little clearer, when I said no throttle response, it was meant be be understood that it's not a normal throttle but it would go from 300 rpm to about 600 rpm as I depressed the pedal. Then there are times when it would go even higher but mostly nothing above 600 and then there were times when it wouldn't do anything at all! Like I said, not a normal throttle.

Anyway with all that said, I checked the 56 relay in the fr junction box as Sammy suggested and looks like we are back to square one because that relay was already removed!

I'm telling you what, it definitely is holding the motor back somehow, someway via something!

It all started when I changed the faulty relay on R3 for the field relay! Acted like it wasn't getting the fuel, so I changed the filters as anyone would. Here is where are!

Ace

[Lin]

Have you tried to put the bad relay back in if that is the only thing that changed?

[Blacksheep]

I pulled the good replacement relay out and tried it and nothing changed. The original bad relay,  I cut open to inspect the insides and found it to have a burnt spot near the contacts.

Ace

[JohnEd]

Lin,

Genius idea!  Does the problem follow the part?

John

[Dreamscape]

Ace,

A burned spot near the contacts is normal in a relay. That just happens every time it's energized a small spark causes that. It's no big deal until the current isn't passed from one side to the other.

FWIW,

Paul

[Ace]

That may true but changing the relay made everything work except acceleration!

Ace

[RickB]

Ace,

I have a thought. Since you didn't reply to whether or not you had checked the turbo, I am assuming you didn't check it yet. Is the caked on oil/fuel residue near the turbo oil supply line?? If you had a major leak in that supply line it may explain all the oil and it may explain the inability to raise your DD above idle. If the turbo is seized from lack of oil, it will definitely rob air from the motor sending weird air/fuel mixture info to your electronics.
Just a thought my friend. I am praying for you, I know how you feel.

Rick

[RickB]

Ace, Went back through your posts and found this:

"Now on my recent trip home the bus had a low voltage problem and showed some irratic shifting just like it did before the solenoid replacement. I related this to be from the actual low voltage I was having but now it has me thinking that the problem I have now with it NOT accelerating could be this solenoid. The mechanic did tell me back then that this solenoid is activated by the throttle response and then tells the transmission when to shift according to your speed, or something similar to that."


I am not an expert by any stretch but if you have electronic throttle response sensors, sounds like you may have an ATEC 741 or another electronically controlled Allison rather than a non electronic 740.

[NJT 5573]

Ace,

The 300, 600 rpm thing makes me think that its not primed. The reference to not sounding right could be air in the injectors or a "hung" injector.

That takes us back to running it a couple minutes and checking the temp of each exhaust port at the exhaust manifold for heat to be sure they are all fireing.

If the jake is on it will sound like a gun fireing and kill the engine.

How did you reprime the system after you changed the filters? Did you use a pump or what? The thing about it running fine for a bit after the filters were changed makes me think it lost its prime. How many times have you changed these filters since you owned the bus? Just putting full filters back on won't get it done. DDEC is very hard to reprime. Did you remove the sensor wire on the secondary filter to allow the DDEC to open the throttle in the presence of air?

How much fuel is in the tank?

[JohnEd]

Ace,

On page 2 Blue-Goose (jack) laid out the procedure for verification of the ECM module.  Great info for you and relates to the current pickle you are in.  Not clear that you did this.  I would check back with Jack on this BUT.... if you perform those steps and it runs that would mean one of those sensors was bad and your ECM and everything else was OK.  Then by grounding one sensor line at a time you could further isolate the problem.  If, on the other hand, you still have the same problem with it running I think the indication would be that the ECM is "bad" """O R """ the problem isn't related to the ECM or the sensors.  Fuel?  Air?

Jack wrote this for you early on in this thread and he is among the many that suspect a prime problem.  I think the suggestion that you disconnect a wire from the filter to allow DDEC to open the throttle might be the only way to clear a loss of prime after the filter according to NJT 5573.  I sure would try that first.  Easiest thing is to lift a wire.  Now if you already have done that well....is my face red ...or what?

Now Ace, if NJT 5573 is correct about there not being enuf fuel in the tank, don't admit to that Ace.   Really, make something up...anything.  That is the kind of story that follows a man to his early grave.   Just a little humor to lighten your moment in the sun Buddy.  Hang in there.

John