I Hate an Intermittant Problem

[Jerry Winchester]

Well I thought I was over this one, but alas it is back.

The engine (8V92TA) runs fine down the road. Pulls good, no problem. Until I stop or the engine comes to an idle. After a few seconds, the yellow and red light for the engine both come on and if you don't idle the engine up, the engine will shut down momentarily.

You can instantly restart it and again, if you idle the engine up the lights will go out. You can also try to pull off and eventually the engine will "resume" running okay (turbo will spool up and the fuel will follow), but not being a DDEC guy, this is perplexing.

Anyone have this problem or willing to venture a guess? I may go a month without it happening again and it never occured during the 2000+mile trip to Florida. I thought one of the sensors might be bad or it got wet (see associated radar photo), but we ran thru some serious rain coming back from POG ONE and no problems.

Also a new first today. The Garmin 396 GPS speaks the words, "Tornado
Warning" as we were going down the road. Guess what? It was right where it said it was.

Eerie.

[Jon Wehrenberg]

Jerry,

Try this real quick. You will have to call Prevost or maybe someone else can post the answer, but jumper between two pins on the DDEC reader. A and H come to mind, but do not trust my guess. All my books went with the old coach.

The code will blink and beep. A call to DD will tell you the code and that should lead you to the problem. Have you checked the coolant level sensor?

Jon

[Jerry Winchester]

Jon,

I really think it is something like the coolant sensor. I know the reservoir is full, but if I unplug the sensor and jump across the terminals, will that make the computer think it is full?

The reason I suspect the coolant level sensor is that this problem used to show up with the engine was first started and somewhat cold. After it warmed up, it would go away.

As it is Saturday of a holiday weekend, I will struggle thru until Tuesday and see what DD says. Thanks for you help.

JW

[Jon Wehrenberg]

Jerry, I know how frustrating it is to try to deal with this kind of stuff, especially on a holiday weekend when away from home.

I do not trust my memory otherwise I would tell you if the circuit should be open or closed. I ran into that with Classy Chassis and a sensor replacement cured the problem. I think this is a case where Prevost has to give you the correct answer. In the meantime I will review my service manual because it might shed some light on it.

Jon

[Jon Wehrenberg]

Jerry,

Your bus may vary because I think I have a later model DDEC, but see if this helps.

The code for a low coolant level is 13 and code 14 may also indicate a coolant level sensor problem as well (in addition to some other problems).

On my coach to access current codes the procedure is to have the ignition key "on", bus off or idling, and to press the override switch. That should bring up the active codes on the stop engine light. There is nothing in the manual to confirm that a jumper between sensor poles will "fool" the computer to thinking the sensor is OK. I wish I could have confirmed this.

Jon

[MangoMike]

It seems to me a seminar at Sante Fe about the ins and outs of code reading would be interesting. Do you need a reader or are the codes displayed on the dash somewhere?

Or in Fast Rogers case instead of code reading it would be palm reading.

MM

[Prevosttech]

Yesterday I read your problem and being that I was on my way out the door did key into your whole problem. My concern is your brief dicription about your turbo spooling up.On and 8V the turbo is fed off the exhuast.The next time you have the power problem take notice of your pyro guages if the temps are not the same or close to it you need to take a flash light and look at the exhaust manifolds for soot also for loose pipes from turbo to exhaust man's.and also closly look at man's for cracks and or holes with the exhaust system to turbo all jiouts need to be sealed because this is what makes boost pressure also give me a day or two to track it down but I have a flash code reader card ,also the software is sold to hook up to ddec to dia. prtoblems with engine but it is costly.

John

[Jerry Winchester]

Well I unwired the low coolant sensor and joined the wires together, but that didn't fix it.

I made it from Loveland, CO to Jackson, WY today and the engine runs fine out on the road. But when you go to stop and it idles down below 1000 rpm, the yellow and red lights come on. If you don't move or shift to neutral and idle up the engine, it will die. And it does it at the worst times.

I hope someone knows which jumpers to use and what the codes are, because I hate to think about driving this thing like this the rest of the trip. I don't know if there is anyone in Jackson that knows squat about 8V92's but if I could get the computer to tell me what the problem was, I'll bet I can fix it. How many sensors can there be?

And John, thanks for the reply. If the engine were not running well (other than the described problem) I would suspect something else. I suppose it could be a faulty sensor somewhere else on the engine, but I don't know what other items are monitored by the DDEC system.

Other than that, the drive across southern Wyoming is lots and lots of nothing followed by some intense scenery you can't imagine. It is snowing here and the temp is 37. But it is a dry kind of cool........

[lewpopp]

Jer... For Cripes sake. You said it was snowing. Your first mistake is that you went too far north.

Prevosttech is on your case. He will come thru for you and us. This form will not let you down. You have too much vacation time.

[Jon Wehrenberg]

Jerry, can you get the codes? Once you can read a code you know exactly where to look. DD and Prevost have 24 hour phones.

You can either read the code as I described above or by running a jumper as I did in my old coach.

As your last description indicated it is a situation found only at idle. The 8V92 is a low oil pressure engine at idle, but there is still a minimum pressure required and now I am leaning toward that just because of how you last described it. I think the oil pressure sensor is located on the forward upper bulkhead right under or near the rear oil pressure gauge.