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DDEC I blues
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127 Replies
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Bill,
I don’t know if DDEC I is even supported any more, but one of our members is pretty savvy on the 2 stroke engines and I believe DDEC and what can be done with it.
Luvrbus, help this poor chap if you can.
But I do not think you are dealing with a single issue. I would treat the Jake problem as separate from your lack of boost. While your issue with lack of boost or performance could be DDEC, I would do a detailed inspection of the exhaust manifold and the manifold gasket. Both have been historic problems with the 8V92, with the gasket blowing out, or the manifold developing cracks both of which will rob you of substantial power. Look for sooting around the manifolds, a sure indication of the problem.
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Bill,
when you replaced your engine, did you replace your exhaust manifolds and gasket
We lost power and of course boost coming home from Palm Springs Feb 2013. Barely, I mean barely crept over Raton Pass at Colorado/New Mexico border. It’s not a big deal, but that day we wer afraid we weren’t go to crest. First gear, less than 12 miles an hour’ we did make. Boost was 9-10 virtually no jake, having brand hew solenoids. And of course, smoke.
After searching ,and after previous power loss being trashed fuel filters, changed them out…nothing…in engine compartment, drives side closest to transmission, all areas nearby were blackened …aha, moment was manifold gasket.. replaced driverside manifold gasket, which seemed to be source of soot, test drive…..no change….gutless. Replaced boost sensor, and oil pressure sensor to ddec….no increasd performance.
After last test drive, we noticed heavy metal like rock bits on the ground. Turned out to be bits of manifold. Removed manifold a second time, only to find chunks missing. Got a new one, presto….the bus had it’s snapped again.
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Bill,
Every one of us long time owners has had issues that were checked and rechecked and mechanics swore everything was OK. Only after persistence were issues resolved often by finding a problem that everyone insisted was OK..
Your problems may be related to DDEC, but I cannot get past your description which sounds like you are losing boost. If you have a new engine I am going to assume it is clean and sooting is going to be easily seen. Look closely at the exhaust manifold, look for evidence of the gasket leaking, double check the clamps at the turbo inlet pipes or a crack in one of the inlet pipes. That is a cheap, easy inspection especially if you have a mirror with an extension because the back of the exhaust manifold towards the transmission is a common area for cracks or gasket failure.
Another simple test is just for grins poke your finger into the turbo after removing the pipe and spin it. There should be no binding, dragging or noise.
Cynic that I am the other two things that come to mind that are not associated with a bad ECM but can affect the power you can produce would be the turbo boost sensor or the throttle position sensor. Usually those rob you of almost all power.
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You mention a vacuum gauge on the intake maninifold. Is it tripped or showing a restriction? Have you checked your air filter and intake system plumbing? 1 to 2 pounds of reduced boost is not going to make your engine run like you say it does. Does it smoke all the time?
I am not up to speed on DDEC 1, but are you getting any kind of check engine lights or codes?
If you have swapped engines out and still have issues, I would look at air, fuel and electrical as the likely culprit.
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I have read your post and others. Can you confirm the ground location for your DDEC ? I would locate the ground
circuit and run direct from ECM.
I know this is somewhat a WAG (wild ass guess ) here is the but….unless there is a secure ground the ECM just scans.
AL
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Well, I did read your rambling posts, and you did mention the restriction gauge a couple of times. It does not and never will measure fuel as you said in the original post. I never said anything about dash gauges. Then later on you say that it isn’t up to the job and it does not go “red” any longer. You say this issue has been going on for many years and also through an engine swap.
Then you complain about taking it to a DD shop and spending $4000 on repairs that did nothing to help. Why did you even leave there if the problem wasn’t fixed? I sure as hell would not spend that kind of money with no resolution.
If you are convinced that it is a wiring issue, maybe the best idea yet is to create a new harness front to back and test that to see if it is the problem. If none are available from Prevost, can you find a shop that will do it for you? Plugs and wiring are common and most shops should have the tools to crimp pins for the connectors. If you don’t want to have one made, then pull the old one out and see if it actually is the problem. Maybe it can be repaired.
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I think Mark may be on to something.
And I agree if everything else has been checked and the only thing left is the wires or cables to DDEC then perhaps the easiest way to verify one way or the other is to run a wire bundle or cable externally from the engine and its sensors to the DDEC ECM.
Through process of elimination one cable or wire at a time can be verified as not having anything to do with the issue or to be the cause.
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