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| Low compression after runaway http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=87192 |
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| Author: | craws010 [ Tue Sep 19, 2017 1:10 pm ] |
| Post subject: | Low compression after runaway |
Hi All, I just picked up another CRD that needs some love. This one suffered a runaway due to a turbo failure. I don't know how long the runaway lasted. I only know that the PO stopped it by blocking the intake. He said that he was able to run it again after removing the turbo. But a compression test revealed that it now has low compression on two cylinders. I am wondering how likely it would be that the damage is limited to collapsed lifters, broken rockers and/or damaged valves. It would be great if I could salvage the bottom end, but my gut tells me that it could be anything if the oil was consumed to a point where it caused bottom end damage or if it redlined too long before it was killed. The price that I paid was based on the assumption that the engine would need to be replaced or completely rebuilt. The Jeep is in otherwise good condition and just had a brand new OME lift and BFG AT's installed shortly before the runaway. He had already deleted the EGR with Weeks Stage 1&2 and installed new Samco's. He even threw in the WeatherTech floor liners. My search here resulted in quite a few threads discussing the theory of diesel runaway. But I didn't find anything indicating an actual experience with a CRD runaway. I know this is one of those situations where the severity of the damage is going to depend on many factors. Just wanted to see if anyone had any similar experiences and whether or not they were able to repair or had to replace the engine. |
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| Author: | papaindigo [ Tue Sep 19, 2017 1:43 pm ] |
| Post subject: | Re: Low compression after runaway |
The only CRD runaway that I recall posted on LOST was a brief one related to oil in the intercooler but I do not recall the details of how; IIRC the engine was ok as the runaway only lasted seconds. A runaway is unlikely but not impossible on a CRD. The "normal" source of a runaway seems to be atmospheric fuel but I presume it's possible for a catastrophic CRD turbo failure to dump enough oil into the system to fuel a runaway and no the flow control valve is not programmed to stop a runaway. The only way to stop it would be to cut air flow to the intake although how the PO did that I don't know. If the runaway occurred not on the highway and if it was stopped quickly and if substantial oil remains if the sump you might have escaped too much damage to the engine. That said if it was mine to fiddle with I'd pull the engine so you can do a full inspection of the top and bottom end to see if the engine can be salvaged. Off hand I'd suspect crank and rod bearing damage due to oil starvation; piston rings shot; and possibly head damage (rockers/lifters and maybe valves). Other than these comments I'll be interested in what others say. |
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| Author: | stp2136 [ Tue Sep 19, 2017 6:20 pm ] |
| Post subject: | Re: Low compression after runaway |
I believe the flow control valve (provided it is still installed) closes for about twenty seconds after you turn the key off. This prevents "run on" and should also stop a runaway. |
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| Author: | APC9199 [ Tue Sep 19, 2017 8:14 pm ] |
| Post subject: | Re: Low compression after runaway |
stp2136 wrote: I believe the flow control valve (provided it is still installed) closes for about twenty seconds after you turn the key off. This prevents "run on" and should also stop a runaway. Good golly miss Molly... viewtopic.php?f=5&t=78562 |
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| Author: | rankom [ Tue Sep 19, 2017 8:54 pm ] |
| Post subject: | Re: Low compression after runaway |
like PAPA said , the best thing in this case is full inspection , disassembly , and go over everything , i seen 2 stroke detroit , CAT 3406 , mack E6 engine damage after runway , some do to blown turbo , some do to improper fuel pump settings procedure , timing advance unit going bad etc ,all no good . yes it is harder to runway ecu controlled engine but it is possible . |
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| Author: | GordnadoCRD [ Wed Sep 20, 2017 12:23 am ] |
| Post subject: | Re: Low compression after runaway |
My limited experience with Runaway diesels, is that motor oil burns differently and much hotter than injected diesel, especially when a turbo is involved. With this head design its less likely to suffer damage there, except for possible heat damage between the exhaust valves. I would look most closely in the combustion chamber area in the piston crown. Hopefully the piston cooling jets had enough oil left to do their job. |
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| Author: | craws010 [ Wed Sep 20, 2017 7:16 am ] |
| Post subject: | Re: Low compression after runaway |
Thanks All for the feedback. I guess I have another big project waiting for me after I finish my current one. I really only bought this one because it had the new lift and tires. I was just going to remove them for use on one of my others and keep the rest of it around for parts. But it does seem like a shame to pilfer parts off a potentially rescuable CRD. |
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