finally got a diesel, question...high reving

[muddybuddy]

well i finally got myself a '86 k10 diesel with 4" lift and 35's with a plow on it for $1100. the previous owner said that the one thing thats weird with it is during cold starts it will start fine, he will go inside and let it idle to warm up, and then when he comes out 5minutes or so later its screaming, he puts it in drive and then its fine. he said it has done that 3 times in the past year. i know the engine will rev a little bit until it gets warm, but he said it screams, like almost redline i would imagine. anybody else experience this? what could cause this?

on a side note, its got the cold weather package from GM, with the extension cord to heat the block, i cant wait to come out on a freezing day and go to a warm truck

 

[tRustyK5]

Sounds like an IP problem. Idle and top rpm are both governed by the IP, so I'd guess something occassionally sticks inside. From cold it should run a little faster and noisier because the cold advance is doing it's thing. As soon as it warms up a little it should drop down the idle and quieten down though.

As for the block heater, that's not some fancy fru-fru option...it's pretty much a necessity with a 6.2 in colder weather. I'm sure a lot of southern US trucks with 6.2's didn't get the block heater, but the great majority of the rest did.

I had my IP and injectors rebuilt by www.accuratediesel.com and they did a fine job for not a lot of money. IIRC it was under $350 including shipping both directions...although it may be more now. I had mine done 3 and a half years ago. I'd wager the guy you bought this truck off of didn't use any fuel conditioner.

Rene

 

[diesel4me]

runaway!...

We had an International Bus at the boneyard that did that after a cold start sometimes...we never figured out what the cause was--but one guy familiar with diesel big rigs told us if any motor oil gets into the combustion chamber,it will cause it to "run away" until its all burnt up!..he said valve stem seals or guide wear,and worn rings can cause it..we always figured it was an injector pump problem or an injector sticking,since it didn't use oil--it usually only did it once during warm up,then it ran OK afterwards...

 

[imiceman44]

We had an International Bus at the boneyard that did that after a cold start sometimes...we never figured out what the cause was--but one guy familiar with diesel big rigs told us if any motor oil gets into the combustion chamber,it will cause it to "run away" until its all burnt up!..he said valve stem seals or guide wear,and worn rings can cause it..we always figured it was an injector pump problem or an injector sticking,since it didn't use oil--it usually only did it once during warm up,then it ran OK afterwards...

This would make sense, if the valve seals leak a little, it could do that at warm up from the build up, and usually if they are not worn too bad, you don't notice the loss on the dip stick.

 

[imiceman44]

a runaway diesel is fuel to the cylinder from an unregulated source. meaning it bypasses the governor, meaning there is no redline, it will continue to accellerate until A) the external fuel supply is removed and the governor can regain control of the engine B) there is a positive air shutoff C) there is a rod or two situated somewhere outside the engine block.


RPM on a runaway climbs....... right friggin now! faster than any governor would let it. If you've ever been around an actual runaway you would have no doubt that it was a runaway and you would never forget it and you would throw those underware away. oil from a work valve guides.....not likely. it'll burn blue but won't run it away.

I was guiding a very new highway coach with a Cat C7 back into the shop for turbo repairs. the engine ran away, within 5 seconds it hit 6000rpm. we know that because we downloaded the ECM after it stopped. and it only stopped because it burned all the oil in the oil pan. through a bad turbo shaft seal. all in about 20 seconds.


anyways........I'd bet on an injection pump/governor disorder. Not engine oil causing runaway.

I went back and read the post carefully, there is no way it would be screaming from a little oil leak, I thought it raised the idle for a little bit, that is why I thought oil leak.
I haven't seen a runaway diesel but heard a lot of stories, enough to not want to see one.

 

[tRustyK5]

We had a JD 4045T run away on the test stand...scary stuff!! This one blew shrapnel through the pan. One of the guys in the shop had the IP apart for something and put it back together slightly wrong... It was a brand new engine.

Rene

 

[muddybuddy]

alright so is this a really big deal that needs to be fixed very soon or can it wait a while, like is it safe to drive as it is now? anything i can do now to help slow it down? what was the fuel thing you mentioned rene?

thanks guys, i really appreciate the help. im a diesel noob, but glad i finally have one ill snap some pics of it tomorrow and post them up

 

[diesel4me]

wait and see..

It might have just been a fluke,if it only did it 3 times in one year...perhaps it was the injector pump acting up,or another thought I had--if it has cruise conrol,maybe it was responsible for the sudden acceleration,if it malfuntioned?..I'd wait and see if it acts up again,then do something about it..might have to wait until if and when it does it again, to properly diagnose the problem...

 

[muddybuddy]

could this be affecting my mpg?

 

[tRustyK5]

Diesel fuel conditioner is an additive you pour into the tank. Lots of different variations out there, but all contain additives that help lubricate the pump as well as Cetane additives and anti-gelling crap. I know, pretty technical stuff...

I find it at parts stores as well as some gas stations. Around here Chevron carries it.

If the IP and injectors need rebuilding it will hurt fuel mileage...

Mine would smoke like a friggin train when cold, and it would take a long time to clear up (but never went away totally) I thought I was in need of a rebuild at first. Now with the rebuilt pump and injectors I get about 5-10 seconds of light smoke when cold and it goes completely away.

Rene

 

[muddybuddy]

thats weird, this truck barely smokes on a cold start. i guess ill have to start putting the additive in, maybe mine arent dead yet.