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6.5 Diesel Hard Starts :(


BronKitis

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I have a 1992 Chevy K2500 with the 6.5L Turbo Diesel. I noticed that it was starting to start harder and harder so I replaced the glow plugs. Even before replacement, they seemed to cycle normally. The truck is STILL starting very hard, and by hard I mean lots of smoke and a miss at idle. It does fire right up with very short crank times but when she fires, she fires HARD. Blueish white smoke is what she blows, and a lot of it. If I rest my foot on the gas pedal and bring the idle up about 100 more rpms, it cleans up and seems to run much better. I really could use some help as I am far from a diesel mechanic! I don't wanna blow my baby up. Thanks!
 


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I have a 93 6.5 very similar trucks.One of the issues with these is starter speed what you can check for is starting to listen to other diesels start does yours sound slower maybe a u-tube video of one starting good.A diesel makes heat when the air compresses and the injector sprays a good pattern in the cylinder below a certain rpm neither of these things happen well enough to start good.The other thing thats weird about these is the starter doesn't quit it just turns slower and slower till the truck won't start.I just had to buy a starter and both batteries recently it sounded like the motor was going to fly out of the engine compartment compared to my old starter speed.

The other two culprits for not starting is a worn out injection pump and bad oil pressure sending unit.The test for a worn out IP is to put cool water on it with a warm engine but be careful this helps slow starter speed as well I was trying to find out why my new IP was bad and I needed a starter.There is a wire going to the IP from the OPSU and it doesn't start until there's oil pressure.If your OPSU is sticking it delays your starts.
 

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I agree that cranking speed is crucial. These are indirect-injected motors so they don't start as readily as a direct-injected motor. My bus has a direct-injected motor about the same size and no glow plugs and it starts on half a crank even in the winter. An indirect motor has a lot higher compression ratio which makes it a lot harder to turn over, and the injection takes place in a seperate chamber--the real injection into the combustion chamber occurs via a bit of the fuel going off and blowing the rest of the charge out of a hole in the injection chamber. There's no heat in there during cranking. If you aren't getting a good 8-second burn out of the glow plugs that would be a problem.

Air in the fuel system would make it idle really choppy and keep dying. Not much smoke though. Lot's of hard cranking, then it fires is when it smokes a lot.

How about a video clip of it cold-starting?

There is one injection pump piston (it's two, actually, but they are in the same bore) and a distributor rotates to aim the discharge down each injection line. If there was a problem with the pump, I doubt it would start at all. If there is air in one or two lines, it could start readily, but hard. I'm guessing an injector or two isn't sealing. they hold fuel in the lines and the new injection event advances the fuel through the injector. If the injector leaks down into the pre-chamber while it is sitting, there will be fuel sitting in there ready to smoke when you start it. And that injector won't have fuel in it so it won't contribute when you first start the engine. I think it's time to get a set of injectors in there.

That's just an opinion, by the way--I haven't had that problem. If you have an electronic pump it could be something with that. I've gotten air in mine, but it was before the pump and the truck doesn't start at all and doesn't smoke when it does start. I also have found that Optima red-tops smoke any other brand I've tried when it comes to hard winter starts. I've had this truck 6 years with these batteries and I was lucky to get 2 out of my Walmart/Exide yellow truck batteries. Also, I installed a battery charger under the hood so when I plug the truck in in the winter it's also warming the batteries. It's very important to keep the batteries at 100% with these.
 

BronKitis

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I believe it is injectors, but boy are those puppies spendy! My crank speed hasn't changed since day one and she usually fires with very little cranking. I mean bump the key and she's running whether it's rough or smooth. I drive a newer duramax at work and I'd say my 6.5 starts just as fast as it. I've never actually had to "crank" the motor to fire. I'll try to post a vid tomorrow after work on youtube and insert a link to show what I'm talking about. I REALLY think it's my injectors, but perhaps a vid and your oppinions will say different.

All the things said here kinda jumped over my head so hopefully I can catch on! I know how a Diesel fires, but that's about it.... Thanks for all the help!
 

BronKitis

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Okay, so I looked up some videos on Youtube and heard a familar noise- a light clacking! Most on youtube were much louder than mine but almost all were connected to injectors. I believe my clacking noise to be coming from rear cyl on passenger side. Looking at injectors on ebay now. Anyone know the benefits to marine injectors? Thanks
 

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moneyslave is about the best injector guy to deal with currently on e bay ...235 to your door us address and funds. i am buying a set right now myself.


unless you had a crap load of bad fuel its hard to see injectors suddenly dying...my injectors are way over due but i use heavy oil mix often and i think it masks the hard start...with clean real fuel i have hard starts comparatively.


this is assuming your not losing coolant, as it sounds like a gasket to me.


pretty happy with my little 6.5.
 

BronKitis

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Hmmm. I am leaking coolant but I dtermined it to be the lower coolant hose... Unless I'm mistaken. If it were a head gasket though, it probably wouldn't run smooth no matter what. As far as the issue I'm having, it started towards the beginning of fhe year and has gotten progressively worse with time...
 

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I still think fuel system, but maybe check out your CDR valve. I don't know what happens when they go bad but it might be adding oil to the intake air. The hose will have signs of oil in it, but if the valve is bad there would be a lot of oil present and I would think you'd be losing oil at a significant rate. Turbo seals maybe too--I don't know if that would cause a run-away/engine destruction on a 6.5 or just be troublesome.

If the head gasket was blown I would think lots of nasty smelling bubbles would be coming up in the radiator. Take the cap off and start it.
 

BronKitis

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What/where is the cdr valve? She does burn some oil but I've always just attributed that to the fact she's a tired diesel... No bubbles in radiator... But my waterpump now seems to be leaking issue.

I wanted to test my plugs to make sure they are recieving proper voltage and what not. Anyone tell me how to test them? I appreciate all the help!
 

Will

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The CDR valve does the same job as the PCV valve in a gas motor, but because the engines are different, it works the opposite way. It's stuck into a rocker cover, just like a PCV. They both serve to evacuate crankcase fumes. The diesel has no vacuum at idle, but does have a little at power. A gas motor has lots of vacuum at idle and little at power. The PCV is mostly closed at idle to keep from drawing to much oil vapor, and too much air. The CDR is open wide at idle and closes off under power when there is too much vacuum which would suck up too much vapor.

The CDR is a lot larger because there is a lot less pressure involved. The failed CDR could suck up a heck of a lot of oil into the engine.
 

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I believe it is injectors, but boy are those puppies spendy!
AC Delco injectors are about 52-55 bucks per injector. The other AC Delco injector is about 64-66. Not too bad. CDR valve is anywhere between 37-100

sources: rockauto
 
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