Hey guys, We are goin to look at some diesels for my friend and he is lookin at the early chevy trucks with the 6.2 or 6.5 diesel but i know nothing about them. Im a cummins guys so im coming to you guys for advice and info.

What are the major differences between the two. are they both turbo or N/A. what kind of things do i need to look for or be aware of when looking at them... also what about the drive trane. body and everything else related to these trucks.

thanks for any tips and advice in advance.

 

6.2 are non turbo

So many have been asking about “should I buy this truck or not?” The answer is, we don’t know. We’ve never seen it. We’ve never rode in it. We don’t know what you wanna do with it.

Here are a few Frequently Asked Questions when it comes to purchasing a 6.5L Diesel:

* What Rear End Gears? Check your RPO Codes.
* Is this a Good Price? You will have to determine that yourself. You can research comparable trucks or do a search on here.
* Common Problems? Common 6.5L problems can be found by looking at the FAQs and the different threads it provides.

► Check Codes

* It is a good idea to check for codes on the truck. Some codes can give a warning of an expensive replacement in the near future.
* To check codes check out the thread for the truck you are looking at: OBD I and OBD II.

► Batteries

* Check all battery connections and make sure they are all tight and corrosion free.
* It is a good habit to keep both batteries the same type and the same age.

► Serpentine Belt

* Make sure there are no cracks on the belt and that the belt is not frayed anywhere.
* It is also good to check for any abnormal noises coming from the accessory units when the engine is running
* Also check the belt tensioner and make sure it doesn't say it needs to be replaced

► Check Fluid Levels

* Pull the dipstick and look for any moisture on it, or a white/gray slimey substance. This indicates coolant in the oil, the engine may need replaced or heads or head gaskets replaced.
* If the oil is black, no need to worry... Most of the time after an oil change your oil will turn black rather quickly
* Also check Coolant, Power steering, and Transmission fluid levels.

► Leaks

* It is always a good idea to check for leaks. Climb underneath the truck (I tend to go in from under drivers door).
* Check to make sure there is no oil leak around the filter area as this is an indication that the oil cooler line quick disconnects are leaking and will soon fail. Another common place the oil cooler lines leak are at the crimped fittings where it goes from metal to rubber. If a skid plate is still on the truck you may need to remove it to check the lines. If the lines are leaking you can get a replacement kit that is pretty much leak proof for around $220 from Lubrication Specialist. It is not recommended to replace oil cooler lines with OEM style.
* If any leaks are running down the bell housing, it may be coming from the engine valley and possibly be fuel. Most common fuel leaks are found around the fuel filter manager (FFM).
* Also check for leaks around the transmission and trasfer case.

► Checking Turbo (engine off)

* With the engine off, take the intake elbow off of the front of the turbo.
* Take the end of the compressor wheel and try to wiggle it side-to-side and in and out. If you hear any clunking or if the fins hit the side of the housing anywhere the turbo is bad and will need to be replaced.
* This would also be a good time to check your air filter condition. A dirty filter will lower fuel economy and cause a loss of power.

► Engine Cold Start

* When starting your 6.5L Diesel you will want to turn the key to the ON position and you should have a "Wait to Start (WTS)" light come up on the dash. Wait for this light to go and and go ahead and crank your engine and it should start. After the truck has started it is normal for the WTS light to blink a few times, this is called "After Glow".
* When you cold start (first start of day, truck sitting for over 8 hours) you want to look for excessive white smoke or rough running when first started. If the truck smokes for 10 seconds or longer and is rough running during that time, it has failing glow plugs (or open wires) and they will need to be replaced.
* After the engine has been started, go in front of truck and squeeze the upper radiator hose. If this is hard it is possible that you have a bad head gasket. This hose should be soft while the engine warms up.

► Checking Turbo (engine on)

* While engine is running, open the hood and walk to the side of the turbo. You will see a cylinder object with a vacuum line going into it and a rod coming out of it. This is part of the wastegate system (controls boost pressures) Note: '92-93 Trucks will not have a vacuum operated wastegate system.
* Grab the rod and try to move it. This rod should NOT move when the engine is running. If the rod moves easily then there is a problem with the vacuum system (the actuator, solenoid, vacuum pump, or lines).

► Checking Blowby

* On a warm running engine, pull off the oil fill cap. If no smoke or a very light haze comes out this is normal.
* If it seems there is excessive smoke coming out, the piston rings or other parts may becoming very worn.

► Lift Pump Operation

* Locate the water drain valve, a brass T-valve located near the oil fill cap.
* With engine running, open the T-valve for about 10 seconds and see if the truck starts to stumble or completely stalls.
* If it runs rough or stalls, there is a problem with fuel supply to the Injection Pump. Please check the Lift Pump Operation thread for more information on the lift pump before replacing parts.

► Injection Pump

* While in Park and the engine running, slowly bring engine RPM up to 2000 and hold for 5 seconds. Then bring back down to idle. The engine should be steady and consistent, if the engine revs wildy up and down or stalls when bringing RPMs back down to idle, it will likely need a new injection pump.

► Engine Running and you are sitting in cab

* After the engine is running it is good to check all the gauges.
* The voltage should be above 12v.
* As the truck warms up the coolant temp gauge should go up. You should not reach temps above 210. Above 210*F is considered unsafe for these engines.
* Cold oil pressure can be anywhere from 50-80 psi. But what you want to pay attention is to warm oil pressure. Warm oil pressure should be above 20 psi @ idle an around 40-50 cruising around 2000RPM.
* Check to see if the heat works (after warmed up) and the AC works (if equipped).
* Headlights, brake lights, marker lights, gauge lights, etc..

► Engine Hot Start

* After the engine has got to operating temperature (180-195*F) shut down the truck and let it sit for about 20 minutes. After waiting, try and start the truck without waiting for the glow plugs to finish their cycle.
* The engine should start right up with little cranking.

► Some things to check during the Test Drive

* Cruise Control (if equipped)
* Truck shifts into all gears and does not slip.
* 4x4 works (if equipped)
* Floor truck from stop and check for black smoke out of the exhaust. It is normal for a truck to smoke a few seconds after initial acceleration but the smoke should clear up. If not this could indicate a turbo problem.

 

Thanks for the info. alot of that stuff is just common things to check on all new vehicles though. are there any problems with these trucks that i should make sure are ok or else they are vert expensive parts?

 

i would look see if the PMD been move to under front bumper and on a heat sink they are the biggest pain in the a$$
There petty good running truck if you keep up on the oil changes and filters
The 6.5 is not going be as powerfull as cummins.
To money for parts to be cheaper then other diesel that why stick with my 6.5 and lot easy to work on also

 

actually there are quite a few 6.2s on the market that are turbo'd the 6.5 turbo fits very well on the 6.2 motor as do most parts. wanna check to make sure both batteries are free of corrosion and leads on them are good and strong. pop off the block fuel filter (if its a pre 94) and smell it to make sure it smells like diesel fuel and not rust. check fuel lines running to the electronic lift pump (these rust easily) pop off 3 little bolts and rubber hose and pull open the ip to make sure nothing is cracked or broken. (this is a $800 part, gotta make sure its good) let it run and get underneath of it, oil leak is normal. remember they are old. make sure you hear no odd cackling sound coming from the bottom of the block , this would mean the main web is cracked. uhh sure im missing some odds and ends. GL on finding one.

 

I bought a 94 gmc 1500 4x4 with the 6.5 turbo. I'm beginning to think I didn't get that good of a deal. I only paid $1900 for it, all I'm using for is my hunting truck and stuff like that. I read all you put on from up above and when its warm my oil pressure going down the road is 20-40 psi and when idle it is 10 psi. how bad is that???????? Also I noticed smoke coming out of the oil fill cap when you take it off. it was about 1/3 quart low after 400 miles but it does leak somewhere, my wife won't let me park it in the driveway. . But it does fine on everything else and the 4x4 works great, so do you think I'll get a little use out of it???????

 

Hi Bjennen and welcome to DB

you should have start new thread

your oil pressure could be from bad OPS it should be around 20 psi at idle and 40 psi going on down the road the smoke comming out oil full is blow by 1/3qt low most likey from oil leaks or blow by

now if your OPS is on it way out your LP will stop working

you take care of the motor it last a long time don't how many miles you have on it?

 

Sorry I'm new to all this, this is my first diesel. I've only had it a month and it has 183,000 on it. What is the ops and what is the lp? Thanks for all your help.

 

Here something for to copy and keep

One suggestion for Faqs acronym decoder I'll start with a few most common ones feel free to add more;


PMD/FSD = same device Pump Mounted Driver (when installed on IP) or Fuel Solenoid Driver (when removed from IP) electronic device controls operation of fuel solenoid.


IP = Injection Pump


LP = low pressure or lift pump depending on users context


HP = high pressure


6.5 LTD = 6.5 litre turbo diesel 6.5L= approx 396 CID cubic inch displacement


CDR= crankcase depression regulator "tuna can" controls crankcase pressure vents toi turbo inlet


EGR= Exhaust gas regulation valve on emission engines center rear of inlet


L56= "emissions engine" usually at 1/2 T truck or some LD frame 3/4Ts (S engine 8th VIN digit code)

L65= non emission HD truck engine (F engine 8th VIN digit code)


LD/HD= light or heavy duty frame, HD frame and suspension a little "beefier" weigh more, heavier tow/load capacity. Check RPO codes HD is usually L65 code


RPO= regular production options ??? list inbyour glove box of options your truck was delivered with


CAT= catalytic converter slang generally L56 trucks have this


WG= waste gate, flapper in turbos outlet that aids in spool up of turbo to reduce lag time until turbo camn make efficient boost


PCM= powertrain control module brain/computer that runs it all.


OPS= oil pressure switch


WIF= water in fuel


SES= service engine soon/check engine in GM manual this is MIL malfunction indicator lite


APP= accellerator pedal position, electronic module on go pedal that talks to the PCM for more or less fuel from the IP


OBD I or II= on board diagnostic generation I or II, in 1996 Congress mandated all US mfg use common diagnostic port and naming conventions OBDII trucks have electronic IP and require scan tool to read codes and perform diagnostic tests.


MAP= manifold absolute pressure mounted on firewall in OBD II L56 trucks provides EGR feedback and baro conditions to PCM, boost sensor mounted on both L56 & 65 upper intakes sends boost pressure signal to PCM,


In L65 OBD II it also serves as baro sensor at start up, OBD I L65 uses a firewall mounted baro, both look the same but are keyed to only accept correct harness connection.


MAF= mass air flow flow sensor used in L56 to tell PCM how much flow in turbo inlet used to help calculate proper EGR flow


VSS= vehicle speed sensor


IAT= inlet air temp gives input to PCM how hot post turbo air is


ECT= engine coolant temp


IC= intercooler or aftercooler air to air heat exchanger that drops post turbo compressed air temp


WMI= water mist injection another way to cool turbo air using fine water mist


DTC= diagnostic trouble code

 

thank you very much, I'll print that out and hold on to it. Are there ways to check those without taking it into the shop