New 6.5 Owner - Engine Misfiring

[6.6/6.5]

I'm a new 6.5 owner ('95 Silverado) and a new member of TDP (first post). I purchased the p/u knowing that it had engine issues. The price was low enough and the body/chassis is in good shape, so the engine issues were an acceptable risk. I have searched the archives of this forum without finding a definitive answer to several questions.

First, the engine is misfiring on at least one cylinder. I will attempt to identify the specific cylinder, but I believe that it is valve related (collapsed lifter?). Besides a collapsed lifter, broken rocker arm retainer or malfunctioning injector, what other sources of engine misfiring are applicable to the 6.5 Turbo Diesel?

Second, the engine (long block, not the accessories) is painted yellow. I suspect the engine has been remanufactured or has been provided by an volume overhaul enterprise. Does the yellow paint indicate a specific company or organization that did the remanufacturing/overhauling? If the company can be identified by the paint, does anyone have a comment about the quality of their work?

I have found TDP and this forum to very informative and I appreciate the value of my TDP membership. Likewise, I will be very appreciative for any answers that might be provided for my questions.

[trbankii]

The "easiest" problem that could cause a "misfire" is air in the injector lines. Hard to say without listening to it, but I'd try bleeding them out. Sounds sort of unlikely if it is just one line - unless someone opened it for some other reason and let air into it.

[john8662]

I remember this truck on ebay (if you found it there).

The engine was painted yellow, and so were some of the engine components (part of the pump, some of the lines, etc.). To me, it was a sloppy paint job right before putting the engine in the truck.

I had my doubts that the engine was fully rebuilt, more like it was taken apart and repaired.

You've hit the highlights of the minor problems that could cause a misfire.

Collapsed lifter, broken retainer on rocker.

Other things to consider would be a failed injector.

The first thing you should do with this engine is purchase a diesel compression tester with the appropriate adapter for a 6.5 and do a complete compression test on the engine.

Get the engine up to normal operating temp, remove the "fuel sol" fuse from the fuse box under the hood (to keep it from starting). Remove a glow plugs, insert you adapter, and connect gauge. have helper crank over the enigne (with fully charged batteries and great working starter) and count 6 puffs on the gauge, the final amount is your compression for that cylinder.

Report back.

[6.6/6.5]

John,

Thank you for the response to my posting. Yes, the p/u was purchased on eBay from a Utah auction firm. The body, chassis and drive train seem to be in very good condition, but the engine is problematic. I need a work truck and it will serve my purposes very well once the engine issues are resolved. I ordered a compression gage and adapter last night and I will report the compression data as soon as they are measured.

Some additional symptoms: The engine smokes heavily (blue smoke) on starting. The smoke clears approximately 2 to 3 minutes after starting. There is oil in the induction hose between the filter housing and the turbocharger. I will replace the CDR as soon as one can be purchased. The engine produces a "clicking" sound at idle. This noise either stops or is masked with higher engine speeds. Probing with a stethoscope didn't provide any definitive information, but there does seem to be a slight increase in the volume of the metallic clicking sound in the proximity of the No. 6 cylinder.

Besides servicing the fluids and filters, I've replaced the glow plugs which has made the starting much better.

Jim

[BobND]

As for the CDR, there's a 90+ % chance the oil in the hose is simply from oil mist condensing out of the engine blowby simply passing through the CDR, as it is supposed to.

The CDR is basically an open, empty chamber with a spring-loaded diaphragm that begins to close off the crankcase ventilation flow if the crankcase pressure begins to go negative.

Realistically, the only time that would happen is with a restricted air filter, or POSSIBLY on an engine in very good condition, with very little blowby, at high RPM's (LOTS of air being drawn in by the turbo.

The CDR's that I have replaced were replaced because the diapragm developed a leak, and oil leaked EXTERNALLY through the tiny weekhole in the side of the CDR.

[moondoggie]

Good Day!

When does it miss? All the time? cruising? Heavy footfeed?

Blessings!

[6.6/6.5]

The engine misses most noticeably at idle. However, I am quite certain that it continues to miss at higher engine speeds. The clicking noise can be readily heard at idle, but is still detectable up to 1500 rpm when the exhaust and combustion noises tend to be more apparent.

[JohnC]

Could be a piece of detritis in one of the injectors. At higher power levels it has less effect. Loosening the fuel lines one cylinder at a time will isolate the offending cylinder, then you may want to have that injector tested.

[gvig]

I purchased a warranty pull out (6.5) that had this very problem, finally found a broken valve spring. When you isolate the cylinder and find no compression at idle speeds, check the valve springs, a valve will float open without enough spring pressure, but the compression pressure at high rpms will blow it shut.

Good luck!

[6.6/6.5]

The following is a report on the compression test. The Matco compression gage and adapter arrived today and the following data were measured:

No. 1 = 330 psi No. 2 = 340 psi
No. 3 = 290 No. 4 = 340
No. 5 = 300 No. 6 = 320
No. 7 = 310 N0. 8 = 220

No. 8 was the first cylinder tested so it had the advantage of a more warm engine than the remaining cylinders (No. 1 was the last tested).

So, tomorrow the intake manifold and rocker arm covers will be removed in an attempt to determine what ails cylinder #8. Given the relatively low compression readings, I suppose that I should be contemplating a "drop-in" remanufactured engine or pulling and overhauling the existing engine. The truck's condition warrants a decent engine. I'll do some trouble shooting first.

[JohnC]

Hey, guys, this really cheap compression tester (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93644) is probably a bargain if it gets through all 8 cylinders! It's even less ($16.99) in the latest sale flyer!

[Warren96]

Let me put my vote in for a broken valve spring,and the noise you hear is the valve tapping the top of the piston!

[Mark Rinker]

Sounds like you are doing a great job troubleshooting.

If you decide to go the route of a replacement engine, I would highly recommend using one of the vendors affiliated with this website. Beware of Ebay reman 6.5 vendors, especially one mentioned on the forums here from the east coast.

Depending on your budget, this would be a great time to invest in some upgrades common to modified 6.5's including splayed main caps, gear driven timing, 18:1 pistons, etc...

A good estimate for replacing the engine is 5K (used engine, installed yourself) to 12K (rebuilt with all new goodies, installed.)

Keep reading the forums, there are many that have gone before you to make your journey more trouble free.

[fshope]

Not to be the bearer of bad news, but what you describe sounds like my 94 when I cracked a piston. The piston caused blow-by and ran better under load. The 6.5 has been known to give piston # 7 & 8. Your compression check should identify a leaky piston. The piston cracked across the top from side to side.

[6.6/6.5]

Removal of the intake manifold and rocker covers didn't reveal an obvious culprit for the low compression for cyl. #8 --- the rocker arm retainers were okay; there were no broken valve springs and the lifters weren't collapsed. Consequently, the engine is coming out of the truck because I think a cracked piston may be the problem. Even if this isn't the source of the problem/noise, the engine is in a rough enough condition that it needs a minimum of a complete overhaul and perhaps a drop-in replacement. An inspection of the bottom end will determine the direction to be taken. (Running the numbers on machine shop services, an overhauled/new fuel sytem, overhauled turbocharger and the necessary replacement internal components make a remanufactured engine rather attractive from a financial standpoint. With either alternative, I will do the R&R on the engine and accessories.) I will post additional information about my saga as appropriate. In the meantime, I appreciate the comments, suggestions and recommendations that have been posted in this thread.

[john8662]

I also vote for a complete removal of the engine at this point, that way you'll be able to identify what's wrong with the engine and complete the overhaul.

Cylinders 3 and 8 are too low in my opinion, #8 being the worst.

None of the compression results are great, a healthy engine should see 380 psi, with 350 still being ok.

Keep us posted on what the culprit ends up being.

J

[6.6/6.5]

The engine is being removed and a "drop-in" replacement will be ordered. When the engine is out of the truck (after my travel activities of the next two weeks), I plan to remove the pan only to check the condition of the bottom end and the pistons. This will be only to answer my curiousity about the engine's condition and source of its problems. Then, the old engine will be reassembled so that it can be returned for core credit upon receipt of the replacement. During the installation of the replacement engine, the plan is to add a remote FSD location, a new engine oil cooler assembly, including hoses, and a new exhaust system. (It is expected that the "kitty" will run away from the shop in the process!)

[Mark Rinker]

If I knew the motor was going to be a 'core', I'd have fun beating the living tar out of it before it came out. But thats just me. Have had fun with some high mile small block gassers that were destined for the scrap yard.

You'd be suprised how long a loose high mile motor will run with water, but no oil. Or, oil but no water.

No water and no oil is generally a quick meltdown.

[6.6/6.5]

The noisy, oil burning, engine was removed today in preparation for the installation of a replacement engine. Out of curiousity, I removed the pan to find a recent, but very poorly done, overhaul. The amount of RTV used was easily 2 to 3 times that required, though only a few pieces were in the oilpump intake screen. The skirt of #8 piston was heavily scored, but the other piston skirts had only normal thrust markings. However, the bottom end is a real mystery to me. The center main bearing caps are splayed, with socket head capscrews in the outer locations. The block has been machined for a "register" for the three middle caps. The caps are not made of billet material as I understand the Kennedy splayed caps to be, but appear to be castings with "REVIVA" moulded into the outer surface of the casting. I didn't remove the crankshaft, so I didn't see any block cracks. What do I have regarding the block? Should I further dismantle the engine with the intention of overhauling the existing engine or should I continue to pursue a replacement?

[6.6/6.5]

My most recent findings and my decision regarding the engine replacement have been posted as message in the "Help Indentify this 6.5 Block" thread.

[Tim.]

Hello sorry probably you guys answered this probable cause but i just recently bought a chevy 2500 96, and i have this wierd problem with and misfire sound like its only in one cylinder driver side but it doesnt misfire all the times it will sometime do it when it idle and the constantly misfire constantly when i reach last gear 2000 rpm but when i pass 2000/2150 rpm itll be all good, any suggestions
Thanks... Tim
Plus at this moment my wastegate isnt functioning cause of the vaccum pump could that cause the problem or not ?

[Robyn]

Hello

Welcome to TDP :):):D:):)

The misfire is likely a failed injector.

Any SES LAMP Showing ???

If so get the codes

With the engine running (And missing) crack open each injector line (one at a time) and see which one does not cause a change... Sort of like pulling a spark plug wire on a gas engine to isolate a misfire...

Once you locate the cylinder not fireing... Remove the injector and switch it to the cylinder next to it (just swap the two) Restart the engine and see if the issue follows the injector.

If the issue follows the injector then the one injector is bad for sure.

If the issue does not follow the injector then there are other issues such as the injector pump ??????




The vacuum pump will not cause the issue, but you need to get it fixed to have the engine operate properly (Turbo boost and power)


Good luck...Keep us in the loop

[JohnC]

Wow! This thread is more than 11 years old...