Help Smoke at Start and Compression Test Results

[nigeljones]

I have just completed my compression test on my 96 Suburban. I have 150,000 miles on it now and this year have had starting issues when cold - lots of chugging and plenty of smoke at start up for 10 - 30 sec and then she finely clatters into life and everything

[john8662]

It's hard to tell with those numbers on the compression without knowing how you performed the compression test. During a compression test you will need a helper or a starter button under the hood. You will hook up your gauge, zero it, and then have someone crank over the engine while you count compression puffs. When you get to 6 puffs, that is your reading. Above this the readings will climb, but we are looking for 6. Also, the engine would have needed to be warmed up to operating temp before doing this, but avoid burning yourself! Here is the cylinder sequence:

Drivers side (starting at the front of the engine):

#1
#3
#5
#7

Passengers side (starting at the front of the engine):

#2
#4
#6
#8

You see odd numbers on the driver's side and even numbers on the passengers side (turbo side).

Other things that could cause your starting issues could be bad injectors, which could be the case with the mileage on your engine. It could also be an air leak in the fuel system, fuel filter housing, hoses, etc, or a weak or non functional fuel lift pump.

[20050420|7|006071|000022|69.19.2.78]

Maby, it`s the timing chain :rolleyes:

[Robyn]

??? Did you have all the glow plugs out when you did the comp test?? this will make a difference as you use less battery to do it and the drag from the other cylinders does not effect things as much also if you have one ot two cylinders that might be leaking a tad bit of oil down from the valve guides can make them a bit higher. As was mentioned earlier do the test hot if at all possible.

[Robyn]

Nova
I swapped a 3208 into a Ford 250 4X4 a number of years ago. "WHAT A BEAST" was a turboed 3208 and that truck really ran hard too. Heavy engine though

[Shad]

I am going through the same situation. I am trying injectors next. Compession numbers are different depending on guage, person performing, engine temp......

[20050420|7|006071|000022|69.19.2.78]

Robyn,
My plans have cheanst a litlle, a had bougt a detroit diesel, it`s an 6V-92 with 276 hp. :D :D
I have to modify the W200 with a sub chassis and put an allison behind it :cool:

[nigeljones]

John8662

I was not sure how to conduct the compression test hot or cold so I choose cold not to burn my self and primarily wanted to check the compression at cold as that

[nigeljones]

Shad

I read your post yesterday I found it when completing a search for compression testing I was looking for a "how too" and what are the specs. Sounds like we have similar cases. Feel free to email me directly to compare notes nigeljonesmied@aol.com

I'm running out of suggestions.

Regards

Nigel

[Ratau]

John8662

If the compression test is done on a cold engine will the pressure be lower or higher than on a warm one?

Danie

[20050420|7|006071|000022|69.19.2.78]

Nigel,

i had the same simtons as you have, about the smoking when starting the engine,

whell, i did have read the dieselpage for a long time, and with the help of all the forum members, i came to the conclusion that it had to be the timing chain, and yes it was slop.
i put a new gearset on the engine and it is like new, the smoking is totaly gone. The engine runs like it had a turbo on it (i turned up the pump also :D )

arjan

[Barry Nave]

Have any of you guys pulled the oil fill off and checked the timimg chain deflection?
150K are a lot on that pcs.

[john8662]

nigeljones,

Doing a compression test with a warm engine gives you the running condition of the engine. Because the engine is warm, the tolerances in the cylinders change due to expansion. This works better to get the overall picture of the condition of your engine. You don't have to do the test just after shutting the engine down, but still quite warm. For testing the #6,8 cylinders you can remove the rubber splash shield from the inner fender to gain access easier. Also note that compression tests can vary, things like a worn out starter, weak batteries can affect the results. How is your cranking speed?

On another note, you can leave your glowplugs in, except in the cylinder you're testing of course.

[nigeljones]

All
I will complete the compression test this weekend and I will complete it in a hot condition. I will ensure that there is only 6 puffs per test. Actually it's quite easy really and the passenger side is more awkward than anything else. I go thru the wheel arch removing the plastic cover as you had mentioned and also the heat shields for cylinders 4 & 6 its better that way no messing about when you try to re-attach the electrical connection. Number 8 cyl you can get to from underneath.

As regards the starter/ battery condition it throws the engine real easy all due to the battery terminal mod posted on this site. I'm talking about the bolt a nut solution Wow what a difference :D . Although wishing to improve I elected not to remove the insulation from around the terminal. What I did was took 3 plane washer the same size as the original bolt and used them as a spacer so the nut does not get buried and you can get the wrenches on to tighten. What I thought I might do to improve further on the washers was to use the spacer that is used between the doubled stacked positive terminal on the passenger side of the vehicle.
And those caps from ACE or perfect :cool: Those batteries have caused me so much trouble over the years - but not any more :D :D :D

Keep you posted on my progress

Nigel

[nigeljones]

The Other thing I can not understand unless it is the timing chain is that random start.

This morning at 11 deg f the truck which was parked out side last night started like a champ no smoke just burst straight into life with NO smoke.

But this evening coming home from work a cold start at 25 deg F I had smoke again.

Any thoughts?

AS always thanks

Nigel

[john8662]

There is a sensor located on the water crossover thermostat tube that tells the PCM how cold the engine is. You could possibly have a bad sensor or a loose connection. When the engine doesn't want to start nice, with all the smoke, does it idle up like it is supposed to when cold? If it just idles low after a cold start (when you get the smoke and chugging) you might want to just unplug the sensor and retry. When unplugging the sensor, the computer will assume the COLDEST setting, and advance the timing far and have the longest glow cycle. It'll be pretty raspy, but it should start easily. If that's the problem, then you need a new sensor. Thats what it's starting to sound like.

[nigeljones]

John8662

I completed another compression test this afternoon. I took the truck out for a drive to ensure she was warm thru and thru.
And the results were as follows.

#1 cyl= 455psi

[nigeljones]

John8662

I changed out the coolant temp sensor this week and there was no improvement. She still bellows white smoke sometimes at start up.

I completed another compression test this afternoon. I took the truck out for a drive to ensure she was warm thru and thru.
And the results were as follows after 6 puffs.

#1 cyl= 455psi
#3 cyl= 380 :confused:
#5 cyl= 400
#7 cyl= 420

#2 cyl= 475
#4 cyl= 420
#6 cyl= 420
#8 cyl= 475

So whadaya think!
Nigel

[john8662]

You really have high compression in some cylinders. But glad you checked, I can't see any compression numbers in that list that are bad. When I did my compression test in my 6.5 the lowerst was 350, but most of the results in the 400's. So pulling the coolant temp sensor plug on the water crossover off before startup doesn't help? It could be the injectors.

Exactly how much smoke do you get at startup, and how long does it take for the exhaust to clear up after a startup?

[nigeljones]

John,

I replaced the fuel enjectors a couple of weeks ago with no improvement. These were brand new AC Delco parts.

I swaped out the Coolant Temperature Sensor with a new one and the jury is still out. I thought I saw some improvement in my typical driving routine. However, I had the truck laid up for a couple of days doing brakes and oil cooler lines. But when I started the truck back up to complete the compression test she smoked something awful.

I have access to Alldata at work and have read up a little. They state that "The lowest reading cylinder should not be less than 80 percent of the highest reading cylinder. No cylinder should read less than 2625 kPa (380 psi)" They also state that "Normal: The compression builds up quickly and evenly to the specified compression on each cylinder. The reading should be within the 2625-2760 kPa (380-400 psi) range .
Leaking: The compression is low on the first stroke. The compression builds up on the following strokes but does not reach the normal level"

The highest value I had was 475psi and the lowest was 380psi which would give me a 20% split so I guess the compression would be OK. Your concurence would be appreciated?

I also looked up timing chain whilst in Alldata. I found the following statement "The timing chain on these engines has an allowable deflection of up to 0.80 inch. However, if timing chain deflection exceeds 0.80 inch, due to component wear or chain stretch, the engine may experience rough idle, low power, poor fuel economy and/ or excessive emission of white smoke". I quess checking/replacing the timing chain would be the next step. What do you think?

I intend to upgrade the waterpump so that would be the time to do it. Do you happen to know approx the part costs to replace the chains and gears as against going with the gear set I seen talked about?

What's your feelings regarding the gear set

All comments welcome

Nigel

[nigeljones]

John,

I didn't answer your question


Exactly how much smoke do you get at startup, and how long does it take for the exhaust to clear up after a startup?
Somedays if I let it idle at cold start up it can smoke for 20-30 sec. However, It's way to embarrasing so I found that some times if you hit the accellerator pedal you can force it to stop.(by the way the truck does not have the usual clatter sound as when it starts without smoke)However, That's not always the case. it's random, sometimes it fires right up or somtimes smokes momentarily. The whole family now comments on the subject.

Nigel

[john8662]

If you are considering upgrading to the new water pump and dual thermostats, you could go ahead and install the timing gear set from DSG. You are going to be half way there already. I'm not quite sold on the gear sets, but they do improve the timing on the engine. I'm of the impression that if your engine has quite a lot of miles on it, then the best rout would be to install a new chain/gears. But on a new rebuilt engine, I would't have anything but the gear set. It's really your choice, the gear set is going to run you 380 (from some vendors) it's more on DSG's website:

www.dieselservices.com (http://www.dieselservices.com)

I concur with your compression results, they are nothing to be worried about. The lowest 380 is not low. I am only concerned with how high some of the numbers were, this can be because of carbon buildup in the combustion chamber/precup.

So, new injectors, new glow plugs, new sensor. Have you had the timing checked at a dealer? What kind of oil consumption are you seeing? If you are seeing high oil consumption, you might be losing oil at the turbo, and it's blowing it into the intake and making your engine smoke. To narrow this out, you can remove the upper intake manifold and inspect it for being excessively oily. Some oil will be present, but that is from blow-by.

[nigeljones]

John


Have you had the timing checked at a dealer? Yes I had it set it was off originally after dealer replaced the IP. It is now set at -.61(which I was told was spec) and I have checked that several times(buddy has a tech2). I thought about setting the timing to something other but not sure how to do that yet. If I get into replacing the timing chain looks like I will be forced into that situation.


So, new injectors, new glow plugs, new sensor. What kind of oil consumption are you seeing? If you are seeing high oil consumption, you might be losing oil at the turbo, and it's blowing it into the intake and making your engine smoke I normally use a quart between oil changes and I change the oil every 5000 miles (it easier than my 3 times table). But now you come to mention it I thought that when I last checked the oil was down, but I put that down to leaking oil lines and a loose turbo oil return line(the bolt backed out after changing the the fuel injectors I needed to get the heat shield out). But I will keep an eye on it. I also replaced the CDR valve for good measure and I thru in a new gas cap.

If I could be sure the DSG timing set would cure my problems I would be tempted to spend the money, so I think I will take your advice and swap out the Gears and chain for like. And keep the money for other things like the exhaust and gages etc.

Thanks for your help to date if I find the cure I will update this thread.

A chap called Shad say's he has the same problem so I'm eager to see if he cured his problem changing out his fuel injectors but alas I have done that already.

Regards

Nigel smile.gif

[nigeljones]

John8662


I swaped out the Coolant Temperature Sensor with a new one and the jury is still out After a week now the jury is in "The sensor did not make any difference It still smokes with milder temperatures 30-40 Deg.

I should have the parts for this weekend to replace out the timing chain and upgrade the water pump. So I will keep you posted :rolleyes:

[charliepeterson]

If you have access to a reader then when you think the weather temps. are right compare what the ECM is looking at for temps. as to what the temp. is at the front of the truck. Any temp. below say 50* should also kick in the fast idle for a short time depending on how cold the block is. Is the fast idle working?

Poor fuel quality can cause smoke at start up as well. Try adding an extra dose of fuel conditioner to the tank. After the truck comes up to temp. it can handle the lousy fuel if this is what's in the tank?

[nigeljones]

Charlie,

I'm interested in the fast idle I don't know anything about it. I know what a fast idle is but not regarding the 6.5TD. Could you explain

I have put a cetene boost and lub products in the tank and it seems to run stronger but not the cure.

Thanks for your input

[charliepeterson]

When the truck's cold the RPM's will be around 900-1000. After the coolant temp. comes up to about 70* the RPM's should drop down to about 650-700. All of this is coming from the coolant temperature switch to the ECM. If you unplug the switch and start the truck the ECM goes into a default setting of -40*F.

If the switch is left off while you drive around the SES light could come on telling the computer something is wrong with the readings. After the switch is plugged back in the light will go out.

The advantage for removing the plug is an extra long glow plug cycle. Many members here have come up with a simple solution of rigging a momentary over ride switch for extended cycle times for when the outside temps do get really cold.

[charliepeterson]

An easy way to tell if the fuel is clean is to open the water drain tube ( T handle next to thermostat housing) and drain a few ounces into a clear container. Let the fuel sit for a few minutes and look for any impurities. You may want to clear the tube first to rid any dirt in it before the test.

A little hint first though, if nothing comes out when the handle is opened, close it off quickly because the truck will stall due to air getting to the injection pump because the lift pump isn't working correctly.

[nigeljones]

Update to this thread

I now have replaced the timing chain and set the TDC offset to -1.76 and the smoke has been minmised. Has it gone for good, I don't know as the weather has got warmer. I have had a few mornings at 37 degrees and it didn't smoke. However, If the truck has sat for 1-2hrs from hot it will smoke for approx 3 sec but no more. So this is a dramatic improvement.

If in the fall/winter the smoke returns I will look at extending the glow plug cycle times.

Thanks for all your help ;)

[Eduardo]

My new-to-me truck (1993 K3500 pickup 6.5 TD mechanical injection pump) also had rough starting in the morning with lots of white smoke. Although it would stop smoking after a few minutes idling, the situation was embarrassing. The glow plugs (the dreaded AC 9Gs) were all working, and so was the cold start advance and fast idle. So I searched for posts about