View Full Version : 6.5 runs great cold but smokes and stumbles when warm
I have read all I can find about this and still no answer for me.
So, the lift pump is new and works great, the fuel filter is new, housing has been cleaned,grounds have all been inspected and cleaned, PMD has been swapped with a known good unit,injection pump has just been done.
The original issue was the IP but the white/bluish smoke is a new issue???
If you get on the pedal it clears up the smoke and makes lots of power so I am quite puzzled by this?
I believe it is above 2000 rpm it clears the smoke. One question, do I have to bleed air from the system, it started easily and ran fine without bleeding any air from lines/filter??
HELP!!!!!!!
Yukon6.2
07-20-2023, 09:17
Whats the story on the injectors that are in the engine?
I have no idea, not sure how to test them...
A bad set of squirts will give all manner of blue white smoke.
POP pressure too low and the spray pattern more like a pee stream
Be a good idea to get them out and have them tested by a reliable diesel shop.
POP pressure about 2100 pounds and a nice conical spray pattern with no dribbles
Pressure needs to be the same on all....STAY AWAY FROM ONLINE sellers offering "High Pop" injectors....
Stock injectors set to factory settings are what you want.
Any codes showing (Check engine light on)
One injector that's dribbling can cause a smoke job......
Blue is unburned fuel
A bad set of squirts will give all manner of blue white smoke.
POP pressure too low and the spray pattern more like a pee stream
Be a good idea to get them out and have them tested by a reliable diesel shop.
POP pressure about 2100 pounds and a nice conical spray pattern with no dribbles
Pressure needs to be the same on all....STAY AWAY FROM ONLINE sellers offering "High Pop" injectors....
Stock injectors set to factory settings are what you want.
Any codes showing (Check engine light on)
One injector that's dribbling can cause a smoke job......
Blue is unburned fuel
no codes.
what I find confusing is that there is zero smoke and it runs perfect UNTIL it warms up then it smokes???
During warmup the timing is advanced more....
This can help burn off poorly injected fuel....
NO CODES IS A GOOD THING...There are several issues with the IP that can cause smoke...But normally there will be DTC'S set...
Did the smoke issue happen just after changing the injection pump ????
Or did the problem come about after some time ??
Yukon6.2
07-21-2023, 09:20
I have my fingers crossed that your issue isn't the same as my Suburban that smoked a lot when warmed up.
Part of a valve face had broke off and one cylinder had no compression.
That could well be the issue......The computer should pop a code if there is a dead hole.....
During warmup the timing is advanced more....
This can help burn off poorly injected fuel....
NO CODES IS A GOOD THING...There are several issues with the IP that can cause smoke...But normally there will be DTC'S set...
Did the smoke issue happen just after changing the injection pump ????
Or did the problem come about after some time ??
the smoke happened right after changing IP, funny thing is it seems like an electrical thing because when I drive it the smoke happens at almost the exact same spot every time, about 3kms......or 1.8 miles for those of you in Merica......lol
the smoke happened right after changing IP,
Are you sure it's timed right?
Check the routing of the high pressure fuel lines at the pump.
You have two fuel lines mixed up at the Injection pump....Easy to do
Here is a diagram...
Firing order 18726543 (Not like the old GM)
Driver side cyls 1-3-5-7 Pass side cyls 2-4-6-8
Check your line routing
The smoke does not occur cold because the exhaust is cold....Hot running.... the fuel being injected is shoved out the exhaust stroke into a hot exhaust and burns off.....
I have seen this before.....Easy mistake to make as the lines will fit fairly easy.
A crow foot on a 3/8" breaker bar is the hot ticket to reach these line fittings and get them tight....
Sadly the intake has to come off....Not a bad job ....
Give this a look see....
Let us know...
Check the routing of the high pressure fuel lines at the pump.
You have two fuel lines mixed up at the Injection pump....Easy to do
Here is a diagram...
Firing order 18726543 (Not like the old GM)
Driver side cyls 1-3-5-7 Pass side cyls 2-4-6-8
Check your line routing
The smoke does not occur cold because the exhaust is cold....Hot running.... the fuel being injected is shoved out the exhaust stroke into a hot exhaust and burns off.....
I have seen this before.....Easy mistake to make as the lines will fit fairly easy.
A crow foot on a 3/8" breaker bar is the hot ticket to reach these line fittings and get them tight....
Sadly the intake has to come off....Not a bad job ....
Give this a look see....
Let us know...
I never removed any lines off the IP, swapped it with lines on it so I doubt thats an issue
I am not sure about the timing, I made a mark and lined it back up to it when installing the replacement pump. How can I check timing???
Thanks for all the input guys!!!!
I made a mark and lined it back up to it when installing the replacement pump. How can I check timing???
It's been almost 20 years since I even owned one, so I could be totally off base, but, is it possible you got the injection pump gear off by a tooth? I'm thinking the cold start timing bump helps it out when it's cold, but when it gets warm, the timing is too far retarded. Lining up the marks should be good enough as long as the gears all still line up correctly.
yes, I was very careful and made sure the marks were correct.
DmaxMaverick
07-22-2023, 14:03
Is the "new" injection pump a reman, one you had rebuilt, or used? Why was it replaced? It sounds like the pump may have internal issues.
Rebuilt pumps do not come with the lines attached NORMALLY
Check the routing of the lines and what cylinder they go to.....
Yukon6.2
07-23-2023, 09:41
I can't imagine trying to change one with the lines attached
Did the original pump throw codes?
Do you have a heat gun to check temp's?
I am very curious on this deal...
Lines never come with a reman pump....And there are two lines that can be swapped....
Since the issue happened after changing the IP.....A bunch of ????????????????????
yes, throwing codes and gutless!
I am almost 100% sure the timing is off, I would really like a code reader that shows the timing, mine doesn't unfortunately, so I am not too sure how I am going to set it!
DmaxMaverick
07-23-2023, 13:57
It's EFI. You don't need a scanner to ball-park the timing. You can't change it w/o a chip, anyway. You are probably seeing default, reduced fueling, perhaps limp mode. What codes are you seeing?
I am not getting any codes, I realize it's EFI.
The reason I think its timing is because of the description I gave ( I think the timing is too far - and after warm up the computer retards the timing and causes it to be even more - thus the unburnt fuel/smoke).
There is software and scan tools that will allow you to see the timing, I just don't want to spend that kind of money for this 1 job.
DmaxMaverick
07-23-2023, 14:45
You don't need to "see" the timing. If it's off, the IP is indexed out of range (by whatever means), can't correct it, and it will throw codes. If no codes, electronic timing is not the problem. If the IP is within the specified physical range, the PCM will adjust the timing to the calibration. It WILL complain if it can't.
That leaves either an external failure (wastegate control/vacuum, air intrusion, etc.), or an internal mechanical failure. As Robyn suggests, verify injector line timing.
Smoke + no power = no/low boost. Check the plumbing. Intake and vacuum (pump, lines, WG solenoid).
What year/OBD? 1996 and later requires an OBDII scanner, while 1994/5 only requires a paper clip to read DTC's.
Ok, truck is a 96, I am aware of it being OBDII, pretty hard to plug an OBDI into a II port lol.
it has had the vac pump deleted so that rules all that stuff out.
I am not dealing with a smoke/no power, truck has lots of power just smokes at low rpm and runs rougher.
I will double check the injector lines but as stated, I never removed any and the IP came off a runner so doubt thats it nor does it make sense to me that it would run really well when cold and then after a 3 km drive start to smoke but I will look at them.
Someone else stated that if the timing was out then when the truck warms the ecu retards timing and that got me thinking that was it. I did see a video where the timing was out of range but no codes so not sure what to think now???
the IP can be adjusted, I am assuming when you say indexed you are talking adjusted?
there are even tools made to clock the pump.
DmaxMaverick
07-23-2023, 19:19
Indexed, as in turned within its mounting stud slots. Indexed out of range, by any means, may mean it's rotated within the mounting stud slots, off a cog on the gear, or sheared pin, and is outside the PCM adjustable range. Any of the above will set codes if it is out of PCM adjustable range. The injection pump can be adjusted (indexed) to push the TDCO (Top Dead Center Offset) to the edge, just before it codes, which is preferred for optimal performance. That's something for another time, if you want to go there. Kent-Moore makes a bunch of nice-to-have service tools that most of us have been surviving without for a few decades. An indexing tool is nice, but more suited to N/A pump timing. I made my own back in 1980-something.
Vacuum delete. That's a different animal. With no vacuum, and no codes, either the PCM has been programmed, or the wastegate solenoid is present (not doing anything, but electronically present) and it has a mechanical wastegate control (Turbomaster, or some such). How much tension is on the wastegate spring? It should be pretty stout. If too loose, the truck will smoke and lose power as soon as you get into the skinny pedal. If too tight, it will overboost under load, set codes and defuel because the PCM can't control it.
The OBD version doesn't really matter. Just wanted to be on the same page.
Ok, I was understanding you correctly!
I am unsure of the wastegate spring tension but can see if I can move it by hand. I think I have moved it once before but I don't think that has any effect on my issue anyways because it smokes heavy at idle once this issue starts.
Now, back to the issue.....how could mixed up injector lines behave this way?
runs perfect when cold and then , as if something switches electrically, start smoking when warm?
Thanks for the patience and help guys!
If the engine is running rough at low speed/idle....I still feel like this is an issue with either a set of lines crossed at the Injection pump or possibly a bad injector.....
A bad squirt can cause the engine to run like crap and smoke bluish at low speeds.
Get some of the extra goodies off of the engine ...Enough so you can get at the injector lines at the injectors.....Start the engine and crack open one line at a time.....AS soon as you open the line it is like removing a spark plug wire....That hole should shut down
You should feel a distinct "Misfire"
Go through all the injectors one at a time....
Trace out the fuel lines to be sure they are connected correctly at the IP....
If the lines are correctly routed then any cylinders that are not firing should have the injectors checked.
That this issue came on after the pump was swapped pretty well negates internal failure such as a valve breaking or ?????
If all else fails a compression test can help diagnose things....
Spinning the engine without glowing it and listening to the cadence of the cranking can ferret out a bad hole.
The cranking sound should be constant .....Example....ZA ZA ZA ZA ZA...EQUAL CADENCE
ZA ZA ZA ZAAAAAA za za za za....A weak hole will take less effort of the starter and will give a distinctly different sound.
Although not very specific as far as WHY....It will indicate an issue that needs further investigation...
This little trick requires no special tools....Just a good ear...
Outfits like Auto zone will pull the codes for you....
These can be extremely helpful in gaining insight into Wasssssup
Check the fuel lines first
Mixed up injector lines is just like a spark plug wire on the wrong plug....The cylinders do not fire....
The injector puts fuel into the wrong cylinder at the wrong time....The raw fuel gets blown out into the exhaust and after the engine is warm it burns off...BLUE SMOKE
The fuel is still getting blown out cold....Just not enough heat in the exhaust to cause the smoke to form
I am not sure if I am not explaining this correctly or if people are misunderstanding me???
The truck runs perfect when cold, no smoke, no miss no issues at all. I doubt it would start and run so perfect if lines were on the wrong injector (as you said,like spark plug wires on the wrong plug would cause obvious issue).
I am not new to mechanics, been doing this for about 40 years but not with these engines. I have learned the 6.5 is it's own animal.....
The reason i chose to swap the pump with lines attached is so they would end up where they belong.
Yukon6.2
07-24-2023, 10:01
My "Guess" is a weak cylinder...
My Sub project last year made me jump through lots of hoops trying to figure out it's issue.
Ran good cold,had decent power.Get back to the shop after a hard run and it would be smoking blue white smoke.
Basing my guess on the owners insistence that the lines are right,used pump was a good one,no codes getting tossed.Add the insite from DmaxMaverick and Robyn.
By the time i got to a dead cylinder...
A good know pump had been installed due to codes,at that time i went through 16 injectors and picked the best 8 that all popped within 100PSI,the brain had been sent to Kennedy for a refresh as it had issues.
Every thing i changed or fixed made it run better but the smoke would roll after a road test. The sub had good power on 7 cylinders for a 6.5.Even after a run down the road it would idle decent while smoking.
One partially broken valve was the smoking gun.7214
Unplug the temperature sensor so the PCM thinks the engine is always cold. Does it still smoke after it warms up?
thanks for the input Yukon 6.2 .
Similar issues but this one doesn't idle nice at all once warmed up and will die.
thanks to you too JohnC !
I will try the temp sensor, I had thought about that but have not tried it yet. Thanks!
What was the source for the injection pump that went on this engine???
Why was the pump replaced????
You stated that the smoke and such happened after the pump was replaced
We need to look at all the data to be able to back track and sort out what happened.....
I have never seen a quality rebuilt injection pump cause issues.....
Getting the codes is paramount to figuring out what is going on....
Clear all current codes and then do a restart and see what comes up......
Some times stuff can be stored in the computer and you end up chasing the wind......
Gotta have more data to sort this out.
Sadly doing diagnostics over the internet without having the rig here in front of us makes the process difficult at best.
The computer will give us a lot of important data as to what it does not like.
Any time the SES lamp is on....The ECM is not happy.....
Get us some info on what codes are showing......Then clear the codes and see what comes back...
The DS4 injection system is impossible to fully diagnose without knowing the full story.....
The OLD DB2 mechanical system can be sorted out pretty easy....Not so with the DS4
There could be a crank position sensor issue, and several other problems that simply can't be figured out with a screw driver and a wrench....
I believe I stated there are no longer any codes.
I agree with diagnosis via web, same goes for over the phone lol, how many times I have been called and asked " hey my car is making a funny noise, what do you think it is ?" hahaha.
I was getting po1218 but not since the IP swap.
DmaxMaverick
07-25-2023, 10:26
P1218 is a missing or incorrect PMD resistor or resistor value. It has no relevance to the physical pump, other than a value read by the PCM for electronic pump calibration. The resistor is a PC card located inside the PMD connector. The pump itself doesn't know or care about it. The pump should never be replaced (or messed with) for this alone.
I am aware of this, the previous person asked about codes so I responded.
The truck had all the issues of needing an injection pump previously, I went through every check prior to replacing the pump . I checked/cleaned all the grounds, checked and replaced all the fuel lines from the filter to IP , cleaned the filter housing and replaced o rings and new filter.
I have heard there can be issues with cheaper filters so the owner has supplied a better quality filter ( I would have preferred the metal top type) so I will replace that next....
ok, I FINALLY had time to get back to this truck! (yaaaa I think?)
I unplugged the temp sensor and the truck runs perfect now......so I believe that means it's in closed loop correct?
What now?
Do I need a temp sensor or is this pointing to something else?
Thanks again for all the help you guys have been on this frustrating issue
Unplugging the temp sensor tells the Computer (ECM) that it is very cold outside and the timing is advanced a lot for cold start conditions.
Sounds like the TDC OFFSET needs to be reset.
A TDC LEARN PROCEDURE SHOULD BE DONE
Timing is retarded......
I cant tell you why this happened.....
The base timing is set with the gears/chain ...The position of the pump can be charged some by rotating the pump .....The actual timing value is done electronically by the ECM
If the pump is physically out of adjustment (Retarded in this case) the ECM can't adjust the timing far enough to meet spec.
Unhooking the advance allows the timing to be closer to what is needed after the engine is warm.
This said.....the check engine light should be on and a code set.....
MAKE A SCRIBE MARK ACROSS THE FLANGE ON THE IP AND THE TIMING COVER FOR REFERENCE ....
With the engine OFF.....Loosen the 3 nuts that secure the IP to the timing cover.....
Rotate the IP towards the drivers side about 1/16" or so and tighten the nuts.
Do a test run with the Temp switch connected.
If the engine still runs poorly try a bit more .
The pump has a particular starting spot that they are physically set at the factory.....This places the inner workings of the IP in a place that the internal advance mechanism in the pump can adjust the timing to where it needs to be....
The actual timing setting is done by the ECM....But the IP must be close physically to allow the actual timing value to be attained.
If the ECM can not reach the desired value the SES lamp will illuminate and a code will set.
Moving the IP a little at a time can get the physical parts close enough that the ECM can get what it wants.
Without a TECH 2 scan tool or equivalent you can't perform a TDC offset
Bottom line is....the physical location of the IP must be close enough to allow the internal adjustment of the advance to reach the set values the ECM wants to see.....
After each test....Clear the code and try again.....Once the light stops coming on....You are as good as you can get without a Tech 2 scan tool to make adjustments..
As long as the ses light stays off and the engine runs good ....NO SMOKE.....You are good to go....
By unhooking the temp sender you are placing the IP in full advance....
The physical pump adjustment is likely off far enough that the internal adjustment is simply not capable of going far enough..
Good luck.....Keep us in the loop
Thanks, this is exactly what I thought was going on!
I did have a code but can not remember what it was unfortunately but it was something like fuel calibration or something along those lines. I wrongfully assumed it was an old code hahaha
I still get 1218 with the sensor plugged in and the engine warmed. I noticed the resistor had been removed so I put one in( does it matter what PMD it came out of?) and it still smokes and runs terrible when at operating temp.
What code will I get if the timing is out?
The resistor tells the ECM about the pump calibration. It has nothing to do with any particular PMD, in fact, Stanadyne just decided the PMD socket was a convenient place to put it. It should stay with the pump.
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