No throttle when cold

[rigger]

I'm a total newbie when it comes to diesel. The 2000 GMC 2500 6.5L TD is my first. Truck runs fine but when I start it and try to go anywhere when cold there is absolutely no power or throttle response. At first I thought transmission but with the fact that there wasn't even a rev increase tells me something else. As for cold I mean only 10c rainy Vancouver weather and after sitting for the night. Things are fine after it warms up. Also after it does start it shakes like crazy as if there's a lack of fuel, I hit the pedal and it will puff a big cloud of smoke then the engine will idle fine.
Ideas?

[twaddle]

Hi,
Does it take a bit of cranking on the starter motor before it fires up when cold or does it fire up quickly?
From you description of clouds of smoke I would Initially guess that some or all of the glow plugs are not working.

Jim-T
PS welcome to The Dieselpage.

[Robyn]

A total absence of any throttle response when cold sounds like a PPS (Electronic throttle issue)

When this is happening is the check engine or service throttle soon light on??

I would recommend getting the thing scanned to see what codes if any are stored in the computer.

There could be one of several issues but the first step since it runs ok when warm is to see what DTC's are present.

Smokey cold starts could be glow plugs but that will not stop the thing from reving up once it lites off.


Keep us Posted

Missy

[rigger]

Hi,
Does it take a bit of cranking on the starter motor before it fires up when cold or does it fire up quickly?
From you description of clouds of smoke I would Initially guess that some or all of the glow plugs are not working.

Jim-T
PS welcome to The Dieselpage.

Thanks for the welcome. Yes, it does take some cranking to start. I have not noticed any engine lights on the dash. Will check for that and plug in the OBD2 code reader to see if there are any codes still stored. Also I will mention that when waiting for the glow plug light to turn off before starting it will go from being on steady to flashing on and off for 10-15 seconds before it finally shuts off.

[rigger]

So, plugged in the truck last night and started without a hitch this-morning. Mind you it didnt get much colder than +2-3C. Plugged in the code reader and came up with "656-Fuel Level Output Circuit Malfunction" that was saved in the computer. Any more thoughts?

[twaddle]

The code you found sounds like it may be a fuel tank level circuit or sensor related. One of the more knowledgable members may be able to chip in on this one. Is the code still present after you clear it?

When you have found that the engine would not increase in revs was the engine shaking like crazy and smoking as you descibed earlier or did it only shake after you were able to increase the engine revs?

There may be a couple of problems as Robyn suggested or you may have an ECU cold weather fault but I don't think the ambiant temperature is low enough for that.
The way you describe the black smoke and rough shaking engine I suspect some of the glow plugs are operating, possibly enough to get the engine fired up but enough glow plugs may not operating to hold the revs back untill they all start firing then it revs and you get this excess smoke as it clears. That's my theory, I might be wrong but if I was you I would check out the operation of the glow plugs. Are they all getting voltage, are any of them burnt out? If you have digital meter that reads volts and ohms you will be able to do some quick checks to varify if the glow plug system is working.

Do you know anyone that owns a 6.5 in your area, you might be able to try another electronic throttle pedal unit just to see if it makes any difference to the fault that you have?

Good luck and keep us posted if you find the fault.

Jim-T

[rigger]

Thanks Jim.

I never cleared the code which I also assume is unrelated. Aside from that, it shook on startup without touching the pedal. When I hit the pedal it shook more and smoked blue not black. I would think that's burnt fuel. The more that I post about this issue it is starting to seem like a lack of fuel @ startup.

[DmaxMaverick]

Not a lack of fuel (assuming your fuel is of adequate quality). If you are making smoke, you are getting plenty of fuel, no matter the color. White or blueish smoke at startup indicates cold combustion (glow plugs, low compression, etc.) and/or very retarded timing (black smoke is plenty of fuel and heat, but too little air). The stumbling and lack of throttle response indicates unstable fuel delivery. I suspect you are getting air in the system. If it's not going on the ground, it's draining back to the tank overnight. Bad injectors can cause poor, smoky starts, rough running, and air intrusion when cold (fuel siphons back to the tank, and air is drawn through the injectors). A bad fuel filler cap vent can also add to this problem, allowing greater tank vacuum as the fuel/air in the tank cools (replace the cap--they're cheap).

It could be a failed IP, but they'll usually throw a bunch of codes by the time it gets this bad. Perhaps several issues at the same time. If the fuel lift pump isn't pumping, or not providing sufficient volume, it can take a lot of running to get the system fully primed.

[phantom309]

Also I will mention that when waiting for the glow plug light to turn off before starting it will go from being on steady to flashing on and off for 10-15 seconds before it finally shuts off.
Maybe you are waiting too long??? you're supposed to crank it as soon as the light shuts off first time,. the flashing on and off afterwards is indicating its trying to keep the glow plugs hot during warm up,.

Nick

[DmaxMaverick]

Maybe you are waiting too long??? you're supposed to crank it as soon as the light shuts off first time,. the flashing on and off afterwards is indicating its trying to keep the glow plugs hot during warm up,.

Nick

Good point, and correct. A start attempt should begin as soon as the lamp goes out the first time. The "after glow" heats are intended for after the engine starts (you should be able to start before the after glows begin). The goal is to help minimize smoke and smooth idle combustion ASAP. If it fails to start on the first attempt, key-off for several seconds and start from scratch to restart the cycle. The first glow cycle creates the most heat. Subsequent cycles are "maintenance" heats.

[rigger]

Maybe you are waiting too long??? you're supposed to crank it as soon as the light shuts off first time,. the flashing on and off afterwards is indicating its trying to keep the glow plugs hot during warm up,.

Nick

Thank you Nick. Like I said, I'm a diesel newbie.


Not a lack of fuel (assuming your fuel is of adequate quality). If you are making smoke, you are getting plenty of fuel, no matter the color. White or blueish smoke at startup indicates cold combustion (glow plugs, low compression, etc.) and/or very retarded timing (black smoke is plenty of fuel and heat, but too little air). The stumbling and lack of throttle response indicates unstable fuel delivery. I suspect you are getting air in the system. If it's not going on the ground, it's draining back to the tank overnight. Bad injectors can cause poor, smoky starts, rough running, and air intrusion when cold (fuel siphons back to the tank, and air is drawn through the injectors). A bad fuel filler cap vent can also add to this problem, allowing greater tank vacuum as the fuel/air in the tank cools (replace the cap--they're cheap).

It could be a failed IP, but they'll usually throw a bunch of codes by the time it gets this bad. Perhaps several issues at the same time. If the fuel lift pump isn't pumping, or not providing sufficient volume, it can take a lot of running to get the system fully primed.

Great information. These are things I will definitely take into consideration over the next while as I start the engine properly from now on.
I'm just uneasy of buying a lemon after getting rid of a ZR2 that was nickle and diming me to death.

Again, thanks for all your replies. I really appreciate joining a new forum and having people respond to issues as you guys have.

[phantom309]

well its interesting what difference a few days makes,.

I Just bought a 94 3/4 4x4 6.5 ,. It does exactly the same as rigger mentioned!!
when its cold (-12c yesterday) it lights off weird,. very quiet,. lots of bluey/white smoke,. and ZERO throttle response,.you can wave the pedal around all you like and nada,. it just idles roughly,.and smelly,.
after a minute or so ( seems like an eternity) it will suddenly change its tune and clear up the smoke and run and sound like a 6.5 should,. It temprature/timing related,(definitely sounds, and smells retarded ) (no jokes about the new owner here,.:D.). because if it sits over nite in the shop,.(50deg or so,.) it only idles roughly and smelly for 15-20 secs) and then changes its tune and clatters away happily,.(almost as someone flipped a switch and added the right amount of timing,.) as long as its warm (above 100deg water temp) it starts just fine,.
Previous owner put a new IP on 85,000kms ago,.
The first thing i,m going to investigate is the temp sensor ,. unplug it etc,. (truck is not home here yet,. saturday i'll pick it up)
The check engine light stays on till it suddenly changes tune too,. so i'll get the code(s) out of it,. be interesting to see whats up,..

Nick

[enormiss]

I have the same issues, and like Rigger said plugging it in makes a huge difference.
I bought a timer and have it heat a few hours before use if it's cold.
It's my 3rd vehicle so doesn't see much use
When I get both the time and money it'll get a new set of glow plugs
If that doesn't work I'll move on to injectors.
The throttle issue is directly related to the cold, but I have no idea how or why.
I'm assuming it'll go away when the rough cold idle problem is cured.
That's my 2¢, keep in mind I'm just a lurker here and not a mechanic


I'm just uneasy of buying a lemon
Makes you feel better knowing others have the same issues HUH
I know it does for me :D

[phantom309]

rigger hope you don't mind me hijacking your thread?

got the truck home today,.drives really great,. smooth powerful happy 6.5,.
it hasn't sat long enough yet to really get cold (tomorrow morning i'll know) i'll pull the ect sesnor and see what happens,.
i pulled two codes out of it ,.
36 injector pulse width error response time long
74 transmission input speed circuit,.
I understand 36,. but can't get any info on how to fix,. diagnose,. repair,. code74,.
http://i39.photobucket.com/albums/e157/wtfuashols123/MVC-935F.jpg?t=1263084988

http://i39.photobucket.com/albums/e157/wtfuashols123/MVC-937F.jpg?t=1263085105

http://i39.photobucket.com/albums/e157/wtfuashols123/MVC-936F.jpg?t=1263085165

I paid $1000 cdn for this truck 326 kms with 3:42's ,. 4X4 works great
SLE trim package with full load,.

nick

[phantom309]

Its sunday,. the wind is blowing its -15c + the wind,. truck is facing into the wind,.
I unplugged the ect sensor,. waited,. it fired off but still the same problem,.rocking and rolling,. steady smoke,. i think it fires on 6 holes anyway,. and has 2 that lag some,. after nearly 3 mins i went back outside (too cold to sit in the truck in my bathrobe :D) i plugged the ect back in and i could hear the timing back off some,. i mashed the pedal a few times,. ... nothing ..but i could hear that the motor started to miss a little worse if i pressed the pedal down slowly and just a little, reminded me of an old carbed gas motor with a bad accelerator pump,
So,. next idea,. is to manually start the lift pump 30 secs or so before i start it and see if that makes any difference,.
Would the throttle pedal assembly have cold issues itself..?? any idea's ??
after it warmed up for about 4-5mins or so i hit the fuel pedal and all is well ,..maybe i could try my method of getting going in the cold mornings,. and pour a cup of coffee in the fuel tank??:D

thanks
nick

[DennisG01]

Wind chill will have no affect on inanimate objects. Don't worry about the wind chill - just go by the actual temperature. Wind chill will pull off heat faster, but an inanimate object will not actually drop below the actual temperature. The wind will just help an inanimate object get to the actual temp faster.

I'm going to say right up front that I have no where near the experience nor the knowledge of many people on this forum. But, I had an idea that I'll share... feel free to shoot it down:)

Knowing the throttles on these trucks are electronic - if a throttle position sensor was "on it's way out"... starting to go bad... couldn't the cold cause no throttle response? Meaning, couldn't the cold cause whatever contacts are inside the TPS to contract just enough so now do not make contact? Thereby, moving the throttle pedal is doing nothing?

Again, this is just a theory with very little actual knowledge to back it up...:rolleyes:

[DmaxMaverick]

No. If you have APP module (throttle pedal module) issues, the PCM will complain about it, temporary or not. The PCM monitors the input/output voltages of the APP and is very sensitive. Any variation of any of the 3 independent circuits will, at the very least, force the STS lamp (Service Throttle Soon), and/or the SES, either with accompanying DTC's.

You very likely have air in the system at startup, or the lift pump is not pumping (for whatever reason) when it should. If it starts and continues to run, the fuel/air is flowing and you have cylinder heat.

Troubleshooting this isn't difficult. You can verify fuel flow at startup (during your no-throttle episode) by opening the water drain valve (at the coolant crossover). If you get no fuel flow, the engine should stall. If you get fuel flow, the LP is pumping as it should. If the lift pump is fine (otherwise, deal with that), install a loop of clear hose (temporarily) at the injection pump return line output after a hot shutdown (when the truck will sit long enough for another cold start episode). Run the engine long enough to fully bleed this line, then shut down for the night. At your next startup, verify you still have the problem, and watch this line for air bubbles. If you get bubbles, air intrusion is the problem.

[DennisG01]

Thanks, DMax. And, thanks for being gentle, too! :)

[phantom309]

thanks for the replys,. here's some more updates,.
around 2pm this afternoon with the wind blowing and the temps down to
-18c it was plenty cold enough for a second try,.
I hot wired the lift pump from the fuse panel to the "G" position on the aldl connector,. the lift pump makes noise anyway,. works fine? (stupid me i should have opened the drain to see what sort of pressure it makes),.,. i let it run for a minute before attempting to start the truck,.made no difference same routine,. (truck does start everytime tho, even with the real slow idle it doesn't quit)
the ses light comes on when the throttle is depressed anymore than mebbe 1/8th travel,.no ses at idle,.(coasting along slowing down and the light goes out) if the throttle pedal is depressed to more than 3/4 (passing or speeding up a hill etc,. ) the ses light goes out,.????
I,ve just cleared the codes again,. tomorrow morning when its bidge cold i'll fire it and check the drain for flow etc,.
I shut the truck off 4 times this afternoon while doing errands etc,. and each time it fires just fine,. no hesitation or stumble, each time off was at least 10 mins and nearly an hour last time.
we'll see in the morning at 4:30 am ,..

Nick

[rustyk]

Froim the Department of Redundancy Department: Many issues (such as those I had a year ago with my all-mechanical 6.5L TD) can be traced to bad grounds.

Now isn't the most enjoyable time of year to be wallowing around under a truck, but connections can be throughly grubbed by the salt on the road in winter.

[enormiss]

its -15c it fired off but still the same problem,.rocking and rolling,. steady smoke,. i think it fires on 6 holes anyway,. and has 2 that lag some,. after nearly 3 mins i went back outside (too cold to sit in the truck in my bathrobe :D) i mashed the pedal a few times,. ... nothing ..but i could hear that the motor started to miss a little worse if i pressed the pedal down slowly and just a little, reminded me of an old carbed gas motor with a bad accelerator pump
thanks
nick

Guessing... Maybe it's not warm enough to burn the exta fuel being sent? I have no codes, but it behaves the same.
Do/Did you plug it in?

[phantom309]

Thanks for the replies and idea's,. grounds is an idea,. but the truck runs excellent after it warms a little,.
as i,ve stated it will shut off and restart fine even up to 4 hrs today (wife drove it)
Its been my experience that lousy grounds are lousy all the time till fixed,.
My other 94 6.5 dually will start with the 5 glow plugs that are working,.and you have immediate input on the throttle pedal with the five that are firing and you can increase the rpm and the others catch pretty quickly then,.
This truck as i,ve stated does NOTHING when you press the throttle pedal,. (till it warms up some)

This morning i fired it,. and while it was coughing belching and rock and rolling,.(at 4 am -22c plugged in overnite) i opened the "T" drain, into a plastic water bottle,. the fuel is a nice steady stream , no visible bubbles, and the truck doesn't quit even running as poorly as it does,..
I dunno whats next,..

Nick

[Splitrimz]

You are not alone, I have the same exact problem on my '94. I've had it a few years now. I chased it for awhile without success. I tried glow plugs, PMD, grounds and fuel filter. I also throw both advance and late codes, forgot what the numbers were, on startup. I have come to learn to live with it in cold weather, or plug it in.

[JohnC]

Did I miss something? What are the codes?

Do we have two trucks with similar symptoms here? I'm easily confused...

Basically, if you push the throttle and nothing happens, either there will be codes describing why the power output doesn't match the throttle input, or, something that's not being monitored is the problem, i.e. fuel available to the injection pump.

When was the last time the fuel filter was changed? Is the fuel gelling? Once the fuel heater kicks in...

[phantom309]

the codes are 36 and 74

not cold enough to gel fuel,.

everybody keeps going to the poor fuel supply,. but as i wrote before i can open the "T" drain while it is rocking and rolling and running poorly,. and the motor does not quit,. which leads me to believe it has enough fuel delivery,.
It ran badly for nearly 10 mins this morning with zero throttle available, 10 mins is a lifetime to watch the truck belching coughing idling slowly and roughly,. but it never quits,. throttle pedal input does nothing,. after "a while" it just catches and runs properly,.

I was told today that the stepper motor? is probably worn out,.??


Nick

[JohnC]

the codes are 36 and 74

36 points to an internal pump problem (fuel solenoid). This is may be the cause. If the PCM can't control the fuel solenoid it won't allow any throttle above idle. Try a double dose of a good fuel conditioner. 74 is unrelated.


not cold enough to gel fuel,.

How cold is not cold enough? Depends on the fuel and the temperature.


i can open the "T" drain while it is rocking and rolling and running poorly,. and the motor does not quit,. which leads me to believe it has enough fuel delivery,.

The T drain is before the filter.


I was told today that the stepper motor? is probably worn out,.??

Unlikely. The stepper motor would set a (different) code.

[oldmechanic]

I have a 96 that does the same thing but with no codes. replaced pmd,injectors,filters & checked every thing else & it still won't throttle below
40 degrees
OM:confused:

[Robyn]

As was mentioned, the DTC 36 points to internal issues with the IP

Specifically its "Response time Long" this is in reference to the fuel solenoid that controls the fuel flow to the engine.

The ECM is seeing a time number that it does not like and is keeping the thing shut to an idle until the numbers are correct.

My bet is that the Fuel Solenoid is sticky and once thing warm up some this issue resolves some.

As John Mentioned, some fuel conditioner might help some.

Even some tranny fluid (ATF) can help clean out deposits that have formed on the parts.

If the IP is a High miler 100K or more I would seriously consider getting the pumps off and having it gone through by a qualified Standyne shop.

Sadly once issues with these pumps start they generally don't heal themselves.

Using the fuel conditioner or ?? can help diagnose the problem though.

What would really help is to get the truck on a real time scanner and see what is happening while the thing is cold.
Watching the data display and then pressing the throttle would give some very good insight into what is going on.


Good luck


Robyn

[phantom309]

36 points to an internal pump problem (fuel solenoid). This is may be the cause. If the PCM can't control the fuel solenoid it won't allow any throttle above idle. Try a double dose of a good fuel conditioner. 74 is unrelated.

Thanks for the fuel solenoid suggestion john,. i think its definitely something like that,.




How cold is not cold enough? Depends on the fuel and the temperature.

I agree but 20deg F shouldn't be a problem,. i,m sure we only have what you call number #1 diesel here in canada,.My series 60 runs just fine, so does the other 6.5 .



[quote=JohnC]
The T drain is before the filter.

exactly,. and she runs great after the first cold start.




Unlikely. The stepper motor would set a (different) code. Ok thankyou i appreciate that.

Information is a funny commodity,.. some folks will offer it free to help you out,. other folks misuse it and charge you money and hide the truth.
Thankyou all for all the help,..
I drove the truck 540kms today,. really is a great old girl,. the 3:42's are perfect combo for this motor
this tankful was 863 kms to the 113litres,. roughly 21+ mpg,. thats good for a 4X4 truck ,. some around town,. some hiway,.keeping it at 110kmh or 68-9mph.

If i was to pour hot water over the pump in the morning,. i wonder if it would "come to life" much quicker,.

nick

[enormiss]

Do we have two trucks with similar symptoms here?


There's a few in this post.
Any relation to the fuel solenoid and the smoke/stumble?
The issues seem directly related in that when the smoke goes away the throttle comes back.

[Splitrimz]

Taking a suggestion from Robyn, I poured a bottle of STP Diesel cleaner in the tank. It started much better this morning, just less than a second of hesitation before the throttle kicked in. It is exactly 32 degrees this morning. I'm anxious to see what happens when the temperature dips again here in CO.

[phantom309]

I bought a bottle of the standyne performance additive put in today,.
we'll see what happens,.
I bought a couple of double double tims for the guys at the pump shop and learned a great deal today,..
there is also a
popett valve in the pump thats supposed to keep pressure in the rotor head,.and this valve can become worn/sticky,.and as Robyn mentioned the fuel solenoid too can "hang" up when its cold,.. first thing they recommended was to add the standyne additive,. they said it really helps a lot of older 6.5's with miles on them as it cleans the varnish/bacteria crap off stuff and makes things work better,.and improves cold starting they said they see alot of this kind of problem and always recommend the additive first. Which i thought was pretty decent of them instead of trying to sell a pump rebuild,..
I told them i was nervous about bringing a pump to any injection shop as i couldn't afford a 2nd mortgage to pay for it,. they told me they,d be able to do what was necessary and clean it all up, and bench test and calibrate it for around $300cdn (plus another couple of coffee's i suspect,)
So right now i'll let the additive have a chance,.and we'll see as time goes on,.
To be continued......

Nick

[Splitrimz]

Follow Up. It was a very frosty 21 degrees at 5:00AM this morning. The truck fired off and throttle response was instantaneous. Never would have thought that the crappy fuel would have caused the no throttle response, but seeing is believing.
I'm going to find a local Standyne distributor and try their stuff.

[phantom309]

short update,. i,ve driven the truck about 200kms since i added the standyne fuell additive,. it is starting to run properly quicker,. still more than 2-3mins or so at 20f.

Robyn is the STP diesel cleaner stronger than the standyne additive?

under hard acceleration the motor bucks sometimes,. maybe the infamous "fishbite"? but it never stalls,. and always starts,.so when i get time, i'll change the fuel filter etc,..
I,m liking this old truck tho,.driving it easy is getting better than 20mpg still,..

Nick