6.5 RPM's and throttle erratic

[jen610]

So I was wondering if I could get any advise on my truck. I have a 1994 Chevy k3500 that has the 6.5TD in it. I am having an issue with my RPM's and throttle being erratic. While at an idle RPM's are jumping between 1000 and 1200. While on cruse control RPM's are jumping between 2000 and 2500 RPM's. the throttle is VERY touchy and will not maintain constant speed, just wants to keep accelerating. Also at an idle or any type of acceleration I am blowing a TON of black smoke.
I'm getting codes 35,36, & 78
Now what I've done thus far!
Swapped PMD with a known good one
Swapped TPS sensor only with a spare
Took it to GM said it sounded like the IP because the truck itself was in time.
So I bought a tested good used one put it on last night still no change.
Swapped with another PMD that was going bad but would run the truck fine just shutdown after heated up, and still no change.
I even went as far as installing my 4" exhaust that I had bought a week prior to this starting, replaced the fuel tank because the old was corroded on the inside, also replaced the sending unit because my gauge did not work before hand. I replaced with clean fuel. No change...
Fuel filter and air filter are clean.
I'm completely lost I have no clue what this problem might be. Any input would be greatly appreciated!

P.S. at the beginning of the year I installed new marine injectors and glow plugs, placed the PMD on a heat sink and outside of engine compartment (inside of bumper). The lift pump was replaced 5 yrs ago and put on a switch to turn it on, and I can hear it running and fuel comes out of pitcock just unsure of psi

:mad2::WTF::???:

 

[NVW]

It sounds like an IP, code 78 is a boost code. excess fuelling may cause the boost code due to over boost.

 

[jen610]

Possible that 2 IP's will cause the same exact problem? It was saposably tested good but they said that they do have bad ones they sell as core, could this one of been bad and thrown in the good pile is what I'm thinking.

 

[WarWagon]

Put a clear line on the IP and see if you have air in the fuel. Also what is your fuel pressure?
Checked a fuel sample for water or gasoline?
Have you cleaned the grounds?

Black smoke and a boost code is a separate issue. This is a lack of boost due to the wastegate being open from bad vac pump, leak in the lines, bad solenoid, etc.

 

[jen610]

I don't have a way to check the fuel pressure. No air in the system. And how do you take a fuel sample. My bro has a diesel ATV and he had put some fuel out of my truck in it just a little bit ago to go play about half And half is my fuel to his fuel. His ATV is now stalling and wants to die at an idle. Exact opposite of my truck. But could affect the systems differently. I have the intake off and some of the injection lines busted free. I was in the mist of takin the pump off and having the company send me another pump. These r used pumps that are tested good with an obd tester. Or I could put everything back together and drain fuel and try all new fresh fuel. OR could send this unit back have them refund me the $150 i paid for it and put it toward a rebuilt pump from DCP.
I did before hand drain all the fuel I could and put in 10 gal of good fuel in it, may of been 3-5 gal of old left that I couldn't get out, added a little diesel 911. Truck ran the same. Dained about 7 gal out after making a trip to GM service and put new tank and sending unit on, put this fuel back in the new tank, really debated doing this but I didn't have any money for fuel since I had bought the used IP. Needless to say the fuel that MAY of been bad is diluted about 1/3 it to 2/3's good. Would it still run bad ?

 

[1tondaully]

jen 610 I've got a 1996 chevy 1 ton dually w/ 6.5l td w/ the same problem & took it to the Chevy dealer & they put it on there big computer & did everything under the sun, shut down injectors, one by one, & then put the lap top on it & went down the road w/ it & said everything was good the injectors had 1500- 1800 lbs. to the injectors checked the app, ip, turbo boost, all the sensors & there all good I'm @ a lose & every diesel mechanic there @ a lose w/ the truck myself I'm replacing all sensors, taking the turbo off & taking it to a buddie of mine that works w/ turbos let him check it out, pulling the injection pump off & let him check it out to I know it's going to be expensive but I've got no choice but to do it I get 24-29 mpg on this truck I don't like a lot of black smoke because of the egt's & yes it will start to melt parts down so becareful, I did a lot of pulling w/ the truck & there's alittle of smoke the ip was turned up alittle bit & 2.5'' exhaust & that's it I don't even move the truck until I get it fixed because I don't need anymore to repair so I'm @ a lose good luck

 

[jen610]

The vac pump was replaced around a year ago. Lines replaced 2 yrs ago and still look good. Solenoid I don't know honestly. I ordered one but didn't pick it up because I read that it may throw a false code do to the pulse width timing. Which I have the 2 codes for it, time to long and time to short

 

[haggus]

Code 78 IIRC was the boost sensor it's a black connector with a green dot on the drivers side of the upper intake. I had erratic throttle response with that one it would stumble and give me a CEL. 35.00 part from the dealer if yours is bad a simple way to tell is to take the electrical connector off and shake the sensor. There is a little brass ball inside if it doesn't move your sensor needs replacement.

I would replace it anyway just to eliminate it.

The turbo on the 6.5 L EFI engine has a wastegate actuator that is controlled by vacuum. The wastegate actuator on the 94-2000 turbo does not have a spring, when no vacuum is applied the wastegate will “flop” back and forth. If the wastegate actuator holds a vacuum and it moves freely back and forth then there is nothing wrong with the wastegate actuator. A turbo boost problem and DTC78 (P0236) is normally caused by low vacuum (need 20 inches HG) or a bad wastegate control solenoid.
To inspect the turbo, remove the inlet hose from the compressor inlet and make sure the turbo spins freely and that the compressor wheel does not rub on the housing when pushed to the side. Some side play is normal, because the bearings “float” on oil from the engine when the oil pressure is up.
The turbo pulls crankcase fumes from the engine through the CDR valve. It is normal for the turbo to discharge oil from the compressor housing. You have to determine if you have more oil coming out versus going into the compressor housing. A plugged air filter or bad CDR valve can cause excessive oil to be pulled out of the engine and discharged from the turbo back into the intake. If the silicone hose connecting the compressor discharge is not sealed with a minor amount of silicone sealant than the hose connection will weep oil past the hose.


DTC35 (P1216) fuel solenoid response time too short, less than 1.2 ms or less than .75ms on later years.

DTC36 (P1217) fuel solenoid response time too long, more that 2.5 ms, can be caused by a weak fuel control solenoid.


Multiple codes can initiate from a single fault get the wastegate control solenoid replaced then check for codes.

 

[jen610]

Well I already got the used pump off. Sending it back to the northeast diesel core in PA under the 30day warranty. Having them send me 1 more pump. Goin to completely drain the fuel system, replace with 100% good fuel and see if it works. If not going to go to a local well known junk yard and barrow parts off their not for parts trucks see if there is any change. Probably barrow TPS pedal and sensor, and the waste gate solenoid. After that ...... We will see!:WTF:

 

[matuva]

You have a 5068 IP right? Did you swap with a 5068 or a 5521? A 5068 can only be replaced with a 5068. If you swap to a 5521, you have to swap to a compatible ECM too.


Also, we had a truck doing pretty similar thing here, and it ended being the ECM which was shot...

 

[greenmeanh1]

We see these codes in the Hummer world as 1216 1217. Couple of thoughts. The dealer when seeing these will try to sell you a new IP. What is happening is the poppet on the rear of the injection pump or fuel solenoid is likely sticking due to the internals being a bit crudded up or corroded causing the poppet to move slowly or not at all in some cases. This also puts a lot of stress on the PMD that needs to make amps to trigger the poppet. I would suggest a lubricity test by way of putting in some additive to clear the pump. Best thing i can think of would be a 2 stage flush.
Step1 With the tank near empty (10 gallons) prepare a 50/50 mixture of dexron 3 and B100. You want about 2 quarts total. Add 250 ML of acetone and make sure it is totaly mixed. Start the truck and let it warm up and then add the contents into the tank. Drive the truck right away for 50-80 miles to let the mixture run through. If its working you will know within a few miles as things start to clear up.
Step 2 run the same mixture again without the acetone and change your fuel filter after you are done.
Report the results of you findings here so others can benifit.
Check the boost sensor and boost switch for the other issue. You can check the actuator as well. Pull it all the way out and start the truck. It should suck all the way back in. If not you either have no vacuum or the actuator is stuck (uncommon) Brand new vac pumps have been known to go out brand new. Check for 20hg vacuum and replace the line or pump if vac is low depending which is the culprit. Some guys just leave rags and tools in the intake and wonder why they have black smoke so in that regard make sure the airway is clear of any obstructions.
If you don't have a scanner to clear codes you can always just disconnect the battery for a minute or so and let the computer reset. You will lose any stored data, freeze frames etc.

 

[ak diesel driver]

parts are expensive and gauges are cheap. my2c

 

[JMJNet]

You have a 5068 IP right? Did you swap with a 5068 or a 5521? A 5068 can only be replaced with a 5068. If you swap to a 5521, you have to swap to a compatible ECM too.


Also, we had a truck doing pretty similar thing here, and it ended being the ECM which was shot...

Make sure the IP is the same problem is you probably already sent in the old one.

Also, I am not sure if an IP can be tested with obd tester?
Somebody is pulling your leg if that is the case.

I would not worry about the turbo boost code yet.

 

[bison]

I don't have a way to check the fuel pressure. No air in the system. And how do you take a fuel sample. My bro has a diesel ATV and he had put some fuel out of my truck in it just a little bit ago to go play about half And half is my fuel to his fuel. His ATV is now stalling and wants to die at an idle. Exact opposite of my truck. But could affect the systems differently. I have the intake off and some of the injection lines busted free. I was in the mist of takin the pump off and having the company send me another pump. These r used pumps that are tested good with an obd tester. Or I could put everything back together and drain fuel and try all new fresh fuel. OR could send this unit back have them refund me the $150 i paid for it and put it toward a rebuilt pump from DCP.
I did before hand drain all the fuel I could and put in 10 gal of good fuel in it, may of been 3-5 gal of old left that I couldn't get out, added a little diesel 911. Truck ran the same. Dained about 7 gal out after making a trip to GM service and put new tank and sending unit on, put this fuel back in the new tank, really debated doing this but I didn't have any money for fuel since I had bought the used IP. Needless to say the fuel that MAY of been bad is diluted about 1/3 it to 2/3's good. Would it still run bad ?

I doubt you can buy a tested IP for $150,. My dieselshop want $300 just to put ot on the test bank.

 

[WarWagon]

I don't have a way to check the fuel pressure. No air in the system. And how do you take a fuel sample. My bro has a diesel ATV and he had put some fuel out of my truck in it just a little bit ago to go play about half And half is my fuel to his fuel. His ATV is now stalling and wants to die at an idle. Exact opposite of my truck. But could affect the systems differently.

Now you have two systems that have possibly bad fuel.

I have the intake off and some of the injection lines busted free. I was in the mist of takin the pump off and having the company send me another pump. These r used pumps that are tested good with an obd tester. Or I could put everything back together and drain fuel and try all new fresh fuel. OR could send this unit back have them refund me the $150 i paid for it and put it toward a rebuilt pump from DCP.

STOP!!! You need to know what is wrong first! Throwing parts at it is expensive, may not solve the problem, and could ruin (used, replacement, take off, rebuilt, new) parts quick!

I did before hand drain all the fuel I could and put in 10 gal of good fuel in it, may of been 3-5 gal of old left that I couldn't get out, added a little diesel 911. Truck ran the same. Dained about 7 gal out after making a trip to GM service and put new tank and sending unit on, put this fuel back in the new tank, really debated doing this but I didn't have any money for fuel since I had bought the used IP. Needless to say the fuel that MAY of been bad is diluted about 1/3 it to 2/3's good. Would it still run bad?

Maybe. Depends on what is going on. Something ruined the fuel level sensor or it died of old age. I have seen what used to be fuel ruin fuel level sensors.

You have got so many problems going on here and you don't know where to start. :sick:

First: drain some fuel from the fuel filter manager via the water drain into a clear container. Let it settle for a few min and see if there is a layer of water on the bottom. Does it smell like gasoline? Does it look like a clear yellow/green? Quit mixing unknown fuel with good fuel - you just make more waste fuel. Possible you have gasoline in the fuel, water in fuel, or bugs growing in the fuel. Any one of these bad things can trash your IP and injectors. With the ATV going T.U. your fuel is suspect! Finding bad fuel means all of it needs to be disposed of. Forcing it through the engine can cause severe (and expensive) injection system damage. To get rid of bad fuel you will have to drop the fuel tank esp. if it is water.

When was the fuel filter changed last? (I didn't say change it.)

Did the dealer check the fuel or make sure the tank sock was ok (not plugged) when they changed the fuel level sensor?

You know you don't have air in the system how? Even a little air from a bad o ring, pinhole leak, plugged tank sock, etc. will cause you extreme issues. (Including these codes.) Test for and eliminate air is the #1 test in the GM manual for diesels.

In addition to testing for air via a clear return line, you need to know if the lift pump is working and providing some pressure to the IP. You could have a kinked hose or plugged tank sock causing diesel to boil in the fuel line becoming a source of 'air'. It is possible to vapor lock a diesel... A fuel pressure gauge is a must have for these engines. A temporary one you put on the water drain and test fuel pressure at each oil change will do the job. These engines move a lot of fuel and return it to the tank so the fuel coming out the drain valve may not be enough due to partially plugged screens or bad valves in a lift pump etc.

The above items should be addressed before you throw parts at it or swap another IP out.

 

[greenmeanh1]

At one time someone from GM who was an ETA guy mentioned that the majority of IP's removed and sent back for testing were fine. Of course that was years ago. Now Humberview Trucks cracks the pumps when they take them off with a sledge hammer so they can never be rebuilt or even tested!! Once the ceramic rollers were introduced there were very few problems with these pumps other than contamination issues.
I forgot to mention in my last post that fixing the lower number codes can also help to clear higher number codes. This could be one of those cases.
As War Wagon mentioned the truck is a bit of a mess and needs a serious maintainence program to bring it back.

 

[dangerousdave]

http://www.thetruckstop.us/forum/sh...ise-needed-have-four-codes-check-engine-light

http://www.thetruckstop.us/forum/showthread.php?24294-DTC-36-cause-and-effect-(mine

http://www.thetruckstop.us/forum/sh...ection-pulse-width-error-(response-time-long)

I know my IP is long in tooth (OLD), but I want to make it last. I've tried 2 stroke, Optilube, and ND-W30 (it's what works best for me).
I add 1 qt of ND-30 with each 20 gallons approximately, to replace the sulfur lube missing from ULSD.
I add +/- 6 oz of Diesel Kleen gray bottle at every fill up to keep the injectors happy.

IMHO, removing the Vac. pump and adding a TurboMaster is a power, reliability, and economy improvement. Our '94s are electronic freaks, and these things I mentioned have eliminated those codes from my travels.

 

[jen610]

The pump was a 5288 pump and swapped with a 5288 pump. Yes I sent the IP back because I was told that even bench testing a pump won't show if its failing (per Heath diesel). Fuel will be drained completly Wednesday. I only mixed it because I did not realize there was much if any left in the tank, and wasnt even sure the fuel was bad at the time. Other wise I wouldn't of put known good fuel in it. I run diesel Kleen in every tank fill up. I am sure that my pump was going bad. For the last year, every so often at an idle in park or drive my RPM's would slightly surge, nothing like it is now. Been trying to save up the money to buy a new one from DCP but hadn't gotten the chance to. Also soon as I can I will buy a fuel pressure tester to have on hand. When I open the valve on top of the filter cap there is only fuel that comes out no traces of air is the only way I knew to check for air in the system. We have checked all the lines front to back for leaks and kinks. I bought an IP only because the GM service tech said that was the problem. And no he did not check the fuel, he only ran the codes did not want to get into the motor. Didn't charge me that day, guess it was only his assumption on the problem.

 

[ak diesel driver]

go to the hardware store and buy a piece of clear plastic tubing (1/4") and put it on the return line coming out of the IP (only need a few inches). start and watch for air bubbles, it doesn't take much air to mess up the system. get a cheapee pressure/vac guage from auto parts store, HF, etc. and about 6' of tubing so you can tape it to the windshield wiper while driving, hook it to the water drain and open the petcock. total investment should be less the $30 and will tell you more about your fuel system than any scanner ever will.

 

[tanman_2006]

The pump was a 5288 pump and swapped with a 5288 pump. Yes I sent the IP back because I was told that even bench testing a pump won't show if its failing (per Heath diesel). Fuel will be drained completly Wednesday. I only mixed it because I did not realize there was much if any left in the tank, and wasnt even sure the fuel was bad at the time. Other wise I wouldn't of put known good fuel in it. I run diesel Kleen in every tank fill up. I am sure that my pump was going bad. For the last year, every so often at an idle in park or drive my RPM's would slightly surge, nothing like it is now. Been trying to save up the money to buy a new one from DCP but hadn't gotten the chance to. Also soon as I can I will buy a fuel pressure tester to have on hand. When I open the valve on top of the filter cap there is only fuel that comes out no traces of air is the only way I knew to check for air in the system. We have checked all the lines front to back for leaks and kinks. I bought an IP only because the GM service tech said that was the problem. And no he did not check the fuel, he only ran the codes did not want to get into the motor. Didn't charge me that day, guess it was only his assumption on the problem.

GM blames ALL problems with the 6.5L's on the IP or head gaskets