View Full Version : 6.5 Turbo wastegate doesnt operate
I have a 95 Chevy 2500 with a 6.5 and lately the wastegate has not been functioning. I replaced the servo on the right side of the intake that the vacum line hooks to and that didnt fix it. I then unplugged the line and used a small line to stick in each one of the tubes and cut a small whole in this piecer line and that makes the wastgate operate at about half open but I would like to solve this problem, please help,
Thanks, Seth
Update to this. I just purchased this vehicle yesterday and I had a friend hook it up to a generic scan tool and it shows nothing wrong with the wastegate. This is when I plugged the vacum line and put a hose in it to keep the wastegate about halfway open. The previous owner said that he had just replaced the actuator\servo that controls the wastegate on the right side of the intake manifold. When the vacum line is plugged in it runs ok till you give it some throotle and it puffs black smoke. Any ideas?
Check vacuum at idle
Pump = 25"
WG = ~15"
WG should be closed at idle, difficult to open
Easy to open\close when engine off
Besides the Wastegate Solenoid, check the Wastegate Switch (follow vacuum lines to drivers side atop intake manifold. Small black rectangular switch with Vacuum line in, vacuum line out) as well as vacuum lines, fittings and Vacuum Pump. I had the same problem. Intermittent boost was fixed by changing the Wastegate Switch and really improved when I replaced the Vacuum Pump. Remember, the Wastegate fails open so the engine does not overboost if a failure occurs. This is why you will see black smoke out the tailpipe. Doug
i checked the vacum and it is good. I can move the wastegate lever freely when it is idleing. So it must be the wastegate switch?
DmaxMaverick
11-24-2006, 23:03
Possibly. Reverse your vacuum lines to be sure they aren't backwards. Also check for voltage at the valve. You should also bypass the valve (only for a test) to ensure the diaphram isn't blown. Not common, but it happens.
well I bypassed the valve and it doesnt smoke like it does when it is connected to the valve. The vacumm line end has this rubber guide so you dont put the line on backwards and it wont let you put it any other way. What next?
DmaxMaverick
11-25-2006, 01:26
With the engine running, check for voltage at the valve. If you have voltage, replace the valve and you should be good to go. If no voltage, it should have stored a code. The circuit is monitored by the PCM.
what type of voltage should I have?
when the engine is off the shaft arm is harder to move when the engine is running? Does this mean anything?
DmaxMaverick
11-27-2006, 17:33
The voltage may be intermittent (pulses), but should light a test light. If you get any voltage, it may fluctuate, but it will be there. A DVOM may bounce around, and an analog meter may flicker. Either of these can be averaged, or buffered out, but you only need to confirm voltage. Try no to overcomplicate it.
You should have 26" of vacuum at the pump and it should be steady and not fluctuating.
The reading should be the same at the waste gate servo at the turbo.
Its should be shut hard at idle and open only under control of the computer when max boost is achieved.
If the vacuum gauge is wiggling the pump is bad. The waste gate solenoid (top rear of drivers side valve cover) will usually set a code if its faulty or not working right. Check the plastic tubes that run from the pump to the solenoid and then to the servo to make sure they are ok. They have a habit or cracking.
You can get a new set from the GM store.
If you have to you can run vacuum hose to substitute.
Mark Rinker
11-28-2006, 11:57
$100 fix to your woes...
http://www.thedieselpageforums.com/tdpforum/showthread.php?t=25351
Ok I tested the switch today. I installed a new one OEM from the dealership. I tested voltage at the plug and it lit up so there is voltage. I then checked the vacumm at the wastegate switch at a idle. I was sweeping from 5 to 15. I then reved the motor to 1000rpm at it was steady at 15" of vacuum. I then tested it at the pump and it swept from 15 to 25. I also reved the motor to 1000rpm at the gauge was steady at 25" What next.
DmaxMaverick
11-29-2006, 23:03
Your vacuum numbers look good, and normal. The PCM modulates/pulses the voltage to the switch, which is why you only get 5-15 inches downstream. 15-25 inches at the pump also sounds normal, being 15 at idle, and 25 at higher RPMs.
What's next?
Well, if the new valve fixed the issue, nothing. If not, you have a problem with the wastegate actuator or the wastegate itself. With engine idling, the wastegate rod should be hard to move. Engine off, it should be easy.
now this vacumm at the wategate switch was the line comming from the vacuum pump. It was not connected to the switch at the time. This was a direct reading from the pump at the end of the vacuum line connection that plugs into the switch. With the line plugged into the switch I then read the reading over at the wastegate at the end of that hose and it read "0" The new wastegate switch did not fix my problem. But could this mean that my vacuum lines that go from the pump to the wastegate switch then to the wastegate its self are bad?
DmaxMaverick
11-29-2006, 23:15
Oh. OK.
Yes. You have a leak between the pump and switch somewhere. Not uncommon. Just trace the line from one end or the other. If you don't find anything obvious, you can use shop air to charge the line. Just plug the other end.
if the lines are not bad could it be the wategate actuator?
DmaxMaverick
11-29-2006, 23:51
Yes, but not all that is wrong. Your test was upstream of the switch, which takes the actuator out of the test. If you are losing vacuum, you have to look at only the parts included in the test. Don't rule out the rubber connectors. Check them for cracks and chunked-off pieces. Get yourself some length of regular vacuum tubing and bypass the each line and retest.
I think you are complicating it. It is what it is. You have a leak along a section of tubing. That's all. The key is to find that section, and repair or replace it. Hard tubing can either be replaced, or spliced (once the broken part is cut out) with rubber vacuum hose. Ideally, the entire line should be replaced, as the condition of the rest of the line is no better than what you are repairing. Want it simple? Just replace all the lines. Done.
Well I will give that a try. If I get it up and working I have one question. How much smoke should I be getting? If I WOT it how much smoke should I get? Thanks and I will let you know tomorrow.
DmaxMaverick
11-30-2006, 00:45
Other than a little puff right when you mash it, there should be almost none. You may see some during night in the headlights of followers, but other than that, you shouldn't see any. If you do, the boost is too low, or fuel is too high for the current load. It is also a pretty good indicator of higher EGT's.
Which side does each hose go on. I have the orange tubr from the vacuum closest to the front and then I ran a single tube from the wastegate actuator to the solenoid and then tried testing PSI and I got the same result, "0" I thought I would ask which hose goes where. Maybe it has been wrong since I have bought it.
Well I replaced the hose harness. I still get smoke and the vacumm psi is at 0 at the wastegate. I finally decided to read the codes because my SES light comes on and off. The code is a 78. Wastegate Solenoid Fault. I have replaced the solenoid less than 2 weeks ago. What could be causeing this?
DmaxMaverick
12-15-2006, 03:04
It's gotta be something stupid-simple.
You've confirmed:
Vacuum to the valve.
Voltage to the valve.
No vacuum after the valve? Or was it just no vacuum at the actuator?
Have you confirmed the vacuum tubing is not blocked anywhere? Tried blowing air through them? Some debris could have been sucked in from the actuator tubing. It is vacuum, afterall. Perhaps the dump is stuck open.
There's not much left. The wastegate solenoid could have failed. I know you just replaced it, but if you have vacuum before and not after, and it is receiving voltage, it should work. If the vacuum isn't passing the valve, and the solenoid is getting juice, it has to be the valve.
If not the vacuum system, it could be the ECM, but I doubt it since you are seeing voltage to the solenoid.
You've got me scratching my head here. I think someone else needs to jump in with a fresh idea. I've looked at mine, and pored over the manual and I'm out of ideas.
moondoggie
12-15-2006, 12:48
Good Day!
In re-reading all these posts, I think you might best invest your time by starting over; there is some ambiguity in what has/hasn't been done. What I propose here really won
moondoggie
12-15-2006, 12:48
(continued from previous post)
If all the above test OK, your boost problem is 1) intermittent or 2) caused by the Wastegate Actuator or the Wastegate itself.
Intermittent boost is best monitored by, even temporarily, monitoring boost. I drilled & tapped the intake snorkel on both my 95
Couple of things:
Power to the wastegate solenoid is only part of the issue. Ground is supplied by the PCM and is pulsed. The duty cycle determines the vacuum provided to the wastegate actuator. A dwell meter will tell you if this is working. Also, wastegate solenoid duty cycle is a scanned value.
The vacuum pump must be connected to the port on the solenoid with the restrictor in the fitting. The actuator is connected to the unrestricted port. It won't eork the other way around.
Vacuum at the actuator at idle should be about 15 inches. IIRC, 14" is the minimum.
If the PCM doesn't like the manfold pressure it will stop providing ground to the solenoid, which removes all vacuum from the actuator, and set DTC 78.
I had a code 78 before I replaced the harness. The harness is hooked up correctly. I have checked the vacuum at the solenoid and is sweeps from 10 to 20 at an idle and 15 at 1000rpm.
Well I got my boost working. I guess you could say I took the easy way out. The problem was something electrical and I didnt want to chase it through the loom. I had power but the yellow wire that goes to the ecm had a short somewhere. I ended up buying a Turbo Master from Heath Diesel. It works great. Now I just need gauges. Thanks for evryones help!
Well I got my boost working. I guess you could say I took the easy way out. The problem was something electrical and I didnt want to chase it through the loom. I had power but the yellow wire that goes to the ecm had a short somewhere. I ended up buying a Turbo Master from Heath Diesel. It works great. Now I just need gauges. Thanks for evryones help!
Don't blame ya for going with the Turbo-Master. My 95 had the same issue and I went through all that could be done short of a PCM change.
Ran with waste gate wired shut and used the boost gage for foot feed.
Times have been good with the TURBO MASTER.
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