Please Help - My 95 6.5 TD has been giving me fits lately. At first it wouldn't start at all - I changed the fuel filter and everything appeared to be alright for a couple of weeks, then it started having problems again - ran real rough, emitted black smoke when I accelerated, and started real rough at times,, but not always. I disconnected the fitting on the discharge side of the fuel lift pump and tested it. No fuel came out when turning it over - NONE. So I replaced the fuel lift pump and it seemed to run alright again for about a week or two. Now it's not having any problem starting however it runs rough. I have a plume of black smoke behind me whenever I drive it, it seems to be worse as engine temp heats up and is definetly worse when I get on the accelerator. It gives off a very rich fuel smell from the exhaust. I also hear a chattering noise, not when I'm on the gas hard or off the gas completely; I only hear the chattering when I'm barely on the accelerator, like when you are trying to maintain a certain speed. A mechanic friend of mine told me he was almost certain that the problem was my injector pump, but I'm not sure if that is it. I was thinking more along the lines of the waste gate... The chattering really has me worried, whatever is causing it can't be good. Hopefully I haven't forgot to include any key parts to my problem. I'm sure the answer to my question is already posted somewhere, but I didn't read anything that sounded exactly like my problem. thanks in advance for any help anyone can provide. Edited by: Mongoose

goose,

Your right to think waste gate. Engine running unplug the
vacuum line at the turbo and check for a steady vacuum pull.
Trace the vacuum line from the turbo back to the waste gate solenoid and
unplug the line from the vacuum pump. It should pull much harder vacuum.

Have you bypassed your OPS with a relay? It may be necessary to wire a 30 amp relay
switched by a working OPS to carry the lift pump. This will keep the 4amp draw of the lift pump from
burning the 1amp rated contacts of the OPS.



after a tank of bad fuel and
When the optical sensor is not reading (sensor failed) the engine will run with alot of clatter, no power.Edited by: quantum mechanic

Should I hook up a vacuum gage??? Do you know approximately how many inches of vacuum it should be pulling? I'm not familiar with the OPS at all, I've seen a couple posts referring to it, but am rather clueless. Do you have any good post you can direct me to. Thanks again for your help.

Chattering is probably wastegate trying to hold exhaust pressure.


Vacuum should be ~25" at pump, ~15" at wastegate at idle.


Check vacuum line for leaks, from wastegate to solenoid to pump.


Wastegate solenoid may be problem, but check lines and measure vacuum, first.


Also check air filter.

OPS is the oil pressure switch. It switches on when there is sufficient pressure powering the lift pump.
When you first turn the key and hear the lift pump it is the fuel pump relay being switched by the pcm to pressure-up
The OPS is behind the fuel filter and you need a special wrench to turn it.
With the truck running turn the drain "T" off the fuel filter. you should see fuel come out,
or you lift pump isn't being powered.Edited by: quantum mechanic

If you have it in park and idling, does it make the clattering noise? Also, while in park and idling, try turning the AC on and off a few times and/or turn the wheels hard to the end and see if it makes a difference. If so, it is pribably a bad crankshaft pulley.

Thanks for all the replies. Whatnot - It doesn't clatter when in park, idling, only when maintaining speed, which also somewhat corresponds with when the majority of the bad black smoking begins. So let me get this straight if the OPS is bad, the lift pump won't receive power or is it the other way around, that you need to make up the lift pump circuit first in order for the OPS to switch on... Pardon my confusion, I'm just a rookie... I'm going to troubleshoot the vacuum readings tomorrow and go from there. Thanks again for the help.

Is the clatter kind of like the exhaust just getting louder? If so, then it is probably the wastgate. The turbo muffles the sound a quite a bit and you can hear the difference when the wastegate opens.


Did you ever get a service engine soon light on? If so, what are the codes?

The OPS switches on when there's oil pressure, and powers the liftpump.

No the clatter seems to be more from the engine compartment. It doesn't appear to be coming from the exhaust. I'll keep you updated on what I find with the vacuum testing. Thanks again.

Aside from wastegate chatter due to low vacuum, these can cause chatter -


vacuum pump bearings - remove serpentine belt to check


idler pulley bearings\tensioner mechanism - same


- these two WILL break the crankshaft at the second main journal -


harmonic balancer - wobbling, or protruding rubber isolator band (between outer ring and hub), caused by oil spills


accessory pulley - rubber isolator cracked, rotted from ozone


If it has a manual trans, the dual mass flywheel rattles\chatters when the rubber isolators have heat\ozone deteriorated - this can break the crank between the rear main and #7\8 rod journal.

Another one is Alt bearings more of a squeal though than a clatter, that doesn't account for the black smoke, but a bad vac pump could , have you checked for vac at the pump, sol, turbo as suggested previously?Edited by: Turbine Doc

OK I've measured vacuum at the wastegate - 15" and at the pump - 23". Those numbers both seem to be OK. I checked for fuel supply from my lift pump by hooking up a piece of hose to the filter vent and cracking it open with the engine running. I had pretty decent flow but did not quantify it, so I think the lift pump is working properly, which I guess means my OPS is fine... I'm getting ready to check for codes but I don't have a scan tool so I need to figure out how to do it. I remember seeing a post on here so I'll just find that again. I'm about 90% sure my problem is the waste gate solenoid, does that seem to make sense to everyone else? Thanks again...

You can unplug the wire connector from the wg solenoid and all vacuum to the turbo vacuum line should stop.
It's probably stuck ( wires unplugged it still has vacuum).
It will also fail if it looses the volt signal from the PCM and/or ground.
It's about $30 from the dealer, or $16 from gmparts direct.
gm # 0199-7227

some will advise you to get a mechanical arm for the wastegate, but I've had good luck keeping mine going since I replaced all the vac line
and put in a new wg solenoid.Edited by: quantum mechanic

Alright, I've been looking for about an hour, I know I read a post a couple days ago that tells me how to get the codes without using a scan tool. I know I need to use a paper clip, or something equivilent as a jumper but I don't remember what points to jump across. If somebody could throw me a bone i would greatly appreciate it. Thanks...

Under the dash near the steering wheel is the ALDL, if your '95 is OBDI
it will have a 12 pin hook-up and you jump the A to B pins.With the key on, engine off.
The check engine light will flash, first one number then the second and repeat it three times.

Expect to see DTC 78, waste gate fault.
it means the PCM is reading less boost than desired range.

If your ALDL is OBDII it will have 16 pins and you need a scantool.



Edited by: quantum mechanic

OK, Here's the latest update. I used the paperclip jumper method and received a code 78. I ordered the waste gate solenoid from gmpartsdirect and replaced it today. Clatter is gone from what I noticed on a short test drive. I am still getting quite a bit of black smoke, more than normal... The smoke seems to be at its worst when the engine temp gets up to normal and when the transmission is in overdrive. If I keep it out of overdrive it seems to be much better. I'm guessing the two factors here seem to be temperature and RPM (based on worse in OD)... Does that make sense to anyone else, or set off any bells as to what else could be wrong. Like I said the 78 was the only code I had and that has been taken care of...

It is still the waste gate/turbo system. You have a vacuum leak in one/both of the lines/connections or
your waste gate is sticking open. Either way your not boosting to a level that provides enough air for
the fuel your burning. Black smoke screams underboost, but is a symptom when a tempature sensor is out or not making a good connection.


Any possibility it could be a clogged soot trap? If you havn't ditched it that is.

I think your code 78 will be back.


I would guess it is the vacuum pump or a vacuum line. If there was garbage in the vacuum line, it could have plugged the new valve too.

Ok the check engine light lit again on my way to work tonight. I still didn't hear any clatter, so I guess that's good. I checked the vacuum at the waste gate (15") and from the pump (22-23") previously... Are you saying I could still have a leak somewhere or a bad vacuum pump even though these vacuums looked OK??? I've never done anything with the soot trap, should I start there? Thanks again...


Joe

I've never done anything with the soot trap, should I start there? Thanks again...


Joe





You might as well. It will run better with it cleaned out or removed even if it isn't causing the problem.


Another think to check is the weld on the wastegate rod. It can break and let the wastegate door flop loose inside even though the linkage it tight.

The OEM vacuum lines are prone to dry rot and crack.
The lines will also leak if not properly seated into the rubber fittings.
Under acceleration even a small leak can cause problems.

If The soot trap is a restriction, so is the muffler and every bend and crimp and foot of length.

A straight pipe (past the cab)costs the least works the best.

I had some of the very same symptoms of the black smoke and rich lean smell, soot build up and turned out that the cataletic converter was plugged, I undid the four bolts just before the cat, ran it for about two blocks to clear it up and I am now awaiting the banks kit to arive.