Hey, I'm new to the forum, great site, great info, THANK YOU ALL!


My 99 van has been stalling for awhile, just started troubleshooting. PMD,I think. Right now though, I have


no fuel coming out at water drain when idling, truck stalled when I opened it and will not restart, however fuel pump is vibrating with key on and while cranking(I think I read somewhere it can still be bad, true?). I will change it tomorrow.


Also, I drove around with engine cover off and noticed the wastegate didn't move at all! I haven't heard turbo whine for a long time now. I'll check vacuum lines tomorrow.


Any advice is greatly appriciated, thanks.

Since you have no supply pressure, when you opened the drain the system was allowed to draw air and thats why the truck stalled. need to make sure the pump operates while the engine is idling, if it is, new lift pump should solve the problem.Edited by: Texas Diesel Guy

Could also be extremely dirty fuel filter element - color should be wet tan\beige. Also check air filter, while at it - good preventive maintenance routine, while you're in there.


If pump runs with key on, could still be dropping out when engine is running due to Oil Pressure Switch failure.


OPS is dual function, independent circuitry. Oil pressure gage can function when lift pump switch has failed.

Check the vacuum line going to the wastegate at idle, should be a strong pull there. if there is no vacuum then your wastegate is hung in the open position and you will have black smoke/low power then you will have either a broken/unplugged vacuum line or a broken vacuum pump or a bad switch. if there is vacuum, see which way the vacuum pulls the wastegate to see if its holding it in the fully closed position. If thats the case, and it stays closed while driving and you still have black smoke/low power then you need to change your air filter, and if that doesnt fix it, you've got turbo problems.

Both filters-less than 5k mls.


Still can't get engine to run since opening bleeder.


Where is the OPS? Oil pres. seems low(stock gauge) about 25psi at idle, 20psi when on brakes?

open the bleeder line and cycle the key repeatedly to run the supply pump, until fuel comes out, close the bleeder, cycle it a couple more times and then try to start it. If you get fuel, then most definitely your OPS is the problem, if you dont get any fuel then you need a new lift pump.


On a 99 van...I am pretty sure the OPS is in the engine valley behind the turbo on the driver's side. Before you change it see if you can see the wires going to it. If there is only one wire, then don't bother changing it, get a new supply pump, its not a part of the circuit, if there are 3 then change it.


It will be a black cylinder about 3" tall and just over an inch across, with steel on the base.

Sounds like the OPS is bad if you have fuel pressure with the key on engine off but none when the engine was running. If it is bad that will shut down the fuel pump. I would replace it first.

I'm pretty sure a 99 doesn't rely on the OPS to run the supply pump, I've seen earlier vans that didnt either, which is why I described this method to diagnose.


Reguardless, if the pump runs and doesnt make any fuel, either he's out of fuel or the pump is bad.Edited by: Texas Diesel Guy

To answer an off-post PM question - OBD-I engines use Start circuit and relay to enable lift pump when cranking, then OPS takes over when oil pressure builds. Three wires in OPS connector.


OBD-II systems, PCM controls lift pump relay until oil pressure builds and OPS takes over. Three wires in OPS connector.


Vans should be no different than trucks, unless another OPS is used in another location - still requires roll-over and dead engine safety shut-off afforded by OPS to meet Fed\State DOT standards.


Scenario - frustrated owners and mechanics, believing OPS to be worthless, sometimes wire around that safety circuitry, eliminating OPS control. May take some hunting to discover that solution.


Best bet, as suggested in the PM, would be to verify three wires in OPS connector, incl one orange - power, and one gray - lift pump for OBD-I and -II.


'99 G-30 Van my harness came from had correct OPS connector and three wiring colors. Oil pressure gage wire is tan, iirc.


Corrections? Additions?

Thanks for all the help!


OPS only has one wire (without cleaning looks to be pink).


It's running again and lift pump is working while idling.


I'll have a new pump tomorrow.


Also, good vacuum at actuator, going for another drive to watch the pushrod a little closer. (the only advantage to a 6.5 van!)


THANKS AGAIN!

Thats what I thought you were going to say, i can't explain the rhyme or reason to it, but I've only seen this single wire OPS setup in the vans and not all year models seem to be the same.

Wastegate actuator pushrod does not move at all while driving. I haven't noticed any black smoke, however it does seem to have a lack of power, although I haven't towed recently. Wastegate moves freely by hand so it doesn't seem to be a mechanical issue. Vacuum is strong, but I don't have a gauge.


Could the actuator be bad(wastegate closed all the time).I plan to tow about 700mls next week through some mountains, I'd like to figure out if there is a problem or not.


Any thoughts???


Edited by: VanHauler

The vacuum switch could be hung giving full vacuum to the wastegate all the time, I've seen this happen once before, also in a van, it would actually cut out at high RPM/Load because the computer would detect high MAP pressures and cut fuel temporarily causing a surging condition. Other than the switch being bad, a faulty or biased MAP sensor could be the problem. High Air Filter restriction, preventing the turbo from making a satisfactory amount of boost could also be to blame. Take the filter out and try it, if the wastegate moves, replace the air filter.Edited by: Texas Diesel Guy

Would a faulty or biased MAP sensor set any code.

if the sensor were inop or unplugged it would, if its biased, that is giving a reading that is lower or higher than what is actually present, the computer probably wouldnt be able to pick it up unless it were way out of range. DTC codes can be very helpful in pinpointing a problem, but they can't be relied on completely...Example, had a suburban come in complaining black smoke low power, they somehow made it to the shop, MAP pressure showed a vacuum on the intake under any load at all, checked vauum pump, actuator, the normal stuff, turns out the turbo was so badly worn out, you could hear it grind to a halt when you shut it down, but still no DTCs had been set.Edited by: Texas Diesel Guy

Would a faulty or biased MAP sensor set any code.


Good question! No ses light at all so far.


I test drove without airfilter(still no movement at all) and it stalled once and tried to stall 2 other times, 2 of 3 were at high rpm going uphill.


Vacuum switch/solenoid...same thing??Edited by: VanHauler

did it stall or just cut-out? This is probably more related to your supply pump problems, which really need to be solved first.


It does sound like the switch is hung open to me, squirting WD-40 in the vacuum line to the wastegate with the engine running so the vacuum will draw it into the switch, might free it up, but it should be replaced. Edited by: Texas Diesel Guy

Stalled once, cut out for just a second twice. I was thinking the same thing as far as the pump causing the stall problem.


I'll look into a new switch and try to change it tomorrow along with the supply pump. I'll post my results.


TDG/others, you guys are better than any manual!! THANK YOU for your time and expertise!

TDG, and others - Several things come to mind on the OPS\lift pump situation, as yet neither proveable nor refuteable from here, as my system is OBD-I.


It has been suggested by some, from some verbiage in the OBD-II manuals, that the PCM fully controls the lift pump, with the OPS as backup, only.


At Ign on, PCM powers lift pump thru relay


When output from Crank Position Sensor is valid, PCM maintains power until OPS picks up.


If no CPS sensor output, as when IGN on is required for some other function such as power windows, wipers, etc, but Start is not intended, PCM drops lift pump relay, cutting power.


If PCM senses Crank, from CPS output, power to lift pump relay is again picked up, with OPS as backup.


If this is correct, and again, it has not been verified, PCM would also drop power at rollover and dead engine scenarios, where CPS output would also be zero.


Doesn't make sense, tho, to install 3-wire OPS circuit in pickup series if PCM is in control - Bean Counters at GM would not stand for such a thing, right? Million trucks times 6 bucks?


On the wastegate thing - only time you will see arm movement under operation is at Start as vacuum picks it up, engine off as vacuum drops, vacuum system failure while running, and when PCM calls for backup limp-home mode\zero Boost.


That is easily proveable, if you can stand driving the van with the engine cover off for a while.


Actual movement is imperceptible.


When PCM is calling for 20% duty cycle under a hard pull, maintaining Boost at factory limited 7.5psi (stock chip), there is only imperceptible movement.


PCM varys response to meet varying condition - it is dynamic control.


The old spring systems held 'gate closed until exhaust pressure exceeded spring pressure, and the 'gate would 'blow' open, similar to a low pressure 'pop-off' valve.


When ep rapidly and repeatedly exceeded spring pressure, as in shifting thru the gears, arm movement was sudden and abrupt, and could be very noticeable.


Point is, don't gage turbo operation by arm movement - you just won't see it while 'gate is under normal PCM control.


Low vacuum levels will have same effect as PCM calling for lower Boost - lower power out.


15"hg vacuum for 25"hg from pump is 67% WG Duty Cycle.


If pump only puts out 15"hg, that would be only 10"hg vacuum on WG at 67%DC, equivalent to only ~40%WGDC at 25" vacuum.


Might behoove you to get a vacuum gage on the system, before the trip.


Work from the pump to the WG Solenoid for 25"hg at idle, checking both ends of tubing


PCM controlled Solenoid output = 15"hg.


Vacuum at wastegate actuator should equal 15"hg, also.


Any difference between pump and solenoid, or solenoid and 'gate will mean leaky vacuum line(s).


Any lower level out of solenoid, reflected at wg, means defective solenoid. About 30 bucks at your local GM dealer.


I'm tired - anybody see any illogic in this, bad math, etc, kick it back at me.


I'm ready for some supper.......

Wastegate arm movement is very easily perceptible. I don't know where you got this theory about the wastegate pulsing to control boost pressure but its just not how it works. Even with the wastegate completely open, and You can prove this on your truck GMCTD by just removing the vacuum line to the wastegate, you will notice the turbo will still build some boost, be it only a few pounds. If you watch the wastegate arm moving, you will notice that under load when the vacuum supply is decreased the arm will move 30 degeees or more from the closed position and provide the 7lbs boost the computer requests.


Because he has the single wire OPS it can only be used to give an oil pressure reading for the Dash/PCM maybe. the 3 wire setup is one hot wire and one wire to the supply pump to power it on with oil pressure. These systems are the ones that are prone to cause failure of the ops because is was never designed to hold that great of current, I've had them apart its just a ball point pen sized contact.

gmctd- I appreciate the in depth diagnostics and I will be picking up a vacuum gauge to see what's really going on. A tool anyone who works on their own trucks should have anyway.


TDG- Am I reading your last post correctly that the 'gate should open with vacuum line removed. Mine did not, closed always.(I removed line while idling, didn't drive that way)


Also, I guess I should have asked by now, should the turbo make any noise at all?? I've heard it whine very slightly only a couple times in 18 months and not at all for the last 10 months or so. Even while pulling steep hills with engine cover off. Pulling those hills seems a little more work the last 10 months too....(reasons I started looking for trouble to begin with)Edited by: VanHauler

The gate will blow open from exhaust pressure, that how the system operates, adjusting vacuum to the pot against exhaust pressure on the wastegate. Not uncommon to have a 6.5 that doesnt make any turbo whine...but it is nice to hear. Rev the engine with the line off and it will blow open, if it doesnt the only thing that could cause that is a broken wastegate... but if that were the case boost pressure would be very very low, you'd have black smoke, codes and most likely damage to the exhaust fan of the turbo.

I changed supply pump today. Started up easily when finished, ran for about 5 min. then stalled. Started right up again and ran for a few minutes, cut out for a second but kept running, then stalled again a minute later. Started easily a third time and kept running? I'm hoping this was just air in the lines (and not the PMD), about to take a test drive. Edited by: VanHauler

A good Boost\vacuum gage is available from jcwhitney.com for about 20 bucks - 20psi Boost, 30" vacuum, 2.125"dia, backlit black plastic face, white scaling Edited by: gmctd

Air can take a couple minutes to be purged completely from the system. Normally a stall from air will cause the engine to stumble a for a couple seconds, PMD stall will just die, normally. Let me know what you find, I've got a customer coming in tomorrow with almost the exact same vehicle and complaint as you.Edited by: Texas Diesel Guy

gmctd- thanks I'll try jcw.


Drove for about 2hrs today after changing pump. It is running better than it has for many months! It runs smoother and actually seems to have more power, didn't stall, stumble, ran great. I'm wondering now if this is whats been wrong all along, its been stalling and acting sluggish on and off now for months. Its had symptoms of a bad PMD(according to what I've read) but I'm hoping it was just this pump starting to go. I guess only time will tell, I'll keep my fingers crossed.


Thanks again guys!

100+ miles since changing supply pump, started-up to go somewhere, after letting it warm a few minutes it stalled, started right back up, stalled again, started after about 10 seconds of cranking. It was ok for about 1 mile down the road then stalled and took some good cranking before it would start again, then same thing a few miles later. Round trip was about 6 miles, on the way back it started and drove fine. It ran good once it reached normal temp.? I'm confused, I don't think there could still be air in the system? Is there a second fuel filter somewhere ?? I appreciate any help/thoughts guys, thanks.

Hmmm... very similair to the van we had in today, Stalls intermittently, found a fuel filter that was black as coal, changed it and it ran beautifully for a while, stalled still no codes. C-Time at cranking showed 0.00 so we changed PMD, ran great for a while again, died, hasnt kicked since....just what I need a headache first thing in the morning ;) Kind of an oddball one, I've never worked on an '02 6.5!Edited by: Texas Diesel Guy

Well... if the new PMD didn't solve the problem on that one, I'm not ready to go that route yet $$$ kind of outta ideas at this point though. (I always carry advil just for those kind of mornings...)


'02 6.5, when did they stop using these motors?? (or do they still in vans??)

Check the inlet screen filter in the inj pump - dirty primary filter can dump garbage into the inj pump inlet over periods of time.


Failure to clean the filter cannister when changing a really bad filter can also dump much crud into that very small saftey screen.

If the ´99s/´02s still have the solenoid bank, check the wiring of the solenoids. A broken wire could stall the engine without setting a code.

GMCTD- Debris entering system after filter change really not a problem in vans, filter is different from trucks, its encased, under the chassis and mounted upside down, no bowl to clean.


Olee- Vans are all EGR less, no room for one really with the split manifold design, so there's only one vacuum solenoid, not likely a problem in shorting the harness.


Van Hauler- Actually the 6.5s are still in production, in fact there is a new DS model out for '04, the 5827, not sure about the app, I'm def going to look into it more tomorrow, it has the updated DE style 17v Fuel Solenoid, a new cam ring and some other slight changes.

Well this may or may not be much help to you...but we did actually solve our van problem. Fuel filter was filthy for one, and you could actually see how it was bowed in at the middle from all the pressure/restriction. Second, the truck had the wrong, non-diesel/non-vented fuel tank cap. Basicly the truck was having a hard enough time feeding the pump through the filter, but when the vacuum starting building in the tank, the supply pump just didnt have enough oomph to feed it at all and the IP would starve.

On second thought....van came back today, but we DID solve the problem this time. On cranking, I noticed the closure time was 0.00, which sounds like PMD failure, which is what we thought last time. Pulled the sub harness for the engine off....found 3 of the 4 wires in the connector that plugs to the pump harness were burnt or broken. Don't know if this helps or not, but we soldered and heatshrinked 3 new connectors and I"m very confident that was his whole problem.