View Full Version : Engine stalls, new IP, new lift pump,
1995 TD 270,000 miles New injector pump, new lift pump, new sensor to lift pump, new fuel filter
This truck stalls for no obvious reason. Plenty of fuel, new fuel filter etc. I will drive it from anywhere to 10-100 miles then out of the blue it will stall. It could going down the highway, at a red light or just driving down the road at 35 mph. I have learned that if I loosen the breather on the fuel filter, the truck will start. I will have to do this about 4 times (start, stall, loosen, start, tighten, move stall: that is the squence). After about 4 times it runs great for awhile.
I have taken it to 2 Chevy dealerships and they want to replace all the brand new parts that they installed (and charge me, but that is besides the point). I took it to Columbus Diesel (3 times now) and each time they fix something and tell me its fine, but, it stalls after they same program (drive 10-100 miles than stall, start, stall etc).
It seems weird that every time it stalls, I can start it just by loosening the fuel filter breather.
Any ideas?
DmaxMaverick
09-18-2010, 12:05
Try a new (correct) fuel filler cap.
I suspect that your oil pressure switch has failed.
It supplies the lift pump power when the engine is running and can burn out over time,but leave the gauge working normaly.Replace it with only a genuine gm switch,the aftermarket switches are un reliable.
If you are comfortable with wiring you should search here or google for"oil pressure relay mod" and install.
Or you can just order a premade kit from Kenedy Diesel and install it.
The relay mod should be mandatory for your truck since GM incorporated it in future models.The relay will take the strain completly off of the oil pressure switch.
I just reread that the dealer replaced the sensor for the fuel pump so if it was the oil pressure switch you could have a wiring problem like a bad ground to the lift pump,.A bad ground will draw much more current through the switch and could make it fail prematurely.
I would determine which wire is the ground wire to the lift pump and then measure the resistance to ground-it should be almost 0.If it reads anything higher than a few ohms you could tap an accessory gound wire into the harness and connect the other end to a good clean ground on the frame.
The relay mod should be mandatory for your truck since GM incorporated it in future models.The relay will take the strain completly off of the oil pressure switch.
What year has the relay installed? I'm trying to remember if I have a 2 connector or 3 connector OPS. I think that is how to tell the difference. I changed it a few months ago as the previouse one started leaking. (about 18 months on it). The one I have now is a BWG. I'll go to GM if I have a problem again.
Right now I think I'm having PMD failure. It stalled at Walmart today and would restart after letting it sit for 5 minutes or so but only run for about 30 seconds at most.
I changed the fuel filter, and bled it with no help. Also poured in a few bottles of heet in case of water.
I had it towed home and it ran for 3-4 minutes as I was paying the tow driver but then quit. I let is sit for several hours and then rebled the filter, started it up and opened the drain "t". It seems the lift pump is working fine. A steady stream of fuel came out of the drain hose with no engine hesitation. The truck ran for 15-20 minutes before stalling again. It will restart but only run for a couple minutes.
I'm going to pick up a scan tool in the morning and check for codes, but the next step is probably to install a remote PMD kit. It's stock now.
Not trying to hijack the thread, but thought some of this pertains to the same issues.
What year has the relay installed? I'm trying to remember if I have a 2 connector or 3 connector OPS. I think that is how to tell the difference. I changed it a few months ago as the previouse one started leaking. (about 18 months on it). The one I have now is a BWG. I'll go to GM if I have a problem again.
Right now I think I'm having PMD failure. It stalled at Walmart today and would restart after letting it sit for 5 minutes or so but only run for about 30 seconds at most.
I changed the fuel filter, and bled it with no help. Also poured in a few bottles of heet in case of water.
I had it towed home and it ran for 3-4 minutes as I was paying the tow driver but then quit. I let is sit for several hours and then rebled the filter, started it up and opened the drain "t". It seems the lift pump is working fine. A steady stream of fuel came out of the drain hose with no engine hesitation. The truck ran for 15-20 minutes before stalling again. It will restart but only run for a couple minutes.
I'm going to pick up a scan tool in the morning and check for codes, but the next step is probably to install a remote PMD kit. It's stock now.
Not trying to hijack the thread, but thought some of this pertains to the same issues.
I am not certain but I belive that the oil pressure senders are all 3 wire.
The obdII systems have the relay from factory so 96+.
If you have a good fuel flow from the tee valve when running then I expect your lift pump is ok-pmd seems likely.
What year has the relay installed?
As far as I can tell, the fuel pump is powered through the oil pressure switch regardless of year. The difference is in how it is powered when the engine is not running. Early ( through '95) trucks were powered through the relay when the starter was engaged. Later trucks were powered through the relay for a preset time by the PCM.
Once oil pressure is established, the OPS powers the pump directly.
Someone with a later truck could verify this conclusively by putting a volt meter on the fuel pump prime connection. If it is hot when the engine is running then the relay is not energized and power is coming only from the OPS. If it is not hot then the relay is closed and it is (also) powering the lift pump.
I belive that the attatched schematic is from a 98 so you can draw your own conclusions.
the lines in red are mods which can be performed.Since ther is some whiteout used it may not be a complete schematic.
This attatchement is from a 98 .
I can't find the OPS in this diagram but it clearly shows relays controlling the lift pump's in the run position which are activated by the OPS and the balance module for the secondary transfer pump.
Thanx to Turbine Doc for posting this schematic originaly.
... it clearly shows relays controlling the lift pump's in the run position .
All I can say is that diagram bears no resemblance to this one from a '97. The orange wires are hots and clearly the lift pump is powered but the OPS...
I think the diagram above is the transfer pumps for dual tanks. Not the note in the schematic below referring to the wiring for the balance relay as "w[ith]/dual tanks". Note also that, for single tank, it indicates a pump with the fuel level sender in the tank...
Every bit of information helps as great deal, as per your suggestion I will check the prime connection on my 96 for power and will report back.
I tried checking today but was unsure about the test light I was using,but will check again tomorrow.
I also found this bit of info for your consideration.
"Independent study by Turbine Doc and gmctd have found that the OPS and the lift pump relay will BOTH power the lift pump on the OBD-II systems (post 96 model year). If the OPS fails, the lift pump relay will still power the lift pump will the engine is running. As long as the ECM is seeing that the engine is rotating, it will continue to power the lift pump. OBD-I systems (pre 96) did not. Lift pump relay was only on during the cranking/starting only. This is why some will prime by placing the automatic transmissionhttp://images.intellitxt.com/ast/adTypes/mag-glass_10x10.gif (http://www.dieselplace.com/forum/showthread.php?t=39350#) in gear and turn to "start." This will actually cause the lift pump to run with the lift pump relay, but the neutral safety switch will not allow the starter to turn the engine over."
Originaly posted by knreb.
"Independent study by Turbine Doc and gmctd have found that the OPS and the lift pump relay will BOTH power the lift pump on the OBD-II systems (post 96 model year). If the OPS fails, the lift pump relay will still power the lift pump will the engine is running.
The diagrams are a bit confusing, but, as far as I can tell, this is not the case. Could be wrong, and I don't have access to a vehicle to test. Regardless, if you do that test light test we can be certain. If the primer line is hot when the engine is running then the relay is *not* pulled and cannot be powering the pump.
I missunderstood or did not remember the test correctly.
When I checked this mourning the primer line was cold -no light with enguine running.
That's why i was suspect of the test light,I forgot the sequence you described and when the light was not lit I figured there might be a problem and did not want to report my findings until I could verify they were correct.
I will still check again tomorrow.Severe back pain today so I am not using the truck.
DmaxMaverick
09-20-2010, 10:26
I tried checking today but was unsure about the test light I was using,but will check again tomorrow.
I also found this bit of info for your consideration.
"Independent study by Turbine Doc and gmctd have found that the OPS and the lift pump relay will BOTH power the lift pump on the OBD-II systems (post 96 model year). If the OPS fails, the lift pump relay will still power the lift pump will the engine is running. As long as the ECM is seeing that the engine is rotating, it will continue to power the lift pump. OBD-I systems (pre 96) did not. Lift pump relay was only on during the cranking/starting only.
I'm with JohnC on this one. I've never seen one that worked this way, and none of the diagrams I've seen support it. There may be a brief cross-over period when the conditions exists, but it has never been the case in my experience.
This is why some will prime by placing the automatic transmissionhttp://images.intellitxt.com/ast/adTypes/mag-glass_10x10.gif (http://www.dieselplace.com/forum/showthread.php?t=39350#) in gear and turn to "start." This will actually cause the lift pump to run with the lift pump relay, but the neutral safety switch will not allow the starter to turn the engine over."
Originaly posted by knreb.This only works on 1995 OBD-I models, and none other.
I retried to check the purge circuit today with a volt meter and test light.
At no time did I find vlotage on the red wire although it is tough to do alone.
To confirm I was on the right wire I supplied 12 volts and the lift pump did run.
So during prime,cranking and running there was no voltage on the filter purge wire.
I intend to re check when I can get some help and verify connections.
So during prime,cranking and running there was no voltage on the filter purge wire.
OK, AFAICT the only 2 ways that could happen are 1) as suggested, the relay is on when the engine is running, or 2) the OPS is bad and the pump is not running when the engine is running.
Have we determined that the pump is running when the engine is running, or is that why we're talking about it in the first place???
OK, AFAICT the only 2 ways that could happen are 1) as suggested, the relay is on when the engine is running, or 2) the OPS is bad and the pump is not running when the engine is running.
Have we determined that the pump is running when the engine is running, or is that why we're talking about it in the first place???
The lift pump and ops are fine in my truck,lift pump runs when engine running and has after pump until oil pressure dissapates.
So I belive we were trying to establish the role of the ops on obdII equipped 6.5's.
From what I have read the ops is partly responsable for lift pump operation but not entirely,the ecm can control the lift pump relay by using not only OPS info but also crankshaft signal info.
So I have also lost track of what the discussion was meant to prove.
So I have also lost track of what the discussion was meant to prove.
What?
OK, I guess we can say there is no benefit to adding a lift pump relay to an ODB II truck.
What?
OK, I guess we can say there is no benefit to adding a lift pump relay to an ODB II truck.
That answers my question! :)
I do have the full 4 volume shop manuals from GM, so if I get a chance over the next week or so I'll try to do some testing on my '99. Who knows why we are doing these tests, but maybe someone will search the threads later and be able to resolve an issue. :D
I do know that my lift pump works when the key is turned on and also fuel flows steady out of the drain "T" when the engine is running. So, lift pump is working good. Right?
Something I don't quit understand is that my manual says to purge the fuel filter by opening the bleed on the top of the filter, remove the ECM 1 fuse, and crank the engine for 15-20 seconds until fuel flows without bubbles from the filter bleed. Wait 1 minute between crank cycles for starter cooling etc.
Are they trying to use the injector pump at this point? Because the lift pump doesn't operate during this procedure. Or maybe I have something broken after all? Either way, the procedure doesn't work and I ended up putting the fuse back in and letting the lift pump spray fuel all over as the new wix filter I bought has a different configuration and the bleed valve will not direct fuel to a hose. :(
DmaxMaverick
09-22-2010, 07:23
That answers my question! :)
I do have the full 4 volume shop manuals from GM, so if I get a chance over the next week or so I'll try to do some testing on my '99. Who knows why we are doing these tests, but maybe someone will search the threads later and be able to resolve an issue. :D
I do know that my lift pump works when the key is turned on and also fuel flows steady out of the drain "T" when the engine is running. So, lift pump is working good. Right?
Something I don't quit understand is that my manual says to purge the fuel filter by opening the bleed on the top of the filter, remove the ECM 1 fuse, and crank the engine for 15-20 seconds until fuel flows without bubbles from the filter bleed. Wait 1 minute between crank cycles for starter cooling etc.
Are they trying to use the injector pump at this point? Because the lift pump doesn't operate during this procedure. Or maybe I have something broken after all? Either way, the procedure doesn't work and I ended up putting the fuse back in and letting the lift pump spray fuel all over as the new wix filter I bought has a different configuration and the bleed valve will not direct fuel to a hose. :(
This only works on some model years (don't ask me why). The reason for pulling the fuse is to prevent all that air from being pumped through the injection pump, lines and injectors. You can do the same thing by pulling the ESS connector (pink wire) from the IP. You don't have to crank the engine or mess with electrical if yours operates the lift pump at key-on. Just cycle the key as many times as necessary to complete the prime. Or, jumper the relay to operate the pump (some folks install a permanent "prime button/switch").
phantom309
09-22-2010, 13:08
perhaps wait until ted2020 weighs back in again,.??
new ip doesn't mean new pmd does it?
if there are small rusty pin holes in the fuel line,. it'll cause havoc,. along with snot on the sock in the tank etc,.
but the original complaint was random shut downs,. with enough time between cranking to play with fuel caps etc,.to let the pmd cool a little would be my guess,.
If a diesel shuts off suddenly when its rolling,. its not usually a fuel problem,.
New guys often don't describe the symptoms very well either,. someone with experience would realise its down on power,, chugging, making tinkling noises as its running out of fuel,.etc,. the other type of stall is just like the key was turned off,. and we know that problem,.pmd it could be a worn wiring harness shorting the shut down solenoid etc,.bad grounds etc,. but it often times seems as if 1 idea gets expounded upon without any one asking the much needed many possible diagnostic questions,.
nick
This only works on some model years (don't ask me why). The reason for pulling the fuse is to prevent all that air from being pumped through the injection pump, lines and injectors. You can do the same thing by pulling the ESS connector (pink wire) from the IP. You don't have to crank the engine or mess with electrical if yours operates the lift pump at key-on. Just cycle the key as many times as necessary to complete the prime. Or, jumper the relay to operate the pump (some folks install a permanent "prime button/switch").
Thanks for confirming my thoughts on the procedure. I need to make a note in the MM so I don't try the book procedure again next time!
The latest is clear lines to the fuel filter. So far no bubbles. Naturally the shop can not reproduce my problem. Not blaming them, but still frustrating.
The oil pressure Switch or relay was replaced last week and the truck still stalls.
Someone suggested a fuel filler cap and I believe mine is original, but I am not sure how that applies.
the 95 is an obd 1 with a 12 pin connection
The injector pump was supposed to come with a new PMD.
They put a clear fuel line on and we are waiting for bubbles to form.
That is where we are at.
DmaxMaverick
09-27-2010, 14:29
The oil pressure Switch or relay was replaced last week and the truck still stalls.
Someone suggested a fuel filler cap and I believe mine is original, but I am not sure how that applies.
the 95 is an obd 1 with a 12 pin connection
The injector pump was supposed to come with a new PMD.
They put a clear fuel line on and we are waiting for bubbles to form.
That is where we are at.
GM Diesel fuel filler caps vent both ways. If yours is original, that's reason enough to replace it for no reason at all. If it fails to vent properly, in either direction, it can, in some cases, cause the symptoms you are experiencing. Excessive system pressure impedes fuel return. Excessive system vacuum impedes fuel pump operation (both, LP and IP). Either condition can cause stalling. It may or may not be the cause of a problem, but if it isn't venting properly, it will exploit/exaggerate any other issue that may be present.
It seemed, according to your original post, you had already replaced all the usual suspects, with no change to the situation. "Loosening" the "breather" (bleeder) on the fuel filter was another indication of possible excessive system vacuum.
If you have the clear line on the IP return outlet, and aren't seeing bubbles (should be visible very soon after engine start), the problem isn't a suction leak issue (between the tank and LP, assuming the fuel lift pump is pumping). This is a simple, but effective test, and should show results almost immediately. No bubbles in a couple minutes = not the problem. Next.
Forget the relay. Unless the fuel lift pump system has been modified, it is out of the loop any time the engine is running. Power to the LP is supplied solely by the OPS circuit. However, installing a relay, energized by the OPS, to power the pump, is an excellent remedy to frequent OPS failure.
I will replace the fuel cap. I assume that it will be specifically for diesel and that an "auto parts" store will have them.
Currently a new PMD is being installed. We will see how that works. Columbus Diesel had it stall on them and had a portable PMD that seemed to correct the issue. Hopefully that is the magic bullet.
You can always just loosen the fuel cap and see if that helps.
Well the good news is that the truck is running consistently. Although I am not thrilled that we did not "Nail" down the problem, it seems that replacing the PMD fixed everything. THanks all who posted.
Ted
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