Diesel Place banner

41 - 60 of 97 Posts

·
6.5TD Post Addict
Joined
·
9,886 Posts
Air in fuel can also affect the P0251,as can a faulty OS electronic noise filter.

The EGR codes may affect performance significantly,codes are often caused from bad vacuum lines or weak/no vacuum to the various parts of the EGR system.

The glow plug performance code is unlikely to affect performance unless it is shorted wiring problem with contact to other ECM controlled systems-still should be looked at.
 

·
Registered
Joined
·
87 Posts
Discussion Starter #43
Lift pump arrived monday payed the $16 duty to customs and after a diesel bath ( the flow is fine to the pump fittings) new pump fitted and problem solved.
Thanks guys for the help and advice .
Untill the next problem arrises
cheers
 
  • Like
Reactions: OkDually

·
Registered
Joined
·
87 Posts
Discussion Starter #44
Problems back again

Fuel problems again
new fuel lift pump fitted in February this year AcDelco EP158.
truck cutting out lack of power and no black smoke when you put your foot down ( this is not normal I usualy have a little black smoke )So
with the top off the fuel filter fuel will not run so not being pumped from lift pump.
intake to lift pump fuel flows to pump so can the pump go bad in 6 months?
what should the flow rate be from the tank to the LP. incase sock is blocked Do not want to drop tank it has some bad connections and may give out on the third removal I have looked at replacing the tank, sender unit and would need ne fuel lines $350 Pluss $ 600 postage feeling poor right now and also the 4 week wait for parts and the duty at 40% feeling:bigglasse
will disconnect feed to lift pump and check flow other than that looks like a another new LP $60 +$70 postage and $16 duty and still 3 weeks to get it here:hole:
 

·
Premium Member
Joined
·
9,478 Posts
Do you have any DTC codes from the truck's computer?

How much fuel is in the tank?

Do you have a voltmeter? If so,

1. Disconnect the electrical power to the lift pump.
2. Put transmission in D (drive)
3. Turn the ignition key to ON (not start)
4. Check for voltage at the the connector the lift pump plugs into.
5. Do you have power at the connector?
 

·
Registered
Joined
·
5,266 Posts
Sorry to here.. If the lift pump was aftermarket junk and not ACDelco, its not only possible the LP can fail frequently, its more likely to occur..

FWIW. Anytime you replace the lift pump, it is reccommended that you also replace the OPS (use ACDelco only) at the same time regardless if its only 6 months old. A failing LP will often damage the OPS before being discovered..
New LP, old damaged OPS (LP switch) not providing enough power thus compromising the new LP performance and longevity.


Wish I could provide you the "Fuel Pump Relay Circuit Diagnosis Chart" specifically for OBD2 models. Been asked for many times, unfortunitely we're still waiting..
I know its supposed to have a redundent power supply (PCM) yet theres been several OBD2 guys finding "inop LP's" due to a faulty OPS. :confuzeld
I suspect that redundent PCM power supply is more likely a feedback loop during "normal engine operation" (to informs PCM of any LP Circuit- power malfunctions which would be required to generate corresponding DTC) and that PCM feedback loop only "powers" the LP during glow time. But thats a conversation for another day I suppose..

FWIW




FUEL SUPPLY SYSTEM CHECKS
If the fuel supply system is not delivering enough fuel, or air is being drawn into the fuel injection system, driveability could be greatly effected or a "Cranks But Will Not Run" symptom could exist. If other diagnostics indicates, or if the fuel supply system is suspected of not delivering enough fuel or drawing air, it should be tested as follows:

!!Important!!!!
-- Air leaks or restrictions on the suction side of the fuel pump will seriously affect pump output.
-- Make sure there is sufficient fuel in the tank.
-- Check for leaks at ALL fuel connections from the fuel tank to the injection pump.
-- Tighten any loose connections.
-- With engine running, check all hoses and lines for flattening or kinks that would restrict fuel flow.



Lift Pump Flow Check
1. Disconnect the electrical connector for the engine shutoff solenoid at the injection pump.
2. Disconnect the pipe at the lift pump outlet fitting.
3. Install a hose at the lift pump outlet fitting and place a 1 liter/quart container at the hose to collect fuel.
4. Crank the engine and measure the amount of fuel :
-- If more than .24 ltrs (1/2 pint) in 15 seconds, refer to "Lift Pump Pressure Check" in this section.
-- If less than .24 ltrs (1/2 pint) in 15 seconds, refer to "Lift Pump Suction Line Check" in this section.



Lift Pump Suction Line Check
1. Remove the fuel tank cap and repeat the "Lift Pump Flow Check."
-- If more than .24 ltrs (1/2 pint) in 15 seconds, replace the defective fuel cap and refer to the "Lift Pump Pressure Check."
-- If less than .24 ltrs (1/2 pint) in 15 seconds, go to the next step.
2. Separate the lift pump suction line from the fuel sender.
3. Connect the suction line to a source of clean fuel, using an additional hose.
4. Repeat "Lift Pump Flow Check."
-- If flow is more than .24 ltrs (1/2 pint) in 15 seconds, remove the fuel sender and check it for restrictions.
-- If flow is less than .24 ltrs (1/2 pint) in 15 seconds, go to step 5.
5. Check lift pump suction line for restriction:
-- If restriction exist, repair it and recheck the lift pump flow.
-- If no restriction exist, replace the lift pump and recheck lift pump flow.
6. Attach the lift pump suction line to the fuel sender.



Lift Pump Pressure Test
1. Install a tee adaptor at the injection pump fuel inlet connection.
2. Connect a pressure gauge with a dial indication of 0 to 103kPa (0 to 15 psi) to the tee adaptor.
3. Run engine and measure fuel pressure.
-- If pressure is at least 3 psi or 27 kPa go to step 4.
-- If pressure is less than 3 psi or 27kPa, refer to Chart A-5 in SECTION 3 (Fuel Pump Relay Circuit Diagnosis) before replacing lift pump.
4. Remove pressure gauge and tee adaptor.
5. Connect outlet pipe at the lift pump outlet fitting.
6. Clean any fuel spillage.
7. Run the engine to check for fuel leakage.



Fuel System Air Leak Test
1. Install a transparent hose between the fuel manager/filter outlet and injection pump fuel inlet.
2. Start and idle the engine, observing the fuel for air bubbles.
-- If air bubbles are not present, stop the engine and go to step 6.
-- If air bubbles are present, stop the engine and go to step 3.
3. Check the lift pump suction line for air leakage:
-- Disconnect fuel pipe from the fuel sender and plug it.
-- Disconnect the fuel pipe from the lift pump, and install a hand held vacuum pump with gauge.
-- Apply vacuum to the fuel pipe and observe the gauge reading:
--- If vacuum does not drop, connect fuel pipe and go to step 4.
--- If vacuum drops, repair the air leak in the suction line and install the suction line pipe and hose.
4. Check the fuel sender for air leakage:
-- Remove the fuel tank.
Remove the fuel sender from the fuel tank, remove strainer and plug the bottom of the pickup tube.
-- Apply a vacuum to the upper end of the pickup tube, and observe the gauge reading.
--- If vacuum does not drop, install the fuel sender and fuel tank.
--- If vacuum drops, replace the fuel sender, install the fuel tank, connect the fuel pipe and go to step 5.
5. Start and run the engine, observing the fuel for air bubbles:
-- If air bubbles are present, stop engine and recheck steps 3 and 4.
-- If air bubbles are not present, stop the engine and go to step 6.
6. Remove the transparent hose and connect the hose of the fuel manager/filter outlet to the injection pump inlet fitting.
7. Disconnect the return hose from the injection pump.
8. Install a transparent hose between the injection pump and the hose of the return line.
9. Start and run the engine, observing the fuel for air bubbles:

NOTICE: It is OK to see a small stream of air bubbles on snap acceleration

-- If air bubbles are not present, go to step 10.
-- If air bubbles are present, replace the injection pump.
10. Stop the engine.
11. Remove the transparent hose and attach the fuel return hose at the injection pump.
12. Clean any fuel spillage.
13. Run engine and check for fuel leaks.


Following any "Fuel Supply System Check(s)" outlined aboved or otherwise, or any routine maint procedure(s) eg fuel filter change, or any repair(s) eg lift pump replacement and normal engine operation has been restored.. The last step of the process is to check for, make note of, and CLEAR DTC(s).



Good Luck..
 

·
Registered
Joined
·
87 Posts
Discussion Starter #48
Codes yes 6 of them Po 251,370,380.4104,406 and 236 I think most relating to lack of fuel
will be there in the morning voltmeter in hand with newly charged bats ran them down a bit today with testing the lift pump
I may sound impatient .But I am on an island I the truck to town is the life line and the missus wants me to by a new Toyota hilux from Thailand cant afford it anyway .
Cheers from the tropics no rain now for 3 months who said it would
rain?

Do you have any DTC codes from the truck's computer?

How much fuel is in the tank?

Do you have a voltmeter? If so,

1. Disconnect the electrical power to the lift pump.
2. Put transmission in D (drive)
3. Turn the ignition key to ON (not start)
4. Check for voltage at the the connector the lift pump plugs into.
5. Do you have power at the connector?
 

·
Registered
Joined
·
87 Posts
Discussion Starter #49
Tank is half full

Do you have any DTC codes from the truck's computer?

How much fuel is in the tank?

Do you have a voltmeter? If so,

1. Disconnect the electrical power to the lift pump.
2. Put transmission in D (drive)
3. Turn the ignition key to ON (not start)
4. Check for voltage at the the connector the lift pump plugs into.
5. Do you have power at the connector?
 

·
6.5TD Post Addict
Joined
·
9,886 Posts
Sorry to here.. If the lift pump was aftermarket junk and not ACDelco, its not only possible the LP can fail frequently, its more likely to occur..

FWIW. Anytime you replace the lift pump, it is reccommended that you also replace the OPS (use ACDelco only) at the same time regardless if its only 6 months old. A failing LP will often damage the OPS before being discovered..
New LP, old damaged OPS (LP switch) not providing enough power thus compromising the new LP performance and longevity.


Wish I could provide you the "Fuel Pump Relay Circuit Diagnosis Chart" specifically for OBD2 models. Been asked for many times, unfortunitely we're still waiting..
I know its supposed to have a redundent power supply (PCM) yet theres been several OBD2 guys finding "inop LP's" due to a faulty OPS. :confuzeld
I suspect that redundent PCM power supply is more likely a feedback loop during "normal engine operation" (to informs PCM of any LP Circuit- power malfunctions which would be required to generate corresponding DTC) and that PCM feedback loop only "powers" the LP during glow time. But thats a conversation for another day I suppose..

FWIW




FUEL SUPPLY SYSTEM CHECKS
If the fuel supply system is not delivering enough fuel, or air is being drawn into the fuel injection system, driveability could be greatly effected or a "Cranks But Will Not Run" symptom could exist. If other diagnostics indicates, or if the fuel supply system is suspected of not delivering enough fuel or drawing air, it should be tested as follows:

!!Important!!!!
-- Air leaks or restrictions on the suction side of the fuel pump will seriously affect pump output.
-- Make sure there is sufficient fuel in the tank.
-- Check for leaks at ALL fuel connections from the fuel tank to the injection pump.
-- Tighten any loose connections.
-- With engine running, check all hoses and lines for flattening or kinks that would restrict fuel flow.



Lift Pump Flow Check
1. Disconnect the electrical connector for the engine shutoff solenoid at the injection pump.
2. Disconnect the pipe at the lift pump outlet fitting.
3. Install a hose at the lift pump outlet fitting and place a 1 liter/quart container at the hose to collect fuel.
4. Crank the engine and measure the amount of fuel :
-- If more than .24 ltrs (1/2 pint) in 15 seconds, refer to "Lift Pump Pressure Check" in this section.
-- If less than .24 ltrs (1/2 pint) in 15 seconds, refer to "Lift Pump Suction Line Check" in this section.



Lift Pump Suction Line Check
1. Remove the fuel tank cap and repeat the "Lift Pump Flow Check."
-- If more than .24 ltrs (1/2 pint) in 15 seconds, replace the defective fuel cap and refer to the "Lift Pump Pressure Check."
-- If less than .24 ltrs (1/2 pint) in 15 seconds, go to the next step.
2. Separate the lift pump suction line from the fuel sender.
3. Connect the suction line to a source of clean fuel, using an additional hose.
4. Repeat "Lift Pump Flow Check."
-- If flow is more than .24 ltrs (1/2 pint) in 15 seconds, remove the fuel sender and check it for restrictions.
-- If flow is less than .24 ltrs (1/2 pint) in 15 seconds, go to step 5.
5. Check lift pump suction line for restriction:
-- If restriction exist, repair it and recheck the lift pump flow.
-- If no restriction exist, replace the lift pump and recheck lift pump flow.
6. Attach the lift pump suction line to the fuel sender.



Lift Pump Pressure Test
1. Install a tee adaptor at the injection pump fuel inlet connection.
2. Connect a pressure gauge with a dial indication of 0 to 103kPa (0 to 15 psi) to the tee adaptor.
3. Run engine and measure fuel pressure.
-- If pressure is at least 3 psi or 27 kPa go to step 4.
-- If pressure is less than 3 psi or 27kPa, refer to Chart A-5 in SECTION 3 (Fuel Pump Relay Circuit Diagnosis) before replacing lift pump.
4. Remove pressure gauge and tee adaptor.
5. Connect outlet pipe at the lift pump outlet fitting.
6. Clean any fuel spillage.
7. Run the engine to check for fuel leakage.



Fuel System Air Leak Test
1. Install a transparent hose between the fuel manager/filter outlet and injection pump fuel inlet.
2. Start and idle the engine, observing the fuel for air bubbles.
-- If air bubbles are not present, stop the engine and go to step 6.
-- If air bubbles are present, stop the engine and go to step 3.
3. Check the lift pump suction line for air leakage:
-- Disconnect fuel pipe from the fuel sender and plug it.
-- Disconnect the fuel pipe from the lift pump, and install a hand held vacuum pump with gauge.
-- Apply vacuum to the fuel pipe and observe the gauge reading:
--- If vacuum does not drop, connect fuel pipe and go to step 4.
--- If vacuum drops, repair the air leak in the suction line and install the suction line pipe and hose.
4. Check the fuel sender for air leakage:
-- Remove the fuel tank.
Remove the fuel sender from the fuel tank, remove strainer and plug the bottom of the pickup tube.
-- Apply a vacuum to the upper end of the pickup tube, and observe the gauge reading.
--- If vacuum does not drop, install the fuel sender and fuel tank.
--- If vacuum drops, replace the fuel sender, install the fuel tank, connect the fuel pipe and go to step 5.
5. Start and run the engine, observing the fuel for air bubbles:
-- If air bubbles are present, stop engine and recheck steps 3 and 4.
-- If air bubbles are not present, stop the engine and go to step 6.
6. Remove the transparent hose and connect the hose of the fuel manager/filter outlet to the injection pump inlet fitting.
7. Disconnect the return hose from the injection pump.
8. Install a transparent hose between the injection pump and the hose of the return line.
9. Start and run the engine, observing the fuel for air bubbles:

NOTICE: It is OK to see a small stream of air bubbles on snap acceleration

-- If air bubbles are not present, go to step 10.
-- If air bubbles are present, replace the injection pump.
10. Stop the engine.
11. Remove the transparent hose and attach the fuel return hose at the injection pump.
12. Clean any fuel spillage.
13. Run engine and check for fuel leaks.


Following any "Fuel Supply System Check(s)" outlined aboved or otherwise, or any routine maint procedure(s) eg fuel filter change, or any repair(s) eg lift pump replacement and normal engine operation has been restored.. The last step of the process is to check for, make note of, and CLEAR DTC(s).



Good Luck..
For OBDII primary power for the LP is as shown in the diagram,the ECM activates the prime cycle through the relay and once it sees a running engine from OS/CPS signals activates the relay for constant run operation.
Should the relay circuit fail,the OPS is backup LP power-it also operates the LP after engine shutdown while oil pressure bleeds off.

To the OP:
Behind the underhood fusebox is a single red wire with a female spade terminal and a white or black insulator-this is the test lead for LP activation or priming a new fuel filter.
If you apply 12v to that red wire the LP should run through the normally closed contacts of the relay.

The OP might also need to check out the condition of the LP ground wire that should be located along the frame very near the LP-high resistance at the ground can cause excess amperage draw.
 

·
Premium Member
Joined
·
9,478 Posts
Codes yes 6 of them Po 251,370,380.4104,406 and 236 I think most relating to lack of fuel
P0236 Turbocharger Boost System
P0251 Injection Pump Cam System
P0370 Timing Reference High Resolution
P0380 Glow Plug Circuit Performance
P0406 EGR Sensor Circuit High Voltage

Not sure what "4104" is :confuzeld

Corrosion must be a problem where you live. Recommend you thoroughly clean your ground connections. See this: http://www.dieselplace.com/forum/63-gm-diesel-engines/21-6-5l-diesel-engine/163087-grounds-grounds-grounds-importance-good-grounds.html. Cleaning your grounds may help get rid of some of these codes.

P0251 & P0370 are usually related to the injection pump Optic Sensor. Most likely dirty and needs a thorough cleaning by using heavy doses of "Sea Foam" or "Diesel Kleen" fuel additive.
 

·
Registered
Joined
·
5,266 Posts
Heres a very insightful and informative 6.5L Diagnostic Check List



For OBDII primary power for the LP is as shown in the diagram,the ECM activates the prime cycle through the relay and once it sees a running engine from OS/CPS signals activates the relay for constant run operation.
Should the relay circuit fail,the OPS is backup LP power-it also operates the LP after engine shutdown while oil pressure bleeds off.

P0231 Fuel Pump Feedback Circuit Low Voltage

Racer. Not that I dont believe you, but I want to see the OBD2 6.5L diesel specific "Fuel Pump Circuit Description" and "Diagnostic Chart" with "Test Description(s)" for myself. Copied directly from an authorized factory service manual, much like I routinely provide for OBD1 owners. Not some randumb internet source or someones "independent" studies..

Please. Can SOMEONE provide the applicable "Fuel Pump Relay Circuit Diagnosis Chart" with the "Circuit description" for OBD2 models that can confirm the info being provided is completely accurate. Thanks..

Everything I find about P0231 nearly confirms our current understanding of the OBD2 lift pump relay circuit description, only its applicable to gasoline engines. Cant find ANY specific to C/K 6.5 diesels (OBD2) from any FSMs.

Sorry Freddy but that "wiring schematic" isnt factory authorized...
Looks alot like this '94 Engine Schematic I found at autozone. Notice the LPR circuit,, oh pooh wheres the OPS represented at? Wait thats not right at all.
Stands to reason if that '94 schematic is inaccurate, I wouldnt put much stock in that '96-98 schematics accuracy, most likely came from the same source of misinformation...





To the OP:
Behind the underhood fusebox is a single red wire with a female spade terminal and a white or black insulator-this is the test lead for LP activation or priming a new fuel filter.
If you apply 12v to that red wire the LP should run through the normally closed contacts of the relay.

The OP might also need to check out the condition of the LP ground wire that should be located along the frame very near the LP-high resistance at the ground can cause excess amperage draw.
X2 Thankyou for articulating that point far better than I.
If theres a LP or LPR Circuit problem, regardless what is eventually found faulty. Take a few extra minutes and actually clean the grounds too..
 

·
Premium Member
Joined
·
9,478 Posts
Racer. Not that I dont believe you, but I want to see the OBD2 6.5L diesel specific "Fuel Pump Circuit Description" and "Diagnostic Chart" with "Test Description(s)" for myself. Copied directly from an authorized factory service manual, much like I routinely provide for OBD1 owners. Not some randumb internet source or someones "independent" studies..

Please. Can SOMEONE provide the applicable "Fuel Pump Relay Circuit Diagnosis Chart" with the "Circuit description" for OBD2 models that can confirm the info being provided is completely accurate. Thanks..
Sorry Freddy but that "wiring schematic" isnt factory authorized... Looks alot like this '94 Engine Schematic I found at autozone. Notice the LPR circuit,, oh pooh wheres the OPS represented at? Wait thats not right at all. Stands to reason if that '94 schematic is inaccurate, I wouldnt put much stock in that '96-98 schematics accuracy, most likely came from the same source of misinformation...
No what I posted is not a factory wiring schematic.

I cannot verify these two are either, but at least page 2 has the OPS circuit(s). I swiped these from here: http://www.dieselplace.com/forum/63-gm-diesel-engines/21-6-5l-diesel-engine/442682-lift-pump-not-getting-juice.html#post4469709
 

Attachments

·
6.5TD Post Addict
Joined
·
9,886 Posts
Actually they both have the OPS in the circuit and ARE from the 2001 6.5 L65 3500HD manual.

Trouble tree to follow as requested for informational purposes only.
 

Attachments

·
Registered
Joined
·
87 Posts
Discussion Starter #57
where will I find the fuel pump test terminal ? Weather here is hot 30 just about to get the boat over to work on the truck have down loaded all the check info I could find and will go through it. fingers crossed cheers .if you ever need a holiday check out my place Beach house on private island - Home
 

·
Registered
Joined
·
87 Posts
Discussion Starter #58
Do you have any DTC codes from the truck's computer?

How much fuel is in the tank?

Do you have a voltmeter? If so,

1. Disconnect the electrical power to the lift pump.
2. Put transmission in D (drive)
3. Turn the ignition key to ON (not start)
4. Check for voltage at the the connector the lift pump plugs into.
5. Do you have power at the connector?
No power at connector.
I think I may have a faulty oil pressure switch is there a bypass I can do for now ? I also had a kink in the fuel line just in front of the sender unit. Straightened that a little .I ran power to the pump to prime the filter
.
Truck is running for now no fault codes see how it goes to town Monday. Off now for a swim
Thanks for the help:bigglasse
 

·
Registered
Joined
·
5,266 Posts
Do you have a FSM diagnostic chart or trouble tree for DTC P0231?

Thats odd Racer.. Your "Circuit Description" nor "Diagnosis Chart" never mentions the OPS nor what role, if any, it plays in the Fuel Pump Electrical Circuit as shown in this schematic which appears to be significantly different than the schematic in post 47. so to eliminate any further misinformation, could everyone please limit there info to and provide the GM Title(s) and publication number(s) of any/all reference material.


Assuming this schematic is accurate.. Take note of the ECM-B power feed. Virtually a straight shot to and through the OPS before reaching the lp...
It appears to me the PCM D8 (?) connection is the glow/LP prime signal. Then once the OPS is HOT (engine "ON"), the PCM simply monitors the LPR circuit via PCM D5 connection.
The OPS wouldnt be in the loop if it didnt play some role... How do you explain OBD2 LPR circuit faults and/or inop LPs resulting from just a faulty OPS?
Not lookin for an argument, just ensure that we are passing on accurate info. That is all..




 

·
Premium Member
Joined
·
9,478 Posts
Assuming this schematic is accurate.. Take note of the ECM-B power feed. Virtually a straight shot to and through the OPS before reaching the lp... It appears to me the PCM D8 (?) connection is the glow/LP prime signal. Then once the OPS is HOT (engine "ON"), the PCM simply monitors the LPR circuit via PCM D5 connection.
The OPS wouldnt be in the loop if it didnt play some role... How do you explain OBD2 LPR circuit faults and/or inop LPs resulting from just a faulty OPS?
Not lookin for an argument, just ensure that we are passing on accurate info. That is all..
My thoughts:

1. GM didn't eliminate the safety role of the OPS. Loss of oil pressure shuts off lift pump.

2. PCM D8 seems to be designed to sense interruption in current flow from both the relay and the OPS. How does it do this....:confuzeld

The OP states he does not have voltage at the lift pump connector. So, if the OPS is active in LP operation, then a bad one could cause the ECM to cut the power to the lP. And/or the LP relay is bad. Should be able to test each gray wire going from the relay and OPS for 12v to figure out which is not working.
 
41 - 60 of 97 Posts
Top