How to check fuel return rates - Chevy and GMC Duramax Diesel Forum
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Old 02-01-2011, 06:26 PM   eBay Motors  #1 (permalink)
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How to check fuel return rates

OK, I don't have a tech II and most of us do not.

So for those who do not have the tech II, is there a process whereby we can check fuel return rates? And what are the return limts which indicate a bad injector or leak under the hood?
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Old 02-01-2011, 06:51 PM   eBay Motors  #2 (permalink)
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Old 02-02-2011, 04:21 PM   eBay Motors  #3 (permalink)
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OK guys, I hear everybody talking about the return rate test...anybody done this test? (Not balance rate, but return rates)>
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Old 02-02-2011, 04:59 PM   eBay Motors  #4 (permalink)
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The balance rates are the individual adjustments to fuel delivery based on engine RPM. Think of it like fuel trim, just on a cylinder by cylinder basis. If a injector is leaking, too much fuel gets into the cylinder. This will cause the piston to speed up faster than the other cylinders. The ECM monitors the crankshaft revolutions. When it sees the unusual increase in speed, it reduces fuel and a negative fuel trim number appears. The ECM can also adjust the cylinder before and the cylinder after the problem cylinder all in a effort to keep the RPM balanced. The normal ranges for automatic transmissions is +/- 4 mm3 in park or neutral, and it can go as high as +/- 6 mm3 in gear. Starting on 2006 all Duramax injectors use an injection quantity adjustment number on top. This is established by Bosch during testing. This number is stored in the ECM and the ECM uses it to further fine tune fuel delivery. Most trucks 06 and newer, the balance rates will be +/- 1mm3 or less. I am unaware of any aftermarket scan tool that reads balance rates, but I very well can be wrong. The only way I have seen balance rates is with a Tech II. Another thing is balance rates are only active at idle, off idle, they are turned off.

The only manual test you can attempt it to remove every return line from the injectors and somehow attach a hose to each injector. Run the lines into 8 measuring cylinders and measure the return rate. They should all be the same. This test is tricky too because you have to get all the air out first. This is how we diagnose injectors with excessive return volumes and the balance rates usually coincide with high return volumes.
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Old 02-02-2011, 05:32 PM   eBay Motors  #5 (permalink)
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Someone should do a DIY on this!
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Old 06-11-2011, 04:03 AM   eBay Motors  #6 (permalink)
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Quote:
Originally Posted by lugnut View Post
. I am unaware of any aftermarket scan tool that reads balance rates, but I very well can be wrong. The only way I have seen balance rates is with a Tech II. Another thing is balance rates are only active at idle, off idle, they are turned off.
My Edge CTS will read balance rates, very nice feature for sure.
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Old 06-11-2011, 05:14 AM   eBay Motors  #7 (permalink)
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This is old, but EFI Live v2 and most good scan tools will as well.

The question was originally about return rates which went in-answered. I'm under the impression with no first hand knowledge that the Tech 2 is one of the few scan tools that will read return rates.

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Originally Posted by MTL_Dmax View Post
My Edge CTS will read balance rates, very nice feature for sure.


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Old 08-19-2011, 09:07 AM   eBay Motors  #8 (permalink)
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Originally Posted by TDFDiesel View Post
This is old, but EFI Live v2 and most good scan tools will as well.

The question was originally about return rates which went in-answered. I'm under the impression with no first hand knowledge that the Tech 2 is one of the few scan tools that will read return rates.

There is no scan tool that I am aware of that wil read Duramax return rates (balance rates, yes). There is no sensor to monitor returning fuel flow so any checking of injector fuel return rates must be done manually by tapping into the fuel return fittings on the top of each injector. This can be done at home if you just use a little ingenuity to set up your own test rig.

Injector return rates - Dmax Central
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Old 08-19-2011, 09:22 AM   eBay Motors  #9 (permalink)
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Quote:
Originally Posted by MTL_Dmax View Post
There is no scan tool that I am aware of that wil read Duramax return rates (balance rates, yes). There is no sensor to monitor returning fuel flow so any checking of injector fuel return rates must be done manually by tapping into the fuel return fittings on the top of each injector. This can be done at home if you just use a little ingenuity to set up your own test rig.

Injector return rates - Dmax Central
Kent Moore also makes a tool set for it.....but they think alot about it and it is Extremely Pricey.
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Old 08-19-2011, 03:54 PM   eBay Motors  #10 (permalink)
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Here is what I have from GM on the test procedure. - I am hoping to do a step by step by step DIY with pictures for testing the return rates, but I have not got a round to it yet.

Fuel Specific Gravity Testing
Use a J 38641-B Diesel Fuel Quality Tester to measure the fuel specific gravity (API Rating). Follow the instructions on the tool to btain the proper temerpature-adjusted value. This information must be accurate for the proper diagnosis of the fuel system.

Fuel Injector Return Flow and Fuel Pressures
The fuel return from the fuel injectors to the tank will vary based on the API value of the fuel. Measure the Fuel API with the Diesel Fuel Quality Tester. For this reason the Fuel System Diagnosis-High Pressure Side values will vary for identifying a fuel injector or fuel pump concern. Use the following tables when referred to by the diagnostic. The first table is to be used during the initial diagnosis to identify the worst fuel injectors. After the fuel injectors that fail the first part of the test are replaced, the return flow from each fuel injector must be measured again. This is because the fuel system is returning less fuel to the tank, and thus the fuel pressure is higher during the retest. Failure to use the correct table may result in the replacement of good fuel injectors.

API Rating = Maximum Single Fuel Injector Return Flow = Maximum Fuel Injector Bank Return Flow
30-34 = 3 ml = 12 ml
35-39 = 4 ml = 16 ml
40-44 = 5 ml = 20 ml

Retesting Fuel Injector Return Flow Values
API Rating = Maximum Single Fuel Injector Return Flow = Maximum Fuel Injector Bank Return Flow = Fuel Pressure at cranking speed (FICM Disabled)
30-34 = 4 ml = 16 ml = 176-180 Mpa
35-39 = 5 ml = 20 ml = 134-178 Mpa
............................... 176-180 Mpa
40-44 = 5 ml = 20 ml = 114-135 Mpa

Test Procedure
The fuel flows through a pre-filter screen in the tank and to the engine through the fuel supply lines. There is no lift pump in the fuel tanks or on the frame. The fuel passes through the base plate of the fuel injector control module (FICM) to cool the module. From the FICM the fuel flows to the fuel filter assembly, which combines a water separator, a prime pump and a filter element. Within the assembly, there is also a fuel heater. An integrated hand pump is used to prime the fuel system after changing the fuel filter or servicing the fuel system. The fuel injection pump at the front of the engine valley includes a fuel supply pump and a high-pressure pump. Fuel is drawn to the supply pump from the primary fuel tank by the supply pump and delivered to the high-pressure pump.
High Pressure System
The much larger section of the pump assembly is the high-pressure fuel injection pump. The pump is engine-driven by the camshaft gear. From the high-pressure pump, the fuel flows through the junction block. The junction block routes pressurized fuel to both common fuel rails. Each common fuel rail supplies one bank of four fuel injectors.
Return System
The Fuel Return System routes fuel from the fuel injectors, the junction block, and the fuel injection pump. The return fuel travels to the fuel cooler and then to the fuel tank. This fuel is used to cool and lubricate the injection pump and the injectors.
Important:
• If you were not referred to this test from another diagnostic, do not perform this procedure.
• Only perform this test when the fuel is more than 18C (65F).
• The fuel return volumes vary based on the API rating of the diesel fuel.
• A fuel injector may have high fuel return flow only at higher engine temperatures.


Were you referred here from one of the following diagnostics?
• DTC P1094
• Surges/Chuggles in Symptoms
• Rough, Unstable, or Incorrect Idle in Symptoms
• Fuel Injector Balance Test with Tech 2
- If you answered Yes, go to the Fuel Pressure Regulator Graphing after step 48.
- If you answered No, go to Step 2.
Remove the air duct from the air cleaner assembly and the turbo inlet.
Remove the air intake pipe. Refer to Air Intake Pipe Replacement .
Drain the coolant and remove the water outlet tube. Refer to Water Outlet Tube Replacement in Engine Cooling.
Object Number: 744233 Size: SH
Click here for detailed picture of above image.
Remove the fuel injection pump fuel return rubber hose from the junction block (2). Cap the fitting on the block with a 3/8 inch rubber cap (1) to prevent fuel leakage.
Object Number: 744234 Size: SH
Click here for detailed picture of above image.
Attach a rubber hose (1) with a barbed fitting to the fuel injection pump return hose and insert the other end into a 1 gallon clean fuel container (2).
Remove the ignition 1 relay or EDU relay, as equipped, using the J 43244 Relay Puller Pliers.
Object Number: 660433 Size: SH
Click here for detailed picture of above image.
Remove the glow plug harness bracket bolt.
Remove the glow plug harness bracket nut from the valve cover.
Remove the glow plug controller/relay mounting nuts.
Reposition the glow plug controller/relay.
Object Number: 755230 Size: SH
Click here for detailed picture of above image.
Remove the fuel line retainers.
Object Number: 660446 Size: SH
Click here for detailed picture of above image.
Remove the banjo bolt (2) from left rear cylinder head.
Object Number: 844173 Size: SH
Click here for detailed picture of above image.
Install the black hose (1) of the J 45873 Fuel Return Volume Test Kit to the left rear cylinder head and install the other end of the hose into one of the J 45873 graduated cylinders.
Object Number: 744233 Size: SH
Click here for detailed picture of above image.
Remove the banjo bolt (3) from the leak-off block.
Object Number: 844176 Size: SH
Click here for detailed picture of above image.
Install the other black hose (1) of the J 45873 to the leak-off block (2) and install the other end of the hose into another J 45873 graduated cylinders.
Object Number: 744233 Size: SH
Click here for detailed picture of above image.
Remove the banjo bolt (4) from the junction block (2).
Crank the engine for 15 seconds while observing the fuel pressure relief valve on the junction block for fuel leakage.
• If fuel is leaking from the fuel pressure relief valve, replace the fuel pressure relief valve. Refer to Fuel Pressure Relief Valve Replacement .
• If no fuel is leaking from the fuel pressure relief valve, go to step 19.

Object Number: 850646 Size: SH
Click here for detailed picture of above image.
Crank the engine in 15 second intervals, with one minute cooling time between, until fuel starts to flow into one or both of the J 45873 graduated cylinders (1).
Elevate the hoses (2) to retain the fuel in the hoses, and empty the graduated cylinders into a suitable container.
Install the hoses (2) into 2 of the graduated cylinders (1). Important: The engine cranking speed must be more than 150 RPM.
Crank the engine for 15 seconds.
Measure the quantity of fuel in each of the graduated cylinders. Refer to Fuel System Specifications for fuel return flow specifications.
• If there is more than the specified quantity of fuel from either cylinder bank, remove the valve cover from that bank. Refer to Valve Rocker Arm Cover Replacement - Lower Left Side or Valve Rocker Arm Cover Replacement - Lower Right Side , then go to step 24.
• If there is less than the specified quantity from each cylinder bank, replace the fuel injection pump and repeat steps 19-23.
• If the fuel injection pump has already been replaced in this repair and there is less than the specified quantity of fuel from each bank, go to step 45.

Object Number: 660477 Size: SH
Click here for detailed picture of above image.
Important: When the fuel injector pressure lines are removed, debris will fall into the fuel injector inlet fitting. Vacuum the debris from the inlet fitting of the fuel injector.
Remove the return line from injectors.
Object Number: 847742 Size: SH
Click here for detailed picture of above image.
Install the four yellow hoses (2) from the J 45873 to the injectors (1) and the other end of the hoses into each of the J 45873 graduated cylinders. Notice: Refer to Fastener Notice in the Preface section.
Install the 4 injector supply lines. Tighten
Tighten the supply lines to 44 Nm (32 lb ft).

Object Number: 674653 Size: SH
Click here for detailed picture of above image.
Connect the engine-to-chassis harness connectors to enable the starter.
Object Number: 674616 Size: SH
Click here for detailed picture of above image.
Install the fuel filter hoses, FICM hoses, and the fuel supply hose. Push the fuel supply hose in until it locks.
Install the black hoses from the J 45873 into the container that the fuel injection pump return hose is in. Prime the fuel system 30 times to remove air from the fuel system. Air will be forced out of the system within 2 minutes.
Crank the engine in 15 second intervals, with one minute cooling time between, until fuel starts to flow into one or more of the graduated cylinders.
Elevate the 4 hoses to retain the fuel in the hoses, and empty the 4 graduated cylinders into a suitable container.
Install the hoses in the graduated cylinders in numerical order. Important: The engine cranking speed must be more than 150 RPM.
Crank the engine for 15 seconds. Important: A fuel injector may have high fuel return flow only at higher engine temperatures. If the high return flow ceases between the bank return flow test and the individual injector return flow test the fuel injectors may need to be heated to an operating temperature before performing this test.
Measure the quantity of fuel in each of the graduated cylinders. Refer to Fuel System Specifications for fuel return flow specifications. Remove the fuel feed pipes from any injectors that have high return fuel flow, and install the EN 47589 Fuel Pressure Test Adapter Cap(s) to the fuel rail outlets. Then go to step 35.
Repeat steps 30 through 34 until no fuel injectors have more than the specified quantity of fuel flow.
Were both banks of fuel injectors tested with steps 30 through 35?
• If the answer is YES, go to step 44.
• If the answer is NO, go to step 37.
Ensure that the hoses are still installed as they were in steps 14 through 17.
Prime the fuel system 30 times to remove the air from the fuel system. Air will be forced out of the system within 2 minutes.
Object Number: 850646 Size: SH
Click here for detailed picture of above image.
Crank the engine in 15 second intervals, with one minute cooling time between, until fuel starts to flow into one or both of the J 45873 graduated cylinders (1).
Elevate the hoses (2) to retain the fuel in the hoses, and empty the graduated cylinders into a suitable container.
Install the hoses (2) into 2 of the graduated cylinders (1). Important: The engine cranking speed must be more than 150 RPM.
Crank the engine for 15 seconds.
Measure the quantity of fuel in each of the graduated cylinders. Refer to Fuel System Specifications for fuel return flow specifications. If there is more than the specified quantity of fuel in either of the 2 cylinders, remove the valve cover from that cylinder head. Refer to Valve Rocker Arm Cover Replacement - Lower Left Side or Valve Rocker Arm Cover Replacement - Lower Right Side . Then perform steps 29 through 35 on the bank of fuel injectors with the high fuel flow, Then go to step 44.
If both of the cylinder have less than the specified quantity of fuel, go to step 44.
Replace all of the fuel injectors that had fuel rail outlets capped. Refer to Fuel Injector Replacement .
Install all disconnected and removed components. Refer to the applicable procedures.
Start and idle the engine. You may have to prime the fuel system before the engine will start.
Connect a scan tool.
Command the fuel pressure control to 160 MPa with a scan tool.
• If the fuel pressure is more than 145 MPa, the system is OK.
• If the fuel pressure is unable to increase to more than 145 MPa, replace the fuel injection pump. Refer to Fuel Injection Pump Replacement .

Fuel Pressure Regulator Graphing

Set up the scan tool in the following format:
1.1. Select the Data Display on the scan tool.
1.2. Select Engine Data 1.
1.3. Select the More softkey 2 times.
1.4. Select the Live Plot softkey.
1.5. Select the Engine Speed, Actual Fuel Rail Pressure, and Desired Fuel Rail Pressure parameters by highlighting each parameter and depressing the ENTER softkey.
1.6. Select the Accept softkey.
1.7. Select the More softkey, then select the Change Min/Max softkey.
1.8. Select the More softkey, and adjust the parameters to the following Min/Max ranges:
• The Engine Speed Min/Max range is 0 to 1000 RPM.
• The Actual Fuel Rail Pressure Min/Max range is 1.0 to 160 MPa.
• The Desired Fuel Rail Pressure Min/Max range is 1.0 to 160 MPa.
Start and idle the engine.
Good Fuel Pressure Regulator Graph, 0 Miles

Object Number: 877557 Size: MF
Click here for detailed picture of above image.
(1) Engine Speed
(2) Actual Fuel Rail Pressure
(3) Desired Fuel Rail Pressure
Good Fuel Pressure Regulator Graph, 26K Miles

Object Number: 877556 Size: MF
Click here for detailed picture of above image.
(1) Engine Speed
(2) Actual Fuel Rail Pressure
(3) Desired Fuel Rail Pressure
Fuel Pressure Regulator Graph, Surging

Object Number: 877558 Size: MF
Click here for detailed picture of above image.
(1) Engine Speed
(2) Actual Fuel Rail Pressure
(3) Desired Fuel Rail Pressure
Observe the live plot for sharp changes in the Actual Fuel Rail Pressure above and below the Desired fuel rail pressure while performing one of the following actions:
• Idling the engine.
• Shifting the transmission from Park to Drive, and back to Park.
• Turning the steering wheel from lock to lock.
• Turning the air conditioning ON and OFF.
If there is a violent fluctuation in the Actual Fuel Rail pressure, as seen in the third Graphic above, replace the fuel pressure regulator. Refer to Fuel Pressure Regulator Replacement .
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Last edited by DuraTitus; 08-19-2011 at 05:50 PM.
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