How to Test a 'No-Start' 2003 DodgePosted 4/4/2007
By Tom Vadnais
The tech called, saying he had a 2003 Dodge diesel truck that was towed into the shop as a "no-start." The usual diagnosis is to check the low-pressure fuel delivery with these suggested steps:
Step 1: Disconnect the wiring from the fuel lift pump.
Step 2: Connect a volt ohmeter between the wires and actuate the fuel pump with a suitable scan tool. The voltage should be more than 11.5 volts. If it's not, check the wiring and the engine control module (ECM.) If the voltage is OK, continue the test for the low-pressure fuel system.
Step 3: Reconnect the lift pump wiring and inspect the fuel line between the lift pump and the high-pressure pump for damage; repair as necessary.
If the line is OK, follow these steps:
Step 1: Disconnect the fuel supply line from the lift pump hose at the frame rail connection.
Step 2: Install a suitable fitting and connect a vacuum pressure gauge to the fitting.
Step 3: Remove the fuel supply hose from the high-pressure pump and route it to a large container.
Step 4: With the scan tool, actuate the fuel pump for 10 seconds and record the amount of fuel in the container. If it is 53 to 56 milliliters (1.79 to 1.89 ounces) per second with less than 5.5 inches of vacuum, the flow and restriction are normal. Higher vacuum and lower flow indicate a restriction; lower vacuum and lower flow indicate a bad lift pump.
While verifying the complaint, it was discovered that if starting fluid was added, the engine would start and then continue to run on its own. The cranking fuel pressure on the scan tool was showing less than 2,000 psi even though the low-pressure system tested OK. But when the engine started, it showed more than 6,500 psi.
As the tech was working on the vehicle, I was doing some research. I found one of our hotline archives that described a similar situation involving fuel return volume.
The suggested test is as follows:
Step 1: Operate the engine until operating temp is reached.
Step 2: Remove the top rubber hose between the high-pressure pump and the fuel filter. Connect a longer hose from the high-pressure pump to dump into a bucket.
Step 3: Clamp off the fuel return hose located under the fuel filter near the fuel supply hose.
Step 4: Use a pop can (12 ounces) to measure the amount of fuel coming from the exposed steel line that was connected to the rubber hose removed in Step 2.
Step 5: Get the engine running and measure the amount of fuel collected in two minutes. It should be less than 12 ounces in two minutes.
Step 6: If it is more than that, remove the injector lines and torque the fuel connector tubes in the head to 37 lbs. ft.
Step 7: Reconnect the injector lines.
Step 8: Retest the fuel returned in two minutes.
Step 9: If the return is still excessive, remove the line and cap off the feed to the injectors one at a time and rerun the test. When the one or the ones causing the excessive flow are located, remove that connector tube and injector to inspect the mating surfaces for wear or damage.
When the connector tubes come loose or are damaged, the fuel can bypass the injector and be returned to the tank. If this is the case, the fuel pump can't produce enough volume to pressurize the rail at cranking rpm. It takes more than 2,000 psi of pressure for the fuel to enter the injector.
Whenever the fuel system is going to be opened, always wait at least 10 seconds from engine shutdown. Normal running pressure for this system is from 4,351 to 23,206 psi. Cracking a fuel line to check for fuel is not recommended.
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