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GM Tech (Cam)
GM Tech (Cam), GMC Mechanic
Category: GM
Satisfied Customers: 29534
Experience:  GM Grand Master Technician 2007. 14 years experience.
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I test my duramax injection pump for leaks, tried dye checking..flow

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How do I test my duramax injection pump for leaks, tried dye checking but there is too much oil flow to see results.

Greetings and Welcome to Just answer.

The best way is you put oil dye in the fuel, then take the oil filler off. Run the engine and see if there is dye coming around the drive gear under there.


Customer: replied 7 years ago.
As I stated I have alreadt tried that and the oil must be washing away the dye before I can see it, is the another way of checking the pump?

No that is the only way that GM says.

I have no acccess at the moment to part numebrs of the pumps so I am not sure if they will interchange.


Customer: replied 7 years ago.
ok I will wait for your reply, I was just asking for an alternative to the dye check, if I could hook up an air hose to the pump to find the leak. I am getting approx 2 gals of fuel in the crank case. As I stated before I have checked th lines and pump with the dye.

Did you check the return lines under the valve covers? They can crack and cause this or there may be a line leaking under the valve cover.


Customer: replied 7 years ago.
tes dye checked the return line along with the high pressure lines, replaced the head gaskets and installed new seals on the return line fittings.

Did you run the engine with the valve covers off to check for leaks?

This can only be the front of the injection pump, the injectors, the high pressure lines or the return lines and seals.


Customer: replied 7 years ago.
Yes we had removed the valve covers and reconnected all the lines. Also we removed the fuel regulator to raise the fuel pressure to max pressure. Max fuel pressure only goes to approx 13,000 psi.not the 23,000 psi expected.

Was there dye in the system for that test?

Customer: replied 7 years ago.
yes we had dye in the fuel filter at the time and checked for leaks using a uv light tester

OK, if you did not see any at the injectors, lines or return lines, then all that is left is the pump.


Customer: replied 7 years ago.
Is there anyway other than dye checking to check the pump (cant see any dye) to confirm that this is the root cause of the leak and is there a rebuild kit available for the pump? It is probably the most expensive part to replace and I just wanted to make sure before making such a large investment. Is there a rear seal that goes bad in the pump to cause the leak and is this a common failure mode?

The dye is the only way that GM has or puts instructions for on these pumps. No rebuilds.

The are seals at the back of the pump but only the front seal is inside the crank case so if the rear seal was leaking, it would dump on the ground.

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