No start no rail pressure - Chevy and GMC Duramax Diesel Forum
01-04.5 LB7 Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #1 of 3 (permalink) Old 01-05-2020, 03:45 PM Thread Starter
Join Date: Dec 2019
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No start no rail pressure

Bought an 02’LB7 that Only started with fluid, guy said it just needed a new CP3. Got a new CP3 installed (I am mechanically inclined)it myself, double checked all my lines & fuel fittings made sure everything was good bled the hell out of it but still no start. No rail pressure On scanner. swapped out the fuel rail pressure regulator, blow Out all the lines, still not start. Did a rate return test and didn’t get any fuel, cracked the line to the fuel rail tee and 1&8 inj and got fuel and removed all the glow plugs and turn motor over see inj we’re stuck open but cylinders were dry. Looked through all prior post but didn’t see anything. Any help would be greatly appreciated.
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post #2 of 3 (permalink) Old 01-05-2020, 08:02 PM
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Question A Mystery...

Hello and welcome to the Forum!

As you have learned, relying on advice from the PO can be risky, unless the CP3 was professionally diagnosed, in writing.

... cracked the line to the fuel rail tee and 1&8 inj and got fuel.

A visual indication of fuel at the points you noted above says nothing about fuel pressure there but If it is adequate, whatever pressure sensor that is talking to the FICM may be defective or a signal is not getting to the FICM because of a wiring problem.

As you probably know, the Fuel Injection Control Module (FICM) will not wake up and fire injectors until it is informed of around 5000# of rail pressure. Im not sure where the FICM gets that signal, but should be easy to learn.

Cant recall where you can tap an injector firing signal. Relatively high fire volts that drops down to hold volts I believe.

Or, all is well up to the FICM and injectors are not firing because it is defective. Good move on pulling glow plugs to check there. If GPs are still out, R&R of those inexpensive items would be a smart move.

Some things to consider and Im sure others will weigh in.

Keep us posted.

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post #3 of 3 (permalink) Old 01-07-2020, 01:04 PM
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Where did the CP3 come from? Also might be high return rates on the injectors allowing the truck not to build fuel rail pressure.
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