[solved - see below]

Hey all…

I have a 2000 Blazer LS, 2WD that has been randomly shutting off while driving. When this happens, the dash lights stay on (like a stall) and it may or may not start on the next attempt. Each starting attempt does result in the normal dash/check light sequence and starter turning over, but not always the fuel pump priming. When it does prime, the Blazer will start.

Fuel System Checks:

- When I turn the key to ON, the fuel pump does not always engage for 2 seconds. This problem is intermittent (waiting 10 seconds between attempts).

- All fuses and relays appear fine in the fuel system.

- If I jumper the N.O. connection at the relay, the fuel pump kicks right in and runs.

- Checking the coil at the relay, there is a flash of a signal (like .5 seconds) from the PCM, but not the expected 2 second prime pulse.

- Wiring from the PCM to the relay seems okay (1 ohm contact-to-contact)

- Verified connectors are tight on PCM and fuse and relay connections were clean and tight.

- Shade-tree check -- Sometimes gently banging on the top of the PCM will cause the fuel pump to kick in for the prime pulse (ignition on). Then I can start the vehicle.

I want to assume there is a cracked solder joint or other issue in the PCM and replacing the computer will solve the problem.

Anyone have any thoughts on what could be causing this before I tell my friend to hunt down a new (used) computer? (Anyone know how to tell if the Blazer has the ZN4 option when looking for a computer?)

Thanks in advance! The info on this site is always useful and help me solve other issues with this Blazer.

-- Issues was solved by installing a used PCM (same service number and reprogrammed to the VIN). Thanks for all the replies! --

 

It does sound like a connection issue at or in the PCM. You will need to get the PCM reprogrammed to your VIN to be sure, but you could compare the RPO codes in the glovebox of the donor for the ZN4 option and AU0 (Remote locks) as well as a host of other options. If the RPO codes do not match exactly, it is not guaranteed that everything will work as it should.

 

it sounds like its eathor your injectors a clog in the filter or a clogged cat

 

you could also need new plugs