Fuel pump relay bypass.

[waffles]

Hello everyone! Does anyone know of a write up on how to bypass the fuel pump relay in the ccrm to a standalone relay? My car will stall with no pressure at the rail and when I bang on the ccrm it comes back to life.

 

[turbo79]

I couldn't give you specifics on which circuits/wires to find to insert a relay (there are wiring diagrams about CCRMs here if you search), but the first thing that comes to mind is that all of the functions that the CCRM controls are run through the PCM, and if you bypass the CCRM, or change the value of the signal sent to the fuel pump through the CCRM by the PCM by inserting an extra relay, the fuel pump switching could/would become erratic.

When asking for repair advice, you need to identify what SHO you have. Is it the car in your sig line?

Also, CCRM functions differ over the years, and through the Gens.

Why not get a replacement CCRM?

 

[Off Road SHO]

I think pin 19 (pink with black stripe wire) of your PCM is the trigger but it "T's" into another Pink/with Black Stripe wire coming from pin 5 of your CCRM module labeled "Fuel Pump Power", before it heads to the safety interrupt switch in the trunk. It would be best to monitor pin 19 to see if it is sending out a +12 volts at key-on, or a ground signal that causes the CCRM to send the +12 volts that the fuel needs.

Wait, never mind, you'd have to separate those two wires to determine which is sending what.

Tom

 

[waffles]

I thought that the 93 came with only a single speed pump? Would I not want that running all the time when the car is running?

 

[sperold]

I think you can bypass that relay, but you miss out on that impact shut off switch feature that shuts off your pump in an accident.

I think about 10 years ago there were discussions on how to fix / change that relay inside the Integrated Relay Control Module (CCRM), but changing the whole thing was just too easy a fix.

 

[Off Road SHO]

I was wrong. The 3.0 PCM sends a ground as a trigger from PCM Pin number 41 via a Tan w/ light green wire to the fuel pump relay in the CCRM via CCRM pin 18. The CCRM then sends +12 volts to the fuel pump from its pin 5 via a pink w/ black stripe wire. This pink wire then goes to two places: 1) the fuel interrupt switch in the trunk on the driver's side behind the liner, AND back to the PCM pin # 19 to be monitored.

To the original poster: send +12 volts to the feed side of that safety switch in the trunk and you will be able to power your fuel pump and be safe in an accident.

OCMO (Other codes may occur)

Tom