[macpeppers]

I used a 1995 ecc-iv donor with the vcrm controlling the fuel pump and fans. my vcrm has failed and i'm thinking about deleting it. I don't have AC. anyone have any tips on this or pitfalls?
thanks,

 

[macpeppers]

it's a mark viii donor

 

[Fasterpatrick]

Shouldn't be to difficult, been running mine for years with out it used a temp sensor in the block for the fan via a relay and sent the fuel pump signal to a relay for that as well. You just wont have the variable speed for either.

Patrick

 

[macpeppers]

thanks Patrick, I've found a temp sending unit that closes at 200f, do you think that's about right? where in the block did you install it?
thanks

 

[mn12]

That's about right the stock Mark Viii calibration was 190 if I remember correctly


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[macpeppers]

Shouldn't be to difficult, been running mine for years with out it used a temp sensor in the block for the fan via a relay and sent the fuel pump signal to a relay for that as well. You just wont have the variable speed for either.

Patrick

i'm going to use my existing high speed fuel pump relay, when you say "sent the fuel pump signal to a relay", do you let the PCM energize the high speed fuel pump relay? looks like I could energize the relay directly from the ignition switch in the run/start position but the pump would run all the time the switch is on and that may be ok, but with the PCM controlling the relay, I guess it would run the pump a few seconds when you turn the ignition on then stop if you don't go to start (i'm guessing at this). which way do you think would be best?
thanks,
mac

 

[Fasterpatrick]

Yes, use the PCM signal to fire the relay. also i found a 190 temp switch (gm Part), I double checked for a placement I put that one in the cross over tube as well as the sensor for the PCM the gauge sending unit went in the block under the driver side header toward the rear.

 

[macpeppers]

thanks for all the help. I see the vcrm also has a relay that powers the pcm, I've got 4 unused relays in my fuse box, i'm going to use the auto head light relay for this.

 

[macpeppers]

Yes, use the PCM signal to fire the relay. also i found a 190 temp switch (gm Part), I double checked for a placement I put that one in the cross over tube as well as the sensor for the PCM the gauge sending unit went in the block under the driver side header toward the rear.

do you recall what circuit you used to fire the fuel pump relay? I tried circuit 926, pin 18, (fuel pump input) from the PCM but it didn't work. I thought I had previously measured 12vdc at this circuit but now I only measure <1vdc. I think the PCM is powered up ok, if I fire the fuel pump relay with +12vdc from the switch, it starts and runs fine.

 

[Fasterpatrick]

Try fuel pump output enable pin 22. I'm at work right know when I get home I can look at my notes and let you know exactly. it's been six years so I would like to be sure.

 

[macpeppers]

Try fuel pump output enable pin 22. I'm at work right know when I get home I can look at my notes and let you know exactly. it's been six years so I would like to be sure.

sorry Patrick, I wrote down the wrong end of that circuit 926. it is pin 22, fuel pump enable. when I was troubleshooting to find out that the vcrm was bad, I thought I read +12vdc on it at the data link connector.

 

[Fasterpatrick]

Did some digging though my notes and found the trouble, okay this may sound a bit weird. you will need to run the ground lead from the new pump relay coil to pin 22 on the PCM. The hot should come from the ignition switch (run, start). the switch side of the relay is supplied from fuse box, output side is run through the inertial cutoff switch and to the pump, with a tap after the relay running to Pin 8 on the PCM. I have a wire break out cheat sheet I worked up if you PM me your email I can get it to you quickly.


Patrick

 

[Fasterpatrick]

Found some easier to understand info.....

The ECM generates an initial ground pulse (FP signal at pin 22) to activate fuel pump relay when ignition key is turned on (pump prime). Subsequent FP pulse generation will depend on the presence of the PIP pulse, generated by the Crank sensor when engine is cranking or on.
The FP signal (FP relay triggering), wire, and relay coil are known as / referred to as the PRIMARY circuit.
At the same time the FP pulse is generated the ECM monitors a 12-vdc signal, from the FP relay, to confirm the fuel pump is receiving power, or its ON/OFF status at pin 8 in the ECM. This signal is identified as the Fuel Pump Monitor (FPM) 12-vdc signal, also identified, or referred to as the SECONDARY circuit.

That help.

Patrick

 

[macpeppers]

thanks Patrick, I hooked it up like you said and it works great. can't think you guys enough, without help from you guys a lot of these projects would be abandoned.

 

[93markviii]

thanks Patrick, I hooked it up like you said and it works great. can't think you guys enough, without help from you guys a lot of these projects would be abandoned.

sorry to revive a 6 year old thread but my 93 Mark VIII fried the VCRM and finding a replacement is impossible. Think you’d be able to go a little more in depth on how you bypassed the VCRM? Ac and fan control isn’t an issue.Getting it running is my goal. You can also email me @ [email protected]