Running the fuel pump relay. and VR question.

[crazy0000]

After looking over the wiring diagram for LH 2.4 I'm confused about hooking up the fuel pump relay to my PnP harness for MS.

I was under the impression that the fuel pump relay triggers both fuel pumps individually, but by the diagram it seems as though only one part of the relay trigger 2 pumps. This doesn't seem right to me.

Do I need to trigger both grounds from the Relay? Or just one (pin 20) on the ECU? to run both pumps



Also, I have a question about the VR sensor in my car. after looking at the diagrams, and what people have done, it seems for the EZK they only jump 2 of the 3 wires for the VR sensor in my car. the one thats not jumped is the ground for it. Is it just a different system with MS where you don't need to ground the VR sensor?

The only jumped pins are, 4 to 23, 8 to 16, and 10 to 17. one is for the powerstage, and the two are for VR but there is also another pin on the VR (pin 11) that says it gets grounded through the EZK, so do I have to jump that one as well?


Thanks, so close to being done....

[The Aspirator]

Maybe the ground listed is just for the shield wire from the sensor to the EZK box? I dunno, I'm guessing.

[B-dub]

I'm having a similar problem with my relay board. The voltage out from the relay board drops to 10-11volts and my fuel pump turns off/runs really low pressure.
Is there anything wrong with running the fuel pump on a independent switched circut? It would seem silly to do if I have MS to control it, but I wouldn't hesitate to do that if it fixed my problem.

[crazy0000]

Maybe the ground listed is just for the shield wire from the sensor to the EZK box? I dunno, I'm guessing.

That makes sense to me, thanks john

Anyone know about this fuel pump relay though?

[The Aspirator]

The fuel pump relay is really big and complicated, right? Not your normal 5 pin jobbie? Then yes you might have to ground two pins to get both pumps to run, maybe it's a 2in1 relay like the headlamp/highbeam one. Try it and see! Make sure the relay is all powered up with the proper wires, then use an alligator clip or something to ground one of the relay pins at a time. See if it brings both pumps to life or just one of them.

For what it's worth I've never had MS control my fuel pumps. In the blue 244 I just had a defroster switch on the dash that controlled an aftermarket relay which turned on both pumps. But I'd have to flip it every time I got in the car. Great theft control, became second nature after a while, but I've since wired up the 242 so that the same switch/relay is now ignition switched. I can still switch if off if I'm parking in teh ghetto.

[Captain Bondo]

The fuel pump relay is really big and complicated, right? Not your normal 5 pin jobbie? Then yes you might have to ground two pins to get both pumps to run, maybe it's a 2in1 relay like the headlamp/highbeam one. Try it and see! Make sure the relay is all powered up with the proper wires, then use an alligator clip or something to ground one of the relay pins at a time. See if it brings both pumps to life or just one of them.

For what it's worth I've never had MS control my fuel pumps. In the blue 244 I just had a defroster switch on the dash that controlled an aftermarket relay which turned on both pumps. But I'd have to flip it every time I got in the car. Great theft control, became second nature after a while, but I've since wired up the 242 so that the same switch/relay is now ignition switched. I can still switch if off if I'm parking in teh ghetto.

Do the pumps still shut off on their own if you're in an accident or something?

[The Aspirator]

Nope :oops:. When the ignition key is on, they're on. I tend to forget about smart little details like that. When I re-wired my MS I did set up a fuel pump output wire, just never got around to wiring it up since my old wiring worked.

[crazy0000]

Its not uber complicated. Its 6 pins instead of 5. So maybe its one ground the grounds out 2 power signals to pumps. Ill try that way.


Does MS prime them? and kill the pumps when the engine stalls? It should right? just like the stock ECU

[MrDoug]

Does MS prime them? and kill the pumps when the engine stalls? It should right? just like the stock ECU

Yes, MS will prime the pumps for 2-3 seconds then shut off.Pumps should only run continously whan the engine is running.If the pumps stay on with key on/engine off, you have a wiring/config. issue. On LH 2.4 it's pins 20 & 21 for the fuel pump relay.

For the VR, pin 11 is the internal ground, pin 10 is VR+ Pin 23 is VR-. I cut the connector off an old EZK box & ran 3 jumper wires- from pin 11 to 20 for the ground, 23 to 17, and pin 10 to 4 to bring the VR signal to pins 1 & 28 on the ECU connector. This is for a 1990 740 turbo,with a V3 board- so your car might be a little different

[crazy0000]

Yes, MS will prime the pumps for 2-3 seconds then shut off.Pumps should only run continously whan the engine is running.If the pumps stay on with key on/engine off, you have a wiring/config. issue. On LH 2.4 it's pins 20 & 21 for the fuel pump relay.

For the VR, pin 11 is the internal ground, pin 10 is VR+ Pin 23 is VR-. I cut the connector off an old EZK box & ran 3 jumper wires- from pin 11 to 20 for the ground, 23 to 17, and pin 10 to 4 to bring the VR signal to pins 1 & 28 on the ECU connector. This is for a 1990 740 turbo,with a V3 board- so your car might be a little different

Hopefully Not because I've done all that! Except I only Jumped pin 20 for the fuel pump(DOH!)

Also I jumpered the wire for the Powerstage, right? or else the coil wouldn't fire, am I right? I've gotta do that ground jumper.


Thanks for verifying all of it though, makes me feel a bit better.
I had the MS plugged into the car tonight, couldn't hear the relay click, but because I only hooked up pin 20 neither pumps will prime(I think 21 is the power feed for 20 aswell, in the relay). So is it alright to let MS trigger two relays? Won't over stress it?

Everything seems to be working other than that though!

Also figured out how to make it prime, woo hoo, Im excited.

[MrDoug]

you need to connect Pins 20 & 21 to get both pumps to run-I trigger both relays directly from MS- some people say to use a relay(especially if you're using a 2.2 board) I Can't help with the Powerstage, I am using a VB921/BIP373 to drive the coil directly

[crazy0000]

Okay, I just wanted to make sure I wouldn't hurt my MS by grounding out both of the switches on the fuel pump relay with the same wire coming from MS.

I'm pretty positive that the way I hooked up everything else is correct.

[linuxman51]

use a relay to ground both sides, you're asking for trouble if you don't/.

[The Aspirator]

Well there's your answer, go Kenny go.

[crazy0000]

What kind of trouble are we talking about?
Your early version of PnP didn't use one right? I guess I might as well.

I'm kind of confused on the easiest way to do this.

Maybe connect both pins (21 & 20) to 30 or main power on the relay, relay power to just 12v, and ground, and then switch to MS.
Would that be easy? where would I power the relay from since I don't want to hack any of the wires in my car up(Hence the harness), same pin powering MS?

[The Aspirator]

Well that new fuel pump relay relay won't draw much juice at all, just enough to trip the real FP relay, so get power from anywhere convenient. I forget all the numbers but on a 5 pin relay two of the pins opposite eachother trip the relay with power and ground. Give one power, MS will ground the other. Then for the other two pins that are left put one to a good ground and the other to trip both pins of the FP relay.

I assume Kenny is worried about too much draw from MS if it has to trigger both sides to that FP relay.

[crazy0000]

Okay, I've got everything hooked up.

Just put in the Bosch 139 and switched the pin.

The MS is getting the VR signal(I can tell cause the tach moves in MT) but its not triggering the coil, I don't get tach signal on my tach in the car.

I think everything is set up right.