MPI Relay and Fuel Pump Question

[mooserage]

So, I used the instructions in this thread: click and checked two MPI relays that both came up perfect. But when I try to start the car it won't start, the fuel pump relay is not getting 12v. If I jump +12v to the fuel pump relay (bosch relay rewire) it will start fine. I am also running AEM and not a stock ecu. So, I have come to the conclusion that there may be a problem with the wire that runs from the MPI to the relay to turn it on. I am wondering if anyone knows the pin I can check on the MPI connector for continuity back to the wire that turns the relay on. Any help would be great, thanks guys.
-shamus

p.s. For anyone wondering why I wouldn't just continue to use a switch to manually turn the pump relay on and off there is a very good reason. One of the functions of the MPI relay is to cut the fuel pump if the engine should stall, this is an important safety measure. If I were in a rollover or any accident and the fuel lines ruptured, the still connected battery would continue to run the fuel pump, spraying fuel all over an accident. this is the biggest reason I would like to get this situation fixed, simply for safety. Thanks.

 

[bazeng]

Was it ever running with the AEM in there?

The AEM I'm assuming activates the fuel pump via grounding.
Most aftermarket ECU's do.
If this is the case, you need to make sure the AEM fuel pump wire is grounding the relay going to the fuel pump. Or even better, grounding the MPI.

I've got them jotted down in my notebook when I made my plugin loom.

I had a similar issue.

The VFAQ pinouts aren't detailed enough.
I'll post up the info when I get back home.

 

[mooserage]

This was happening before the AEM was installed and the +12v has been jumped since I had the problem with the stock ecu in. The AEM EMS is plug and play with the stock harness and my understanding is that there isn't any setup for the fuel pump when running the stock configuration. I could be wrong, but I've never heard of having to wire it up differently or set up the programming through the AEM. Thanks.
-shamus

 

[bazeng]

Ok, if its plug and play it should be right then.

The ECU actually activates the fuel pump via the MPI (it grounds the MPI).

The MPI then send 12v to the fuel pump therefor that VFAQ relay rewire works well due to the voltage loss from the ECU to the fuel pump.

I'd grab a multimetre and check for continuity from the 12v+ feed on the relay at the fuel pump end all the way to the MPI.
You should quickly find your MPI wire.
If mot, then obviously you have a break somewhere.

I can check for you tommorrow on the AMG. The wire colours should be the same.

 

[mooserage]

Yeah thats a good Idea, I may get some time today to do a little work on it and I'll try tracing it. Thanks for the help!
-shamus