no check engine, no spark

[dsm908]

1990 Tsi

so i'm driving home the other day, and i notice that my afc turns off, ok, im thinking wtf. thankfully I'm going down hill because i go to give it gas and there is no throttle response. So i immediately pulled over and when the car stopped moving the engine died off. i initially tried cranking the car and i noticed there was no check engine light ( cel ). so i automatically assumed with the given variables that my caps probably leaked out and shot my ecu. WRONG, i threw in a friends old ecu and same thing, so i naturally thought maybe that ecu was bad too, i put my original ecu in his car, fired her right up, so WTF !!!

i don't know where to look now, i checked all of my fuses and nothing. please some info. i also checked the cas plug, and it isnt receiving any voltage.

 

[dsm908]

yeah i believe that may be the problem as well, but when i tested the plug coming from the harness, there isn't any voltage reading. what would cause that

 

[toofast82]

Whats that relay thats under the radio? I believe its ASD relay. Doesnt that cause this problem and is fairly common. Just another possible option to check.

 

[dsm908]

Ok,does anyone else got info on this relay, I'm on my way to the junk yard so I will try to get this piece

 

[steve]

Did you check the MPI fuse in the positive battery terminal that provides power to the MPI relay your asking about? The ECU turns the MPI relay on to power itself and about half of the engine bay on including the CAS.

Make sure you actually check the fuses with a multimeter not just look at them.

 

[dsm908]

ok so I will check those fuses, but where is this MPI relay located, i will look into that because it seems as that is what my problem is, but would that cause my car not do display the check engine light while the key is in the on position ?

 

[steve]

ok so I will check those fuses, but where is this MPI relay located, i will look into that because it seems as that is what my problem is, but would that cause my car not do display the check engine light while the key is in the on position ?

There are several things that would cause that but they are related, starting with the fuse being blown and includes the ECU having failed. The MPI relay is the gold box bolted to the inside of the passenger side center console support below the radio.

 

[dsm908]

ok great thank you steve, im going to take a look at these tomorrow morning, so is there a way to test the relay?, or its basically change it and see if it works ?

 

[steve]

It's a relay, well actually two of them in the box. If you have the wiring diagram it's shouldn't take much to figure out how to test it.

I'm not much of a parts swapper, I usually diagnose problems even if it takes me twice as long.

 

[dsm908]

so there are 2 MPI relays, or is one the MPI relay and the other one is just there so that one isn't lonely

 

[steve]

so there are 2 MPI relays, or is one the MPI relay and the other one is just there so that one isn't lonely

Let me guess, you don't have the FSM for the car.

Inside the MPI relay box there is one relay for powering the MPI circuit. It's gets power from the MPI fuse on the battery and is activated by the ECU pulling the one end of the coil to ground. The other relay in the box is the fuel pump relay and it has two coils. One is connected to the starter circuit to activate when you crank the car and the other to the ECU who pulls it's coil low to keep the fuel pump running as long as it's sees CAS pulses.

These might help.

http://www.dsmtuners.com/forums/new...ht-need-help-troubleshooting.html#post1521402
http://www.dsmtuners.com/forums/problem-diagnosis/239406-no-power-ecu.html#post151003065
http://www.dsmtuners.com/forums/newbie-forum/293581-why-my-mpi-relay-not-working-right.html

 

[dsm908]

wow steve thank you got all the intel, i got her running, it was the mpi fuse, i never noticed it because the previous owner had the battery located in the trunk and the fuses that were supposed to be attached to them he wrapped them in electrical tape. so i coincidentally went to the junkyard with my friend and noticed these fuses in a junked car, thought to myself hey, i dont have those, bought it, went home noticed it under a heap of tape, the fuse was blown !!! changed it and she fired up after i cleaned up the plugs. thanks for all the help guys you rock