Bjeralds

iTrader: (1)

Car is 91' S5 NA with turbo engine swap

So a few weeks ago my car started cutting off randomly and would restart after about 5 minutes. Then one day it didnt start at all. I have no fuel or spark.

I have tried swapping my spare CAS, my spare ECU, checked my grounds and my fuses and no luck.

It has ran fine for over a year and this was just all the sudden. And it was inconsistent, as one day it shut off three times in about 7 miles on my way home from work. And another it didnt shut off all day while out and about.
Everytime it shut off it was up to operating temperature.

Not sure where to go with it now. Any ideas would be appreciated.


Thanks, Ben

satch

iTrader: (1)

Focus on the Main Relay. It has two plugs. With respect to the two wire plug the B/W wire must have voltage w/key to on. The other wire is a ground. This ground runs to the fender wall just under the trailing coil. A poor ground will cause the engine to cut. Also, check the four wire plug. Both the White/Red and White/Blue wires must have "constant" voltage. Jumpering the W/R to the B/Y wire and the W/L to B/W wire will bypass the Main Relay. Doing this will tell you if the problem is the relay and if the problem is caused by the two wire plug or the relay itself. If you have an intermittent connection on either of the constant voltage wires that too would cause your problem. And when the car shuts off try checking the wipers or turn signals w/key to on. If they don't work then the Ignition Switch is not powered properly.

j9fd3s

iTrader: (3)

in my experience if its not getting fuel either the ECU isn't on, like satch says, or its not seeing an RPM signal.

Bjeralds

iTrader: (1)

It's the Main relay as Satch said. Pulled the connector and the plastic was melted a bit. Looks as if the relay overheated some how. I jumpered the connector but no luck, do I also need to do something with the round plug? I just want to test to make sure that is the problem. One of my friends has a spare but I cant get it till he gets back in town.

satch

iTrader: (1)

Just the jumpering of the wires in the four wire plug is necessary. When jumpered the plug is left unconnected to the relay. Also, the checking of the EGI fuse plus checking for constant voltage to the two White based wires in the four wire relay plug that are powered by the EGI fuse should be looked over.

Bjeralds

iTrader: (1)

Could the EGI fuse cause lack of bith spark and fuel?

satch

iTrader: (1)

A bad EGI fuse would prevent spark and fuel injection, but if the 15 amp Engine fuse is good then the fuel pump would run w/o the need of the EGI fuse w/key to start or w/key to on if the fuel check connector was jumpered.

Bjeralds

iTrader: (1)

My fuel pump is on a switch. Thats how I determined it isnt injecting fuel was to watch the pressure gauge while cranking with the pump off. The EGI fuse is good, swapped it with another 30 amp. And the 15 amp engine fuse is good as well. I have not checked for constant power to the two white wires yet.

And aside from the plastic connector being a bit melted, the relay connector and wiring on the engine side look ok.

Bjeralds

iTrader: (1)

I am also wondering if this could have been the source of my battery drain. As a malfuntioning relay (i would think) would condsume some power.

So i need to wait for my jumper box to charge before i can do more testing as my battery is dead.

Bjeralds

iTrader: (1)

The two white wires have constant voltage. The wipers work with key to on, so I guess the ignition switch is ok. Goingto try swappingmy CAS again for the one i pulled out. I know its good. The other has been sitting for a year.

The tach is not registering rpms when i am cranking it.

RotaryEvolution

iTrader: (30)

check the "engine" fuse inside the car at the left side kick panel. this fuse can blow if the ECU is being overloaded by a short in the engine harness, such as say an AFM wiring harness that is rubbing through on the chassis which i have seen on some shotty "cold air intake" installs.

Bjeralds

iTrader: (1)

That's one of the first things i checked. It's good. Thats why i'm stumped as to the problem. I thought i'd checked almost everything and it still doesnt work.

satch

iTrader: (1)

You also might want to take a reading from the Brown TPS wire w/key to on and it should read 5 volts and this is the Vref.

Bjeralds

iTrader: (1)

From what I have seen I believe the problem originated at the main relay as the plastic four wire plug is slightly melted and discolored.. But jumpering the plug has not made a difference. So is there more to it. The two wire plug appears to be fine.

So basically I have no RPM Signal, no fuel injecting, and no spark. When my friend gets back he isgoing to get me his spare main relay.

Bjeralds

iTrader: (1)

BTW if it makes any difference it is one of the white based wires with constant voltage which is the one that melted. It's just one terminal in the plug that got hot.

RotaryEvolution

iTrader: (30)

plug in the main relay and turn the key on, disconnect the connector to the leading coil pack and see if there is 12v to the thick black/white wire. if yes then it isn't the EGI or main relay but likely the ECU not turning on, which is fed power from the EGI to engine fuse then to the ECU. make sure the engine harness is securely grounded to the engine as well.

i have also seen a faulty AFM cease spark and injection(not the more common fuel pump circuit fault), disconnect the AFM and see if the car starts and runs for a few seconds(granted it was an S4 but the S5 is still very similar).

Bjeralds

iTrader: (1)

And also, I belive it must be the main relay because none of the light on the idiot cluster light up other than the door and brake light. Which I believe means the ECU is not getting power.

Is there another way to provide power to the ecu to be sure that this is the case.

Also, thanks everyone for your help. I can do mechanic work, but at times my diagnostic abilities are not what I wish they were.

satch

iTrader: (1)

The idiot lights turn on w/key to on because the alternator supplies a ground signal that causes the lights to illuminate. It could also be a poor connection to the cluster assay.

And the Brown/White wire at the TPS would tell you if the ECU has power.

W/key to on the B/Y wire at the coils should have battery voltage. There is a three wire Green check connector near the leading coil. Two wires are Yellow based and the third is B/W. This wire powers the ECU so it too should have battery voltage w/key to on.

And connecting a spare CAS to the harness w/key to on and spinning it should cause both the coils and injectors to click.

Bjeralds

iTrader: (1)

I was able to get it to start by cleaning the main relay connectors. But that doesnt tell me why the relay overheated. And though i got it running it sounds like crap. Like it wont rev much. Like its not getting enough fuel or spark.

satch

iTrader: (1)

Which white wire had a burned pin at the relay. Have you checked for codes?

Bjeralds

iTrader: (1)

I'll check and let you know. Gotta run out for a bit. Havent checked for codes yet. Didnt try to drive it as I didnt want to mess it up.

Bjeralds

iTrader: (1)

It's the black and white wire on the four wired plug that has the burned pin. Still need to check for codes.

satch

iTrader: (1)

The B/W wire powers the ECU.

Bjeralds

iTrader: (1)

That explains why it cut out and wouldnt start. What could cause that to overheat?

And I suppose that could be why it didnt sound as though it is running good is maybe it's not making great connection and is not giving the ecu full power.

Any recomendations?

satch

iTrader: (1)

Until you check more things it's still up in the air as what your problem is. You "could" measure the Brown/White wire at the TPS w/key to on or perhaps not. The B/W wire also powers the Emission solenoids. A grounding of this wire could cause the wire to heat up.