Electrical Nightmare.

[Tony90TSI]

Ok i am putting this here because i know its something simple i am overlooking.

Car is a 90 Eagle Talon.
Issue- The Fuel pump and ignition never get fire.
Things i have done- With a voltage/ohm meter checked all fuses and relays to make sure none were bad and replaced the ones that didnt check out. Switched ECU to one of the 3 i have at the house, checked power to the pump, all came back with nothing car still doesnt fire/get fire but if you hit the key the engine spins over.

Question - What am i missing to get this car running again, I know its something stupid and simple i am just not getting it. Any help would be great guys thanks.

 

[perley03]

Bad crank/cam sensor. Either one will stop the spark/fuel to keep the engine from running. Not too sure on how to check one, using ohm meter maybe. I don't have my manual here, but maybe someone else will chime in and help.

 

[Tony90TSI]

I wouldnt think that a bad sensor would keep the pump from even coming on. I mean its like the ecu is doing nothing. The lights come on on the instrument cluster but the guages arent reading and the fuel pump itself never turns on. I know the pump isnt turning on because it has a walbro 255HP pump in the tank and that thing is loud.

 

[TALONTRAX]

It could be a bad cas. on a 1G. If the ecu does not receive pulse signal from the cas, it will shut down fuel pump operation . . .

 

[steve]

Does the ECU power up? You can tell that is does if the CEL turns on for five seconds and then goes off whine the boost gauge goes to the zero mark and stays when you first turn the ignition on.

You can check the CAS by pulling it and turning it by hand. It should cause the fuel pump to turn on and you'll hear the injectors pulse. If you pull a spark plug and ground the end it should fire too. You can use your multimeter and look at the CAS or TDC signals. You'll see that the ECU pulls them up to 5v and the sensor pulls them low when you turn it. Two pulses per turn for the TDC line and 4 per on the CAS line.

Steve

 

[Tony90TSI]

Maybe i am missing something but initially when you turn the ignition on the pump should prime and pressurize the system, correct? The pump never comes on and never gets any power to it. When i turn the key on the lights across the bottom all come on including the check engine light but it doesnt look like any of the guages are registering. I mean i know the car has atleast 12 gallons of fuel in it because thats how many gallons my extra cans can hold and i emptied them into the car but the guage is still reading 1/4 tank. The guy that had it before me took the stock boost guage out also. Any other ideas guys?

 

[steve]

Maybe i am missing something but initially when you turn the ignition on the pump should prime and pressurize the system, correct?

Nope. A few people with 90's say that their pump primes when they turn the ignition on but they don't on most DSM's until you crank the starter. It would have to be caused by the ECU if it did.

The pump never comes on and never gets any power to it. When i turn the key on the lights across the bottom all come on including the check engine light but it doesnt look like any of the guages are registering. I mean i know the car has atleast 12 gallons of fuel in it because thats how many gallons my extra cans can hold and i emptied them into the car but the guage is still reading 1/4 tank. The guy that had it before me took the stock boost guage out also. Any other ideas guys?

Does the CEL go off after five seconds? Since you say the boost gauge is gone I don't care about the rest of the gauges other than to ask if what your describing is different than when the car ran.

 

[sawnuoff]

I have run into this same issue accept my car does start and i have notice it more lately because i have been driving it, but any ways my gauges arent working at all when i turn on the key but if i reach down and tap on the fuse panel or move it around all my gauge come on and the lights on the dash so you might want to make sure there isnt a grounding issue with your fuse box or in that area i have not looked at mine to determine that actual cause of my problem but most electrical problems come to a bad ground.

Let us know what you come up with.

 

[Tony90TSI]

Does the CEL go off after five seconds? Since you say the boost gauge is gone I don't care about the rest of the gauges other than to ask if what your describing is different than when the car ran.

The light does go off after a few seconds. As for the issue with the guages i dont know. I bought the car from a friend broke and i just now started putting it back together as i need a daily driver while i finish up some things on my current daily driver. When i go home tonight i will recheck all the grounds again and also pull the cas. Anything special i should look for or check with the CAS?

 

[Tony90TSI]

Got a chance to mess with it a little this morning. Starter checked out fine. Cables are fine as they were checked with an ohm meter. Battery was showing to have 12.5 volts but on a load test had a bad cell and not enough power for the entire system so i bought another one. Still no spark and still no pump. And ideas on what is good and bad on a CAS? And the proper way to ohm one out? Also the coil doesnt seem to be the problem as i switched coils from a running car and still notta.

 

[steve]

You can check the CAS by pulling it and turning it by hand. It should cause the fuel pump to turn on and you'll hear the injectors pulse. If you pull a spark plug and ground the end it should fire too. You can use your multimeter and look at the CAS or TDC signals. You'll see that the ECU pulls them up to 5v and the sensor pulls them low when you turn it. Two pulses per turn for the TDC line and 4 per on the CAS line.

There is nothing to Ohm out except the wires running from the ECU to the CAS connector, you can check the operation of the CAS with the voltmeter functions of a multimeter.

Steve

 

[Tony90TSI]

So i finally got some time to work on the car again. The fuel pump not coming on has been fixed. Swapped the relay beside the ecu in the car and the pump comes on. Now the bad side. Still no spark.

So yesterday(saturday) we spent most of the day working on the talon trying to figure out what was/is wrong with it. Still no spark. First we tried a different CAS to see if it wasnt sending the signal to fire. But when you spun it in your hand you could clearly hear the pump start up then spill fuel everywhere(I forgot to put the hose clamp on the fuel return line) so the CAS wasnt it. So next we took the coils and transistors off of another running 90 dsm and put them on the car. Still no spark. So went back to stock and switched ecu's with the 90. Still no spark. So then we started checking power and ground everywhere. And the power was there. The ground was there. WTF?!? So we check the power on the back of one of the running DSM's there. Took the cas out spun it over and the test light would flicker everytime it fired that coil off. So we went back to mine with this new found idea and looked at it. Put the test light on it, spin the cas but no flicker and no fire of the coil? So far i cant find any reason for it and the only other person i could get in touch with said it could be a ground from the connector to the coil going bad and not letting the coil fire like its supposed to. any other ideas as to why it wont fire?

 

[steve]

The coil gets fed power from the ignition circuit to one side of both coil primaries. The power transistor and '90 tach gate are connected to the other side of the primaries. The ECU drives the bases of the power transistors which causes them to pull their side of a primary to ground charging the coil and when the ECU switched them off the magnetic field collapses inducing a voltage in the secondary and fires the two spark plugs connected.

You can't really use a test light on the ECU to power transistor connection or you'll damage the ECU but you can use a multimeter while somebody turns the CAS and measure the voltages. Check at the output of the PTM and then at the inputs. That should narrow down the problem.

Steve