Quick question about ignition pulses and fuel delivery.

[Auladan]

I've got a quick question about ignition pulses and fuel delivery.

Say that everything else in the car is running properly except the CAS (cam/crank angle sensor) on a 1990 Eagle Talon TSi AWD. Could a faulty CAS disrupt the initial power delivery to the fuel pump when the key is turned?

The fuel pump makes an audible whirring sound when the car, properly working, is turned on. Right now my car is down and the fuel pump won't whirr when the key is turned. Though after testing I found the pump and relay and all that are fine, and bypassing the computer and what-not will make the pump whirr as it should, so I know the pump isn't broken.

I have the computer out and am ready to send it to some place in Florida to have it tested and repaired if necessary. But before I do that I want to know if a faulty CAS, assuming the computer and all other systems are working, could disrupt the power to the fuel pump that would keep it from whirring as it should.

Anyone?

 

[steve]

On a 1G the fuel pump shouldn't run until the ignition is in the start position not just on.
The MPI relay has two inputs for switching the fuel pump on. One come from the starter circuit and is the one that initially runs the pump. The other is from the ECU. I can't remember right now if it's the CAS or the signal back from the coils that the ECU monitors for running the pump after the engine is running. But a bad CAS won't keep the starter part of the circuit from working.

Have you checked your ECU for capacitor leakage? It's not uncommon for the electrolyte to eat the trace for the fuel pump up under the metal heatsink where the EMI capacitors are or to take out the power to the all solenoid drivers including the one for the pump. I wind up fixing that sort of problem all the time.

Steve

 

[Auladan]

Well, I've taken the ECM apart and looked it over and from what I can see I have no leakage. However, I contacted Pina Motorsports up here in Kent (a few hours from me) and they told me that there can and most likely is leakage from the caps even if I can't see it.

Also I listened to the fuel pump (hand on it and everything) while having someone else turn the motor over and it still didn't whirr. Only when I bypassed everything did it come on. I tested a relay box that's right near the computer under the dash and without it in the system the car wouldn't even start. With everything in as it is (computer and all) the car will start then die immediately after.

I'm really thinking it's the ECM. I've smelled a foul stink from my vents for a long whlie now and just before my car started doing this I heard a random ticking from in/under the dash, which I read is another sign of a failing ECM.

A few years ago I had a broken plug in my old motor's coil pack and it was arching really badly; it reset my computer a few times I believe and my have caused some damage. Killed the car and made it so it wouldn't even turn over for a day or to, and reset all my CD player settings to default. Happened twice before I found and corrected the problem.

I'm really thinking it's the computer, though it looks in perfect condition.

 

[steve]

Well, I've taken the ECM apart and looked it over and from what I can see I have no leakage. However, I contacted Pina Motorsports up here in Kent (a few hours from me) and they told me that there can and most likely is leakage from the caps even if I can't see it.

Also I listened to the fuel pump (hand on it and everything) while having someone else turn the motor over and it still didn't whirr. Only when I bypassed everything did it come on. I tested a relay box that's right near the computer under the dash and without it in the system the car wouldn't even start. With everything in as it is (computer and all) the car will start then die immediately after.

Nick and his crew are correct, it's quite possible for the caps to leak and never make it out from under the capacitor. If these are original caps I can pretty much assure you that they have leaked.

The relay box you described is the MPI relay I was talking about. If the car starts and then dies within a few seconds the odds are real good that the ECU has been damaged. If you can ground pin 7 on the MPI relay (forcing the pump to run) and the car continues to run then the ECU is at fault, either because of damage or due to it not seeing that the engine is running. It won't spark at all if it doesn't see CAS signals

Steve

 

[Auladan]

Alright, my CAS isn't failing in that case. I tested my plugs and have spark all around.

Would you know of any reputable places that can do diagnositc/repairwork on ECM's (mine is Eprom)? This place in Florida (name escapes me) says they'll take the computer and a $160 money order then diagnose and repair if necessary, and if it isn't damaged they'd send it back with the money. I'm not so trusting, but...

 

[DarthBulk]

I have never used them, but I came across this place:

http://www.ecmtogo.com/

That is where I was considering sending my ECU. Maybe someone else on here has used them?

 

[oldman]

Alright, my CAS isn't failing in that case. I tested my plugs and have spark all around.

Would you know of any reputable places that can do diagnositc/repairwork on ECM's (mine is Eprom)? This place in Florida (name escapes me) says they'll take the computer and a $160 money order then diagnose and repair if necessary, and if it isn't damaged they'd send it back with the money. I'm not so trusting, but...

Ha funny you asked that because you were just talking to one of the best I know, steve. I've just sent out two of my own ecu's to steve for repair. Here's link to his site.

http://www.xnet.com/~steve/Auto/DSM/ECURepair.html

Give him a call, you will find him extremely knowlegeable when it comes to cars and ecu's especially.