XFI switching to bank-to-bank to troubleshoot?

[Blazer406]

LC2 based Turbo V6 with Fast XFI

I was thinking..... if you have a car...... that isn't running right or is refusing to crank in SEFI mode, can you simply just put in in bank to bank mode (in the fast settings) and crank it to help confirm or eliminate the cam sensor as being an issue. I would assume it would not matter if you left the cam sensor plugged in or not.

In our case.... this car cranks sometimes..... but currently it isn't cranking... so I can't just unplug the cam sensor after it starts and force it into bank-to-bank.

I read (in the XFI help) if you do this, that you need to zero out any individual cylinder timing corrections as it will still be making the corrections and it doesn't know what cylinders are what without the cam sensor. I'm having a hard time wrapping my head around this because it knows when to fire the plugs......it knows when #1 is at TDC...... what it doesn't know is if #1 is on the compression stroke or exhaust stroke..... since it is waste spark.... it shouldn't matter.....

Any thoughts?

 

[HighPSI]

I'm not 100% clear what you are trying to accomplish but, you can't unplug the cam sensor until after the car is running. Otherwise the CCCI won't know what cylinder to fire. Also, realize the XFI will crank in B2B mode even if it's in SEFI mode

 

[Blazer406]

I have a car that won't crank most of the time..... in troubleshooting we have determined we think it is getting a cam signal and a crank signal.... per the lights on the XFI. From what I can tell..... it is reading correctly on the CTS and ATS and the MAP...... It did crank up and run for 5-10 min the other day on spare coilpack and module I had, but 15 min later went to popping and eventually stalled. It really hasn't cranked since. On this particular car, the 2 hot wires on the module are hotwired and are getting full voltage. The motor will hit every once in a while during cranking.

I had assumed it cranked in SEFI mode if it was getting a cam sync pulse during cranking. I remember now that you mention it... that I noticed the injector lights flashing bank-to-bank while trying to start.

I was just trying to temporarily take the cam sensor completely out of the loop by telling the fast to run bank-to-bank.... and see if it would fire up and run correctly.

Question: If this car is hot wired all the time to the two wires on the module...... how does the XFI turn the car off with the key? Does it just not send a points pulse to fire the coils?

I am recommending to him to fix the module wiring where it isn't hot all the time.... but I don't think that is causing the no-start issue we are seeing right now. The way it is set up now... he cuts the car off and gets out and hits the battery disconnect anyway.... so the voltage is cut then going to the module.....

 

[TurboBob]

if the wiring (other than the hot wires) is stock, then the XFI will not get crank reference pulses until the ignition module syncs. So a CAM sensor is required to get any cranking fuel.

It almost sounds like the hotwires are wired so they drop when cranking. I would put it all back to stock and start there.

make sure the CAM sensor is timed properly and not 'busted'....

Bob

 

[Blazer406]

I'm thinking wiring issue as well.... he last told me it is almost like it hits the instant he lets off the key when cranking. That screams wiring issue to me. That is why I was asking how the car is "cut-off" by the key if the ign module is hot wired.

 

[TurboBob]

ecms have an ignition input that is fed by the key, so the injector pulses should stop based on that.

Bob

 

[pacecarta]

i know this doesnt answer your question. but for future

crank is when the starter turns the motor , if it doesnt turn then you can say it doesnt crank
if it cranks and doesnt fire then thats something different from a car that doesnt crank and the term is it wont fire

yours sounds like it wont fire
get a noid light and verify injector pulse when cranking
get a spark tester and verify spark when cranking
check plugs make sure they arent fouled
a flooded motor wont fire no matter how much you crank

and get the cam sensor in correctly timed at 25ATDC on the #1 compression, its not rocket science
and recheck your crank fuel and injector constant settings in the xfi ,

it is possible in his hotwired debacle that he used a source for the relay coil from a swicthed ign source thats not live during cranking
hook a volt meter to the power input to the coilpack and see if it has 12v during cranking

 

[DR BOOST]

if the wiring (other than the hot wires) is stock, then the XFI will not get crank reference pulses until the ignition module syncs. So a CAM sensor is required to get any cranking fuel.

It almost sounds like the hotwires are wired so they drop when cranking. I would put it all back to stock and start there.

make sure the CAM sensor is timed properly and not 'busted'....

Bob

exactly....the factory wires should have been used as the relay trigger. it sounds like the coilpack is not getting power while cranking.

 

[Blazer406]

The car was already wired with both hot wires that go into the ign module were tied together and ran to the back of the alternator...... No relay.... Apparently this has not been an issue since he got the car probably almost 2 years ago.....not my choice to hook it up like that, but it has been that away for awhile.

 

[Blazer406]

i know this doesnt answer your question. but for future

crank is when the starter turns the motor , if it doesnt turn then you can say it doesnt crank
if it cranks and doesnt fire then thats something different from a car that doesnt crank and the term is it wont fire

yours sounds like it wont fire[\quote]

tuche'

Guilty as charged.....

 

[Blazer406]

I suck at typing code manually...... I meant to close the quotes above before I typed tuche'.....

 

[Blazer406]

Update.

Turns out the cam sensor had sheared off the the part that keeps the windowed wheel from moving. So we could set the cam sensor, and the car would run. 10 min later, it would start running like poo and then no start. The cam sensor was getting out-of-time. It was a bugger to run down but now that we know what to look for, next time this happens it won't take as long.

Good news is, the car has a new cam sensor, new crank sensor, new coilpack and module, new ignition switch, and some wiring that has been cleaned up. This will provide some spare parts for later troubleshooting except for the cam sensor.

Thanks for the help guys.