car not starting up, no fire to the cylinders

[jo_91gs]

ive had this kind of problem before with my gs. car not starting up, no fire to the cylinders. luckily all i had to do was replace the ecu due to leaking capacitors. now its with my 91 talon tsi fwd. ive already sent the ecu to get rebuilt but no difference. engine turns and turns but wont fire. also noticed that with the key turned, no fire to sensors, unless thats normal. already checked fuses and relays, all good. also no noticeable physical damage to crank/cam sensor and coil pack. had assistant crank car while i check the wires for fire and nothing. also made sure there was good compression, all wires connected right, fuel to the rails. the car hasnt ran for a year or so. i bought it like that with 90k miles and previous owner refused to invest so i got it off their hands. i really want to start on this project but i wish i could get it running already. anyways, some good advise from an experienced dsmer would really be appreciated.

 

[talonalex92]

you can try a new coil or ignition transistor?

 

[steve]

There is a tech article to help people with diagnosing problems getting their engine to start rather than stupidly throwing parts at it. http://www.dsmtuners.com/forums/showthread.php?t=217951

Steve

 

[talonalex92]

i didnt mean buy, i meant try.
theres nothing wrong with swapping things to try them if you dont have proper equipment to test them specifically dude.

 

[steve]

theres nothing wrong with swapping things to try them if you dont have proper equipment to test them specifically dude.

The most important piece of test equipment you have is between your ears.

Telling somebody to start swapping parts before looking at the big picture is failing to use that equipment.

For example. Just what does "also noticed that with the key turned, no fire to sensors" mean?

I don't know from the posters comment and if you don't know then your just telling him to be a part swapper. I provided a link to help them figuring out what's wrong or develop a plan to figure out what you know and what you don't so you can start testing ideas. Once you have a plan it might make sense to swap parts, if you have no other way to test them, as you attempt to eliminate variables.

Steve

 

[jo_91gs]

yeah, from what i remember, when i turn the key forward 'to acc' there would be fire to cran/cam, airflow, tps. another thing, you know the black wire with the blue strip from the ecu then splits to two terminals to the fuel injector relay, on my 91 models, well that wire shorts out causing no fire to my system as it did when my ecu on my gs went out. so i was also wondering if that same wire shorts out if another sensor goes bad. i still havent tested the coil pack yet. like you said about the part swapping i totally agree and am trying to use the little dsm experience i have to solve this problem. so if there is anything i can answer to clear anything up just ask, and i appeciat the help.

 

[steve]

I assume fire = power as compared to fire = spark, you're not seeing 12v on the wire?

The only black w/blue stripe wire I see is the wires going to ECU pins 63 and 66 from MPI relay pin 8. That is the wire that the ECU pulls low to turn on the MPI relay. So it will have 12v until you turn the ignition switch on to RUN and then go low.

Is that the wire you mean?

Steve

 

[jo_91gs]

yeah that wire. well i dont know what made me think of it but when i had the no start problem with my gs, i found out that by grounding the wire (still connected to mpi relay)
would give the 12v to the sensors (key turned to acc) and i somehow bypassed the problem in the ecu making my car run for a bout another 2 or 3 weeks, then i bought a rebuilt ecu and havent had problems with it since. well i tried the same thing with the talon, got 12v to sensors (with key tturned to acc) but still wont fire. thats why i ask if the ecu will sort of short itself out with a certain sensor or other part that is damaged so the car wont start. like i said there doesnt appear to be any damages on the coil pack or transistor. also swapped spark plugs and wires but no difference. hope i can get some more advise so i can finally start my 4g63 project. any help is appreciated.

 

[steve]

Time to have your ECU checked. See if you can put it in a friends car or send it out.
It's not turung the power on like it should or booting up if you force the power on with the MPI relay.

 

[ekanddsm]

is there a MIL on, does the pcm,ecm,ecu- turn on the engine light when you turn the key on?

what are you not getting power or ground 2? The problem is right in front of you but you have to identify it for us to help you narrow it down.

 

[jo_91gs]

nope. no check engine light, if thats what you mean by mil. yeah, when i turn the key to acc, none of my sensors power up.

 

[steve]

nope. no check engine light. yeah, when i turn the key to acc, none of my sensors power up.

Except when you force the MPI relay to turn on by grounding pin 8 on the relay (ECU pin 63).

 

[jo_91gs]

yeah but still no start, just the motor turning and turning. ive heard its not always a good idea to send an ecu to get rebuilt, rather than just buying a rebuilt one. i ended up sending it to florida through a website, autoecu.com, and still have warranty so ill be sending it back to them to get it checked again. id hate all the waiting but if i dont come up with any more ideas thats gonna be my last choice. im pretty sure someones heard of the website.

 

[steve]

yeah but still no start, just the motor turning and turning.

Which is to be expected if the ECU isn't functioning. The issue with rebuilding vs buying a replacement boils down to a cost call. Sometimes it is cheaper to find a better used ECU and have the caps replaced before they go bad than it is to fix the damage cause by them leaking.

There are lots of other choices than the one you picked, some closer to home and possibly cheaper and perhaps better quality. I've yet to be impressed with any of the larger "rebuilders" work. I think most put the warranty stickers on the cases so you don't see what a hack job they did.

Since you aren't getting a CEL when you turn the key and you aren't when you trigger the MPI manually and see 12v to the ECU the odds are really high that ECU isn't working. The place you got it from should take care of the problem.

 

[oldman]

There are lots of other choices than the one you picked, some closer to home and possibly cheaper and perhaps better quality.

Wait a minute, I remember you now, you're one of those choices aren't you!!!!!! It's all coming back slowly now.

OP, this dude is the guy you should have sent your ECU to.

 

[jo_91gs]

well, i just sent in my ecu to get checked so i will be getting back with yall when i do get it back.