4.9 VATS Bypass problems

IT RUNS! The bypass needed to be 30Hz and once i got that
right she fired right up... kind of, its got a pretty big
cam and it took a bit to start, but it keeps an idle great.

Good work on the troubleshooting so far. The visual on the injectors is a good answer, the one I was hoping for. Same for the fuel pump.

If you have the funds, I'd buy a replacement ignition module. If it ends up not being the module, it's very good to ahve a spare on board anyway, so it's not wasted money.

I'd also try the 30hz waveform. Couldn't hurt.

 

Chay

I am sure it is the injectors because i ran it with the
fuel rail out of the head and i saw that they fired then
stopped so then i checked the fuel pump, which i have
wired directly to the battery with a switch, and it was
on the whole time and after the injectors stopped firing
i checked the fuel rail pressure and it still had a lot
of pressure. This is how i know it isnt the fuel pump,
and for the cam sensor i am unsure, but when i first
tried to start it i sprayed starter fluid in and it kept
firing so ignition is ruled out. What im wondering about
though is the cam sensor, it seems it is missing from the
harness, but i do have cam hi and cam lo and i checked
the distributor and its all hooked up except the tack. So
as of now i still see it being the bypass.

It would start right up if the VATS is your problem.

Perhaps you have another problem though. The most dificult problems to troubleshoot are multiple failures with the same symptoms. It's possible this is what you have bumped into.

 

F generators typically want to go faster then 30hz. I hope the new one will work for you.

 

I'm trying to come up with some other reason that the injectors would work, then die.

On a standard Fiero, this occurs when the ecm or injectors are not powered up (It fires due to the cold start injector). Yours does not have a start injector, but primes via the main injectors.

Some engines (Computers) require an input from the distributor in order to keep sending fuel. I had a Chrysler mini van which requires a cam sensor signal or it shuts off the fuel pump.

What I'm getting at, without knowing your system, is that there may be a cause besides the VATS holding you back.

How is it that you are sure it is the injectors which are not firing, rather than the fuel pump shutting off, or loss of spark?

Chay

I can see that time is becoming an issue for you.

 

Don't get too frustrated. It sounds like you are on the edge of success!

 

What you should do is come and coach my 8 year old soccer team. Then you'll know what frustration is! Ha. Actually they were really good the other day.

Do you have a frequency generator available to you? You mentioned it before. If so, try the 30hz frequency. Set the F generator for 5V peaks, and 0 volt lows. It should sink current as well as source it, so no problem.

 

I may have time to whip up a variable oscillator and send it to you. You could set the F with a 'scope or a meter.

 

It sure would be nice to verify the VATS is still on in your chip, otherwise you are wasting your time with the VATS. Can you/have you tried contacting rockcrawl?

 

Chay

 

It would be great if you had access to a 'scope so you could see it happening.

 

Chay

 

 

Ok, now we're getting somewhere.

Look at the circuitry at the top right of what I posted. The ECM provides the power, at 5 volts.

The vats module switches it to ground, causing the signal to go to 0 volts.

 

So, you should have a square wave, from 5 to 0 volts.

It's funny that the diagram above doesn't show the switch being pulsed.

 

http://myplace.frontier.com/~vze7erz1/id14.html

 

Looks like they used more than 1 frequency. Perhaps you are supposed to be at 30hz?

 

A diy cct for 50hz, you could modify it for 30hz. Let me know and I can build one and confirm values.

 

Chay

http://home.hiwaay.net/~davida1/passkey.htm

 

 

 

Chay

 

Looks like it diables the starter too....does your engine crank?

 

If so, maybe it's not the vats!

Ok, check that, who knows how your engine has been wired. I'd definatley trace some wires here though!

Chay

Well the injectors do turn off after 2 seconds and the
computer and harness came with a Bypass module, so im
assuming the PROM doesnt have it disable. But im so
confused right now its ridiculous, PLEASE help me trouble
shoot this, i need this project done!

What is PROM? And the injectors turn off within 2 seconds
so i dont thing i have it disabled in the PROM

My ECM is 16132240, which frequency would it be, i got a
frequency generator to test. I tested the Bypass module and
it seems to be putting a 50Hz frequency out.