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4.9 VATS Bypass problems |
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orange 
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Joined: 15 September 2010 Location: United States Status: Offline Points: 106 |
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 Posted: 04 October 2010 at 2:50pm |
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I have tried my frequency generator at 30 Hz but i could
not get the right amplification i needed, my physics teacher has one that would work that i will borrow. And i do not know how to contact Rockcrawl and he made the chip proly 5 years ago so i dont know if it would help. Plus if the chip had the bypass then wouldnt it start right up? |
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Orange 4.9
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CFoss
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Joined: 13 February 2007 Location: Canada Status: Offline Points: 580 |
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Posted: 04 October 2010 at 3:48pm |
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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 |
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86 SE 3.4
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Dr.Fiero
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Joined: 12 February 2007 Location: Canada Status: Offline Points: 1726 |
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Posted: 04 October 2010 at 4:03pm |
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Funny you should say the above - I was just thinking about the same thing. If the ignition module (remember it does more than one thing!) goes south, you'll loose the input to the ECM after 400rpm and it'll shut down.
It probably wouldn't even run, but you could TRY backing the idle down to sub 400 and see if it keeps going. Try just trickling fuel down the throat also to see if it keeps going (eliminates an ignition problem anyhow!). |
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orange
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Joined: 15 September 2010 Location: United States Status: Offline Points: 106 |
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Posted: 04 October 2010 at 6:02pm |
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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. |
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Orange 4.9
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Dr.Fiero
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Joined: 12 February 2007 Location: Canada Status: Offline Points: 1726 |
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Posted: 04 October 2010 at 6:17pm |
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If it's the same as Davids setup - the cam sensor is part of the distributor (it WAS quite a number of years ago I did his harness though!!!!).
This doesn't rule out the ignition module though. Like I say - the ECM runs without the reference pulses UNTIL 400 rpm. |
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CFoss
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Joined: 13 February 2007 Location: Canada Status: Offline Points: 580 |
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Posted: 05 October 2010 at 9:06am |
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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 |
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86 SE 3.4
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Dawg
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Joined: 15 August 2009 Location: Canada Status: Offline Points: 988 |
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Posted: 05 October 2010 at 9:38am |
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Try to find something called a "function generator". They are more geared for this sort of testing I think. For one, they tend to have a lot of output and will easily go down to below 1 Hz. They also have many different waveform possibilities and tend to have better interconnections available.
The Dawg |
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You dream it up....I'll make it
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orange
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Joined: 15 September 2010 Location: United States Status: Offline Points: 106 |
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Posted: 08 October 2010 at 10:07pm |
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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. |
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Orange 4.9
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CFoss
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Joined: 13 February 2007 Location: Canada Status: Offline Points: 580 |
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Posted: 09 October 2010 at 3:09pm |
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Sweet! hth!
Chay |
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86 SE 3.4
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