no injector pulse, but fuel on spark plugs - Miata Turbo Forum - Boost cars, acquire cats.

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Old 02-26-2008, 11:40 AM   #1
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Default no injector pulse, but fuel on spark plugs

Hello,

I am working on a 92 1.6 Miata US.
We checked for a lot of possibilitys, but car wont start.

- sparks are firing
- without spark wires, sparks are wet from fuel
- its a engine with problem crank, but TDC is fine.

I hooked up my Emanage Ultimate datalogger,
for any reason, I get zero injector pulse.
But as said above, there is fuel on the sparks.

I guess the ECU is dead, leaving injectors all time open,
but other ideas would be great.


Falk
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Old 02-26-2008, 12:03 PM   #2
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well, if the ecu was dead, i wouldnt think it would hold the injectors open like that, i would say that the injectors are opening, but your datalogger cant tell. lets see a list of mods, that would be a good place to start.
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Old 02-26-2008, 12:11 PM   #3
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No mods, basic 1.6 Miata,
its not my car, just a friend with car shop asked
me to take a look on this because he checked
all standards without success.

That why I hooked up the Ultimate to see some
data in the logger.

Falk
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Old 02-26-2008, 12:13 PM   #4
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I've seen injectors wired wrong that just stay open and don't pulse. But you'd be getting tons of raw fuel out the exhaust pipe.
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Old 02-26-2008, 12:18 PM   #5
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Noone touched them,
car stoped driving and thats what we have now.

I was thinking the AFM is dead, but datalog shows fine
voltage. Else parameters like temperatures are fine too.

From what parameters is the ECU generating the injector pulse?


Falk
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Old 02-26-2008, 03:10 PM   #6
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Quote:
Originally Posted by Falk View Post
From what parameters is the ECU generating the injector pulse?
The fuel and ignition pulses are triggered by the two CAS lines, and referenced to a load value computed off the AFM.

The fact that you are getting sparks suggests that the CAS triggers are being received. Was the engine running previously and then stopped, or did this happen as soon as the EMU went in? If that be the case, I'd ask about the wiring between the ECU and the EMU, and between the EMU and the injectors.
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Old 02-26-2008, 03:24 PM   #7
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Hello Joe,

the EMU was only hooked on to find the problem,
we have these pnp harnesses here.

The car was running correct before, no issues.


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Old 02-26-2008, 04:47 PM   #8
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Quote:
Originally Posted by Falk View Post
Hello Joe,

the EMU was only hooked on to find the problem,
we have these pnp harnesses here.

The car was running correct before, no issues.


Falk
isn't there an easier way to figure out a problem without adding more problems to it. i don't think the EMU will help you figure out any problems but that is my opinion. start without the EMU
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Old 02-26-2008, 04:59 PM   #9
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Yup. What he said. Adding complexity isn't a good troubleshooting method.

This is where having access to an oscilloscope starts to become less-than-optional. You would be well served by having some way to look directly at whats going into and coming out of the ECU in real time.
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