I drove the car last thursday, ran fairly rough but had some power. Did some tuning, and had this very odd firing problem. I spent some more time today digging into this, here is what i found:
INJ1 bank hooked up to cyl 1 & 4
when either injector connector disconnected rpm goes up
when either spark plug removed no change
INJ2 bank hooked up to cyl 2 & 3
injector disconnect, seriousl drops rpm
Tried both combos. Alternating, 4 and simultaneous 2. reqfuel 9 / 4.5
So my conclusion is that all cylinders are getting spark, but only two are really firing. Furthermore a quick touch of the exhaust port shows that cyl 4 is running much cooler than cyl 3 after idling for a few minutes. I swapped the cyl 3 and 4 injector drivers and noticed an immediate change in head temp. It sounds like the cyl 1 & 4 are getting fuel, but not igniting. When those cylinders no longer receive fuel, the rpm goes up indicating no combustion, but resistance to compress the fuel.
Make any sense to anyone? I attached my .msq file. I double checked my setting, i made sure i'm only running off 1 table. I just took apart my MS box and can't find any obvious shorts, burns, etc. Keep in mind i'm only looking for this problem at 1000-1500rpm. It's not injector related, its driver related.
Anyone?
Attached File(s)
megasquirt200604241728.zip ( 3.29k )
Number of downloads: 39
Yarin
Get someone to help you check spark. Make sure you have fire in each hole. I suspect you have spark but no fuel.
I believe there is an option in the fueling menus somewhere that lets you turn off 1 bank of injectors. Why they would have that I don't know. I got stuck on that once. If that's not the case start looking for problems with the hardware.
Dave
I think the one bank thing is if you're running all of your injectors off one driver, which you can certainly do with a four, and a number of people do so. If you're suspecting one driver is bad, try wiring all four up to the one good one, set this option, and run that way. Solves the alternating/batch question, too.
If this is so, then the driver FET may have let the smoke out...
Yarin check the menus. I think you can turn one of the banks off. At least when I had that prob I found some obscure option to deselect and all was well. Certainly worth looking for before you start taking stuff apart.
Dave
Yes, one driver can handle four low-Z injectors. This is how V8s run. I think one driver can even handle 8 low-Z injectors, so long as you use resistors or PWM properly.
You also don't have to turn off the driver. With no load across them, they can be triggered with no harm (assuming the "bad" FET isn't actually bad at all). People ask this regularly when trying to run MS as spark only. I believe Eric Fahl (author of MegaTune) is running at least one of his cars with all four injectors on one driver.
I moved all injectors to INJ2, set injector driver to simultaneous, 2 injection and reqfuel of 9. Started it up, noted the following:
Idles much higher, ~1700rpm, unstable idle
AFR jumps erratically between 14 - 16
Pulls much more vacuum ~27kpa
According to the timing light one plug doesnt fire consistantly, it misses which appears to cause the unstable idle.
My next step is to check the valves. Last time I checked them a year ago they were in spec. Might as well check them again for piece of mind even though I haven't really driven the car. Can't valve clearance issues be the cause of my problems?
Checking the valves wouldn't hurt, though I doubt that's the source of your problems. You changed plugs recently, I assume. When was the last time you changed plug wires? Cap? Rotor? How are you firing ignition right now?
I am sure you mentioned this somewhere, but are you using PWM or injector resistors?
I suggest injector resistors around 5-10 ohms per injector until you get everything figured out. PWM is risky in my opinion. Too easy to blow stuff up unless you know the settings in advance.
I agree with James, make sure your ignition system is totally working before you get too far down one troublshooting path!
I changed plugs, but the suspect cylinder looks fouled again. I have one plug left i'll change. Is there any way to clean the plugs? Sand the electrode a little?
Stock dizzy with mechanical advance.
PWM should work fine if its setup correctly which is easy to do. essentially 30%, 1.0ms, 1.0ms are your base settings. There is no need to go with inline resistors if your hardware supports PWM.
I'll try to throw my MS on a scope tomorrow and capture a few waveforms.
I have only loosely followed your posts yarin, but wonder if you may be having EMI issues? What does the configuration of your harness look like? Did you use any twisted pair or shielded wiring? Is the harness physically routed away from the ignition wires? What is the configuration of your ground circuits?
Yes, but are you using a flyback board?
I don't think MS recommends driving 4 low Z injectors without the flyback board, especially if it's off one driver transistor. It's easy to burn up the board.
I spent some more time on the car tonight... here is my update. Anyone and everyone please chime in and give me your thoughts, i'm stuck.
I tried the suggestion of running all 4 injectors off one bank with the same pulse width modulation settings. ~20%, 1.0ms, 1.0ms, 66us. Car ran, a bit rough though. MAP dropped to 27KPA, no idea why. Idle wouldnt drop below 1400rpm either. I tried unplugging each injector one at a time, all caused a drop in RPM. Good sign.
I wasn't getting anywhere trying to solve the unstable / high idle issue with all injectors on one bank so I moved back to both banks.
The other day I brought my MS II to work with the stim and checked output on both injector banks probing off the LED to +12V. I captured the waveforms, will post tomorrow... bottom line is the signal coming out of my MS box looks perfect. PWM behaves exactly as defined on both channels. Of course I don't know how it performs under load.
When going back to 4 injectors split over two banks the following changed. Idle MAP back up to 37KPA. Idle dropped to 800rpm with idle screw all the way in. I even tried reflashing with firmware 2.33. I started from scratch with megatune as well, all new settings. SAME PROBLEM:
One injector drive signal causes the strangest problems. When disconnecting the injector, idle goes up. When disconnecting spark, nothing changes. This occurs for 2/4 injectors on the same bank. The other two behave as expected. When all injectors were connected to the same bank this did not happen. Which leads me to believe it is an injector driver problem. Tried alternating and simultaneous injections as well, same result. I know the "weird" cylinders arent firing properly because those two cylinders are cooler to the touch.
Strange right? Problem follows the injector bank. Spark is good, plugs are ok. timing light fires as expected when clipped to each spark plug wire.
Please give me anything you can possibly think of.
Yarin, at this point, I am lost.
The only thing that I can suggest is eliminate the variable of the PWM by using a 10ohm resister.
This is the only way I have run mine. Give
it a try, nothing to loose at this point...good luck!
yarin...I know your probably frustrated as hell right now but keep fighting the good fight. For guys like me that want to install a MS at some point, its wicked interesting and helpful to read your progress reports.
Seems like a real challenge....
Is there anything going on with your cold start injector? The one on the plenum?It should be unhooked and not leaking.
Have you checked that your fuel pressure is good? you could try removing all the injectors and firing them into jam jars to make sure it's fuelling right?
I'm also suspicious of your ignition system - is your timing right? Can you verify that 1&4 are firing correctly using the timing light (i.e. try clipping it to both those HT leads).
Do you have an oxygen sensor hooked up? What happens to the mixture when you see the effects you in your first post?
I dont know how to interpret those scope shots, but it doesn't look right. I would think they should be even pulses like shots 7+8, and not look like 5, 6, 9. MS is probably just doing what it been told to do like any machine, so are the settings correct? What are the 5 scope shots of and why are they different?
Near as I can tell the scope looks fine. I'm running out of ideas but I really distrust the DB 37 connectors. I'd check those for continuity from the ECU to the relay board.
I've had to repair mine a couple of times and my next build will not use them.
Dave
Yes the scope output is perfect. The signal is pulse width modulated. Here is a link to a quick explaination of PWM from the megasquirt site: http://www.megasquirt.info/ms2/PWM.gif
The 5 shots are as follows:
5,6 - One injection signal. Initial rise and hold followed by PWM (quick on off cycles to keep the injector open)
7,8 - Basically zooming into the individual pulses in 5,6.
I'll double check wiring again to the brain... i ran a 12V lamp to the relay box and both lit up fine. Great suggestions.. keep em coming!
Do you know about your engine internals? You came from carbs, right - so is it possible you have a strange vacuum signiture casued by a wacky cam?? How wild is the cam?
If your cam is way wierd - you could look at doing alpha-n tps based maps instead of the map stuff. With MS-II you might even be able to blend the two (not sure about that).
Just ideas...
It ran better (I think) on one injector driver, but now you've switched back to two and have flaky injection again? Pretty much proves that the INJ1 driver is bad.
It sounds to me like you need to go back to one injector driver, and figure out why you were getting flaky ignition on one cylinder. Then you need to solve the unstable high idle problem, which is almost certainly an air leak, not an injection problem. You're fighting several problems here, but you seem to be focussing way too much on injector performance and/or trying to attack several problems at once. You're never going to solve it that way. Attack one problem at a time.
Once you get the car running on one injector driver, and you get all four plugs firing, then pull out a can of ether or carb cleaner and try to find the air leak that's causing the idle problem.
What does the O2 sensor say all this time, btw?
Go Go Go!
You can do it! Don't give up!
Ya, I hate to sound like a broken record, check conductiviity from the ECU through the DB37 connectors to and through the relay box and out through the harness to the malfunctioning injectors. Also check the resistance. There is a lot of cable and plenty of connections that could be the culprit. Cut the metal ends off of a resistor and stick them in alligator clips to use as probes for the DB 37 connectors.
Dave
..sunday night bump...
The ignition spike is very familar to me, I had the exact same thing when I was running fuel only. The bosch blue coil seems to make a lot of noise there. I change R57 to ~750 ohms to dampen the feed back. That clean up the mess a good bit but I still could see minor noise in the logs. I finally replaced the coil witha non-bosch one and that got rid of the spike totally.
I'm now controlling timing with MS so I could probably go back to using the blue coil but I haven't bothered. If you do install R57 don't forget to clip it when you start controlling ignition, I didn't notice any problems with it installed but the instructions say to remove it or it will mess up your dwell. Better safe then sorry.
The ignition is not run through a relay or even fused in the 914, nor is it in most cars from that vintage.
Exhaust leaks can indeed throw off the O2 reading. Even leaks downstream of the bung can cause a problem, which is why you can't just stuff the sensor into the tailpipe. The sensor should be as far upstream as possible.
Yarin
You might consider resistor plugs. I know it will sometimes clean up tach noise. most of the people running EDIS have to use them for that very reason, myself included.
Dave
I added a 1K R57 resistor. No change. However a 1k pullup on the (-) coil solved the ignition spike problem. So far so good.
Tomorrow i'll look into my WBO2 readings a little more. I might have an upstream leak somewhere. Any idea how to seal a 4-2-1 header system properly?
I attached before and after of quickly clipping a 1K resistor from +12V to the (-) coil. Notice the AFR goes full lean after a rev. hmmm..... It's also still not idling properly, leads me to believe i might have an air leak at the intake side of one cylinder.
Attached thumbnail(s)
Where is your O2 sensor mounted? How far from the end of the tailpipe?
I didn't take the time to look at your logfile yet, but heres a couple of things.
I had an MS running really nicely with the pertronix, but I also experienced RPM spikes - I cured these by using this setup.... I would at least thoroughly read the page through event if you don't implement the suggestion....
http://www.ep90.com/index.php?id=42
Also - I agree with the others - there's something funky between your two injector driver circuits. Perhaps you could run the engine with the scope attached to the two circuits and see if they look different.... they shouldn't other than the phasing (if you're doing alternate injections).
I'd also make sure you've read http://www.megasquirt.info/ms2/tune.htm all the way through - it talks through a reasonably complete tuning process and provides a lot of background to what's going on.
Hope this helps!
Fiid.
Still fiddling with this problem.
The engine idles a bit rough with all injectors on one bank (INJ2). When i switch them all over to INJ1 it runs pig rich, black out the exhaust, MAP up to 50 from 27KPA, needs a lot more air to maintain a really rough idle.
I just pulled apart my relay box, its all good. Continuity from injector connectors to DB37 at the brain is good. I even checked impedence looking into the brain through the cabling across the+12V source and signal with the power off. Equal.
I haven't driven the car with the existing setup since last week. But at idle when i rev the engine the AFR goes to max lean on decel. Even when rev up slowly and let off AFR goes near lean. When I had the injectors evenly spread across both banks i never had this issue. Not sure what it could be. Sadly it idles so much better on two fully functioning cylinders.
I'd really like to figure out why the 2nd bank doesn't work. I even checked the injector outputs on the stim using an oscilloscope. They look perfect.
What to do?
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