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?

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...

Can the driver handle 4 low impedence injectors with PWM on one bank? I'll try this tomorrow.

Dave - I believe spark is OK based on my timing light. I get a consistent equally spaced strobing for each plug wire.

I might bring my MS to work tomorrow and hook up the injector outputs to a scope and see whats going on. Would be neat to capture the PWM waveforms.

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

I can't find anything. It might be an MS I option.

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.

Jeff,

It's possible... The MS brain is mounted under the dash. My harness is running to the relay box in the engine compartment. No twisted pair. Shielded wiring only on the ignition wire from the dizzy all the way to the brain. The ignition is in the same bundle as the ignition wire. However i'm only getting a tach signal, i'm not firing a coil using MS yet.

Ground is going to a ground bus in the relay box which is bolted to the engine/tranny. No voltage spikes.

MS II V3.0 has built in flyback circuitry, so PWM with 4 low Z injectors is OK.

Also checked the valves the other day. The #4 cylinder was about 0.002" tight on both exhaust and intake. This is the cylinder that ran for a few minutes with an open injectors. I adjusted and checked everything else. No problems there. Also tried dual tables, still the same funky injector issue. ?????????

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!

I'm also running low on ideas here. Tonight i'll read the AFR off one cylinder and see what it says.

Here are the waveforms from each injector bank that I captured. Hooked up the scope to the LED output on the stim and +12V.

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?

No cold start injector. Everything is capped off. I started from scratch coming from carbs.

Fuel pressure is via a manifold referenced adjustable FPR. ~30psi at idle.

Might be an ignition problem. Firing order is 1-4-3-2. Timing is dead on 29degrees BTDC at 3500rpm.

WBO2 is hooked up, mixture goes lean when its unplugged.

Drew - i'm hanging in there. getting a little frustrating because i've never really driven this car and i've owned it for a year. i know success is near, just takes some more thinking and troubleshooting. i'll keep everyone updated.

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...

Thought about that.. My MAP signal is stable indicating the cam isn't terribly aggressive. I still think the problem is the injector driver despite clean waveforms. Those waveforms looks good, but not under load. If I could get a scope on the car while running that would tell me everything. However there is no way in hell i can borrow a $4k scope from work. I'm gonna throw my brain at it this afternoon and see where I get.

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?

It suggests a problem with the inj 1 circuit including connections. I'd look at continuity and then resistance. Remember the scope looks fine.

Dave

I hooked everything back up to INJ 1 and INJ 2, same weird issues. Idle goes up when injector is disconnected on two cylinders and spark disconnect doesnt change anything.

Ran all injectors off INJ1, idle was very rough, jumped up. Unstable.

Ran all injectors off INJ2, got it to idle OK, still a little rough. According to the timing light cylinders 1, 2 are fouling. 3,4 are OK.

I took data pulling each injector followed by each spark plug. So the sequence of the datalog is 1(Fuel), 1(spark), 2F, 2S, 3F, 3S, 4F, 4S. The start of the event is marked at the following times on the datalog: 148s, 160, 169, 180, 190, 197, 205, 215s.

I expect my AFR at idle to be much higher than where it is now. I think its running rich, which is why my plugs are fouling. When I disconnect fuel to those two cylinders the timing light shows normal spark behaviour. As soon as i connect the injectors back the timing light shows inconsistent spark. Perhaps i'm having injector issues?

I'm stuck.

Go Go Go!

You can do it! Don't give up!

Course of action for tomorrow:

*Spray intake with carb cleaner looking for leaks
*Read WBO2 off two individual cylinders (bungs there, capped)
*Switch injectors and see if symptoms transfer

Anything else?
It's beer time now.

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

Spent the entire friggin day on this thing.. here is where i am at:

Measured resistance from the DB37 connector at the brain through the relay board back to the injector connectors. 0.25Ohms, all good. Checked the +12V constant line as well, all good. Measured injector impedences, ~2.45 - 2.60Ohms.

Tried to fire all 4 injectors off INJ1, ran rough, unstable, no go. Tried to run one injector off INJ1 and 3 off INJ2. Idled OK, but same issues with disconnecting the injector plug and spark.

I compared the AFR of one cylinder (i have two individual exhaust bungs, and a third at the end) when fired by INJ1 and INJ2. I spent a while trying to get all 4 injectors setup on INJ2. I finally got somewhere and got the car running decently.

Sprayed carb cleaner on the throttle body, intake runners, boots, etc.... no change in RPM.

Last couple of days I've been having issues starting the car. I had the coil powered by the fuel pump relay. Whenever the relay would latch the coil would energize and issue a false RPM signal to MS. Then it would think the engine is running and inject some fuel along. Sometimes i could hear the fuel pump cycle 6- 7 times before it settles. I believe I solved this by moving the +12V power for the coil to the switchen ignition output. Presently more often than not the engine cranks, catches and it stops sending fuel. I attached data logs ofthe issue. I can see huge spikes in my RPM and drops to zero.

And now my new issue... ready for this one guys??

So i'm driving driving... car is actually running surprisingly well considering i hadn't tuned it at all. Drving driving.. give it some gas, DIES. I found that exceeding 3500rpm generates a false tach signal and shuts down, probably hits fuel cut and kills fuel. I attached data logs of this as well. This is my new issue that just creeped up today. I tried revving the engine with no load, same issue. I tried moving the coil +12V from the fuel pump relay to a constant+12V source, same difference. I tried a new rotor, same issue. Check the logs.. my tach signal drops to zero and the engine dies.

I don't have any input filtering and haven't had issues like this up until now. The tach signal looks clean otherwise... maybe its noise above a certain RPM... i really dont know. I replaced the coil 6 months ago, its possible that after a few hours of driving time it became a little noisy. OH yeh.. one last thing.. Pertronix, could that be giving me problems?

Also... as you can see in a few datalogs when i lift off throttle and decel my AFR goes to full lean. I learned something very interesting this afternoon. With a bung upstream of the WBO2 uncapped my AFR displayed full lean. I guess its pulling in enough clean air to completely throw off the reading. I'm thinking maybe on decel its pulling in air from somewhere, or one cylinder isn't combusting and flowing unburned oxygen.

Anyway.. thats where i stand tonight. Kinda dissapointed that I won't be able to autocross the 914 tomorrow... oh well. I hope i can iron out these issues before next weekend.

Hit the max for attachements so here is a link to the data plots from Megalogviewer: http://coewww.rutgers.edu/~yarin/dataplots...on-problems.zip

..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.

Where is your O2 sensor mounted? How far from the end of the tailpipe?

5" Before the muffler right after the 2-1 collector.

Here is a pic of the exhaust. how do i make sure this thing is sealing? here is a pic unassembled. The gaskets are good, however I'm not confident the couplings are leakfree. The design only gives me about 1" - 1.5" of overlap.

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.

RPM spikes are gone with a 1K pullup from (-) coil. I didn't have any low rpm rpm issues so no need for a dave cap. MS II has better tach filtering anyway.

For now i'm going to try to tune with 4 injectors on one bank. Once i'm tuned in i'll switch everything to the other bank and see what happens.

For now my only issues are:

Intake leak (idle at 27KPA, 800RPM with throttle plate hole blocked off... no normal)
Possible exhaust leak upstream of WBO2.

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?