Megasquirt - Assistance Needed, Very strange problem Options

[yarin]

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.

[JeffBowlsby]

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?

[DNHunt]

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

[yarin]

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!

[fiid]

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...

[yarin]

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.

[lapuwali]

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?

[DNHunt]

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

Dave

[yarin]

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 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.

[Qarl]

Go Go Go!

You can do it! Don't give up!

(IMG:style_emoticons/default/boldblue.gif) (IMG:style_emoticons/default/clap56.gif) (IMG:style_emoticons/default/mueba.gif) (IMG:style_emoticons/default/smiley_notworthy.gif)

[yarin]

Go Go Go!

You can do it! Don't give up!

(IMG:style_emoticons/default/boldblue.gif) (IMG:style_emoticons/default/clap56.gif) (IMG:style_emoticons/default/mueba.gif) (IMG:style_emoticons/default/smiley_notworthy.gif)

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. (IMG:style_emoticons/default/clap56.gif)

[DNHunt]

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

[yarin]

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

[yarin]

..sunday night bump... (IMG:style_emoticons/default/drunk.gif)

[agrump]

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.

[lapuwali]

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.

[DNHunt]

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

[yarin]

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.

[Qarl]

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

[yarin]

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.