Experiencing starting issues and was getting a Malf code 51 (Bad EPROM). Pulled EBL Flash ECM to check connections and potentially loose EPROM everything seems OK. Back together still not starting but it's no longer giving me a malf code 51 or any other code. Observing CEL light with ignition only on and the CEL blinks once briefly. Is this not an indication that the ECM & EPROM are good? Can I assume this?

Also - Had a similar issue last year code 51 came and went away like now. Back then I replaced my DUI coil and the ignition module and it started. Been driving it for a good 100 miles since then and bam, same issues. Checked coil (that only has about 100 miles on it) found resistance is within spec so I replaced the ignition module - no luck still not starting. Have an MSD 6A which I thought might be bad so I disconnected it and re-wired for stock set up - no help. In fact getting fewer pops during starting attempts which tells me the MSD unit was probably OK. Any suggestions on what to check next? Thanks.

 

Start at the basics. Do you have fuel pressure, spark, injector pulses? You very well could have a bad ebl ecm, but you don't want to waste time chasing your tail when it could be something completely different. Did you talk to Rbob about the ecm?

 

Thanks for reply. FP = good, Injectors pulsating… Need to check spark. I did send Rbob a private message he said the ECM is fried but because the issue seems intermittent (code 51 gone/CEL blinks) I was thinking a short because when chips go isn’t it either it works or it fails? I'm hesitant to sink new ECM $$$ into it if it's really a short. Expressed that to Rbob waiting for his response.

 

Apparently the ECM is running properly evidenced by the key-on single CEL blink. OK, so I'm going to change the coil again and see what happens. Hard to believe it failed again since it's prctically brand new. Perhaps the MSD/DUI combination isn't getting along though in the past it has. Feel free to Jump in with your thoughts Thanks.

Maybe I should just go back to the stock HEI set up???

 

Are you losing spark?

 

Haven't checked it yet. First thing on to-do list after a little road excursion this week. Thanks for replies...

 

Back home, getting spark but it appears weak.

 

Well an esm can't be the cause of weak spark. So if you do indeed have a weak spark problem then the msd/distributor is having an issue. Some how some way. I'd start by checking for strong power and ground to everything then probably taking the msd part out to rule it out of the equation. If it isn't the problem you can always loop it back i if you want it.

 

Good assessment, pulled MSD first thing as I've read it can cause issues as it fails, no luck. Replaced ignition module - not the issue and a new coil is going in today. Both were almost brand new. My concern even if the coil fixes it is the potential it can recur as the same issue with MALF code 51 occurred recently. Can an ignition issue cause the ECM to throw a MALF code 51 (bad ECM) or is it more likely an intermittent short causing both? Not looking for an answer to that just stating the dilemma. ...or perhaps the MSD module is frying the coil??? BTW, how do you test for STRONG power and grounds? Will be researching that... Thanks for reply.

 

https://www.onallcylinders.com/2019/...ground-issues/
this is a good basic start. I'm not an electrician by any means but repairs to older type 12v and 5v reference circuits are often simple to diagnose and repair in the grand scheme of things.

 

Engine ground is solid, distributor getting 11.6 volts with key on... So I decided to put the new coil in - No luck AND the ECM started throwing Malf code 51 again. Also Check Engine light is flashing with key on. Must be an intermittent short somewhere to the ECM no? Start testing and playing with the ECM connectors tomorrow...

 

Took connector readings all grounds are solid with 0.3 Ohms to 0.0 Ohms resistance. Started taking voltage readings with key-on and connectors off ECM, is that the correct way? Got some strange stuff compared to manual.

 

I'd suggest leaving them connected and backprobing the terminals

 

Got it. For the record power pins all checked out at 12 volts.Thanks.

 

Signs aren't looking good for that ecm

 

Back probe readings pretty much the same - good grounds and getting 11.8 to 12.3 volts on "battery" pins. Did get some strange voltages vs Shop Manual on a few others but all power and grounds looked good. What a PIA that was cuz my ECM has a ham board; I had to map it to get to the correct pin connections. That said looks like you and Rbob will tell me the ECM is fried, just have a couple of questions for you/community -

1. The fact that the ECM faulted then checked OK to a point of normal operating blows my mind. Don't microchips fail and not degrade i.e. they work or they don't?

2. Can a bad ECM prevent the engine from starting?

Thanks.

 

Edit - Retracting this, decided to hang on to it for a bit - Fried ECM with hamboard up for sale. S&H $15 - PM me with offers.

 

Just curious, how old is your EBL? Maybe Bob at Dynamic EFI will take a look at it and tell you if it's really bad or not? It may also be able to be repaired...Worth a shot, right? If it's bad, I have an EBL ready to go out if needed. If you need another EBL, I have one ready to go out. GL

 

Over ten years old... Was once told he has no way of testing hamboarded modded EBL's.

 

Had a PM exchange with Rbob and he gave me a couple of things to try before writing off the ECM. To cut it short it appears some of the loaded BINs somehow got corrupted because when I cleared the code and switched to a very old BIN in another bank the Malf code disappeared.

Interestingly more than once while playing the corrupted BINs I got a jackpot full of codes; 12, 13, 15, 22, 23, 24, 25, 34, 42, and 51 (only 51 was flashing/showing as current). I then reloaded one of the corrupted BINs and no malf code, at least not yet anyway. I'm not completely convinced the EBL ECM is not the causing the faults. It's strange stuff cuz the BINs were working fine for awhile.

So anyway - Did my car start as a result of this? Heck no! I must be dealing with a couple of issues or a fault that’s causing both perhaps. The spark is still weak even with a new coil, ignition module, and capacitor. That needs to get solved. Going to be gone for a few days - tune in later for more head scratching updates. Jump in with a suggestion if you care - is why I'm out here.

BTW these exact same issues, jackpot fault codes and no start occurred last year - I replaced ignition parts same as above back then and it ran well for a good 100 miles.

Could the anti-theft system be the culprit here? Just asking…

 

The vats should be shut off in the ebl, and if it were active you wouldn't have injector pulse. If you do have weak spark then finding it's weird source of a problem is priority. The ignition system isn't very complex when it comes down to it, but finding the problem may be a pain in the butt. Bad coil wire? Problem between rotor and cap? Spark latency waaaay off? I'm kinda spitballin here.

 

Thanks, It's what I need to start looking in the right direction. Will post findings.

 

Back home tearing the ignition system apart again. One thing I neglected to inspect was the distributor cap contacts because it’s relatively new. Looking at the contacts I noted heavy carbon deposits and significant wear. In fact the carbon or whatever that black shtick is is preventing continuity to the spark plug wire connection. Must be bad no? Going to replace it and the rotor will post results but I’m hoping big time this is the issue.

Question - Is there something that causes this to foul so quickly? MSD unit? DUI coil? Or maybe it was just a cheap chit cap.

 

Before I bought a new cap I thought I'd lightly clean the contacts on the old one and try starting It. It started for about 2-3 seconds and killed. Tried again ran for about the same amount of time and killed. On the third and all subsequent tries and it was back to no start at all. Checked spark, still weak. Evaluated dizzy cap contacts = clean i.e. didn't notice any deterioration from my cleaning. It’s something else, I guess. Edit -
Going for new cap and rotor anyway - I mean it's only money, WTF?

 

More playing around -
Volts battery terminal to terminal = 12.1, Ignition on volts to Dizzy 11.5 - That an issue? Dropping .6 volts?
Also while cranking Volts to Ignition drops to 9. That common?

Need some rewiring???

Comments? Thanks.

 

battery volts 12.1 with the key one, engine off?
.6v drop doesn't sound too starnge but I wouldn't say it rules out a problem.
9v cranking at the ign seems low but I'll be honest, I've never thought to check it on anything ever to give a comparison. I'd imagine ign pulls a lot of power. What does your battery voltage drop to when cranking? What about the injectors? What voltage are they getting at that time?

 

Yes. Key on engine off. It refuses to start.
Other stuff will check and reply...

 

[QUOTE=Cartrax;6473280]More playing around -
Volts battery terminal to terminal = 12.1, Ignition on volts to Dizzy 11.5 - That an issue? Dropping .6 volts?
Also while cranking Volts to Ignition drops to 9. That common?

Troubleshooting is best done with a fully charged battery. A good battery at 100% should be 12.7 volts. Low voltage can cause problems. 9v while cranking is a little on the low side.

 

[QUOTE=Larry;6473351]Thanks, you hit it on the head. Let it charge up this AM @ 9 Amps for about 2 hours, post to post read 12.8, then held at 12.4 after some cranking and leaving headlights on for a minute or so just to check drain. New numbers, at dizzy 9.8 Volts while cranking, held steady for 15 seconds, did that a few times same readings. Getting 12.4 Volts positive post to both engine and dizzy grounds. Looks like it's not the battery, plus the thing turns over nicely, no slowing down...

New cap and rotor coming tomorrow, if that doesn't do it IDFKW it could be. Restart trouble shooting, I guess.

Could the ECM be the culprit??? Another PM to Rbob…

 

New rotor and cap, Delco did the trick. Old cap and rotor made in the states (DUI) probably had less than a few thousand miles on it??? Who woulda thunk? The MSD capacitive boost module is not going back on unless I notice a significant drop in performance. Why? Only thing I can think of that could eat up a cap and rotor so quickly. Not going say much more as I may get too graphic and banned... Now I have to get the old tune back and hope my BINs don't get corrupted again.

End of this saga, I hope.

 

Well, the saga continues - Now it just randomly kills. No sputtering just dies like the ignition was turned off. Then just after a minute or less it will restart and run. Smells electrical doesn't it? Researching old posts could be one of just a dozen things. Nothing like an intermittent issue to drive you up an f'n wall. Will post results...

BTW, EBL ECM not throwing any fault codes.

Things I'm temporarily ruling out - Ignition module - It's new and if overheated would take longer to cool down than a minute or less, no? Ignition coil - brand new. Fuel delivery issue - it kills too fast and no sputtering.

Last time it died - jiggled ignition wires = didn't start, then jiggled ECM connections and harness = it started but cannot get it to kill while jiggling ECM stuff.

I read it could even be the alternator, something about bad diodes... Seems to be charging fine. What makes me suspicious is the jackpot of ECM codes I was once getting could have been an alternator issue per Rbob. An intermittent one? Thinking probably not.... but…

Any suggestions… jump in.

 

bad diodes will still show you're getting "charging" voltage. It's testable but the only way I've personally done it is to use a battery/alternator/starting tester. An old one I've got has a tiny led that lights when it detects a bad diode. A fast google lead me to this....
* To check for a possible bad alternator diode, switch your voltmeter to a low setting on the AC (alternating current) voltage scale.* With the engine running, touch the meter probes to the battery terminals.* Your voltmeter should read 0 AC volts. Any amount of AC voltage would indicate a bad diode, so you'll need to replace the alternator.

 

Thanks, read 0.04V AC assuming = OK.

 

Want to test ECM fault operation - how did I get it to throw a forced code? disconnect map vac hose or something like that? Thanks

 

Disconnect the est. Easiest one

 

Thanks, unplugged MAP sensor before I saw this - got the correct code right away. Also, I think, at least I hope I found the issue - I pulled the dizzy cap to check contacts and the power lead just kinda fell out of the clip. Didn't have it locked in. Fixed that and drove it for abour 15 minutes, no issues. Time will tell... So all is well? Not really as iwas playing with it, I couldn't select a different bank or load new BINs. Recall Rbob telling me 90% of time it's the chord. Sure enough new phone cable fixed it. Now I'm just waiting for the next issue - this car is down right spooky. No kidding....

 

Sometimes it just goes that way. I swear my 92 wants to be a permanent source of not being quite right despite 20 years of efforts. (And terrible attempts at efforts ) But that's how the hobby can go.

 

Epilogue - After I changed the spark plug wires and went back to the stock HEI Ignition (was an MSD Capacitive Discharge with DUI HEI coil) it cured a surging issue I had. Why? No clue.

Also virtually eliminated frequent knock counts at high RPM and load. ...and it idles mucho better. Go figure... BTW could not feel any change (decline) in performance.

Save $$$ keep your stock HEI?? Yeah, maybe... could have been the old wires though that were causing the issues.