engine dies problem child hard to isolate.
Thread Starter
6th Gear Member
Joined: Dec 2005
Posts: 5,212
From: Hills of California
engine dies problem child hard to isolate.
Hello
I have finally manged to encounter a hard to isolate engine problem.
Heres the story
1) for some time (last few months) during dead stop easy accelerations the engine air fuel would become slightly rich into the high 12s as expected (13.5 is where it sits at idle)but would momentarily lean beyond 19 and the car would stumble as you let the clutch out. The engine would never die and I blamed it on some dirt in the carb low speed. but delayed cleaning the carb and would apply more power during acceleration to avoid the problem. This problem only occurred during easy dead stop accelerations for about a 1 sec duration. It ran perfect in all other instances.
2) about a week ago the engine stared to die during dead stop normal accelerations after a prolonged stop for example a stop light. attempting a restart was difficult and usually required about 30 to 40 seconds. The engine dying at stops seems to be becoming more frequent.
* Last night I totally cleaned out the carb hoping that would solve the problem...it did very little good at best maybe the engine leaning badly on acceleration problem is solved or at least made less severe( dips into the 16s now sometimes and sometimes not and stays from 13 during accel then back to upper 14s).
** fuel press is 100% fuel volume is normal
*** accelerator pump pisses as good as always and I dont see any worn accel pump linkages.
3) after cleaning the carb the car died once after an idle period of maybe 1.25 minutes and then attempting normal acceleration and required maybe 30 sec to restart.
4) after it died in #3 I drove it again a few hrs later and didnt have any issues at all on the way to the destination (8 miles) then on the way back it died on the freeway at 70...totally smooth so smooth i didnt quite get it for the first second. RPMs from the MSD box reported engine rotation, I had power to all systems that i could tell, A/F ratio was normal (I think), Fuel pressure was 6lbs (pretty sure). I pressed on the gas and it did nothing and I was like okay.....wtf....hope it restarts. I pushed in the clutch and engine RPM reported 0 gave the key a tap and it fired right up like no big deal speed was now 55 to 60 mph.
So the clutch was in initially and the engine had rotation, it had fuel it had air...what no ignition??? then why did it restart when I hit the key? Why didnt it restart before i hit the key???
hummm
-Gun
I have finally manged to encounter a hard to isolate engine problem.
Heres the story
1) for some time (last few months) during dead stop easy accelerations the engine air fuel would become slightly rich into the high 12s as expected (13.5 is where it sits at idle)but would momentarily lean beyond 19 and the car would stumble as you let the clutch out. The engine would never die and I blamed it on some dirt in the carb low speed. but delayed cleaning the carb and would apply more power during acceleration to avoid the problem. This problem only occurred during easy dead stop accelerations for about a 1 sec duration. It ran perfect in all other instances.
2) about a week ago the engine stared to die during dead stop normal accelerations after a prolonged stop for example a stop light. attempting a restart was difficult and usually required about 30 to 40 seconds. The engine dying at stops seems to be becoming more frequent.
* Last night I totally cleaned out the carb hoping that would solve the problem...it did very little good at best maybe the engine leaning badly on acceleration problem is solved or at least made less severe( dips into the 16s now sometimes and sometimes not and stays from 13 during accel then back to upper 14s).
** fuel press is 100% fuel volume is normal
*** accelerator pump pisses as good as always and I dont see any worn accel pump linkages.
3) after cleaning the carb the car died once after an idle period of maybe 1.25 minutes and then attempting normal acceleration and required maybe 30 sec to restart.
4) after it died in #3 I drove it again a few hrs later and didnt have any issues at all on the way to the destination (8 miles) then on the way back it died on the freeway at 70...totally smooth so smooth i didnt quite get it for the first second. RPMs from the MSD box reported engine rotation, I had power to all systems that i could tell, A/F ratio was normal (I think), Fuel pressure was 6lbs (pretty sure). I pressed on the gas and it did nothing and I was like okay.....wtf....hope it restarts. I pushed in the clutch and engine RPM reported 0 gave the key a tap and it fired right up like no big deal speed was now 55 to 60 mph.
So the clutch was in initially and the engine had rotation, it had fuel it had air...what no ignition??? then why did it restart when I hit the key? Why didnt it restart before i hit the key???
hummm
-Gun
Last edited by Gun Jam; Jan 19, 2011 at 11:25 PM.
Thread Starter
6th Gear Member
Joined: Dec 2005
Posts: 5,212
From: Hills of California
If it had lost spark af should have read rich I would think...and maybe it did I was busy with other stuff but I did sweep as many gauges as possible and I dont remember seeing any red flags.
Is there a simple way to monitor spark in real time?
It seems odd that the MSD would be 100% one instant totally dead the next and then 100% again...I did check all the connectors from the box to the coil and dizzy too and they seemed okay maybe slightly corroded but still I would consider okay.
Is there a simple way to monitor spark in real time?
It seems odd that the MSD would be 100% one instant totally dead the next and then 100% again...I did check all the connectors from the box to the coil and dizzy too and they seemed okay maybe slightly corroded but still I would consider okay.
2nd Gear Member
Joined: Aug 2009
Posts: 475
From: Nebraska
Is is possible for electronics to be good, then bad, then good again. The soldier connectons on the board can heat up, pull away and go open. Then with no electricty flowing they will cool down and go to closed again. Kind of like a bi-metallic flasher will. Im not saying this is your problem just that electronics can do this.
4th Gear Member
Joined: Apr 2010
Posts: 1,027
From: NJ
Had a similar issue with my 6M box, turned out to be a loose power cable to the box itself. Easy fix however the box died completely a few hours later. They don't seem to like intermittent power.
However it wouldn't be likely to read lean.....definitely an interesting problem.
However it wouldn't be likely to read lean.....definitely an interesting problem.
6th Gear Member
Joined: Oct 2006
Posts: 6,417
From: Cork, Ireland
no spark will cause lean reading if you use oxygen sensors. Reason for this is that it measures rest oxygen after it burned. If you don't burn then what's coming out of your cylinder is craploads of oxygen enriched with fuel. however the box will read this oxygen. It sounds the wrong way around, but it's that way. you can do a simple test: if you have the bung measuring on the driver side bank, and run idle reads 15 A/F ratio. Disconnect one of the spark plugs on that bank and I bet it will read lean although there's raw fuel dumped out
from what you descibe its either no fuel issue (pump, carb, dirt) or ignition box.
I had both problems in the past and I never found a way to listen what is missing. I can't tell if spak is missing or fuel while driving if one of the goes.
In my case the spark going out. it was a pertronix distributor. and the ground strap going to the module was bolted to the vacuum canister. the screw held the vacuum canister in place. However this was loose and the module would loose ground occasionally. It always happened on sudden load changes (start an overtake ....), then suddenly coming back again with no turning of key or dumping clutch in high gear
With the petrol it was different. if it went it would always go for a longer period. the pressure drops, then the bowls are empty and then you get problems. So if youi can report the fuel pressure to be around 6psi when it happened I would suggest the first thing to look at is the ignition.
The rpm output at box will not give signal when it fired successfully. it will give a wave signal depending on what the distributor is telling it. So from that it could be simply your coil starting to give up or the box itself. or just a diodgy connection somewhere. I once had that with a inline fuse (i myself made a messy connection that haunted me for 1 month). I had to wait until it happened and _hop_ that it doesn't come back automatically so I can troubleshoot. I just touched the cable near fuse and the fuelpump and ignitionbox sprang to life ....
as said hard to troubleshott, but maybe I offered some help ...
from what you descibe its either no fuel issue (pump, carb, dirt) or ignition box.
I had both problems in the past and I never found a way to listen what is missing. I can't tell if spak is missing or fuel while driving if one of the goes.
In my case the spark going out. it was a pertronix distributor. and the ground strap going to the module was bolted to the vacuum canister. the screw held the vacuum canister in place. However this was loose and the module would loose ground occasionally. It always happened on sudden load changes (start an overtake ....), then suddenly coming back again with no turning of key or dumping clutch in high gear
With the petrol it was different. if it went it would always go for a longer period. the pressure drops, then the bowls are empty and then you get problems. So if youi can report the fuel pressure to be around 6psi when it happened I would suggest the first thing to look at is the ignition.
The rpm output at box will not give signal when it fired successfully. it will give a wave signal depending on what the distributor is telling it. So from that it could be simply your coil starting to give up or the box itself. or just a diodgy connection somewhere. I once had that with a inline fuse (i myself made a messy connection that haunted me for 1 month). I had to wait until it happened and _hop_ that it doesn't come back automatically so I can troubleshoot. I just touched the cable near fuse and the fuelpump and ignitionbox sprang to life ....
as said hard to troubleshott, but maybe I offered some help ...
Thread Starter
6th Gear Member
Joined: Dec 2005
Posts: 5,212
From: Hills of California
Okay so you are saying the MSD box will report rotation based on the dizzy regardless if the box is functioning or not? One thing im a 100% sure of is rotation was reported and displayed on the tach after the engine died. So that means my connector between the box the and dizzy is okay.
With the MSD box is there any way to verify power to the coil other than taking the boot off?
Why did it sit there and spin down from 70 at 2200 rpm for like 6 seconds while I tired to figure out what the hell happened and not restart on its own? it had maybe 0 rpm for 1 sec as I verified on the tach it was 0 and safe for key restart as soon as I hit the key it was alive...coincidence?
Thanks for your help
6th Gear Member
Joined: Oct 2006
Posts: 6,417
From: Cork, Ireland
--> Okay so you are saying the MSD box will report rotation based on the dizzy regardless if the box is functioning or not
what I am saying is that if you would run at 6000 rpm in 5th gear (you have a fast car) and then suddenly cut the coil wire from distributor to coil or disconnect the coil itself then you will have the same effect as if you would remove your foot from accellerator, the car will slow down. There will be no spark, however there will be still rpm signal. the signal from the box is unrelated to if it actually sparked at the cylinder. it only shows when it _should_ have sparked, which in normal operation is at the same time.
can you clarify this:
I verified on the tach it was 0 and safe for key restart as soon as I hit the key it was alive...coincidence?
what exactly did you do with the key? turn it off and then turned it back on to 'ignition' or did you go the full way to start?
--> With the MSD box is there any way to verify power to the coil other than taking the boot off?
when using MSD box you should have on coil: two wires from MSD to coil (+/-) and the pluglead going from coil to distributor. Absolutely nothing else. If you do there's a big mistake that has to be removed. A lot of people leave ignition+ and other crap at coil+. Not an option if running MSD. if you can verify that there is a step in the troubleshooting guide that says that you can take the negative wire (from distributor to box). that one that originally goes to coil- for switching can be tapped to ground to see if the box is sparking.
but before you try any of that, respond to the clarification what exactly you did with the key.
what I am saying is that if you would run at 6000 rpm in 5th gear (you have a fast car) and then suddenly cut the coil wire from distributor to coil or disconnect the coil itself then you will have the same effect as if you would remove your foot from accellerator, the car will slow down. There will be no spark, however there will be still rpm signal. the signal from the box is unrelated to if it actually sparked at the cylinder. it only shows when it _should_ have sparked, which in normal operation is at the same time.
can you clarify this:
I verified on the tach it was 0 and safe for key restart as soon as I hit the key it was alive...coincidence?
what exactly did you do with the key? turn it off and then turned it back on to 'ignition' or did you go the full way to start?
--> With the MSD box is there any way to verify power to the coil other than taking the boot off?
when using MSD box you should have on coil: two wires from MSD to coil (+/-) and the pluglead going from coil to distributor. Absolutely nothing else. If you do there's a big mistake that has to be removed. A lot of people leave ignition+ and other crap at coil+. Not an option if running MSD. if you can verify that there is a step in the troubleshooting guide that says that you can take the negative wire (from distributor to box). that one that originally goes to coil- for switching can be tapped to ground to see if the box is sparking.
but before you try any of that, respond to the clarification what exactly you did with the key.
Thread Starter
6th Gear Member
Joined: Dec 2005
Posts: 5,212
From: Hills of California
The key was in the "on" position as expected and required during normal engine run. The engine died instantly and for an unknown reason. During the rev down from 70 the key was in the on position the whole time EXCEPT for a brief moment after I pushed in the clutch the key was moved to the "start" position the starter engaged and the engine started easily... which really makes no sense it was just spinning at 2000 rpm dead with the ignition on and some how 300 or whatever rpm from the started made it fire right up like no big deal...hummm i wonder if its the ignition (the thing the key fits into) its self!!
Thread Starter
6th Gear Member
Joined: Dec 2005
Posts: 5,212
From: Hills of California
I am using the MSD dizzy as well it uses the magnetic pickup lead too. and by "pluglead" from coil to dizzy I read that as the the high voltage (40kv+) 8.5mm coil wire correct?
My system is wired as shown on the top of page 11 "Installing to an MSD distributor/ crank trigger"
http://www.msdignition.com/instructi...pdf?terms=6200