'75 Turns over but won't fire. Normally VERY reliable.
11-11-2015, 03:12 PM
#1
Advanced
Thread Starter
'75 Turns over but won't fire. Normally VERY reliable.
First, thanks in advance for any and all advice. This forum has been priceless to a new Vette owner like me. None of the below made much sense to me even 5 months ago, I owe a lot to your collective knowledge and the power of the interwebz.
Background:
1) Car is a mostly stock 1975 Convertible in excellent condition. Appears to have had a full rebuild ~9000 miles ago. PO put the original engine in a crate and replaced with a '78 350 small block, Edelbrock intake and straight through exhaust. Apparently makes 330hp now, haven't confirmed with dyno yet.
2) As far as I can tell everything else, including the carb, is original.
3) Since owning the car from June (2015), it has run extremely well. I drive it almost daily and have never had starting issues until now. Starter motor seems strong, battery is very new and has plenty of crank.
4) The carb has been very well adjusted by PO. After start the high rpm idle with choke works exactly as it should and at warm idle it is perfect. Can't complain about carb performance when the car is running. Also, the car has zero issues starting when warm (which I read some people experience).
5) Plenty of gas in the tank
Symptoms and fault finding (so far):
Occurence One
1) A few weeks ago the car would not fire, the starter turned the engine over fine however.
2) I consulted the forums and checked a few things:
Occurence Two
1) Two days ago, same problem. Crank with no spark.
2) Left it a full day and tried again. Almost fired after several second of running the starter, but I was too slow on the gas and two quick off the starter and it didn't start. Then it refused to even hint at firing again.
3) Left it another day (today). Nothing, won't fire.
4) I've tried cranking the starter with WOT, sometimes for an uncomfortably long period (15-20 second). I'm starting to worry about damaging the starter :/
Other possible factors (?)
- The weather has been a bit cooler than the past few months (duh), but being in Alabama it's never that cold. We're talking 50s or 60s.
- My start procedure is generally always the same, so not sure how it flooded (if indeed it has). I pump the gas pedal 3 times, then crank and wait for it to fire before feeding more gas. If it goes too long I'll give it a pump or two extra. This is what happened the first time it failed to fire. Is this bad technique?
- I changed the oil about 3 months ago to a synthetic 20W-50 (Valvoline VR1). I figured with temps not even getting below the 50s that would be fine. Not sure if this could be a factor, but certainly the starter doesn't seem to be laboring when it's turning the engine over, so I'm assuming this is unrelated.
At this point I am still thinking it's flooded (again), mainly because it ran completely flawlessly for two weeks between occurrences, which would seem to rule out ignition coil, distributor and fuel supply. If that's the case, I'm not sure why it's flooding, or why after a couple of days it still won't start.
Perhaps (probably) I'm doing something stupid or breaking some cardinal rule - so please tell me if I am, I won't be offended.
Background:
1) Car is a mostly stock 1975 Convertible in excellent condition. Appears to have had a full rebuild ~9000 miles ago. PO put the original engine in a crate and replaced with a '78 350 small block, Edelbrock intake and straight through exhaust. Apparently makes 330hp now, haven't confirmed with dyno yet.
2) As far as I can tell everything else, including the carb, is original.
3) Since owning the car from June (2015), it has run extremely well. I drive it almost daily and have never had starting issues until now. Starter motor seems strong, battery is very new and has plenty of crank.
4) The carb has been very well adjusted by PO. After start the high rpm idle with choke works exactly as it should and at warm idle it is perfect. Can't complain about carb performance when the car is running. Also, the car has zero issues starting when warm (which I read some people experience).
5) Plenty of gas in the tank
Symptoms and fault finding (so far):
Occurence One
1) A few weeks ago the car would not fire, the starter turned the engine over fine however.
2) I consulted the forums and checked a few things:
a) Pulled distributor and checked continuity. All seemed fine. The coil looks almost brand new.
b) Checked spark plug cables. All high-quality aftermarket in excellent condition. No corrosion in connectors.
c) Pulled a spark plug. Also in excellent condition, gap looked fine, no fouling or corrosion. HOWEVER, seemed wet. I don't know what normal is but this made me suspect flooding.
d) Assuming flooding, I ran the starter with the accelerator pedal floored per advice here to help airflow. This did not immediately work.
e) After leaving the car for two days, I tried again and it fired up, no problems.
3) Assuming flooding was the problem, I ceased any further fault finding and drove for another two weeks without any start (or running) problems.b) Checked spark plug cables. All high-quality aftermarket in excellent condition. No corrosion in connectors.
c) Pulled a spark plug. Also in excellent condition, gap looked fine, no fouling or corrosion. HOWEVER, seemed wet. I don't know what normal is but this made me suspect flooding.
d) Assuming flooding, I ran the starter with the accelerator pedal floored per advice here to help airflow. This did not immediately work.
e) After leaving the car for two days, I tried again and it fired up, no problems.
Occurence Two
1) Two days ago, same problem. Crank with no spark.
2) Left it a full day and tried again. Almost fired after several second of running the starter, but I was too slow on the gas and two quick off the starter and it didn't start. Then it refused to even hint at firing again.
3) Left it another day (today). Nothing, won't fire.
4) I've tried cranking the starter with WOT, sometimes for an uncomfortably long period (15-20 second). I'm starting to worry about damaging the starter :/
Other possible factors (?)
- The weather has been a bit cooler than the past few months (duh), but being in Alabama it's never that cold. We're talking 50s or 60s.
- My start procedure is generally always the same, so not sure how it flooded (if indeed it has). I pump the gas pedal 3 times, then crank and wait for it to fire before feeding more gas. If it goes too long I'll give it a pump or two extra. This is what happened the first time it failed to fire. Is this bad technique?
- I changed the oil about 3 months ago to a synthetic 20W-50 (Valvoline VR1). I figured with temps not even getting below the 50s that would be fine. Not sure if this could be a factor, but certainly the starter doesn't seem to be laboring when it's turning the engine over, so I'm assuming this is unrelated.
At this point I am still thinking it's flooded (again), mainly because it ran completely flawlessly for two weeks between occurrences, which would seem to rule out ignition coil, distributor and fuel supply. If that's the case, I'm not sure why it's flooding, or why after a couple of days it still won't start.
Perhaps (probably) I'm doing something stupid or breaking some cardinal rule - so please tell me if I am, I won't be offended.
11-11-2015, 04:15 PM
#3
if you remove the spark plug wire from a spark plug, insert a well insulated screwdriver tip into the plug connector, and hold the shaft of the screwdriver near something metal on the engine while someone tries to start, do you see a spark jump from the screwdriver shaft to the engine?
11-11-2015, 05:13 PM
#4
Melting Slicks
Member Since: Apr 2009
Location: Great Plains Iowa
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Distributor Module? Maybe
Its very likely your distributor module is failing because when the fail they often don't fail all at once. They aren't very expensive so I recommend replacing it and when you do make sure the plugins plug on tightly with noticeable resistance. Those plugins get looser and looser over time until they fail to connect good enough.
11-11-2015, 07:58 PM
#5
Melting Slicks
Its very likely your distributor module is failing because when the fail they often don't fail all at once. They aren't very expensive so I recommend replacing it and when you do make sure the plugins plug on tightly with noticeable resistance. Those plugins get looser and looser over time until they fail to connect good enough.
11-11-2015, 08:08 PM
#6
Advanced
Thread Starter
Yup, HEI.
Yes, I pulled the cap and followed a guide using a multimeter to make sure there was correct continuity. It's getting power and the cap seems fine. No marks to indicate it wouldn't be making contact.
That's a plan. I assume I can't use a multimeter to check the same thing due to the extreme voltages generated?
The plugs are fine, there is very positive connection when you pull them off and push them on. I'm not concerned there, and even if it were a problem, surely it wouldn't affect all eight cylinders at once?
I'll take a photo of the ignition coil and distributor with cap off. They are in such great shape you would swear they were brand new. My gut says that's an unlikely source, but if this keeps up I'll change them on spec.
Lol, I remember that thread. Insulating silicon sealant /= thermal paste. But seriously, any ideas on my actual problem?
-------------------
Any comments on my starting procedures? I'm interested in what other people do.
Yes, I pulled the cap and followed a guide using a multimeter to make sure there was correct continuity. It's getting power and the cap seems fine. No marks to indicate it wouldn't be making contact.
if you remove the spark plug wire from a spark plug, insert a well insulated screwdriver tip into the plug connector, and hold the shaft of the screwdriver near something metal on the engine while someone tries to start, do you see a spark jump from the screwdriver shaft to the engine?
Its very likely your distributor module is failing because when the fail they often don't fail all at once. They aren't very expensive so I recommend replacing it and when you do make sure the plugins plug on tightly with noticeable resistance. Those plugins get looser and looser over time until they fail to connect good enough.
I'll take a photo of the ignition coil and distributor with cap off. They are in such great shape you would swear they were brand new. My gut says that's an unlikely source, but if this keeps up I'll change them on spec.
Lol, I remember that thread
. Insulating silicon sealant /= thermal paste. But seriously, any ideas on my actual problem?-------------------
Any comments on my starting procedures? I'm interested in what other people do.
Last edited by OzBeast; 11-11-2015 at 08:14 PM.
11-11-2015, 08:21 PM
#7
Team Owner
When it happens, leave the key on, and pop the hood and measure the voltage at the pink input wire to the HEI which needs see 12 volts, then measure the TACH wire...the other one next to it....needs see the same 12 volts......if not, solder the crimped wire terminals leading to the coil....caught one pants DOWN some years ago....the crimps did not make contact with the coil wire....due to leaving the formvar wire insulation on there....so just solder them right in position.....
IF that checks out....you probably have a bad sending coil down under the rotor button and weights....requires an entire dizzy tear down to replace it has Green and White wires plugged into the black sending module....if that coil is just a mild tan...it MAY be ok, but over years they turn a heavy shoe polish brown, and so open up and so nothing.....
Obviously it can also be the black trigger/amp chip but eh....doubtful....
not from what you saying anyway.....
IF that checks out....you probably have a bad sending coil down under the rotor button and weights....requires an entire dizzy tear down to replace it has Green and White wires plugged into the black sending module....if that coil is just a mild tan...it MAY be ok, but over years they turn a heavy shoe polish brown, and so open up and so nothing.....
Obviously it can also be the black trigger/amp chip but eh....doubtful....
not from what you saying anyway.....
11-11-2015, 09:22 PM
#8
Drifting
So far the common theme here is flooding.
Try pulling a plug wire, installing another plug, grounding and checking for spark. (as suggested earlier) If you are getting spark (and Im betting you are), flooding is your issue.
Im in no way an 'expert' around here, but of the few times Ive flooded an engine, the WOT never helped me. The only cure was to let it sit. I have stuck a screwdriver into the butterflies to hold everything open to vent better, but cranking it over just seems to add more fuel to an already wet engine.
Tell us more about the carb....
Try pulling a plug wire, installing another plug, grounding and checking for spark. (as suggested earlier) If you are getting spark (and Im betting you are), flooding is your issue.
Im in no way an 'expert' around here, but of the few times Ive flooded an engine, the WOT never helped me. The only cure was to let it sit. I have stuck a screwdriver into the butterflies to hold everything open to vent better, but cranking it over just seems to add more fuel to an already wet engine.
Tell us more about the carb....
11-11-2015, 10:14 PM
#9
Safety Car
Sometimes a bad spark responds to holding the throttle wide open.
I would change the HEI module as it would cause what your experiencing and also check to see how brittle the wires are inside the distributor .
I would change the HEI module as it would cause what your experiencing and also check to see how brittle the wires are inside the distributor .
The following users liked this post:
OzBeast (12-08-2015)
11-12-2015, 03:40 PM
#10
Drifting
Next time it fails to fire, pull the tach wire from the distributor cap. On rare occasions a faulty tach can cause ground out and cause a fail to fire. Also make sure the power wire connection to the distributor is tight and clean. That crimp terminal gets corroded over time (like 40 years) and can cause stalling and failure to fire. Ye, I found this by experience.
12-08-2015, 09:55 AM
#11
Advanced
Thread Starter
Just a follow up post to let you know how this turned out, and to help anyone searching for the same problem...
After leaving the car for a few days it fired up again, so again I thought flooding might be the most likely cause.
It only ran for a few days before the problem resurfaced, and this time I knew I hadn't flooded it. Hmm.
Based on the advice here I changed out the distributor cap, rotor and ignition coil (with fairly inexpensive Duralast components) and all seems well, no start problems since.
I know there is a detailed ignition sticky here, but I still have no idea if I put the 'right' coil in, it was just the one that matched at Autozone for my engine.
Also, how might I check the components I pulled out to see which might have been the real culprit? Either way, I'll leave all the new bits in as I figured it's better to have matching brand cap and rotor of the same age as the tolerances are probably better than mix and matching brands or worn components.
After leaving the car for a few days it fired up again, so again I thought flooding might be the most likely cause.
It only ran for a few days before the problem resurfaced, and this time I knew I hadn't flooded it. Hmm.
Based on the advice here I changed out the distributor cap, rotor and ignition coil (with fairly inexpensive Duralast components) and all seems well, no start problems since.
I know there is a detailed ignition sticky here, but I still have no idea if I put the 'right' coil in, it was just the one that matched at Autozone for my engine.
Also, how might I check the components I pulled out to see which might have been the real culprit? Either way, I'll leave all the new bits in as I figured it's better to have matching brand cap and rotor of the same age as the tolerances are probably better than mix and matching brands or worn components.
12-08-2015, 10:27 AM
#12
Burning Brakes
Just a follow up post to let you know how this turned out, and to help anyone searching for the same problem...
After leaving the car for a few days it fired up again, so again I thought flooding might be the most likely cause.
It only ran for a few days before the problem resurfaced, and this time I knew I hadn't flooded it. Hmm.
Based on the advice here I changed out the distributor cap, rotor and ignition coil (with fairly inexpensive Duralast components) and all seems well, no start problems since.
I know there is a detailed ignition sticky here, but I still have no idea if I put the 'right' coil in, it was just the one that matched at Autozone for my engine.
Also, how might I check the components I pulled out to see which might have been the real culprit? Either way, I'll leave all the new bits in as I figured it's better to have matching brand cap and rotor of the same age as the tolerances are probably better than mix and matching brands or worn components.
After leaving the car for a few days it fired up again, so again I thought flooding might be the most likely cause.
It only ran for a few days before the problem resurfaced, and this time I knew I hadn't flooded it. Hmm.
Based on the advice here I changed out the distributor cap, rotor and ignition coil (with fairly inexpensive Duralast components) and all seems well, no start problems since.
I know there is a detailed ignition sticky here, but I still have no idea if I put the 'right' coil in, it was just the one that matched at Autozone for my engine.
Also, how might I check the components I pulled out to see which might have been the real culprit? Either way, I'll leave all the new bits in as I figured it's better to have matching brand cap and rotor of the same age as the tolerances are probably better than mix and matching brands or worn components.
The following users liked this post:
OzBeast (12-08-2015)
The following users liked this post:
OzBeast (12-08-2015)
03-24-2017, 10:03 PM
#14
Instructor
Having same problem, same year car.
First, thanks in advance for any and all advice. This forum has been priceless to a new Vette owner like me. None of the below made much sense to me even 5 months ago, I owe a lot to your collective knowledge and the power of the interwebz.
Background:
1) Car is a mostly stock 1975 Convertible in excellent condition. Appears to have had a full rebuild ~9000 miles ago. PO put the original engine in a crate and replaced with a '78 350 small block, Edelbrock intake and straight through exhaust. Apparently makes 330hp now, haven't confirmed with dyno yet.
2) As far as I can tell everything else, including the carb, is original.
3) Since owning the car from June (2015), it has run extremely well. I drive it almost daily and have never had starting issues until now. Starter motor seems strong, battery is very new and has plenty of crank.
4) The carb has been very well adjusted by PO. After start the high rpm idle with choke works exactly as it should and at warm idle it is perfect. Can't complain about carb performance when the car is running. Also, the car has zero issues starting when warm (which I read some people experience).
5) Plenty of gas in the tank
Symptoms and fault finding (so far):
Occurence One
1) A few weeks ago the car would not fire, the starter turned the engine over fine however.
2) I consulted the forums and checked a few things:
Occurence Two
1) Two days ago, same problem. Crank with no spark.
2) Left it a full day and tried again. Almost fired after several second of running the starter, but I was too slow on the gas and two quick off the starter and it didn't start. Then it refused to even hint at firing again.
3) Left it another day (today). Nothing, won't fire.
4) I've tried cranking the starter with WOT, sometimes for an uncomfortably long period (15-20 second). I'm starting to worry about damaging the starter :/
Other possible factors (?)
- The weather has been a bit cooler than the past few months (duh), but being in Alabama it's never that cold. We're talking 50s or 60s.
- My start procedure is generally always the same, so not sure how it flooded (if indeed it has). I pump the gas pedal 3 times, then crank and wait for it to fire before feeding more gas. If it goes too long I'll give it a pump or two extra. This is what happened the first time it failed to fire. Is this bad technique?
- I changed the oil about 3 months ago to a synthetic 20W-50 (Valvoline VR1). I figured with temps not even getting below the 50s that would be fine. Not sure if this could be a factor, but certainly the starter doesn't seem to be laboring when it's turning the engine over, so I'm assuming this is unrelated.
At this point I am still thinking it's flooded (again), mainly because it ran completely flawlessly for two weeks between occurrences, which would seem to rule out ignition coil, distributor and fuel supply. If that's the case, I'm not sure why it's flooding, or why after a couple of days it still won't start.
Perhaps (probably) I'm doing something stupid or breaking some cardinal rule - so please tell me if I am, I won't be offended.
Background:
1) Car is a mostly stock 1975 Convertible in excellent condition. Appears to have had a full rebuild ~9000 miles ago. PO put the original engine in a crate and replaced with a '78 350 small block, Edelbrock intake and straight through exhaust. Apparently makes 330hp now, haven't confirmed with dyno yet.
2) As far as I can tell everything else, including the carb, is original.
3) Since owning the car from June (2015), it has run extremely well. I drive it almost daily and have never had starting issues until now. Starter motor seems strong, battery is very new and has plenty of crank.
4) The carb has been very well adjusted by PO. After start the high rpm idle with choke works exactly as it should and at warm idle it is perfect. Can't complain about carb performance when the car is running. Also, the car has zero issues starting when warm (which I read some people experience).
5) Plenty of gas in the tank
Symptoms and fault finding (so far):
Occurence One
1) A few weeks ago the car would not fire, the starter turned the engine over fine however.
2) I consulted the forums and checked a few things:
a) Pulled distributor and checked continuity. All seemed fine. The coil looks almost brand new.
b) Checked spark plug cables. All high-quality aftermarket in excellent condition. No corrosion in connectors.
c) Pulled a spark plug. Also in excellent condition, gap looked fine, no fouling or corrosion. HOWEVER, seemed wet. I don't know what normal is but this made me suspect flooding.
d) Assuming flooding, I ran the starter with the accelerator pedal floored per advice here to help airflow. This did not immediately work.
e) After leaving the car for two days, I tried again and it fired up, no problems.
3) Assuming flooding was the problem, I ceased any further fault finding and drove for another two weeks without any start (or running) problems.b) Checked spark plug cables. All high-quality aftermarket in excellent condition. No corrosion in connectors.
c) Pulled a spark plug. Also in excellent condition, gap looked fine, no fouling or corrosion. HOWEVER, seemed wet. I don't know what normal is but this made me suspect flooding.
d) Assuming flooding, I ran the starter with the accelerator pedal floored per advice here to help airflow. This did not immediately work.
e) After leaving the car for two days, I tried again and it fired up, no problems.
Occurence Two
1) Two days ago, same problem. Crank with no spark.
2) Left it a full day and tried again. Almost fired after several second of running the starter, but I was too slow on the gas and two quick off the starter and it didn't start. Then it refused to even hint at firing again.
3) Left it another day (today). Nothing, won't fire.
4) I've tried cranking the starter with WOT, sometimes for an uncomfortably long period (15-20 second). I'm starting to worry about damaging the starter :/
Other possible factors (?)
- The weather has been a bit cooler than the past few months (duh), but being in Alabama it's never that cold. We're talking 50s or 60s.
- My start procedure is generally always the same, so not sure how it flooded (if indeed it has). I pump the gas pedal 3 times, then crank and wait for it to fire before feeding more gas. If it goes too long I'll give it a pump or two extra. This is what happened the first time it failed to fire. Is this bad technique?
- I changed the oil about 3 months ago to a synthetic 20W-50 (Valvoline VR1). I figured with temps not even getting below the 50s that would be fine. Not sure if this could be a factor, but certainly the starter doesn't seem to be laboring when it's turning the engine over, so I'm assuming this is unrelated.
At this point I am still thinking it's flooded (again), mainly because it ran completely flawlessly for two weeks between occurrences, which would seem to rule out ignition coil, distributor and fuel supply. If that's the case, I'm not sure why it's flooding, or why after a couple of days it still won't start.
Perhaps (probably) I'm doing something stupid or breaking some cardinal rule - so please tell me if I am, I won't be offended.
I have the same problem with my 75 4-speed, it is very intermittent but car will start when I push it off and pop clutch in second. Seems to always start at home, so hard to check for spark and stuff in parking lots.
Thoughts.
03-24-2017, 10:22 PM
#15
Race Director
To check the car in a parking lot -
Harbor Freight sells a spark tester - short wire and a clear plastic section that will spark when given coil voltage.
Pull a cap wire when it will not start and put the tester in. if no spark in the tester - it's an ignition issue.
Sometimes a coil will produce less power when going bad when it heats up.
Harbor Freight sells a spark tester - short wire and a clear plastic section that will spark when given coil voltage.
Pull a cap wire when it will not start and put the tester in. if no spark in the tester - it's an ignition issue.
Sometimes a coil will produce less power when going bad when it heats up.
03-24-2017, 11:33 PM
#16
Melting Slicks
With the cooler temperatures you've been having, I suspect the choke might be adjusted a bit on the rich side.
with a cool engine (let it sit overnight) set the choke and then look at how much spring pressure is holding the choke plate closed. It should only be very light to practically no pressure holding the choke plate closed.....any more than that and you risk flooding your engine, which is what I think your issue is.
with a cool engine (let it sit overnight) set the choke and then look at how much spring pressure is holding the choke plate closed. It should only be very light to practically no pressure holding the choke plate closed.....any more than that and you risk flooding your engine, which is what I think your issue is.