C3 1969 427 - starts then stops
- Thread starter Blondie69
- Start date
Roscobbc
Moderator
Pull off the fuel feed to the carb - put a container underneath the open pipe. Crank the engine over with the HT lead from ther distributor to the coil removed (so it won't start) - does fuel pump-out with some volume?.Ethanol can in time erode the diaphragm in the fuel pump.
If you have fuel pressure and gas is healthily squirting out - reconnect pipe - turn the engine over on the starter again (re-connect the coil if you wish) - if it starts thats OK. let it run for 15 seconds or so and stop the engine. If the carb is a Holley does cranking the accelerator lever on the carb squirt neat fuel in to the carb? (this won;t work idf the carb is a Quadrajet)
How long since the engine was last run? - perhaps carb has dried-out, along with gaskets - maybe accelerator pump/pumps have blocked-up - ethanol can contaminate some of the more delicate carb components with crap and sediment. Does it continue to run if you throw an eggcup sized amount of fuel down the carb mouth? (stand clear if you do that in case of a flash-back!)
If you have fuel pressure and gas is healthily squirting out - reconnect pipe - turn the engine over on the starter again (re-connect the coil if you wish) - if it starts thats OK. let it run for 15 seconds or so and stop the engine. If the carb is a Holley does cranking the accelerator lever on the carb squirt neat fuel in to the carb? (this won;t work idf the carb is a Quadrajet)
How long since the engine was last run? - perhaps carb has dried-out, along with gaskets - maybe accelerator pump/pumps have blocked-up - ethanol can contaminate some of the more delicate carb components with crap and sediment. Does it continue to run if you throw an eggcup sized amount of fuel down the carb mouth? (stand clear if you do that in case of a flash-back!)
Hi Ross sorry for late reply. Messages went into my spam folder. Thank you for your reply. I have done all of the above and still the same.
I have replaced the spark plugs since it last started. Today going to dig deeper.
Many thanks
Yes fuel is pumping through and looking at what it pumped into container, no water.
Will need to check coil but I'm not sure how to check - will get the manual out
Funny you mentioned the vacuum because when you stand next to the driver side when cranking - a strong draft is felt. When I first tried to start it I heard a pop sound - it may be a blind alley but I will look over.
Many thanks
teamzr1
Supporting vendor
Yes fuel is pumping through and looking at what it pumped into container, no water.
Will need to check coil but I'm not sure how to check - will get the manual out
Funny you mentioned the vacuum because when you stand next to the driver side when cranking - a strong draft is felt. When I first tried to start it I heard a pop sound - it may be a blind alley but I will look over.
Many thanks
If you take one sparkplug wire off at the sparkplug and watch your fingers, have the end of that wire close to engine or exhaust
have someone try starting engine and watch for spark arcing from the wire to ground
Of course less light, easier to see arcing
Also test the fuel pressure and pull a few plugs and see if any gas soak ?
Last edited:
Hiya
I've tried to add a video but apparently the video file will not be accepted
. Having a great day . It starts but I think the pump is not pumping enough fuel to keep it going. Plus the fuel filter looks like it's not holding any fuel. What is the best fuel pump for 427 1969 390?
Many thanks
teamzr1
Supporting vendor
You could post your video on Y tube and then post here the link to it
Here is examples for 69 Corvette fuel pumps
Change fuel filter at the same time
Here is examples for 69 Corvette fuel pumps
Change fuel filter at the same time
Last edited:
teamzr1
Supporting vendor
For 427 CI Corvette
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Chuffer
CCCUK Member
The slightest vacuum leak will have an effect on engine running . I had the dread C3 droopy headlights so bought a vacuum test kit to check out the entire vacuum system on the car . I rebuilt the headlight actuators with new seal kits , replaced the non return valve on vacuum line to the manifold that was not non returning at all and fitted an inline filter that was missing completely . I then had properly functioning pop up headlights and as a bonus the engine ran much better too .Yes fuel is pumping through and looking at what it pumped into container, no water.
Will need to check coil but I'm not sure how to check - will get the manual out
Funny you mentioned the vacuum because when you stand next to the driver side when cranking - a strong draft is felt. When I first tried to start it I heard a pop sound - it may be a blind alley but I will look over.
Many thanks
Forrest Gump
CCCUK regional rep
Hi Barb
As John asked in post#2, how long is the engine running before it stops?
When you tested the pump you were getting fuel flow so I would have thought there was enough fuel supply for it to run at tick-over at least. When you start it up can you keep it running longer by pumping the throttle each time it tries to die?
It could be a fuel issue but might be carb rather than the pump.
To eliminate a vacuum leak, temporarily plug the vacuum port at the back of the carb.
As John asked in post#2, how long is the engine running before it stops?
When you tested the pump you were getting fuel flow so I would have thought there was enough fuel supply for it to run at tick-over at least. When you start it up can you keep it running longer by pumping the throttle each time it tries to die?
It could be a fuel issue but might be carb rather than the pump.
To eliminate a vacuum leak, temporarily plug the vacuum port at the back of the carb.
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Hiya
It is literally a couple of seconds before it dies. It starts and I throttle it but it cuts out. I will try to plug the back of the carb.
I've found myself just standing staring at the engine looking for something to look obviously wrong
. Digging deeper now. It's not that it wasn't a runner before. Its not had an engine turn over for a couple of months whilst I've been doing the interior replacement.
Thank you all for your comments
Roscobbc
Moderator
Barb - if you want to 100% 'prove' failure of the fuel pump or fuel line why not try removing the fuel feed to the carb and attaching to a gravity fed petrol container held or clipped above the engine........being careful of course.........the engine should run continuously.
Either block the fuel line from the fuel pump line - or - feed it in to a container to see how much gas pumps-in while the engine is running off the container (presuming it's going to run continuously)
The fuel bowls (certainly the primaries) should fill correctly so you can check the float needles are operating correctly and not overflowing (and not gunged-up)
Its worthwhile cranking the throttle arm when carbs are full and observing the primary accelerator pump jets to see if they are 'squirting' properly.
Either block the fuel line from the fuel pump line - or - feed it in to a container to see how much gas pumps-in while the engine is running off the container (presuming it's going to run continuously)
The fuel bowls (certainly the primaries) should fill correctly so you can check the float needles are operating correctly and not overflowing (and not gunged-up)
Its worthwhile cranking the throttle arm when carbs are full and observing the primary accelerator pump jets to see if they are 'squirting' properly.
Forrest Gump
CCCUK regional rep
Okay, yes very frustrating for you. These cars normally start up without problem after months and months of standing once you turn it over long enough to get the fuel up into the carb. Something has happened here.Hiya
It is literally a couple of seconds before it dies. It starts and I throttle it but it cuts out. I will try to plug the back of the carb.
I've found myself just standing staring at the engine looking for something to look obviously wrong
Digging deeper now. It's not that it wasn't a runner before. Its not had an engine turn over for a couple of months whilst I've been doing the interior replacement.
Thank you all for your comments
When the engine stops (and as Ross said), check by operating the throttle at the carb that you are getting a good squirt of fuel into the carb. If you are then I think we can assume fuel pump is filling the carb okay, and that fuel is also going into the engine when you prod the throttle.
Assume you’ve plugged the vacuum port and that hasn’t helped (I think it would have to be a massive leak for the engine to not run at all tbh)
Perhaps there is a problem with the spark. You must be getting some spark for it to fire initially but maybe theres a loose connection and it’s just not getting enough electrical contact for the engine to run. Check all the wires to the coil and coil to distributor.
CaptainK
CCCUK Member
I can attest to this as I normally leave mine for many months over the winter period, and even during summer I use it only every now and then. I just have my routine now for starting it and it always seems to work - turn key to crank it for a while (10/15 seconds) and I know it won't bother to start as its filling the carb and handily pushing the oil around. Then I stop cranking and I floor the throttle to set the magic gubbins on the carb and release the pedal. Then crank it again and it normally starts after a couple of seconds. If I've used car in the last week, then it normally starts fine without all the faff.
* Magic gubbins - accelerator squirt, auto choke, oompa loompas out to play.... no idea, except I know it works for me.
Thank you.
I changed the spark plugs in November - so will recheck them.
I have auto electrician coming in July so will get him to check the wires. The car is being fiddled with a lot and pinning the issue down is a challenge but you all have given me some options to find the solution.
Back on it at the weekend.
Very helpful as always and I will keep you posted. When it starts you will probably hear my squeals of delight