Help! Starts then stumbles

[litevette]

A while back I had probs with my 68 Firebird. It would start, run fine for a while and then I'd have to keep gassing it just to get home as it would start running rough (barely made it home). After some discussion here, I thought it may be the carb. So I replaced the Edelbrock carb with a remanned Holley. While I was at it I replaced the fuel filter and the line up from the pump. Tokk the car out for about a 2 hour drive, with stops here and ther. IT RAN GREAT! Now, I start it up (fires right up) and then after a few secs it starts to stumble and dies. After that, it might start, but is a little rough and again, have to keep my foot on the throttle to keep it running. What do you think it may be? Could it be the fuel pump is bad? BTW, in the few secs that it does run, I jump out and look at the fuel filter and it's only half full (clear type filter). Should it be all full? Please help a.s.a.p as I'd like to make a parts store run before too late and get this thing on the road. Thanks in advance!!!

[badbu68]

Check the timing, sounds like it needs more.

[litevette]

Check the timing, sounds like it needs more.

If it were timing, why would it start and run great sometimes? Wouldn't a timing issue be consistant? Isn't timing either off some or it's good?

[ZZ430]

I missed your earlier thread, what ignition system you running?

[litevette]

I missed your earlier thread, what ignition system you running?

Stock, points style.

[ZZ430]

Ok, 2 things came to mind.

A shorted tach or a bad coil could be the problem.

[litevette]

Ok, 2 things came to mind.

A shorted tach or a bad coil could be the problem.

No tach, so maybe the coil? Anyone else concur? Just want to make sure. Not that I don't mind buying a coil as they are cheap enough, I just want to minimize how much I replace to solve this issue.

[Jim Nilsen]

The condenser going bad will do just what you are saying when they heat up or are just about to fail.

Get yourself a Pertronics or DUI ignition kit or other brand if you are going to do other mods to the engine later and don't look back, the points are a pain and will always require dwell adjustment. It could just be that the dwell has already gone bad too or the points are about collapsed and you are running on scattered spark.

You can pick up an MSD distributor almost anywhere for cheap and be good.

Good luck and if you don't have a good set of plug wires you will probably need to step them up too along with a new coil. This will all give you a boost in economy and power.

[LS6 Tommy]

Are you running a mechanical fuel pump? the fuel pump eccentric on the cam sometimes gets loose on Ponchos. My buddy had the same sypmtoms on his 68 GTO. An electric fuel pump cured it. When we went to rebuild the engine a few years later, sure enough, th eccentric was loose.

Tommy

[litevette]

The condenser going bad will do just what you are saying when they heat up or are just about to fail.

Get yourself a Pertronics or DUI ignition kit or other brand if you are going to do other mods to the engine later and don't look back, the points are a pain and will always require dwell adjustment. It could just be that the dwell has already gone bad too or the points are about collapsed and you are running on scattered spark.

You can pick up an MSD distributor almost anywhere for cheap and be good.

Good luck and if you don't have a good set of plug wires you will probably need to step them up too along with a new coil. This will all give you a boost in economy and power.

You think like I do. I'm not into repairing basic stuff. Might as well replace it with performance. Looks and acts a whole lot better! I geuss I'm in for an hei, wires and electric fuel pump. I love upgrading!

[litevette]

Are you running a mechanical fuel pump? the fuel pump eccentric on the cam sometimes gets loose on Ponchos. My buddy had the same sypmtoms on his 68 GTO. An electric fuel pump cured it. When we went to rebuild the engine a few years later, sure enough, th eccentric was loose.

Tommy

Will do! Thanks you guys!!!

[David Pozzi]

Don't get the GM HEI. It works great but on a first gen Camaro you will have to hammer in the firewall to get the cap on it!
Get a small body HEI from Dave, or an MSD.

Have you tried a new set of points and condenser? is your dwell set at 30 degrees?
David

[litevette]

Don't get the GM HEI. It works great but on a first gen Camaro you will have to hammer in the firewall to get the cap on it!
Get a small body HEI from Dave, or an MSD.

Have you tried a new set of points and condenser? is your dwell set at 30 degrees?
David

I have ordered a HEI for it. If it doesn't fit, I'll ship it back to them! I din't want to stay with points because of a few reasons.
1. I want to not have to adjust the points, etc.
2. I want to get rid of the coil and free up/clean up a little space there
3. As I make performance mods down the road, I want it to be supported with buying parts again

[David Pozzi]

We have a HEI in a 68 Camaro, the previous owner bashed in the firewall and it still rubs there. The air cleaner hits it too.

Here's Dave's HEI page: http://www.davessmallbodyheis.com/

[John Wright]

Did you check the fuel pressure with a guage to see if the pressure falls off as it starts stumbling? That is easy to do and doesn't cost you anything if you already have a vac/pressure guage in the toolbox.
No guage?
The carb makes a slightly different sound as it runs out of gas and you are pumping the gas pedal or holding the throttle blades open...maybe listen (without the airfilter) to see if you notice it.

Immediately when it stumbles and cuts off...jump out and see if you can see if the squirter in the carb will make a strong stream with a quick opening of the throttle linkage....if the stream is weak or non-existant...it's running out of gas...pump isn't keeping up for whatever reason.