Car tries to start, but stumbles and shuts off

Hi,

Have you checked to make sure the choke isn't stuck closed? Is it possible for you to record what it is doing and then upload it for me to hear?

Let me know.

Joe

Manual choke wired open (live in Vegas, so choke is rarely needed).

Hi,

There could be a few things. Have you checked to make sure there aren't any larger vacuum leaks? Also, have you confirmed that the fuel pump is providing enough fuel?

I realize this is a 68, but has anything been updated as far as ignition? I'm just wondering what we are working with, HEI or points and condenser.

Joe

This is the only upgrade to the ignition system, and a Holley 4-barrel. And like I said , it was running great over the weekend - started it over a dozen times and then a few days later , it's like I never replaced anything. I replaced a few vacuum lines also.

Okay, is it possible for you to record what it is doing with your phone so I can hear it?

Car is at a different location at this time. but basically has a little trouble starting , and stumbles like it's missing on a few cylinders , and quits.

The only thing I can think then is either a large vacuum leak or the carburetor is dumping fuel. Is there any black smoke from the exhaust or anything you can think of? The carburetor looks new, so I'm questioning why would it be fuel related.

Does it always start right back up and then repeat the issue?

Also, I believe that distributor has a built in ignition control module, is that correct?

It didn't smell excessively rich , no smoke and sometimes a backfire out the carburetor when you try to restart it.

Yes , and the control module checked out fine.

And I don't think lack of fuel is an issue. It ran pretty strong throughout the RPM range as I raced it around the block several times on Saturday.

Only thing left I can think of is maybe the rings are so worn that the plugs are oil fouled already. Guess I'll have to pull them all back out , check them and do a compression test while I'm at it.

It seems odd that it ran good for you on Saturday. I wouldn't think low compression would be an issue if it ran good then. However, anything is possible. Is there any blue smoke when you first start it?

Let me know what you find with the compression test. Here is a link explaining how it's done. I don't know if you need it, but thought I would add it just in case.

https://www.2carpros.com/articles/how-to-test-engine-compression

I will watch for your reply.

Joe

So re-checked everything today , reset timing even checked for timing chain play (pretty sure it was less than 10 degrees) and car still wouldn't run right. Then I replaced a connection on a wire leading to the coil , and it fired right up and ran better than it has for years after some fine tuning on the Holly. So after about a 10 minute drive, pull into the garage , start it a few more times to double-check - and then after 15 minutes it barely starts and runs like crap ( like a weak ignition I'm thinking ) ... The distributors been checked (MSD pro billet) coil , cap and rotor , plugs and wires all new. so what would cause this (what seems like an intermittent failure)?
If the timing chain was loose , it wouldn't have run great minutes previous , right?
Could it be a wiring issue that I'm going to have to dig deeper to find ??
I've included it video of it running , but the sound quality is not too good,but if you listen to the whole thing you can kind of hear I would seems to be missing a few cylinders , and dying whenever you give it some gas.

Thanks for any light anyone can shed.

Hi,

What is the clicking I am hearing? Also, what wire was replaced? Have you checked the coil itself? And yes, I agree the chain wouldn't be good one minute and then bad the next.

Joe

It was one of the wires going to the coil (not the ones going to the distributor) .. not sure which one it was , did not want to dig through the harness to find out where it went (even though I believe that maybe my next option because that wire could be bad). As for the clicking , when I listen to the audio on the video , it did not sound like that live .. more like it's missing on all cylinders , or maybe getting barely enough spark to fire.

The coil is supposedly new, plus wouldn't it just crap out , not work and then not work , just to work and not work again ??

A coil can do this if it is going bad. Even though it's new, I have seen them bad. However, since the wire you replaced made a difference, I think you are on the right track. Can you take a pic of the wire so I can see which it is? There should be a + and a - for the coil.

Let me know.
Joe

My eyes were too bad to read which side was which , and didn't feel like climbing in there (or removing it) to read which was which. But I'll probably be testing (and maybe replacing) the new coils resistance along with new wiring to the coil.

That sounds like a good idea. Let me know the results.

Take care,
Joe

Will do. Thanks.

Hello, I'm Danny.

Just to add my 2 cents there is something you need to know about Holley carburetors. Any time you have a backfire through the carburetor it blows the power valve and needs to be replaced.Even if you replace the valve and have another backfire it has to be replaced again.This is most likely the reason you car is running poorly.There is a conversion kit that is offered to prevent power valve damage in the event of a backfire.A hole is drilled in the primary metering block and a check ball and spring is installed.Hope this helps and thanks again for using 2CarPros.

But the problem has been intermittent , car has run great in between. It wouldn't have ran great if it had a blown power valve , right ??

Hi,

I would think if the power valve was bad, it would not change. In other words, it wouldn't be good one time and not the next. However, he is correct about the backfire causing damage to it.

Have you had any progress with it?

Joe

It backfired a bunch of times before I got the distributor right , but then ran great afterwards. have not had a chance to test the coil or check the wiring yet.

Not a problem. Let me know what you find when you get to it.

Take care,
Joe

Hello again.

Yes, the performance would be affected by the power valve after a backfire.After getting things sorted out I would definitely change the power valve to improve performance from the carburetor.Keep us updated.Hope this helps and thanks again for using 2CarPros.

Danny-