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Old 07-29-2018, 11:50 AM   #1
ih8vols
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Need some help troubleshooting - 79 C10 dies and struggle to start

Prior to these problems, I was driving the truck a couple times per week. One morning I fired her up, and went to work.
She was driving great. I got about 4 miles from the house and had just taken my foot off the gas to begin slowing down for
a stop sign and she completely died. Tried starting it and it would not turn over for anything. Pushed it to the side of the
road and waited about 10 minutes and she fired up. I drove to work and all was fine. Leaving work, same thing happened,
except this time I wasn't out of the parking lot when she died. Had to wait 10 mins or so before she started.

Got it back home. Checked ground wires and everything, and nothing looked loose. Did some research and ended up
changing the Ignition Starter Switch in the steering column because the symptoms matched some other people's
problems. She still struggled to start but I was able to drive around the neighborhood with no problems. Neighbor even
commented on how good it sounded when i went to grab some wood from him.

Last Saturday, I go to take it to get some gas to give it a test out on the roads. I try for about 20 minutes and it will not
start. It keeps sounding like its going to start, but just won't turn over. Later that afternoon, I try again, and she starts on
the first try.

Last Sunday morning I go to attempt getting gas again. She starts with no issue. AS I'm pulling out of the driveway, she
just doesn't seem right. Just seems bogged down. I get a quarter of a mile from my house and she dies. I have to sit for a
couple mins and she fires up again. I turn around and head back to the house.

Yesterday, I changed the fuel pump. Got in and she started on the first try. Ran for about 5 seconds and then died. Could
not get her to start again after that. Went back out later, and she started, but again only for about 5 seconds at most
before dying.

Any ideas what my next steps should be? I don't know much about working on cars. I actually bought this one to learn on,
so please dumb your suggestions down for me. I appreciate it.
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Old 07-29-2018, 04:51 PM   #2
Eman
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Re: Need some help troubleshooting - 79 C10 dies and struggle to start

My 78 c-10 has 28,000 miles on a 305...I've put four ignition modules in it over the years.
Have never found a cause. Might be worth a try.
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Old 07-29-2018, 11:18 PM   #3
andyh1956
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Re: Need some help troubleshooting - 79 C10 dies and struggle to start

At this point you have to determine if the problem is electrical, mechanical, fuel or a combination. Since the problem manifested itself all at one I doubt it's a combo.
When you try to start it does the engine spin at it's normal speed or does it drag?
When it tries to start does it try to kick back?
When it won't start look into the carb while you pump the throttle lever & see if it squirts fuel from the accelerator pump.

Next I would rotate the engine up on #1 cyl Compression & the pull the distributor cap off & look to see if the rotor button is indexed to the #1 plug wire.
That's where I would start.
Your truck has an early HEI distributor & the rotor button has a built in resistor that is a well known failure part. A very inexpensive part to try & you need a spare in the glove box anyway.
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Old 08-01-2018, 10:09 AM   #4
LBJ
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Re: Need some help troubleshooting - 79 C10 dies and struggle to start

Since you have a 79 and mine is a 77, you may have the same problem I had - bad gas cap. Mine would start up fine and drive fine, for a few minutes. Then, it would run rough, sometimes backfire, and die. Tried all the usual fixes, fuel pump, filter, etc, no joy. I replaced the gas cap and BINGO, problem solved for less than $10. You can test this first by just removing the gas cap and see if it then runs fine. If it still has the problem, nothing lost but a few minutes time. I'd put some duct tape over the filler neck first and cut a slot so it can vent. Gas caps get plugged by dirt and even bugs over time. I kicked myself for not checking the EASIEST fixes first! But, nothing wrong with a new fuel pump and filter, either, except LOTS of time spent doing the work.

One more thing about a non-venting gas cap. If you have a full gas tank, the problem will manifest itself SOONER that if the tank is nearly empty. With a full tank, there is little air in there to begin with and the vacuum happens quickly. Of course, with a nearly empty gas tank, lots more air in there and takes longer to build up a vacuum.

Last edited by LBJ; 08-02-2018 at 11:21 AM.
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Old 08-01-2018, 09:37 PM   #5
69heavychevy
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Re: Need some help troubleshooting - 79 C10 dies and struggle to start

I had a similar issue happen to me twice within a year. I would only drive my truck once a week at the most. Both times it turned out to be my carb. The ethanol in the fuel would gel up a bit and it would cause all kinds of issues. I'd just take my edelbrock apart clean it, install new gaskets and everything would be back to normal.
I'm now running a QFT carb which has been nothing but a headache, but that a whole different story.
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Old 08-10-2018, 11:50 AM   #6
ih8vols
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Re: Need some help troubleshooting - 79 C10 dies and struggle to start

Thanks for all the responses. I have good and bad news to report.

I changed the gas cap, fuel pump, distributor cap, distributor rotor, ignition coil and the ignition control module.

Now, she starts first try! It's the easiest she's started since I've had her.

The problem now, is that she idles at about 700 rpm. But if I give it any gas while still in park, it starts bogging down and a bit smoke starts coming out the tail pipe.

I'd assume this would be carb issues. Would replacing everything I did cause the carb to need adjusting since the electrical stuff is running more efficiently now?

I was leaning towards what 69heavychevy said and taking the carb off and cleaning it good and then maybe adjusting it a bit. This sound reasonable? Thanks!!
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Old 08-10-2018, 12:44 PM   #7
geezer#99
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Re: Need some help troubleshooting - 79 C10 dies and struggle to start

What carb?
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Old 08-10-2018, 01:02 PM   #8
ih8vols
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Quote:
Originally Posted by geezer#99 View Post
What carb?
Itís the original 4 barrel edelbrock.
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Old 08-10-2018, 01:41 PM   #9
geezer#99
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Re: Need some help troubleshooting - 79 C10 dies and struggle to start

Nothing original about an Edelbrock. They never came stock on your motor.
Look in the carb while it’s running.
It might be flooding a bit.

What color is the smoke out of the tailpipe?
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Old 08-10-2018, 05:05 PM   #10
ih8vols
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I was wrong. Itís a Rochester Quadrajet. The smoke is black. Itís not a heavy smoke. But itís never smoked before.


Quote:
Originally Posted by geezer#99 View Post
Nothing original about an Edelbrock. They never came stock on your motor.
Look in the carb while itís running.
It might be flooding a bit.

What color is the smoke out of the tailpipe?
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Old 08-10-2018, 05:22 PM   #11
geezer#99
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Re: Need some help troubleshooting - 79 C10 dies and struggle to start

Black is rich.
Rich from a high float or choke closed too much.
To check the choke just start it up cold with the air cleaner off. As soon as it fires the choke plate should pop open about 1/4 inch. Test that first.
Let us know what it does.
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Old 08-11-2018, 10:53 AM   #12
ih8vols
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Re: Need some help troubleshooting - 79 C10 dies and struggle to start

I think you are spot on. Below is a video I took of me starting it this morning. Looks like the choke never moves. Would that indicate that it's stuck and needs to be cleaned?

Appreciate the help. I've learned a ton over the past couple weeks and stayed relatively calm thru the process.

https://drive.google.com/file/d/1zff...ew?usp=sharing
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Old 08-11-2018, 02:50 PM   #13
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Re: Need some help troubleshooting - 79 C10 dies and struggle to start

Choke pull off vacuum pot could be shot or the vacuum hose for it is not hooked up. The vac pot normally hooks up to the vac port above your fuel inlet. The port that you now have your vac line for the distributor hooked to.
The vac pot is right there below the fuel line. Appears to have a short black vac hosehooked to it.
Your distributor should be hooked to the red capped port for manifold vacuum or the blue capped port for ported vacuum.
Rearrange the hoses, make sure the pot is hooked up and make another vid.
If that doesn’t cure it I’ll tell you where to get a new pull off pot.
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Old 08-14-2018, 05:17 PM   #14
ih8vols
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Re: Need some help troubleshooting - 79 C10 dies and struggle to start

Hey Geezer,

Couple (probably dumb) questions for you.

1) So I understand correctly, the hose going from my distributor needs to go to the outlet that has the blue cover on it? Here's a photo where I'm pointing at it. https://drive.google.com/open?id=1ZZ...bxA799MakSufmc

2) I noticed on an emissions hose diagram that I'm suppose to have a 4 port delay valve between the distributor and carb. I don't have one on mine. Is this significant and do I need to get one?

In looking at the hose diagram in the Chilton book, mine is not setup anything like it.

I've had this truck about 3 years now and it was hooked up this way when I got it. Is my current setup normal changes someone would make or is my setup done in a way that indicates the previous owner didn't know what they were doing?

Again, appreciate all your help!

Here's a few more photos I took of the hoses last night:

1) https://drive.google.com/open?id=1Wc...pyg8uVi1kXNI1M

2) https://drive.google.com/open?id=1kZ...0CBDjUZNbGBYeQ

3) https://drive.google.com/open?id=1sr...kdY1xdLPPGWcxT
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Old 08-14-2018, 05:55 PM   #15
geezer#99
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Re: Need some help troubleshooting - 79 C10 dies and struggle to start

The blue cap is ported vacuum. Normally you won’t have any vacuum there until the throttle opens.
The redcap is full time or manifold vacuum. Different name, same thing. You’ll always have vacuum there.
Your distributor is presently hooked to another manifold vac source. Your choke pull off is hooked to a manifold vac port right beside the one for the distributor with a shorthose.
There’s always a debate whether you should use ported or manifold vac. Try them both. See which your motor likes best.
Your choke pull off is that small canister on the left front of the carb.
The 4 port delay valve is the tcs(transmission controlled spark). Used to limit vacuum to your distributor until you’re in high gear. Yours runs without it. Nothing to worry about.
Was your choke pull off connected when you took the Video?
If it was then it appears the pull off is kaput.
They’re easy to replace and available here.
https://quadrajetparts.com/
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