Need some advice troubleshooting a Holley DP - Team Camaro Tech
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post #1 of 21 (permalink) Old Nov 13th, 10, 02:05 PM Thread Starter
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Steve
 
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Need some advice troubleshooting a Holley DP

I'm out of ideas on my Holley carb/fuel problem. I've got a 600 cfm, dp, manual choke and mech secondaries. The car ran fine up till a week ago. It started to stumble, got progressively worse then started konking out on the street, and hard to re-start. Pushed it home once (would you believe I got cut off by a pick-up while pushing!!) and towed yesterday. It acts like it's running out of gas. When it starts to die, I can keep it running for a little bit by pumping the throttle, but then it dies and may or may not re-start. I took it apart and blew it out with carb cleaner and then comp air, but it does the same. I have 6 psi all the time and when it dies, I pull the fuel bowl site plugs and they both look fine and when I pull the throttle, the squirters work good. I also let a sample of gas sit overnite in case I had some water..nope. What am I missing?
Any ideas would be appreciated as always while I'm re-charging my battery (the car and mine)!!

69 SS, 350/300 h.p., M-20, 12 bolt, matching numbers.


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post #2 of 21 (permalink) Old Nov 13th, 10, 06:05 PM
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Re: Need some advice troubleshooting a Holley DP

Any chance your losing secondary ignition voltage?You will chase your tail all day long with the carb if an ign module or coil is thermally breaking down.

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post #3 of 21 (permalink) Old Nov 13th, 10, 06:36 PM
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Re: Need some advice troubleshooting a Holley DP

Old saying.."many carb tuned by changing spark plugs"
figerivly speaking, as mentioned above...... electrical stuff.
Also it is quicker and cheaper, easier to check out... to go that route 1st

Nothing changes in a carb once set up, other than a bitr of crap in the float valve if dont have a filter

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post #4 of 21 (permalink) Old Nov 13th, 10, 07:26 PM Thread Starter
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Re: Need some advice troubleshooting a Holley DP

Thanks, changed the plugs a few days ago when I put some HEAT in the tank for the first step. Switched the ignition coil with no luck. It's a points ignition so I monitored the dwell...that's ok. Put a timing light on the coil while with the trigger taped...that looked good. I was thinking ignition but a couple times I could keep it running for a moment by feathering the throttle, which makes me think it's a few problem, but both bowls are up to the site plug. I'm kinda po'd since I just sold my old 750 dp two weeks ago.....Murphy follows me at times. I alsso blew some air through the fuel line back to the tank and heard it bubbling. I'm at a loss and need some help brainstorming!!
Thanks again

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post #5 of 21 (permalink) Old Nov 14th, 10, 07:11 AM Thread Starter
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Re: Need some advice troubleshooting a Holley DP

Forgot to mention that I checked the fuel pump pressure, it pegged my guage at 7psi. Also changed the fuel filter. Most components on the engine are less than 1 year old, but I know that don't mean much. I also checked the rotor and cap, they still look new. I'm going to look into the wiring and connections today. It konks out suddenly at times which makes me think it's electrical, but I don't understand how, on a couple instances, I was able to keep it running by feathering the throttle.

69 SS, 350/300 h.p., M-20, 12 bolt, matching numbers.


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post #6 of 21 (permalink) Old Nov 14th, 10, 09:31 AM
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Re: Need some advice troubleshooting a Holley DP

its easier to ignite a rich mixture ie: accel sguirts into the cylinder. check the roter pointer contact to distributer legs clearence. if too too wide, you'll drop some high voltage across the gap and have less voltage available at the plug. (appear as a weak spark at the plug)

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post #7 of 21 (permalink) Old Nov 14th, 10, 10:49 AM Thread Starter
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Re: Need some advice troubleshooting a Holley DP

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Originally Posted by joe clance View Post
its easier to ignite a rich mixture ie: accel sguirts into the cylinder. check the roter pointer contact to distributer legs clearence. if too too wide, you'll drop some high voltage across the gap and have less voltage available at the plug. (appear as a weak spark at the plug)
That's makes sense to me. Thanks. I have checked the rotor and cap a couple times and couldn't see anything wrong. One question regarding voltage at the pos term of the coil....with key in on position, I get about 6 volts...when cranking I get about 10-12 volts....when I do get it running it's still 10-12 volts. Shouldn't the run voltage be lower like the 6 volts with the key just 'on'?

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post #8 of 21 (permalink) Old Nov 15th, 10, 07:33 AM
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Re: Need some advice troubleshooting a Holley DP

Quote:
Originally Posted by reelknots View Post
I'm out of ideas on my Holley carb/fuel problem. I've got a 600 cfm, dp, manual choke and mech secondaries. The car ran fine up till a week ago. It started to stumble, got progressively worse then started konking out on the street, and hard to re-start. Pushed it home once (would you believe I got cut off by a pick-up while pushing!!) and towed yesterday. It acts like it's running out of gas. When it starts to die, I can keep it running for a little bit by pumping the throttle, but then it dies and may or may not re-start. I took it apart and blew it out with carb cleaner and then comp air, but it does the same. I have 6 psi all the time and when it dies, I pull the fuel bowl site plugs and they both look fine and when I pull the throttle, the squirters work good. I also let a sample of gas sit overnite in case I had some water..nope. What am I missing?
Any ideas would be appreciated as always while I'm re-charging my battery (the car and mine)!!
In your post you said you checked the fuel filter. I am sure with all you have done you checked the filter in the carburetor inlet. Mine has an inline filter as well as one at each inlet of the dual pumper.I had many of the same symptons as you are having. Finally found the filter sock in the fuel tank was split and frayed. It was folding over the outlet and shutting off the fuel. After it sat awhile, fuel would trickle through and it would run for a few minutes. I don't want to send you in the wrong direction, just noticed some of the same symptoms I had.
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post #9 of 21 (permalink) Old Nov 15th, 10, 08:19 AM
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Re: Need some advice troubleshooting a Holley DP

Quote:
Originally Posted by reelknots View Post
One question regarding voltage at the pos term of the coil....with key in on position, I get about 6 volts...when cranking I get about 10-12 volts....when I do get it running it's still 10-12 volts. Shouldn't the run voltage be lower like the 6 volts with the key just 'on'?
If points are closed, current flows through resistive wire and a lower voltage is seen. Points open, current stops, battery voltage.

Cranking voltage of 10-12 volts is from the yellow wire from solenoid to assist hot start condition.

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post #10 of 21 (permalink) Old Nov 15th, 10, 10:00 AM Thread Starter
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Re: Need some advice troubleshooting a Holley DP

Thanks all for the ideas. I really think this is an electrical problem. I got it running yesterday and it konked out after a few minutes, but started right up. (think I complicated my problems originally when I kept pumping the gas pedal and flooded it) I put a timing light on a plug wire while running and kept an eye on it. When it shut down the second time, the timing light didn't trigger while cranking, so I moved it to the coil wire. I then cranked it, seen the light pulsing, the engine started and ran for 15 minutes!!
I think it best that I start a different post regarding ignition.

69 SS, 350/300 h.p., M-20, 12 bolt, matching numbers.


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post #11 of 21 (permalink) Old Nov 15th, 10, 11:14 AM
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Re: Need some advice troubleshooting a Holley DP

Quote:
When it shut down the second time, the timing light didn't trigger while cranking, so I moved it to the coil wire. I then cranked it, seen the light pulsing, the engine started and ran for 15 minutes!!
Thats Classic symtom of running a 12v coil on ballast or balast coil on 12v or a coil dieing.

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post #12 of 21 (permalink) Old Nov 15th, 10, 11:28 AM Thread Starter
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Re: Need some advice troubleshooting a Holley DP

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Thats Classic symtom of running a 12v coil on ballast or balast coil on 12v or a coil dieing.
I had swapped out the coil last week with the same results, but thanks.

69 SS, 350/300 h.p., M-20, 12 bolt, matching numbers.


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post #13 of 21 (permalink) Old Nov 17th, 10, 12:20 AM
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Re: Need some advice troubleshooting a Holley DP

So, when it doesn't start or starts and dies the timing light does not flash? On either the coil or spark plug wires?
Is there still voltage on the positive side of the coil?
Try cranking and watch the voltage on the negative side.
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post #14 of 21 (permalink) Old Nov 17th, 10, 05:43 AM Thread Starter
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Re: Need some advice troubleshooting a Holley DP

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So, when it doesn't start or starts and dies the timing light does not flash? On either the coil or spark plug wires?
Is there still voltage on the positive side of the coil?
Try cranking and watch the voltage on the negative side.
Yes, tried all that. Never lost 10 volts on pos side of coil. I don't know if I cranked it long enough when I had the light on a cyl wire to get a pulse. When I switched it to the coil, the engine started. It has started every time the last couple of days and won't die. I'm waiting for a sunny day for a road trip and hopefully don't need a tow back home. I just hate when a problem disappears!

69 SS, 350/300 h.p., M-20, 12 bolt, matching numbers.


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post #15 of 21 (permalink) Old Nov 17th, 10, 10:27 PM
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Re: Need some advice troubleshooting a Holley DP

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Originally Posted by reelknots View Post
Forgot to mention that I checked the fuel pump pressure, it pegged my guage at 7psi. Also changed the fuel filter. Most components on the engine are less than 1 year old, but I know that don't mean much. I also checked the rotor and cap, they still look new. I'm going to look into the wiring and connections today. It konks out suddenly at times which makes me think it's electrical, but I don't understand how, on a couple instances, I was able to keep it running by feathering the throttle.

I see you're thinking electrical, but when you mentioned you pegged your fuel pressure gauge at 7 psi I immediately think flooding due to overpowering the needle and seat at high pressure and having fuel pour into the carb through the overflow. I had a similar problem with overflow on my old 850DP but was able to limp home by turning my electric fuel pump on and off manually. Your fuel pressure should be set at about 6psi for a holley and should never exceed 6.5psi due to the risk of flooding the bowls. If you don't confirm an ignition issue, you might want to check into your fuel pressure again.

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