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Old 08-18-2010, 10:50 AM
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Starting Problems

I'm new to the forum and this is my first question. Go easy on me! I'll try to be detailed as possible.

My 63 C10 wont start. The motor is a 76 I6 250 with single barrel Rochester carb with integral head.

I started eliminating issues to get it to start, here's what I've done:

Fuel system: Rebuilt the carb, replaced the sending unit, cleaned the gas tank, replaced the inline filter, tested the fuel pump.

Ignition: Replaced with a new HEI from summit, new plugs and wires. Firing order set to 1-5-3-6-2-4 clockwise.

Electrical: New battery. The original wiring was shot & had shorts everywhere. I completely rewired with a minimal setup: battery to starter, toggle switch for power on/off triggering a relay for the 12V to HEI, alternator to battery, push button switch to trigger starter.

Diagnosis: The engine cranks over just fine. The dizzy gets 12V on switched on & about 10V while cranking. There is spark. The timing may be a bit off, but twice I set to TDC and re-setup the dizzy. I even pulled the valve cover to confirm TDC by the lifters. I plugged #1 with a shop towel, cranked over and I saw spark on #1 when the towel blew out on the compression stroke.

I see fuel in the manifold and I've even tried starting fluid... It only backfires.

Is 10V too low for the HEI? I see spark, so I'm guessing either the timing is really f'ed up (180š out) or there is no fuel (or too lean fuel) present in the cylinders. I can't imagine that the fuel is not getting to the cylinders. The previous owner said it ran like a champ - but then they all do, right.

What the hell am I missing? Any help would be appreciated!

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Old 08-18-2010, 10:59 AM
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Quote:
Originally Posted by mstclaire
I'm new to the forum and this is my first question. Go easy on me! I'll try to be detailed as possible.

My 63 C10 wont start. The motor is a 76 I6 250 with single barrel Rochester carb with integral head.

I started eliminating issues to get it to start, here's what I've done:

Fuel system: Rebuilt the carb, replaced the sending unit, cleaned the gas tank, replaced the inline filter, tested the fuel pump.

Ignition: Replaced with a new HEI from summit, new plugs and wires. Firing order set to 1-5-3-6-2-4 clockwise.

Electrical: New battery. The original wiring was shot & had shorts everywhere. I completely rewired with a minimal setup: battery to starter, toggle switch for power on/off triggering a relay for the 12V to HEI, alternator to battery, push button switch to trigger starter.

Diagnosis: The engine cranks over just fine. The dizzy gets 12V on switched on & about 10V while cranking. There is spark. The timing may be a bit off, but twice I set to TDC and re-setup the dizzy. I even pulled the valve cover to confirm TDC by the lifters. I plugged #1 with a shop towel, cranked over and I saw spark on #1 when the towel blew out on the compression stroke.

I see fuel in the manifold and I've even tried starting fluid... It only backfires.

Is 10V too low for the HEI? I see spark, so I'm guessing either the timing is really f'ed up (180š out) or there is no fuel (or too lean fuel) present in the cylinders. I can't imagine that the fuel is not getting to the cylinders. The previous owner said it ran like a champ - but then they all do, right.

What the hell am I missing? Any help would be appreciated!
your not by chance using the origional + wire that went to the old points style distributor are you? points went through a resistor to drop voltage. other than that, from what you described, it is possible that your 180* off on the ignition timing. gl
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Old 08-18-2010, 11:07 AM
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Thanks for the reply. No, it's all new wiring. I know that the resistor wire causes low voltage to an HEI, it's gone. I'm running 10g wire directly from the battery thru a 30A relay to the dizzy.

When I set the firing order at TDC, the timing mark was also showing TDC. The rotor was pointed about 8 o'clock and I went 1-5-3-6-2-4 clockwise. I don't think the rotor position matters so much, so long as the contact point is set to #1 from there. Vacuum lines are plugged.
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Old 08-18-2010, 12:53 PM
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who rebuilt the carb? my confidence level in rebuilt carbs is low.. sure it's setup right? fuel level in float bowl(s) correct? mixture settings in ballpark?

also, have you checked to make sure you're getting enough fuel out of the fuel pump? I know you said there is fuel in the manifold but is it enough? should have 5psi fuel pressure to the carb at all times (running/cranking)

just a few thoughts..




Quote:
Originally Posted by mstclaire
Thanks for the reply. No, it's all new wiring. I know that the resistor wire causes low voltage to an HEI, it's gone. I'm running 10g wire directly from the battery thru a 30A relay to the dizzy.

When I set the firing order at TDC, the timing mark was also showing TDC. The rotor was pointed about 8 o'clock and I went 1-5-3-6-2-4 clockwise. I don't think the rotor position matters so much, so long as the contact point is set to #1 from there. Vacuum lines are plugged.
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Old 08-18-2010, 01:53 PM
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Thanks for the input. I rebuilt the carb. I have a fair experience doing this, but this is my first Rochester. Fuel pressure is great and fuel level is good in the bowl. As for the mixture settings, do anyone have a link to a Rochester tuning guide?

I have been really leaning toward an ignition issue simply because starting fluid won't even ignite. However, thinking about it, the plugs have been dry as a bone. That's either a no fuel or super lean mixture, right?
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Old 08-18-2010, 02:09 PM
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Do you have a timing light. If so you can check the timing while cranking to see if it is close. I doubt you are 180 out as USUALLY it will backfire.

Did you check to see that the plugs are gaped correctly.
Is the choke functioning, closed on a cold engine.

Did it quit running before you did all this work or is it since you changed all the parts.

If you move the throttle do you see fuel squirting out inside the carb.
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Old 08-18-2010, 02:35 PM
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Quote:
Originally Posted by T-bucket23
Do you have a timing light. If so you can check the timing while cranking to see if it is close. I doubt you are 180 out as USUALLY it will backfire.
I do have a timing light - though I never thought to try it without the engine running - GREAT TIP!

It does backfire with starting fluid.

Quote:
Originally Posted by T-bucket23
Did you check to see that the plugs are gaped correctly.
Is the choke functioning, closed on a cold engine.
I gapped them when it installed, off the top of my head, somewhere between .035 & .045. The manual choke does work & closed when I try to start.

[QUOTE=T-bucket23Did it quit running before you did all this work or is it since you changed all the parts.[/QUOTE]

It's never ran for me. The last owner had it running, seen him drive it. When I got it, it'd been out thru the winter with no gas cap. I flushed the entire fuel system to get rid of old or watered down fuel. Rebuilt the carb & replaced the sending unit.

I started in on the ignition and the old HEI dizzy was in bad shape, so I switched to a new unit integral unit.

Quote:
Originally Posted by T-bucket23
If you move the throttle do you see fuel squirting out inside the carb.
I do see is squirting in and looking down the open butterfly i see fuel in intake.
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Old 08-18-2010, 02:41 PM
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If it is backfiring the timing is off. Recheck everything again.
If you have a helper pull # 1 plug, put a finger over the hole and bump the key quickly until it blows your finger out, bring up the mark by hand, it should be close at this point, and check the rotor to cap orientation.
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Old 08-18-2010, 04:34 PM
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Make sure all the valve are opening and closing completely. I had this problem on my 350. 3 of the exhaust valves were staying open and it didn't want to start. It also sounds like you're not getting fuel.
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Old 08-18-2010, 04:56 PM
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Quote:
Originally Posted by bigdog7373
Make sure all the valve are opening and closing completely. I had this problem on my 350. 3 of the exhaust valves were staying open and it didn't want to start. It also sounds like you're not getting fuel.
Thanks for your help. Yeah, i have not done a compression test yet (other that the shop towel test on #1). I'll do that this afternoon.
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Old 08-21-2010, 04:59 PM
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Hey, i just wanted to follow up.

First, thanks to everyone who commented. Definitely some great tips. The ignition was dead on and the carb is fine. After doing a compression test I found the problem. I only tested 2 cylinders before I stopped. #6 was only 80 lbs. and #5 was < 15 lbs. Either there is a some stuck valves or the head gasket is blown.

I really want to put a 350 & a 5 speed in it, but for now, I guess I'll just rebuild this one...

Thanks again!
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