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Old 07-11-2010, 07:06 PM
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Cold start diffficulties

I have a big block Chevy motor in my 72 Fleetside truck. I Have a 750 Rochchester quadraject carb. I don't have an auto choke so I have butterflies open at all times.

Just recently, in the first morning start I have difficulties starting the truck so I changed the coil, spark plug wires and spark plug. Still the same problem. I advanced/retarded the distributor to ge the timing right but still no start. It is only when I spray (starting fluid) into the quadtrajet carb it starts and once the engines warms up, I can start it with no problems.

Any recommendations welcome. Thanks!

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Old 07-11-2010, 08:20 PM
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Does pumping the gas peddel a few times before you crank the engine help any?
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Old 07-11-2010, 09:19 PM
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yes, I have pumped the gas pedal multiple times.

tomorrow, I am going to change the insert fuel filter in the quadrajet and do a fuel volume test (1 pint flow in 30 seconds).

If I still have problems, I will pull the carb and inspect the gaskets.
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Old 07-11-2010, 09:39 PM
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Quote:
Originally Posted by juiced66malibu

tomorrow, I am going to change the insert fuel filter in the quadrajet and do a fuel volume test (1 pint flow in 30 seconds).

If I still have problems, I will pull the carb and inspect the gaskets.
That was going to be my next recommendation if pumping didn't help. You might want to check the accelerator pump also before you pull the carb. Remove the air cleaner and manually pump the linkage and check for the squirt from the accelerator nozzles. It's easier to check on the engine than off.
I've got a 600 holley on my 350 and in the summer time, one pump and it fires right off with no choke. That could very well be your problem being it fires up with a shot of starting fluid. Might try just a small prime with gas also.

Good luck.
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Old 07-11-2010, 11:42 PM
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Quote:
Originally Posted by juiced66malibu
yes, I have pumped the gas pedal multiple times.

tomorrow, I am going to change the insert fuel filter in the quadrajet and do a fuel volume test (1 pint flow in 30 seconds).

If I still have problems, I will pull the carb and inspect the gaskets.
Sounds like you have the common problem to many Q-jets- a leaky fuel well(s).

There are wells that extend down to the bottom of the carb that are sealed w/either a soft metal plug or a disc w/the metal peened over the edge of the disc to seal the wells. If these leak, over time the fuel will drain, drip by drip, from the float bowl into the intake manifold where it will either evaporate or pool, depending on the engine temp and how fast the leak drips fuel.

This condition causes the engine to have to be cranked over until the pump fills the fuel bowl back up w/fuel. It's worst w/a mechanical fuel pump.

The "cure" is either sealing w/epoxy, re-peening (carefully) the seals, using the black foam seal piece that's included in carb kits or a combination of the above.

That all said, there's usually enough fuel left in the accelerator pump well to provide a couple squirts of fuel into the carb- which is usually enough to get the engine to start, or at least try. If you're getting a good accelerator pump squirt or three and the engine still doesn't even try to start, you have other problems.
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Old 07-12-2010, 06:10 AM
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Thanks for the help on this Cobalt. I wasn't aware of the well seals but was thinking along the same lines as if there is no or weak pump shot that either the accelerator pump was shot or fuel is disappearing somewhere or a combination of both.
I think we've got him going in the right direction though.
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Old 07-12-2010, 06:36 AM
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The pencil is pointing to the main well plugs, the primary side can leak, too- just less likely. One of the primary wells can be seen in the bottom left of the photo:



The PRIMARY plugs also can be removed and the holes tapped for short 8-32 screws.
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Old 07-12-2010, 07:11 AM
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Quote:
Originally Posted by juiced66malibu
I have a big block Chevy motor in my 72 Fleetside truck. I Have a 750 Rochchester quadraject carb. I don't have an auto choke so I have butterflies open at all times.

Just recently, in the first morning start I have difficulties starting the truck so I changed the coil, spark plug wires and spark plug. Still the same problem. I advanced/retarded the distributor to ge the timing right but still no start. It is only when I spray (starting fluid) into the quadtrajet carb it starts and once the engines warms up, I can start it with no problems.

Any recommendations welcome. Thanks!
Hook the choke up............
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