72 Chevelle Cranks but Does Not Start - Chevelle Tech
Troubleshooting Diagnosing problems done here.

  • 1 Post By oldcutlass
  • 1 Post By EdCarpenter
  • 1 Post By dyno jonn
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post #1 of 10 (permalink) Old Oct 21st, 18, 9:31 PM Thread Starter
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72 Chevelle Cranks but Does Not Start

A while ago I bought a 72 Chevelle Malibu, 350 engine, originally a 2-barrel carb. Last work that was done (15 years ago) was replacing the carb (a new Holley 1850-9), and I honestly donít recall if I ever had it running after replacing the carb. So the car has sat, un-started/maintained for ~15 years.

Recently I got the car to my home and have just re-started work on it. So far Iíve drained the old fuel, added 5 gal of new fuel with stabilizer and replaced the battery, spark plugs, and fuel pump.

Iím somewhat mechanically inclined, but diagnosing and troubleshooting isnít my forte. Iím looking for some direction.

The car cranks but does not start. It occasionally makes a pop and puff of smoke out of the carb, but doesnít turn over. Fuel looks like it just drips very slowly into the carb when I throttle itÖ not a spray like I was expecting.

So before I start replacing piece after piece, I wanted some input on where to start.

My thoughts are to get a spark plug tester and check for spark. If no spark, replace the points and distributor etc.
If there is spark, remove carb and rebuild.

Any thoughts or suggestions? Thanks, CJ
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post #2 of 10 (permalink) Old Oct 22nd, 18, 6:19 AM
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Re: 72 Chevelle Cranks but Does Not Start

It is getting spark because you got a pop & smoke. Whether it is getting a strong enough spark, & at the right time, is another story....

With a car that has sat for so long, there are lots of things that cause a no-start, apart from those mentioned.

Stuck valves & lifters etc. I would rebuild the carb with new gaskets.
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post #3 of 10 (permalink) Old Oct 22nd, 18, 9:40 AM
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Re: 72 Chevelle Cranks but Does Not Start

If the fuel does not spray when you operate the throttle, then either there is no fuel in the carb or the accelerator pump is no good.
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post #4 of 10 (permalink) Old Oct 22nd, 18, 9:43 AM
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Re: 72 Chevelle Cranks but Does Not Start

Pour a little gas down the carb and see if it will fire off. If it does, youíve eliminated the spark as being the issue. If it isnít getting a steady flow of fuel and dies, the fuel system needs investigated.
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post #5 of 10 (permalink) Old Oct 23rd, 18, 7:35 PM Thread Starter
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Re: 72 Chevelle Cranks but Does Not Start

A quick update:
As EdCarpenter suggested I dumped some fuel down the carb (about a ľ of a soda can) and tried to start it. It backfired loudly, then just cranked and popped a few times. Re-tried that a few times and just got the car to crank, but it never turned over or sputtered to life at all.

As Gtogeoff and oldcutlass mentioned, I believe that I do need to rebuild the carb/accelerator pump as the fuel spray when I throttle the carb is just a drip. Looks nothing like the spray at the 1 min mark here:

So assuming that the backfire/popping/smoke means I have some sort of spark, I may have a timing/distributor issue. I did have the car running at some point, and I donít recall changing anything with timing etc since then. So I think my next course of action will be to focus on fuel delivery and eliminate that problem first-- Iíll rebuild the carb. Also in the mean time I will replace all spark plug wires, and vacuum hoses since they are all old and will need replacement soon anyway.

Once I get the re-built carb back on the car, Iíll repost. Thanks for the help and I welcome any other thoughts/suggestions.
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post #6 of 10 (permalink) Old Oct 23rd, 18, 8:05 PM
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Re: 72 Chevelle Cranks but Does Not Start

If you poured that much (1/4 soda can) fuel down the carb at once, that's way too much and flooded the engine. Dribble a little gas in and see if it fires.

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post #7 of 10 (permalink) Old Nov 11th, 18, 7:45 PM Thread Starter
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Re: 72 Chevelle Cranks but Does Not Start

An update:

I rebuilt the carb, cleaned it and re-assembled it. Ended up managing to break the accelerator pump housing, so if it wasn't working before I know it isn't working now. I'll have to order the part and replace it. Tried tricking fuel into the carb, less than previously this time, but still just ended up with pops and smoke but couldn't manage to get it to turn over.

I still have to replace the spark plug wires, and I'm going to pull the plugs and check their gap again. I'll check for spark at the coil then at the plugs. I'll also check for compression. I'll take off the valve covers and see if I can see anything with the valves/lifters... what should I be looking for with a stuck valve/lifter?

Another random questions: One of my spark plugs is behind my exhaust header. I can get my current plugs in and out, but the new ones which are the same brand/model are slightly longer. This makes it impossible to get the wire boot on. Has anyone had a similar issue? Any suggestions?
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post #8 of 10 (permalink) Old Nov 11th, 18, 8:44 PM
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Re: 72 Chevelle Cranks but Does Not Start

Champion CJ8 or DJ8 (or equivalent) depending on whether it has a gasket or tapered seat, are both very short plugs that may give you enough clearance. Usually available in the lawnmower section of parts stores / mall stores / hardware stores.
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post #9 of 10 (permalink) Old Nov 11th, 18, 8:53 PM
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Re: 72 Chevelle Cranks but Does Not Start

I use Delco R44T plugs, the book will say they are not the right plug but I have been using them for almost 40 years (gosh I am getting old).

Did the car run prior to the carb replacement? I am assuming you had to change the intake. Did you do anything else to it? I would suggest removing the valve covers, disconnect the coil wire and spin it over. Do you see all of the valves moving? I would also pull the plugs and check the compression on all of the cylinders.

Next I would check to see if you are close to being in time by checking TDC compression on the number 1 cyl and where your dist is pointing. If it never ran after the carb replacement your dist may not be timed properly, that will cause a pop back.

Be careful with the gas, while doing the same thing you are I blew up 2 mufflers, it was an awesome explosion! Raw gas ignites in the exhaust. My bet is your timing or firing order is off.

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post #10 of 10 (permalink) Old Nov 11th, 18, 9:49 PM
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Re: 72 Chevelle Cranks but Does Not Start

It would help if we had a little more background info. Did the engine run before the carb was changed? Was it a carb AND intake change? Would that mean the distributor was out? Was there anything else changed since the last time it ran?

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