New build won’t idle; have to pump the throttle...

[TonkaJim]

I just bought a ‘72 in mid-restoration. It has body work and new paint, some interior work and a rebuilt longblock (which was put in the car, but never run). The previous owner tells me the it is 1976cc (although I know that’s wrong), but has no paperwork and can’t remember any other details including where he got it (I’ve contacted a few engine builders with no luck). The engine block is an AH code, so I think it was a ‘73 - ‘74 1800cc.

I finished off the engine including reconnected the electrical, tore down and cleaned the EMPI 40 HPMX carbs, replace the electronic ignition distributor with a Bosch mechanical advance, installed a fuel pressure regulator and cleaned out the fuel system (including new tank).

Even after doing all that, I can’t get it to stay running. It will fire (and cough and pop), but only when I keep pumping the throttle... actually pump the throttle, not just hold it open. Seems like a carb issue to me, but not sure what else to do. I know there’s a lot to consider to get it to run wall (carb size vs. engine size, jetting, timing, etc.), but can’t even get it to idle to check and make adjustments.

I’ve searched the forum and found some great info, but nothing specific to this issue (please point me in the right direction if I missed it). So, any thoughts?

Thanks in advance!

[djkeev]

Compression
Fuel
Spark


You need all three at the correct time and in correct quantities.

So.......
Do you have compression on all four cylinders?
Is the compression fairly equal ?

Do you have fuel to the carb?
A nice stream out of the hose?
Take off the air filter, operate the throttle lever and look in the top of the carb, is there a squirt of fuel?

Do you have spark?
Check it at the coil to distributor cap, yes?
Check it at the distributor cap to tge plug wire, yes?
Check it at the plug wire to plug, yes?
Is the firing order correct? 1432 yes?
Is #1 wire placed where the rotor points when the crank is top dead center #1 compression stroke? (Crank rotates twice per combustion cycle)


Dave
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[jeffrey8164]

Well if pumping keeps it running, albeit badly, could be idle circuit blocked or vacuum ports not plugged or really bad intake leaks and probably a few other things I’m forgetting. Maybe timing too.
The accelerator pumpers are working and there is fuel and spark as evidenced by the symptoms. Which is good.

As always, triple check your valve lash and get the fuel filter out of the engine compartment.
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[TonkaJim]

Thanks!! I'm pretty sure I gave gas and spark, but I'll start working down the list starting with eliminating potential for intake leaks. I took off the carbs, and thus the intake manifolds, several times, so the gaskets may not be doing their job any more. The carbs are new and I tore them apart to clean, so don't think it's a clogged jet, but I'll check.

j

[Danwvw]

It should idle nicely with dual carbs! Must need to clean them.
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[xzener]

Same problem with my Ghia when I purchased it. It had a bad vacuum leak. After that was resolved, and a quick tune up, she purred like a kitten. Also had bad gas. My mechanic put some octane booster in the tank. I emptied it out and burned it in the lawn mower.
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[Era Vulgaris]

[TonkaJim]

Thanks everyone, I got it idling and even went around the block a few times. I think it was a combination of valves (they were out of adjustment), timing (was close, but not quite right) and some trouble with the 3/4 cylinders... which is still an issue, but I will post that in another thread.

j