Still having to prime my carb to get my car to start

This is getting real old. I thought the fuel pump was bad. Changed out the Precision Pump for a nice Carter M6903. Still when the car has sat for a long time the pump is not getting fuel to the carb while trying to start it. Only after the car fires after the carb is primed does the pump have enough pressure to get the fuel to the carb. Car is freshly restored except for the fuel sending unit.

Could it be the fuel vapor canister? This is new

Bad fuel sending unit? I did not replace this when I restored the car.

Thanks

Lawrence

What is a fuel sending unit? Cars can do this. Some add an electric pump to prime the carbs before starting.

You can break the fuel fitting after the pump and vapor cannister at the carb. Crank car and see if you get fuel out of line. Even measure pressure if you have a gauge. If not some thing amiss and work your way back to the pump.

But it can take a long time to prime the carb(s) and line when the car sits and the fuel evaporates.

When these cars sit, the fuel evaporates from the bowl.

What you have described is very normal.

I use an old mustard bottle properly cleaned & filled with gas to refill the carburetor via the vent tube.

Yes I bet the sock on your pickup in the tank is dirty if you have not checked it.

I have a 440 and a 340 with stock mechanical fuel pumps and fresh socks in the tanks. They both start after sitting for months. Yes I have to crank them for 15-20 seconds while pumping the gas petal but they start consistently for more than 10 years now. The 440 has a 6 pak and the 340 has a edlebrock 600 on it with mechanical chokes that work. The chokes help too. I haven't had the air cleaners off in years literally.

Besides the sock check for any rust, even the smallest pin hole will cause problems starting in your steel suction line. Can't have any leaks in your suction line, check it.

I have the same problem. I think my AVS has leaking plugs on the bottom of the carb.

Stock air cleaners do better than open air filters, IMO because there is less evaporation. I used to have the usual chrome open air air filter on my car. Then went back to stock on the air cleaner and I think it helps with evaporation.

This car sat at home outside under a awning for the last 4-5 years. I haven't started it since about May of this year. I fired it up just a few days ago to drive it down to my hanger for the winter, probably permanent home. 20-30 seconds of cranking and it fired up. I am telling you the choke helps a bunch. I did not even open the hood until I got to the hanger and was checking for mouse nests since I haven't driven it since Jan of this year in the snow and ice/salt.


Wife and doggy.

Just the way gas is now a days. If my car sits more than 2 days I have to crank it to fill the bowls.

Got a different hanger this week, the car fired up in 10 seconds instead of 20 seconds. I plan to drive it much more now, too cloudy to fly? Then I drive the muscle car around the block for stress relief.

[i][/i]

Fuel pick up in the tank with the sock is what I should had said. What my car is doing is not normal. It did not do this prior to the resto and the fuel vapor canister. I did re use the fuel pick up and should had changed it.

I did take the fuel line off the carb after cranking if for a long time and it was bone dry. Did the same with the line off the carb and had the line in a bottle...no fuel. Did not crank real long though. Since the fuel gauge is not 100% correct might as well change out the gauge sending/pick up with a new sock and see if that fixes it

Will do thanks

Agree with all the "above", but would like to add: check length of your fuel pump push rod against a known good one (this fooled me recently) and seems I remember reading that some of the repop six pack vapor canisters had a return orifice that was too large? May be worth looking at if your pickup sock and fuel pump pushrod prove to be good. jess

Only thing to add is there should be some fuel in bowl when first starting.
It should not need the fuel pump to run to refill it. There should be enough fuel in the bowl to start and run it for a minute or so.

Quick check: Remove air cleaner lid and see if the accelerator pump shoots fuel out.
If yes. Do it again to see if there's enough fuel in bowl to refill the pump.
If no. remove top of carb to see if there is fuel in the bowl.
If yes, accel pump may need new seal or check valve.
If no, its either weeping out or evaporating.

Also, just know there's several service bulletins in 70s addressing the issues of starting. Some models got an internal bypass in the pump which helped hot starting but made cold starting more difficult.
http://www.imperialclub.org/Repair/Lit/Master/307/index.htm

Today's Ethanol laced fuels evaporate at a much higher rate than normal "gas" and that is your problem. If you let the car set for more than a week all the fuel in the carb will evaporate and you wind up having to crank the engine for a while to fill the bowls again. You don't find this problem with fuel injected cars since they all use electric pumps and run on high pressure. You also won't find this problem with a carburetor setup when using an electric pump.

With the crap we have for fuel now days you basically have three choices. Change to an electric pump and eliminate the mechanical pump, add an electric pump with a check valve to bypass the mechanical pump so you can fill the bowls before starting, or fill the bowls manually before starting.

Those are pretty much your options. Good luck.

Actually, only the light end evaporates faster. T50 is about the same and T90 is generally higher than pre-RFG. Thats why there should still be fuel bowl if not the accel pump itself.

Do modern cars have this problem? No. Do modern cars have carburetors? No. The answer to the OP's problem lies here, modern fuel is gonna evaporate from open reservoirs.

Gas is formulated for EFI these days. Nobody has sold a new car with a carb for at least 30 years. It is only going to get worse so I switched all of my stuff over to EFI.

Not actually true. Its formulated to meet a lot of different requirements, some of which vary by state, region, and season. EFI has an advantage in two ways. Its less sensistive to RVP because the system is mostly closed (less so with TBI) and feedback loops can compensate mix and timing to some extent for variations.

The T50 is pretty much the same as its always been. You can blame the RFG for the first 20% evaporated being worse than 25 years ago but not the rest.

this... got me new push rod was the fix !

Same here. If the car hadn't been started for an extended time period (maybe a week or two - can't remember) then no matter how long I cranked the engine it would not start. To get the engine to start I also had to manually prime the carb. I eventually found that the push rod was worn and once replaced the problem was gone.

3RD vote for a fuel pump push rod being worn. I had this problem before on one of my other Hemi's when it sat for a period of time. Seems it would not give it large enough pump shot while cranking. Once fired it would idle & run fine. Once it changed out for a new push rod the problem went away & start right up every time afterwards. Even seemed to pull harder at higher RPM also, so it must have been losing fuel pressure at high RPM's also.

Not to highjack this thread, but does anyone make a good aftermarket fuel pump push rod with harden ends these days? Suggestions. I could use one myself. Thanks.

Simple vacuum leak in the fuel line, like a cracked hardened rubber fuel line, loose hose clamp, bad gasket at the tank pick up, bad vapor separator, too low float level, weak accelerator pump or restricted accelerator pump passages. Shouldn't the fuel line stay primed all the way to the fuel pump and the carburetor float chamber(s) stay full from when the engine is shut off. Check the accelerator pump function before you attempt to start it the next time after it's been sitting it should pump plenty of fuel if it has fuel in the carb

speaking of fuel vapor separator weren't there some bad ones out there that didn't work correctly? Bypass it and see if that's your problem.

Check out this thread and scroll down. Person sells oem mopar fuel pump rods.

https://board.moparts.org/ubbthreads/ubbt...tml#Post2515947

I don't run Ethanol fuel only real gas.

I know I have a bad fuel sending unit so am going to replace and see if that helps. Perhaps a vacuum leak in the line? When I change the sending unit I will check the hose clamps. All the rubber hose is new.
I hear you on the fuel push rod...I will first check the easier things then move to that.

Thanks for the help

Hey - another possibility - it could be your fuel pump pushrod is worn down so it hardly pumps until the engine is running at higher-than-cranking rpms.. Just a suggestion.

There is an allen screw in the block under the fuel pump, pull it out and the fuel pump, then the pushrod drops out, check for length. I have a post about it somewhere here.

I had the same basic issue, really hard to start, excessive cranking after parked for a week, had to keep filling the bowls manually before starting.. and in hindsight I had intermittent fuel starvation too... The fix cost $16 and took 20 minutes.

But - I still refill the float bowl with a squeeze bottle so I don't have to crank the 20 seconds first. Now it fires up nicely and stays running.

Best,
- Art

Not sure I agree.

Been running the Ethanol (garbage?) for years.
My 76 truck and 77 van start right up after two pumps on the gas pedal.
Sets choke and adds fuel.
Sometimes they sit for months at a time.
Maybe it's the low compression but they always fire right up.

I have a 75 Cordoba that needs a shot of fuel dumped down the carb.
I think the Dobies trouble is sticking front brakes.
The heat created boils out the fuel after shut-down.

Come spring I'll do a brake job, then I'll know the outcome.

How about installing 2 clear fuel filters, 1 between the pump and carb and 1 before the pump..run the car till both is filled up, then shut it down and see which filters go low in fuel