Fuel Problem

[TL44]

70 RR 383, 4-spd, Edelbrock carb, Carter mechanical fuel pump. The car will idle fine and drive good for about 20 minutes and then it starts to hesitate and just stalls out. I'll check the carb and it's not getting gas, if I pour a little gas into the carb it starts back up (this is how I got it home twice) I've been able to recreate this in the garage, started it normally let it ide and it stalled out at 22 minutes and then a few days later after 40 minutes, same thing , no gas pumping into the carb. I just put in a new Carter mechanical fuel pump & push rod (from Mancini) with no change at all. Anybody run into this kind of problem? Ideas? All appreciated.

 

[threewood]

How old is the fuel tank? Could be picking up debris and clogging the intake sock in the tank. What do the filters look like?

Pull off the line going into the pump and put it in a 5 gallon gas can and pull fuel from there. If it doesn't stall it's going to be the lines/tanks/pickup. If it still stalls, something down stream.

 

[BeepBeepRR]

Is there any ticking in the engine compartment? A worn fuel pump push rod will cause fuel to barely flow. I have replaced 2 in the same car. Symptoms are similar to what you are saying. But Threewood is on it too.

 

[eldubb440]

is your tank/cap vented?

 

[#41]

Since it comes on over time, I would not look at the pickup or fuel pump first. First I would look at pressure lock or vapor lock, both of which would come on after run time had passed.

 

[TL44]

How old is the fuel tank? Could be picking up debris and clogging the intake sock in the tank. What do the filters look like?

Pull off the line going into the pump and put it in a 5 gallon gas can and pull fuel from there. If it doesn't stall it's going to be the lines/tanks/pickup. If it still stalls, something down stream.

Not sure on the tank age, car was restored in 85, I've had it since 2016. I put in a new OEM filter a couple years ago. I had the tank out in 2019 to replace the sending unit (John Wolfe rebuilt the OG unit) this is a problem that just started happening. Ok thanks, I'll get some fuel hose and try that.

 

[TL44]

Is there any ticking in the engine compartment? A worn fuel pump push rod will cause fuel to barely flow. I have replaced 2 in the same car. Symptoms are similar to what you are saying. But Threewood is on it too.

No ticking at all. I kind of thought it was the pushrod too so I changed that when I did the pump the other day.

 

[TL44]

is your tank/cap vented?

Yes it is.

 

[TL44]

Since it comes on over time, I would not look at the pickup or fuel pump first. First I would look at pressure lock or vapor lock, both of which would come on after run time had passed.

Ok thanks. So if it's pressure/vapor lock would priming the carb with gas allow it to start? I always thought you had to wait until it cooled down before it would start up when experiencing that.

 

[Black_Sheep]

One thing to check is the rubber lines between the tank and pump. If they are cracked it’s like trying to drink through a broken straw, you get more air than liquid…

 

[#41]

Ok thanks. So if it's pressure/vapor lock would priming the carb with gas allow it to start? I always thought you had to wait until it cooled down before it would start up when experiencing that.

Yes, dumping some gas down the carb adds the fuel it has been lacking under those conditions, and meanwhile temps come down and pressure lock may leak down. However, the run problem would soon return.

 

[TL44]

Yes, dumping some gas down the carb adds the fuel it has been lacking under those conditions, and meanwhile temps come down and pressure lock may leak down. However, the run problem would soon return.

Oh ok, thanks! I always thought it had to be hot outside for VL to occur, it was barely 60 F degrees when it happened recently.

 

[TL44]

One thing to check is the rubber lines between the tank and pump. If they are cracked it’s like trying to drink through a broken straw, you get more air than liquid…

Alright. So probably like cracked on the inside but not enough to actually cause a gas leak. Thanks!

 

[RogerRamRod]

It doesn’t have to be hot outside for vapor lock. It was more prevalent in the “old days” when it was hot out, because gasoline was formulated differently. Todays gas boils easier.
Vapor Lock and How to Avoid It | Prestige Motorsports

 

[lewtot184]

if you have a cellulose filter on the suction side of the pump it will create vapor lock. some of the re-pop 2 valve pumps aren't very good either.

 

[twecomm]

Another possibility is the fuel pump push rod. If it's never been replaced it's quite possible that it is worn enough that it is barely stroking the fuel pump arm.
I had a similar issue on my 383 many years ago that seemed like vapor lock but not the problem. Push rod was worn down by almost 3/8 inch. Relatively easy to check. New push rod is 3.25 inches long. Requires removing pump, and plug screw under pump on the block. That will allow the push rod to be removed out the plug hole.

 

[TL44]

if you have a cellulose filter on the suction side of the pump it will create vapor lock. some of the re-pop 2 valve pumps aren't very good either.

I don't have a cellulose filter, have the metal OEM type.

Another possibility is the fuel pump push rod. If it's never been replaced it's quite possible that it is worn enough that it is barely stroking the fuel pump arm.
I had a similar issue on my 383 many years ago that seemed like vapor lock but not the problem. Push rod was worn down by almost 3/8 inch. Relatively easy to check. New push rod is 3.25 inches long. Requires removing pump, and plug screw under pump on the block. That will allow the push rod to be removed out the plug hole.

That's what I thought it might be, I put in a new one when I installed the new pump.

 

[Sixpactogo]

I doubt if it is vapor lock. If your pump is doing its job then more than likely you have some rusty gunk in the gas tank that is plugging up the filter sock at the bottom of the tank. I would pull off that metal inline filter and blow it out into a pail with compressed air. If you see any rusty junk come out of it, you will more than likely need to drop the tank and clean it. Then put on a new sock and filter.

 

[Geoff 2]

Install a Carter #4594 elec pump to fix your problem. Bypass the mech pump; & no regulator reqd.

 

[TL44]

I doubt if it is vapor lock. If your pump is doing its job then more than likely you have some rusty gunk in the gas tank that is plugging up the filter sock at the bottom of the tank. I would pull off that metal inline filter and blow it out into a pail with compressed air. If you see any rusty junk come out of it, you will more than likely need to drop the tank and clean it. Then put on a new sock and filter.

Alright thanks! Now that I think back when John Wolf restored the OG sending unit he said he doesn't put a sock on when he restores a sending unit b/c they break down and disintegrate into the tank over time.