Is This Enough Fuel?

[Wildaugust]

I'm just trying to sort some poor running/performance issues. My engine starts and runs, but not really running great. I did a fuel volume test. My engine is a 383 with a mechanical fuel pump and 5/16" fuel line. This is the amount of fuel pumped while idling for 20 seconds. I think this is around 250-300ml of fuel.
Should there be more or does this look about right?

 

[Davea Lux]

That is probably a little on the low side for 20 seconds of running but it is enough to keep the car running. What are the symptoms? If the engine pops and quits under full throttle application, you likely have a fuel delivery issue. If it just runs lousy all the time, you could have tune up issues or a carb in need of a rebuild. If the engine bogs on throttle application and then takes off, likely a bad accelerator pump in the carb. Would be helpful if you can tell us what you symptoms are and what work if any has been done to the car.

Dave

 

[413]

You don’t test it at idle, rev the damn thing up and see what it will put out. Kinda like a date. LOL

 

[detmatt]

There should be a lot more. I recently had the carb and intake off my 383 and was rotating the engine over by hand a handful of times
(Don’t ask) and I had every bit of that in the bottle not to mention what came out onto the floor after I removed the upper fuel line.
Check your fuel pump pushrod.

 

[Big_John]

I think there should be more too.

When I've done a fuel pump volume test, I did it with just the starter turning the engine over and it pumped more in less time. Never heard of anyone doing it with the engine running, but I suppose that's just another way. I don't think it's the safe way though with too many opportunities for the gas to go somewhere it shouldn't, like a hot manifold.

As @detmatt said, fuel pump pushrod is a possible culprit.

 

[Wildaugust]

Thanks for the suggestions, everyone! I'm sorry to take so long getting back. I've been busy and haven't had much time to work on my car. I did check for vacuum leaks, because I've suspected that for some time. I didn't find any.

Davea, I did think it wasn't enough. My 390 pumps quite a bit more. I figure both engines would require pretty much the same amount of fuel.

I'm suspicious that the sock may have clogged again. I had to replace it several years ago. At that time, I also had the tank cleaned and lined. They sprayed some red stuff in, which has since turned grey. I'm hoping the liner isn't dissolving and clogging the sock. The fuel in the tank does seem clear and clean though. So, I won't assume anything just yet.

Detmatt, Big John, thanks for the suggestion. I changed the pump a few years ago. At that time I didn't know the push rod was a wear item so, I just reused it. I can't remember how long the pushrod was then so, I will be checking it now.

 

[Davea Lux]

Thanks for the suggestions, everyone! I'm sorry to take so long getting back. I've been busy and haven't had much time to work on my car. I did check for vacuum leaks, because I've suspected that for some time. I didn't find any.

Davea, I did think it wasn't enough. My 390 pumps quite a bit more. I figure both engines would require pretty much the same amount of fuel.

I'm suspicious that the sock may have clogged again. I had to replace it several years ago. At that time, I also had the tank cleaned and lined. They sprayed some red stuff in, which has since turned grey. I'm hoping the liner isn't dissolving and clogging the sock. The fuel in the tank does seem clear and clean though. So, I won't assume anything just yet.

Detmatt, Big John, thanks for the suggestion. I changed the pump a few years ago. At that time I didn't know the push rod was a wear item so, I just reused it. I can't remember how long the pushrod was then so, I will be checking it now.

Not all tank coatings are created equal and the preparation given to the tank before lining it is very important. Pull the fuel sending unit and check the sock. If it is clogged, the tank lining has probably started to peel off. I would suggest replacing the tank with a new unit if one is available. If the sock is clear, you may have a pin hole in one of the rubber hoses that connect the sections of steel line together. Steel lines on rust belt cars sometimes have small rust holes in the which can cause a vacuum leak on the suction side of the pump. The rubber used in the 60's and 70's does not fare well when exposed to modern moonshine blend gasoline. As John suggested, the pump rod could be short. The other issue is that Chi-Com fuel pumps are piss poor quality and are noted for leaking check valves, so if you got one from Auto Bone or Car Crap, that could also be the problem.

Dave

 

[413]

Run a hose from the inlet of the pump to a gas can then see what it pumps out for ya.

Bypass the tank sock and lines for a test.

Starting back at the first post, what’s up with the color of that fuel? Not what they sell out west. You stated they sprayed some red stuff in the tank, that gas appears red from here. What say you?

 

[Wildaugust]

I'll try pumping directly from a jug and see how it flows. The tank appears to be completely grey inside, so I don't know, but there is some stabilizer in the gas.

Thanks guys! I'll post again when I know something.