fuel delivery issues

[jctucker]

Ok, I put the Mityvac on the fuel feed hose AFTER the first filter and before the fuel pump, gave it several pumps and gas cam a'flowin' from the tank. So, I know my pickup is working and I don't have any ridiculous holes or kinks in my fuel line.

Funny thing was for kicks I decided to crank it over. It actually started right up and idled really low, like 300-400 rpm low. As soon as I went to move the throttle at all it died. Tried to restart and just cranked. Weird. I'd almost say I've got a giant vacuum leak, but that still doesn't explain why the fuel pump is pulling fuel nor pushing it up to the carb.

[seabeelt]

It almost sounds like the fuel is not getting to the carb. Trying to follow the post,
You have checked fuel pick up - test OK
You have two fuel filters, one pre pump, one post pump Have you checked fuel pump output (disconnected from carb) test OK - caveat - before fuel filter(s) or after??
I would start there and start eliminating components, fuel filters, fuel pump etc until I get fuel to the carb.
What year and type of carb ( should be on the base plate)
Based upon description - sounds like a mechanical pump , not electric, correct?
If you have fuel at the carb, then, what are fuel starvation issues : float is stuck closed , not letting any fuel into the carb, inlet screen plugged, not letting fuel into the carb, vacuum issues ( vapor lock)

[jctucker]

Both fuel filters I can blow and suck thru really easily.

I've replaced the fuel pump already. I had actually ordered it a few days before the car quit running. New mechnical fuel pump, same issue. I'm getting any fuel up the lines at all. Zero.

It's a stock '79 ADHA carb. I've replaced a leaking accelerator pump diaphram. There is another pump on the 'front' (side facing forwards) that has been leaking for a little while. Not sure what this is. Webers are pretty new to me.

Right now with the fuel line FEEDING the carb off, I'm not getting a drop of fuel out of it.

[jctucker]

***Update**

I pulled the pump and had someone crank the car over. The lobe is spinning around. Fantastic news.

Also, I'm getting at least some fuel to pump. When I yank the feed hose to pump off fuel spills out every time after I've crank it. So, there's got to be some suction going on, which means the pump is installed on the lobe. I left the out hose from the pump to the carb off to watch how much fuel came out of the pump. Every once in awhile a little squirt, but mostly nothing. I re-pulled the pickup, no holes there. The only thing I'm really left with is that the new mechanical fuel pump I got from IAP is bad.

Has anyone ever run into where the fuel pump lobe rounded some of itself off and caused really low pressures?? I can see the lobe spinning around in there. I'm just shocked that the new pump is bad and that it's the same thing as with the old pump. Very weird.

[seabeelt]

Ok, The pump mechanical arm needs to align properly with the lobe. If mis aligned, no pumping. Are the fuel filters good/new?

[jctucker]

Just updated my post right above yours. I'm pretty sure too that if the arm is on it works, if not - nothing. There are no half measures, no?

[majicwrench]

Stick the vacuum gauge on the inlet of the pump. Should pull good vacuum with engine cranking. LIke engine vacuum 15-20 what-ever-units.
Keith

[baltobernie]

I've pulled the cap (checking for vapor lock).

This test is not for vapor lock. It's to insure that you have make-up atmospheric air pressure available (the evap system isn't plugged). The fuel pump can't pull fuel from a sealed container.

Your M/Y Spider has all the fuel system hoses running under the car, right? None under the carpet? You've checked all of them for leaks, etc.?

[jctucker]

Yeah, I think they all run along the 'frame'. I can see vapor lock being an issue when its hot, but after sitting for 5 days? I'm not familiar with this EVAP setup, obviously.

I can pull fuel via a vacuum pump pretty quickly all the way into the engine compartment. I can't pull any fuel thru the mechanical pump however.

[jctucker]

***more updates***

I took apart the old pump and couldn't find anything wrong with it. Bench tested it and it's pushing 4psi. Sucks and blows just fine. Re-installed it. Again, barely pullin' fuel down, nothing coming out. Both the new and old pumps are doing the same thing. This has to lobe on the aux shaft having gotten worn out. What's crazy is the engine only has 69k on it. I bought it from my boss and confirm the mileage thru all the records.

Again, I pull plenty of fuel to the mechanical pump using a vacuum pump. Where I can see the fuel lines, they look good. No leaks.

If anyone has an aux shaft, lemme know.

[bulldog4444]

Well JC, you must be getting pretty frustrated about now but keep working. My Italian tech in LA once told me to ditch the old lever action pump for a new low pressure electronic unit. He said "just put it inline and hook it up only when your regular unit fails". Well JC, you could skip the lobe issue and call it failed. At least the electronic unit would take one more "possible" issue off the table. You do have to have a low pressure unit since I think these carbs need just 3.5psi.
Good luck buddy!

Bull

[redek]

I see that you are considering installing a new auxiliary shaft, and I agree with bulldog4444. It seems like it would be easier to change to an electric fuel pump. It should fix your lack of fuel, and prevent you from digging into the engine.

[jctucker]

That's probably a great idea. Now that I know the shaft is ok the oil pump is going to be fine.

I was digging around last night trying to find actual specs as to what the fuel pump readings should be out of curiousity. With a battery that's probably pretty weak by now it's making 3.5lbs of pressure (dry, just hooked up to a vacuum gauge) on the outlet side and 7-9 inches of vacuum on the inlet side.

[baltobernie]

I can see vapor lock being an issue when its hot, but after sitting for 5 days? I'm not familiar with this EVAP setup, obviously.

Once again, I'm not talking about vapor lock, which occurs in a hot carburetor. I'm describing a condition where no air can enter a sealed container, so flow is impeded. Imagine attaching your vacuum pump to an empty gallon milk jug. You could pull some vacuum, sure, but only for a brief period of time ... until the pump limit was reached, or the container collapsed. Same thing happens with the gasoline can for your lawnmower. If you don't open the tiny vent opposite the spout, it goes "glug, glug" as exiting gasoline competes with incoming air.

Since the seventies, automobile fuel tanks are prohibited from venting to the atmosphere. There's a system of valves, liquid/vapor separators, etc. to allow atmosphere into the tank to replace consumed fuel, but vapors cannot escape. One failure mode of the evap system clogs the incoming port, so a little bit of fuel can be withdrawn, but then the fuel pump cannot overcome the vacuum. You get essentially the "glug, glug" as described above, until pressure in the fuel tank returns to zero, then the cycle repeats.

Will you please just humor me and unscrew the fuel cap a few turns, and try to start the car? If this doesn't work, then we can move on to other ideas, such as collapsed fuel lines.

[jctucker]

Just unscrew the filler cap? That was probably the second thing I did when it died. It's been loose the whole time I've been checking and the diagnosing the system.

I'm going to smoke test the fuel line between the tank and the engine compartment this afternoon to make sure I don't have some kind of hairline crack causing the pump to suck air. There are some ratty ass fuel line hoses under the car I'm going to eyeball pretty closely.