Potential bad fuel pump?

[tkelley72]

For the first time my car wouldn't start today. Engine spins over perfect, plenty of spark, just won't fire. What's the easiest and safest way to check the fuel pump operation. If I remember correctly, can't I just disconnect the fuel line at the carb. , disconnect the coil wire, insert the fuel line into a plastic bottle and have someone crank it over for 10-15 seconds or so and check for fuel flow? Thanks

 

[Hemikiller]

The standard output for a V8 fuel pump is 1 pint in 20 seconds at 500 engine rpm.

Since your engine won't start at all, first thing is to check for fuel in the bowl. Pop the air cleaner off, hold the choke plate open and work the throttle a couple times. You should have a steady stream of gas each time from the accelerator pump nozzles. If not, dribble some gas down the throttle bore and see if it'll fire. If it does, you have a fuel delivery problem. If not, then it's ignition related.

 

[tkelley72]

Thanks Hemikiller but I still need more help from you or anyone else that may have had the same problem. I checked and didn't have any fuel from the "squirters" on my carb. It' a Holley, don't know the size but I think it's a 600/650 cfm. Nothing special. I pulled the squirter off, unstuck the valve under it and it now works. Tried to start the car and it fired right off, ran for about 15-20 seconds and died. Wouldn't restart. Here is what I've tried so far:
1. As stated, got the squirter working.
2. Pulled the fuel filter off to eliminate the possibility of a clogged filter and ran the fuel line direct from the fuel pump to the carb.
3. Pulled the fuel line from the carb. and inserted into a plastic bottle and had my wife crank it 1 to see if the fuel pump was pumping gas... it was.
4. I have a Pertronix 1 module. Checked the resistance on the coil and the module and it is all within spec. The gap on the module is at .30 per spec. as well.

I am at a total loos as to what to do now. Is it possible that the Pertronix has an intermittent problem? Can the fuel pump have an intermittent issue? (thought a mechanical pump was either good or bad?) The only thing I haven't touched is the cap/rotor. I looked at them and they looked ok but wouldn't hurt to change out I guess? This is really frustrating since the last time I started it ( a month or so ago) it fired right off and ran perfectly. I would really appreciate the expertise of anyone and everyone on this site. It's tough on an old guy like me in this Texas heat to work all day and accomplish nothing! Ha! Thanks in advance to anyone that can possibly solve my problem.

 

[tkelley72]

One last thing I forgot to mention. When I pulled the fuel line from the carb. to check the fuel pump operation, fuel sprayed out at the carb. nipple as if it were under pressure. Is there a filtering screen or metering valve at the hose nipple connection on a Holley that could be clogged? I know I'm grasping at straws here but I'm running out of ideas. Definitely not a fuel system expert so please excuse my ignorance!

 

[Hemikiller]

Tap on the needle and seat adjustment screw with the handle of a screwdriver. Sounds like it's stuck closed and not letting fuel through.

 

[tkelley72]

Tap on the needle and seat adjustment screw with the handle of a screwdriver. Sounds like it's stuck closed and not letting fuel through.

Are you referring to the squirter hold down screw or another screw on the carb.? I am by no means a carb. expert. Know enough to get into trouble.

 

[SteveO_71]

Does that Holley carb have a bonjo bolt at the fuel inlet? If it does and you remove that bolt, there is another little filter screen that is inside that inlet. Maybe check that screen also.

 

[mjlan]

This is a Holley 750 vacuum secondary carb, the arrows point to the float adjustment screws/ nuts. Under them is a needle and seat that admit fuel to the bowl when the float level drops an pulls the needle off of its seat. As Hemikiller suggests, if you have no fuel spraying from the squirter when move the throttle linkage but there is pressurized fuel at the bowl inlet when you crack the fuel line loose its possible that the needle is stuck. Try tapping on the adjusting nut to dislodge the needle.

 

[tkelley72]

Does that Holley carb have a bonjo bolt at the fuel inlet? If it does and you remove that bolt, there is another little filter screen that is inside that inlet. Maybe check that screen also.

It does have a banjo bolt. Can I remove that screen and if so how? If not can I just use carb. cleaner and spray it down real good? Thanks

 

[tkelley72]

This is a Holley 750 vacuum secondary carb, the arrows point to the float adjustment screws/ nuts. Under them is a needle and seat that admit fuel to the bowl when the float level drops an pulls the needle off of its seat. As Hemikiller suggests, if you have no fuel spraying from the squirter when move the throttle linkage but there is pressurized fuel at the bowl inlet when you crack the fuel line loose its possible that the needle is stuck. Try tapping on the adjusting nut to dislodge the needle.
View attachment 77892

Got it. I'll give it a shot.

 

[Hemikiller]

Why don't you post a pic of your carb? Some Holleys did not have externally adjustable floats. Also, on the front of the choke tower, there will be a stamped LIST number, Post that as well.

 

[SteveO_71]

It does have a banjo bolt. Can I remove that screen and if so how? If not can I just use carb. cleaner and spray it down real good? Thanks

It should come out when you take the banjo bolt off or, if its sitting in the carb, grab it (tweezers etc) and pull it out. Its a fine mesh so you clean it or order new ones from Holley.

 

[tkelley72]

Finally SUCCESS! Not sure which did it but I tapped on the adjustment nut/screws and removed the screen behind the banjo bolt at the fuel nipple and cleaned it. It now starts and idles like normal. Haven't driven it yet....kind of paranoid at this point. I do have one more question:

When I pulled the fuel line off to access the screen behind the banjo bolt (after running the engine) fuel sprayed everywhere as if it were under pressure. Is this normal? Even though I cleaned the screen with carb cleaner, the way it's made it's folded over on the end increasing the restriction. If I have an inline filter between the pump and the carb do I really need this screen? I guess if being under pressure is normal it's a dumb question? Would really appreciate all inputs before I chance driving down the road and getting stranded. Thanks for everyones help so far. Hoping for your continued guidance. Thanks

 

[Hemikiller]

I've never had an issue with the screen in the inlet plugging up. Pressure is normal, that means the valves in your pump are working properly. If you didn't get much junk out of the screen, then you should be good to go. I'd consider replacing the needle and seat assemblies as a precaution.

 

[tkelley72]

Thanks Hemikiller. Is replacing the needle and seat a simple process and can it be done without removing the carb. from the car?

 

[mrgmhale]

Thanks Hemikiller. Is replacing the needle and seat a simple process and can it be done without removing the carb. from the car?

I am so tempted to say, "Even a caveman can do it," but will resist, but I am jumping in here despite you asking Hemi-Killer to asnwer your question. I could not resist, and ask forgiveness of any offended party.. The top of the Autolite 2100 carburetor can be removed with the carburetor still mounted on the intake manifold. Just remove the larger diameter air cleaner mounting stud, and the 4 flat hear screws that retain the air horn of the carburetor. You will need to diddle with the linkage to the choke little a bit, or unscrew the small screw on the enter shaft of the choke plate. I suggest you take a photo of its linkage before removing it.

Once the 4 screws and air filter housing stud are removed you can carefully lift up the air horn at the carburetor. Once the air horn is off you can easily get to the Needle and Seat once you detach the float's retaining pin. Before reassembling, using a new carburetor top (air horn) cover gasket, be sure the retaining pin in the hinge of the fuel float is secured with the little wire clip that designed to clip into the groove on the brass inlet (seat). There is no need for gasket sealer on the top cover gasket.

Also, Mr. Safety says do not have any open sources of combustion in the area while working on the carburetor. You do not want to see the fuel in the fuel bowl get ignited. That would ruin anybody's day real quick.

 

[tkelley72]

Thanks for the detailed explanation of the process but I may not have been clear on what I am asking. My carb according to the list number is a Holley 600 CFM. The needle and seat I am referring to are the ones that adjust the float level on the top of the carb. I did a search on the internet and it looks like a pretty straight forward process....remove the screw, use the nut to back out the needle and seat, reverse the process. I do appreciate your taking the time to go into such detail. Everyone has been VERY helpful helping me with my issue. Thanks to all!

 

[Hemikiller]

Yes, you can replace the needle assemblies on the car.

https://www.holley.com/products/fue...s_and_components/needle_and_seats/parts/6-506
Use a wrench to hold the nut, then crack the screw loose and remove it. Remove the nut and clean off the old gaskets. Take a measurement from the top of the needle to the top of the fuel bowl so you have a ballpark setting with the new needle, then put the nut back on and unthread the needle and remove it from the bowl. Lube the o-ring on the new needle with some gas and thread it in to your measurement. Place in order: large gasket - nut - small gasket - screw - into place, hold the nut with a wrench and snug the screw. You can now start the engine and let the fuel level stabilize and check for leaks.

At this point, you're ready to adjust the float level. Holley has a decent video on it.

 

[tkelley72]

Perfect. Thanks again for the assistance. Last question...I promise. I haven't driven it yet but it does start, run and idle as it did before I had this issue. Is it possible that from sitting for a few months that the needle and seat got stuck due to varnish or some trash when I tried to start it? I'd like to run it around the block a few times to see how it really runs but I don't want to chance getting stranded. As I stated in my original post, nothing like this has ever happened before so could it just be a one off event?