The Stovebolt Site Forums The Shop Area Engine Shop Fuel pump over pressure

Hello, I have been struggling with my carb over filling with fuel (59 235ci, 3100, Carter yf2100S). Been in and out of the carb scratching my head. With a suggestion from John (Carb King), he recommended checking fuel pressure. Engine is new so I bought a new Autozone fuel pump that had the correct clocking for the in and out hard lines (in at approx. 6:30 o'clock, out approx.2:30 o'clock). The old orig had a part# of 40217 (no manufacturer name but was stamped Made In USA). Sure enough it pegged my pressure gauge to it's max of 10psi. John says the psi should be between 3-1/2 to 4-1/2psi. So its obviously over powering my needle and seat. Does anyone have a source to a quality fuel pump with the correct clocking that puts out the correct pressures. I can't trust the box stores. There are many on ebay that say NOS but it's hard from the pics if the clocking is correct as my 235 was factory hard lines so it needs the correct clocking . Thanks in advance.
Keith

Have the Original one rebuilt . Then & Now back East.
They rebuilt my original dual fuel pump...worth every cent I paid.

Follow Shaffer's advice.

All the pumps you buy new today are absolute garbage. They're all made in China regardless of brand name. They will fail soon after installation if they even function at all out of the box.

Send your original pump to Then and Now Automotive or purchase one of the NOS pumps online and send that to be rebuilt. Calling them on the phone is the best method of contact. They're website is not very helpful.

They did my original pump 10,000 miles ago after 2 new pumps failed. One would not pump a single drop right after installation. The requisite fuel pressure for the 1950 216 is 2-4psi. My pressure is 2.5psi at the carburetor.



Then and Now Automotive

447 Washington St
Weymouth, Ma 02188
Ph: 781.335.8860
Fax: 781.335.1925
https://www.thenandnowautomotive.com/

Otto -Just a note to say please delete your old saved link to Then and Now Automotive as it has been taken over by bad guys and will only cause grief to fellow Bolters.

The link I replaced yours with in your post is the correct and safe way to contact the business.

Keith - You can also rebuild yours existing "40217" pump using kits from a number of our usual sources, including ordering a kit from Then and Now Automotive if you're up to a DIY.

Otherwise, check out ebay. There is current listing for a rebuilt "42017" pump. Pictures in that ad show the correct port layout as mentioned in your details (see screenshot below).

For what it may be worth, since 1997 I've used an electric fuel pump in place of the mechanical one. And what a positive difference it has made. Engine starts immediately, runs well, no worries. Around 2018 I bought a new one (same make and model) and replaced the one from 1997. Not because it wasn't working but just as a pre-emptive move. The make is AutoBest, the model number is F4027 and the output pressure is 3 to 3.5 psi which is all you need for any of these engines. Around $30 delivered to you. Also it is designed for use with ethanol. There are other copies of this pump bearing the same number (F4027). I don't know about those but they all are rated at 2.5 to 4 psi. IMPORTANT NOTE: If you adapt to an electric pump, please mount it back as near to the gas tank as possible (on the frame with a known good ground). These pumps are all designed to push rather than pull. You can also wire in a mercury switch to cut the pump off in case you flip your truck...or some people use an oil pressure cutoff switch.

For what else it may be worth, I ran the oil pump lines out a special cover I made (where the old mechanical pump once sat) and connected those to a spin-on oil filter adapter.

Dang! I thought I had that changed it to the new address on my list. I'll delete it permanently.

I have had the same experience with new fuel pumps. Regardless of the advertised pressure, they all put out over 10 psi. I kind of solved the problem by installing an in-line fuel pressure regulator.

Down side of using the oil pressure cut off switch is that the engine has no/little oil pressure while cranking and therefore no fuel pumped towards the carb. You can "fix" that problem with a push button bypass to the oil pressure cut off switch.

Or you can power the fuel pump with the start terminal of the ignition switch (if you have that), bypassing the oil pressure cutoff switch, although if the carburetor bowl is full, there should be enough fuel in it to allow the engine to start.

Forget the fuel pressure regulator. A needle valve controlling the volume of a bypass line back to the fuel pump inlet can control the volume and pressure supplied to the carburetor. Install a temporary pressure gauge just ahead of the carburetor and adjust the flow until you get the desired pressure. This also prevents fuel pressure buildup and flooding in a "hot soak" situation in the summer.
Jerry

Thanks to each one of you that responded. First call this morning was to Then and after. Very, very nice people. My complaint is extremely common there. They are several months back logged for rebuilds but did have the kit for my original 40217 model (thank god I kept it). They boxed it up and sent it within a hour of my call to help me. Fantastic people. Baffling, that the big box stores sell these knowing of the complaints yet nothing changes. Again, excellent advices guys, I'm going to buy a spare also.

I fabricated a bypass line similar to what HRL describes, I didn't include an adjustable metering device, just a tee in the 3/8" line at the carburetor and a 1/4" line back down to a 3 port fuel filter ahead of the pump. The bypassed fuel can go to the pump or when the engine is shut down it can bleed back to the tank, no residual pressure is allowed to force fuel into the carb.

I'd suggest at least installing a small diameter restrictor in the bypass line. Since I have dozens of Holley carburetor jets left over from my round track racing days, drilling and tapping one leg of the tee for a jet allows for a metered pressure relief without compromising total fuel flow when it's needed for full throttle operation.
Jerry

For the time being, it works quite well. Some how I got lucky when I bought the fuel pump, I didn't buy an expensive one 'cuz I just wanted to get the truck running and diagnose issues. Of course this is more simple than the glass/vacuum/pump combo on the 6 cylinder, mine being a 283 cu.in. V8 Rochester 2G. Anyway, it's still working after 9 years and it doesn't starve at heavy load nor do I have heat soak issues with the bypass fix.

I suppose I have been lucky (knock on wood), the off the shelf Fuel pumps I'm using work great. I haven't had a Fuel pressure issue or any problems with reliability. I have several OEM pumps on hand with plans to rebuild them at some point.

I got in touch with them and after and they shipped out a kit for my original that thank god I kept. Followed there rebuild videos which went easily. Reinstalled and works perfectly. Tested with my pressure gauge, the rebuild is putting out 4lbs.
I am however getting a little dripping of fuel after shutdown from the main jet which I should prob start another thread on. Need to search first. Thanks again gentleman’on the rebuild suggestion. Worked perfectly and I can’t say enough about them and now. Fantastic folks there old school service.

I'm glad you got it straightened out, Keith.

Then and Now does a lot more than just fuel pumps. They rebuild water pumps, oil pumps, distributors, master cylinders, brakes, etc. They re-vulcanize motor mounts and balancers.

They also sell NOS timing gear and chain sets, valves, springs, keepers, pistons, bearings, gasket sets, suspension parts, king pins, carburetors, and all other kinds of antique car stuff.

Such a great resource. Thanks again

I tested my pump pressure and it show 5.5, is that too much? I am experiencing some leakage from a fairy fresh rebuilt carb.

It seems that the spring inside the pump is what determines that pressure. What if anything can I do to the spring to adjust my pressure?

Yes. That's too high. 2-3psi is ideal.

FSM recommends 2-4psi as the range for fuel pumps on 216/235 engines.

My truck operates at 2.5psi.

What can be done to the fuel pump itself to lower its pressure?

I'm not sure much of anything can be done to a fuel pump to lower it's output pressure. Maybe a different diaphragm that's more flexible or uses a smaller backup plate. Or maybe a different spring. But by the time you try that, you might as well just get a different pump.

Pump pressure is controlled by the spring that pushes the diaphragm after the cam lobe and lever compresses it. Installing a spring with less tension would be the logical way to reduce the pressure. Shortening a spring doesn't reduce its strength- - - - -if anything, it would increase the tension. Someone would need to find a spring approximately the same free length as original, with smaller diameter coil wire for less push.
Jerry

What if I took a spring from my old pump and installed into the new pump???

Could be a good solution- - - - -IF the old pump was making the right pressure.
Jerry

Or buy a rebuild kit from Then and Now Automotive. Or send the high pressure one or the old one and have them rebuild it.

Then and Now Automotive

447 Washington St
Weymouth, Ma 02188
Ph: 781.335.8860
Fax: 781.335.1925
https://www.thenandnowautomotive.com/auto-parts-store

FYI
I just got this response from an e-mail query to Then and Now.

I'm sorry but that website is not operational, at this time and unable to process orders.
Please contact the store to complete your purchase.
We are very shorthanded and only have designated telephone staff on Monday and Thursday, 9-3 pm EST. We do try to cover as many calls as we can the rest of the week .
Thank you,
Tom,
Then And Now Automotive
447 Washington St
Weymouth Ma 02188
781-335-8860
www.thenandnowautomotive.com

I called to place an order for a rebuild kit and a nice lady answered right away. She was very helpful in getting the order placed.

I believe the website works to search for the correct kit, but when I tried ordering online the only payment option was “Pay by cash” which doesn’t stuff into the computer that well. 🥴

I have noticed that often when I release my gas cap there is pressure released. I am thinking maybe this pressure is what's blowing past the needle and seat because my dampness around carb shows and accumulates even went the truck is parked for days without any running. My question is where is my tank supposed to be vented at? At the cap itself? I have replaced the cap with new one that was supposed to be for my year truck.

Your gas cap pressure relief valve is faulty. All of these new gas caps you buy for these trucks are defective from the factory.

You'll need to take it apart and take out the little valve and spring in the center and put it back together. The problem is the fuel pump is pulling the fuel out of the tank and no air is replacing it, creating a vacuum inside the tank and forcing your fuel pump to work harder than it should.

It will be the first thing on my list of things to do tomorrow. Thanks for the sharing of knowledge.

Do you think this could be the cause of my seepage at carb even when its not been run?

Probably not the reason your carb leaks.

If your gas cap is like this one, fold those two metal wings open with a screw driver or pliers.

The entire valve assembly with a spring will come out. Just remove the inner rubber valve and spring and then reassemble it.

The cap should vent but these new caps are all plastic junk and don't work.

I removed whatever came out after I bent the two tabs over. Seems to be working now, no pressure relief when I remove the cap, but I havent driven it yet either