VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc OEM mechanical fuel pump for 1970 Small Block

(motor was running great)then fuelpump stopped pumping gas up to clear FuelFilter. I installed a new OEM fuel pump in this SB/350 1970 motor, it did not work, I took it back to store, and exchanged for same lifetime warranty brand, it too does not work. There are no unusual noises durng cranking engine, and I took Gas tank off and inspected Fuel sender and Sock filter(this motor is in a '55 chevy sedan). I also checked fuel lines. It is installed correctly and the Cam rod appears OK. >My Question" Is there a test/ check I could try?" should I pull off Fuel Pump and hand crank engine to check Cam rod travel?
-Thank you for the reply!

55 chevy
A quick test, undo the pipe where it fits into the carb and extend it into a container while cranking engine. If you get no fuel take the line that comes from the tank get someone to gently pressure the tank with air.
This will tell you if it is a blockage or a problem with the pump.
Some of the carbs on those motors had a bronze filter between the pipe in and the needle and seat, check it. They generally had a second fitting with a much larger hex on it that the pipe fitted into.
Tony

Did you check the pump actuating rod that fits between the fuel pump arm and the camshaft? sometimes it will wear or fall out of position and the fuel pump no longer works. I knew a very good IH truck mechanic (with no experiance on a SBC Chevy), almost loose his cool because this rod fell out and he changed out several fuel pumps on the side of a road..

I have took the inlet hose, line off the fuel pump, put it into a five gallon basket, then used a rag to seal an air nozzle in the fuel tank filler port and GENTLY put pressure on the tank to see if fuel will flow to the pump, you may have a blockage in the fuel supply line. Sometimes dirt will acumulate in a sharp bend or a tubing connection and prevent good fuel flow.

on small block chevy engines, there are two bosses, drilled and tapped on the left front face on the engine(these were used to attach the motor mounts brackets on the 55 thru 57 chevy small blocks) anyway, remove the lower one, and install a longer bolt ( by about a 1/2" longer). don't tighten it till you turn the engine over such that the fuel pump actuator push rod is on the low side of the cam(when the rod is closest to the enter of the camshaft). then lightly tighten the 1/2" longer bolt till it bottoms out on the actuator rod. this will keep the rod closest to the cam and allow the fuel punm to be installed without a bunch of pressure on the fuel pump arm. good luck, mike

PS: forgot to mention that removal of the 1/2" longer bolt and reinstalling the original bolt is necesary.mike

Mike are you talking about the driver's side (left) or the passanger's side (right) of the engine? Now I am as confused as JYD. :confused: :confused: :confused:

Fuel pump is located on the right (passenger) side. Therefore, the bolt to remove and replace with the longet bolt is on the right side and the bolt is on the right front of the engine.

I have found that a big old gob of Marfac #1 cramed up into the pump rod hole will hold the rod in place, at one time I knew where the distributor rotor needed to be to make the pump replacement easier, but in the last 40 years I seem to have forgotten that important tidbit of information. It is important to also know the length of a proper functioning rod, unless you replace it with a new rod just for changeing's sake. have never changed one myself, just kept on using the original one. I do use a vacuum -pressure test gauge to test a questionable fuel pump unless it is obvious it is bad and dripping gas all over the floor.

I have NEVER seen a pushrod wear to the point that there was no fuel pump action! It is possible that the cam wiped out a lobe but doubtful. What I have seen is a crack in one of the rubber lines not allowing the pump to build pressure. Did you try priming the new pump? Did you try to get fuel to the line side of the pump?
John

John, Excellent Suggestion:I did not Prime the new Pump. I may have damaged it by not doing so. In the past, I never did, I have owned this car for 20 years with same 350 S/B motor installed, I have in the past R&R'd 3 fuel pumps without priming(although this may have shorten life of Fuelpump, by not priming).
I tried testing Fuel Pump with a quart of gas in emtpy Oil container filled with Gasoline with a 1' foot length of hose connected to inlet of FuelPump, I cranked it(1 minute) to see if Gas went through line to Visible clear Fram G2 Fuelfilter > STILL NO GAS.

--Mike McCagh, Excellent Tip on the Way to hold the Actuation Rod in place instead of Standard screwdriver or NeedlNose Pliers >Thanks!

--TonyW thanks for the Idea of checking Tank to Fuel Pump Lines. I will also check this, since I never did in 20 years(tons of original Gas Tank sediment.) Tony Thanks!

MrMack, the Suggestion of holding the Pump rod in place With Marfac #1 Glob is Great, its like Wheelbearing grease.
Perfect for re-install.Thanks Mr Mack!
Thanks for the Clarification ANTIQUE MECHANIC #13.
....I appreciate all replys! Have a great week-

In this case looks like the pump is bad. Like master cylinders it is often best to prime and bench test before installing. Most mechanical fuel pumps can easily be tested dry by pushing the lever arm and listening for the sucking or air flow. Putting a finger over the intake (check for vacuum) or outlet (for pressure) also works if you have enough hands (might take three if you have to hold the pump in one and operate lever with the other). If that is the case you can put a hose on intake or outlet and check for air flow or liquid pickup. It is not necessary nor a good idea to squirt gas across the shop when testing the pump.

Bench testing is not fuel proof (sorry, devil made me write that) if arm, activating rod or cam lobe are not correct.

A good first test particularly for the older cars or those stored for extended periods of time is the check the fuel inlet line. Take the fuel inlet line off the pump and install a short section of rubber hose. Using the hose blow back into the tank. You should be able to tell if air in going into the tank either by the sound or the fast that the pressure is decreasing or both. Once you are sure that the line is clear (it may not stay that way if there is circulating crud in the tank) then check the pump again. It is becoming more common for inlet lines to get plugged or restricted by trash in the gas tank.

I am not 100% sure if it is on the 350's but on the early small block's there is a bolt on the lower front side of the engine on the fuel pump platform, and just before the timing cover. If that bolt is there remove that bolt and install a longer one finger tight and that will hold the push rod in place.
Remember that just because the fuel pump is new does not mean it was recently rebuilt. We have been in the age of electric fuel pumps for over 20 years, so the diaphragm could be as dry as toast inside.
John

Chipper, I just used your Tip and added a hose to 1955 factory stock steel Fuel line next to A-Arm and blew back air into Gas Tank(with Gas Cap Off) -no blockage, clear line, tank filled with a half a tank of Gas, --air went through.
Excellent Idea - Thanks for your input.

I'm going to do the Bench test next.. I have a 50 lb. Vise on my workbench. I'll remove fuel Pump then Hook it up on Vise to secure it so as I can manually actuate the arm to see if it works properly, thanks! for that great suggestion, John348, makes total sense to run gas through it first, to check the diaphragm. I Also have a Brand new Carter Mech Fuel Pump for 350 SB, that I wanted to use, but the Pump Hits the Cross Member of the 1955 ChevSedan by a 1/2 inch when I tried to install.

When you blew the air back did you listen for bubbles in the tank? I had the same problem and it was a crack in the rubber line from the tank. This new fuel eats up the rubber!
John

I clamped the Pump in the Vise and Carefully used "ViseGrip" Pliers on Actuator Arm of pump,I had flexible Gasline to Plastic Oil quart Container w/gas.
I moved actuatorArm 2X, the pump Shot Gas -new Pump works Fine. I removed CamRod Retention(2 bolt) PumpBracket/plate for Cam Rod, Removed it/inspected Cam Rod, -it looks OK.
Its gotta be a worn Cam Lobe, although this engine has about 25,000 miles on it from rebuilt with a brand new Engle RV Cam(Hi Mid).
Once Again, -thanks for Ideas + the help to All!

Look at the rubber line from the tank
John

Did you test the pump before you removed it of the engine. You may have removed it unneccessarily.
I seriously doubt a cam lobe would give out that quick. If you get fuel flow at carb inlet lift the carb top and check for blockage in there and then look at electrics.
Tony

John, You are most likely right,the CAM is Fine.
It has to be an air leak.
This weekend I'll drop Gas Tank and replace all rubber fuel lines and add new Fueline clamps from gas tank to Engine, the Carb is a Holley Universal 4BBL 650 CFM(boughtNew 1985), on an EdelBrock Performer Manifold. I'll post results.
...Thanks for the input Tony on the Cam OK, -55

I had it happen to me about 20 years ago and it drove me nuts! I was driving my 63 Impala back from Super Chevy Weekend at Maple Grove Speedway in PA. I was bucking and stalling on every bridge, I replaced the pump several times, and everything else. Then finally it just stopped. I found a hairline split on the rubber line that would open and close pending on the movement of the line.
Good luck