New fuel pumps

[Charlie ny]

I recently finished testing a batch of the new fuel pumps that many
of the big names are selling and thought I'd pass along what I found. The
pressure is pretty inconsistant...out of 25 there were 8 that put out
2 1/2 - 3 1/2 psi the balance were all above 6 psi. They all pumped
and picked up fuel quickly. My test motor has a gas tank 18 inches below
the fuel pump inlet and none of the pumps had any trouble pulling gas up.
All the pumps used the 8ba push rod cup which as we all know is bigger
in diameter than the '33 - '48. It seems like the early push rod would tend
dance around excessively during operation.
I took the 6 highest pressure pumps and switched the bases and springs
with bases and springs from my stash....old stuff but still in good
condition.....in all cases the pressure settled in at 2 1/2 - 3 1/2 psi.
The diaphragms were different thicknesses but that did not seem to
have any bearing on the effectiveness of the pump.
Over and out !
Charlie ny

[Lawrie]

Thanks for that good info.
Lawrie

[ken ct]

Thats the reason i dont recommend buying them Charlie,thanks for the testing project you did.Got some more stems for you to do about 25-30 of them.Pumps have been flying out the shop lately.Are you going to the Ga. national in june. It would be a pleasure to see you and Alice again.Give her my best.ken + peg isidor ct.

[JM 35 Sedan]

Charlie, what were your underlying reasons/purposes/insensitives for running these tests? What is your personal conclusion? Who is the manufacturer and what is the country of origin of these fuel pumps? Realizing the forum you are posting on here but what make/model/year vehicles do these tested pumps fit? What blend of fuel did you use (% of alcohol?) and did the diaphram material withstand deterioration? For what other reason/reasons would we not want to buy these pumps to use on our old cars, if we already happen to be using an in line pressure regulator on our car? Just wondering all these things after reading sort of a test report that seems to begin in the middle of the story and finishes with no real apparent conclusions.

Originally Posted by Charlie ny

I recently finished testing a batch of. the new fuel pumps that many of the big names are selling and thought I'd pass along what I found. The
pressure is pretty inconsistant...out of 25 there were 8 that put out
2 1/2 - 3 1/2 psi the balance were all above 6 psi. They all pumped
and picked up fuel quickly. My test motor has a gas tank 18 inches below
the fuel pump inlet and none of the pumps had any trouble pulling gas up.
All the pumps used the 8ba push rod cup which as we all know is bigger
in diameter than the '33 - '48. It seems like the early push rod would tend
dance around excessively during operation.
I took the 6 highest pressure pumps and switched the bases and springs
with bases and springs from my stash....old stuff but still in good
condition.....in all cases the pressure settled in at 2 1/2 - 3 1/2 psi.
The diaphragms were different thicknesses but that did not seem to
have any bearing on the effectiveness of the pump.
Over and out !
Charlie ny

[JWL]

I have a fuelpump test system on which I have done a number of new and rebuild tests. However, my tests included spring compression measurements, mounting height measuremnts, vacuum and pressure measurements, time to achieve various levels, etc. My findings are somewhat different with respect to spring swaps.

[31chevy]

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If the pressure is to high what is the fix ? Change or modify spring or ? Mine is on a 34 pickup. Thanks in advance.
Gary.

[ken ct]

Usually an original spring is ok to use.ken ct.

[BILL WZOREK]

Ken ct. / Charlie ny
You both mention old spring give proper tension ( maybe wrong term) for the pumps.
is it possible to have new springs made of the correct pressure.
The reason I ask is because in The past for our sand & gravel operation we had a supplier would build us springs for our screening needs and they could make us what ever pressure /recoil rate we needed. Don't know if they are still in business or if they could do such a small spring.

[G.M.]

Charlie At least you took the time to do some initial testing and gave us the results you found. The other rebuilders have no idea of what their rebuilds do and testd I would expect similar results to what you found. These cars will run on between 1 and 7 lbs pressure but at a constant steady flow they run best. The springs are mass produced and can vary slightly plus used springs could change from prolonged use. I have two spring load test machines. These have height and pressure gauges so you know exactly how each spring performs. Look on eBay, they show up on there. If you want send me a batch of springs, lable one you think is best and I'll test and adjust all of them to the sample. It will only take a few hours and I will get them right back. N/C. The other thing you want to check is the free play and where the rocker arm engages the diaphragm, this is the active pumping range. The length of the push rod also changes the pressure, this go's back to the pumping range. I just completed adjusting the fuel pressure on my 39. This was on and 42 raised deck engine, cast iron manifold airtex glass bowl pump and the special diaphragm I have been testing for over 2 years. Stock push rod length is supposed to be 8.875 my NOS rod never installed was 8.870 but I installed a .065 thick gasket under the base to help insulate the base from the manifold heat. At the length of 8.770 I had 3/4lb pressure, 9.060 8lbs with gas pushing past needle valve, flooding over the fuel bowl and squirting out the pump rod on top of the carb.
At a length of 9.005 5 lbs and at 8.995 3 1/4 lbs which is exactly where I want it cold. The pump pressures drop a little when the pump gets hot. If you take .055 off the rod length, .065 gasket less .010 for the old gasket I ended up with needing a 8.940 rod acording to calculated lengths. but needed a rod 8.995 to get 3 1/4 lbs of fuel. I THINK it all depends on spring pressure and when the push rod just starts moveing the diaphragm. To get consistant pumps that all pump the same you need springs that are all the same and a simple fixture that bolts on the pump mounting holes with a screw in type of dial indicate into the rocker arm socket that tells when the push rod starts to move the diaphragm. With the new gas and the way heat effects the pressure of it I THINK a constant fuel pressure is important. Yesterday at 82 out and driveing localy for 2 hours I don't think this car ever ran so consistanly perfect. G.M.

[Charlie ny]

Guys,
The pumps were a mix of early and late and there was no one
type that did better or worse....the psi inconsistancy vs type was random.
Understand my goal was to determine the quickest way practically to get
a new pump to behave.....those were my instructions. At this point I'm
not sure nor whether the problem is in the geometry of the
lower half of the pump or the spring. Variation in pivot pin hole location
on the base we know will change the stroke ,ditto for the dimensions of
the arm. I'm thinking the culprit is dimensional issues in the bases and
arms. The pumps were supplied to me.
I guess that's my answer....your conclusions are yours to make.
If you run a good regulator like the Holley it seems as though these
off shore pumps could be ok.
Charlie ny

[Charlie ny]

George, and all,
The spring is certainly important but as your in depth study
shows stroke seems to be the bad guy.
Since there are a multitude of variations I caution my customers
to install my pumps on the stand then rotate the motor so the push rod is
all the way up. Install the pump/stand on the intake and determine the
gap between it and intake while using gentle arm force to overcome
the diaphragm.....its good to have a 3 arm buddy to assist. If in the above
the stand smacks nice and solid on the intake I suggest using a .003 to
.005 thick gasket.
On the '33 to '48 motors the ears on the stand are quite
often stretched down because the proper steps were not done in
prior installations....that face has got to be flat.
Charlie ny

[TomO]

The spring controls the fuel pump pressure. The push-rod moves the diaphragm to create suction and the spring returns the diaphragm to the neutral position, putting pressure on the fuel. The stroke can affect the pressure because the spring tension is non-linear.

[richard crow]

the spring controls the pressure. the dig. rod has an enlonged slot so once the pressure is reached the lever gust moves in the slot not moving the dig. now if you lenthen the rod travel you are over comeing the slot so the pump pressure goes up . use the right spring the right rod & the right gasket if the camshaft ectrenc is worn then fiddle with longer rods

[richard crow]

ask an old time mech how we checked fuel pumps with a coffe can. when we weren,t talking to our torque wrenches THERE IS NO SUBSTURTE FOR EXPERANCE i just wish i remembered how to spell

[Ol' Ron]

Who makes a proper rebuild kit for an 8BA fuel pump (Single stage)

[G.M.]

Look out Ron your about to get a PM

[JWL]

There is some good information written here. However, the more important points have not been made in a way that explains what is happening. Of course the spring is important. But after checking several I found that none of the new springs(from new pumps and new rebuild kits) were above the Ford specification. For the pumps I was testing the Ford spec. is 7.1 to 8.6 pounds at a compressed height of 5/8". All of the new springs I checked were less than 8 and slightly more than 7 pounds. So, if the springs are "right" why do some pumps have more or less pressure? Two reasons:1. The effectiveness of the check valves 2. The assembled operating range of the diaphram. By cutting a 2" hole through the center of the diaphram section of a upper pump casting I could replace the original top piece and observe/measure the mounted and operating height of the spring. This is done by first measuring from the intake deck surface to the spring seat location with parallels and depth gauges. Then when assembled, and allowing for the thickness of the metal diaphram clamping pieces, the spring height can be determined by measuring to the metal "washer" in the center of the diaphram. On the various pumps I measured, which included Ford pumps and several "aftermarket" maunfacturers, the maximum diaphram stroke height varied from .636 to .891 and everywhere in between. The actual stroke varied little at .195 to .205. In checking 2 new pumps from Mac's, one with a special 5 lb. spring, I had installed, and one with the original 7 lb. spring I found both to be satisfactory but the pump with the weaker spring had 5 lbs. of pressure after 2 minutes with a .035 bleed-off orifice while the pump with the "stronger spring had only 4.2 lbs. using the same measuring critera. In another example of a pump in which I installed a new kit, the pump had only 2 lbs of pressure with a 7 lb. spring. Further investigation found the vacuum that pump was pulling was DOUBLE the levels found in the 4 to 5 lb. pumps. This was an obvious case of the check valve limiting output. There is much more that could be said and several more measuring values I could write about but the more important stuff has been covered and I am tired of typing.

[Charlie ny]

JWL,
I was hoping you'd weigh in. You and GM are the headmasters on
the Barn,,,,in my opinion.
Charlie ny