Quote from: tuxblacray on March 08, 2011, 03:43:27 PM

I believe on the 1.3 it is a mechanical pump mounted to the block.

That is exactly my point - if there was some design rule or safety issue governing the placement of the pump - it would not have been where it is.

Quote from: ack on March 08, 2011, 07:47:43 PM

There is a distinct lag between the time that you turn the key to "IGN" and the engine-mounted pump finishes pressurizing the fuel line.  It is a waste of time trying to start the engine if the fuel pump is trying to build fuel line pressure by sucking fuel from the tank. I have to wait about 20-30 seconds before starting after the truck has been standing for more that a couple of hours.

Really?  I was under the impression you had to turn the key and crank the engine before the engine mounted pump would move fuel.

Also - we are discussing a carburetted engine here - the engine really should start & run on the contents of the float bowl, at least mine do (I have two, one with a mechanical engine mounted pump, and the other with a low pressure "in-tank" pump), and they both start with less cranking than my EFI one, regardless of whether it's been sitting for 2 minutes or 2 days.

Seriously - if you have to wait 20~30 seconds before you can get a start after the engine has been sitting for a couple of hours, I'd suspect you have a leak someplace - you're probably draining the float bowl and have to wait for it to refill.

Yup.

If my Samurai sits for more than 12 hours, I have to let it sit with the ignition on until the clicking sound of the electric pump quiets down because it has finally primed itself.

It'll start with the bowl contents but it'll die immediately if you don't first let it wait a few seconds to get the fuel system fully pressurized.

The physics are the same as long as you are on this planet.

Now Mars, you would have a hell of a time drawing fuel more than 12".

There are 2 principles in moving liquids, Barimetric pressure on the drafting side, and Hydraulics on the pumping side.

Also, just remember the 1st rule of hydraulics. you CAN NOT COMPRESS A LIQUID. Remember that the next time you
suck in water into your engine on the next "Water Swamper"  loon shit hole you get into.

Just here to help!
CAPT

Quote from: JesseWSmith on March 07, 2011, 04:47:06 PM

1.3 88.5 mostly stock-replacing stock carb with brand new weber 32/36.  Can someone tell me exactly what type of pressure regulator I need?  There are topics and replys that mention a jeep filter, some say use a pressure regulator.  I cant find the right post that has this answer.  Just not clear which regulator to buy.

WHat is this about mounting the carb backwards?

Thanks a ton,
Jesse

I don't know know exactly what type of pressure regulator to use (it's dark and cold outside...) but I just went to the O'Reillys Auto Parts near me and found a small round regulator (approximately 2.5 inches in diameter)  with a dial on it's face along with a small pressure gage.  I plumbed into the fuel line at the engine end and set it to 1.5 pounds.

I also plumbed the return line to the port opposite of the fuel inlet on the carburetor (they form an inverted Vee on the side of the carb).  I did this after having to replace the fuel lines due to overpressuring...

This setup, along with a cheap universal fuel pump (also mounted in the engine compartment - not a particularly good idea...), has worked just fine for 7 years.


Mounting the carburetor "backwards" (Choke facing the Head) , allegedly helps keep the carburetor from starving on steep inclines.  I cannot specifically speak with actual knowledge that the above statement is actually true, but it certainly did not hurt my truck by mounting it that way!

I hope that this helps

The idea works with my vehicle. An incline is not a problem. I showed this trick to my friends and guess what i got lot of appreciation. Thanks friend it was impossible without you.

Yup.

If my Samurai sits for more than 12 hours, I have to let it sit with the ignition on until the clicking sound of the electric pump quiets down because it has finally primed itself.

It'll start with the bowl contents but it'll die immediately if you don't first let it wait a few seconds to get the fuel system fully pressurized.

I still think you have a leak somewhere.

Presumably, from the clicking sound your pump makes, you have a diaphragm style pump where a solenoid moves the diaphragm, and the click is the diaphragm switching positions - how old is it?  I haven't seen one in maybe 30 years.  It possibly has worn or leaking valves.

On my very first mechanical-to-electric pump conversion, I mounted the electric pump high up on the firewall, roughly the same height as the original pump, connected the lines, hooked it to an ignition feed and away we went - the pump was still working fine when I scrapped the car many years later, and never once gave me issues.

The physics are the same as long as you are on this planet.

So - can you show me a fuel pump that uses the bernoulli principle that you described in your first post?

1st post was how I set up my Sammy with a Weber Carb system.

2nd post was that to draw a liquid, max lift is 22 ft at sea level.

"Bernoulli's Effect" is how a carb "Atomizes" fuel by the "pressure drop"
as MOVING AIR across a tube, atmospheric pressure would then be higher
in the fuel bowl causing "Draft" and the liquid to rise into the air stream.

Now on your fuel pump question of Bernoulli's Effect,
Have your fuel tank vent get plugged up.

"I might not KNOW everything......BUT I have an OPINION on everything.... and anything....JUST ASK ME!

Happy Trails
CAPT

P.S.

Hey Guys & Gals; Mom's & Dad's & Kid's of ALL AGES..........

Capt's journey home;
Made it to Rawlins, Wy "UNEVENTFUL" !!!!
Leaving out to my next stop, Lincoln, Ne, just after I check out the internet weather!!

CAPT

Now on your fuel pump question of Bernoulli's Effect,
Have your fuel tank vent get plugged up.

Last time I saw that happen the tank collapsed - and it had nothing to do with bernoulli's principle - there was no moving air involved - it was a simple case of a pressure differential, the pressure on the outside surface of the tank was greater than that on the inside surface.

What I suspect you're trying to suggest is when the fuel in the tank is below atmospheric pressure, there will no longer be a large enough pressure differential in the carburettor for it to draw fuel through the jets - maybe if you plug the float bowl vent you'll achieve that - but it would have nothing to do with the fuel pump then.

Care for another try?

Then you are applying Bernoulli's principles  and my statements to the wrong theory.

I think that I stated it correctly that draft (Sucking) has it's limitations
without outside influences. In the tank pumps submerged, or primed pumps below the liquid storage
level HAVE NO DRAFT and are PURE PRESSURE PUMPS. And there's always the trade off....
Pressure vs volume.

And you are correct. If you have a strong enough pump (AND YOU ONLY CAN BRING IT TO PERFECT VACUUM...0)
and the structure of the tank is too weak, it will collapse.

And Bernoulli  had some other really neat other principles about air flow, It's how airplanes can fly!!

CAPT

(I apologise if this sounds like I got up on the wrong side of the bed this morning...)

In response to all the highly techical and  mildly snarky   posts on this thread:

I dunno, maybe my experiences have been an illusion - but all I am doing is reporting exactly how my fuel setup works and all of it's quirks.

Many manufacturers put the fuel pump near the tank for some reason.  Maybe it has to do with fuel injection systems requiring higher pressures to work properly. 

Maybe a mechanically-powered pump exists on the 1.3 engine simply because it seemed to Suzuki as an efficient design at the time.

All I know is that:

1. If I hadn't fixed the overpressuring problem by connecting the return line, I could easily imagine the rubber fuel line bursting.  The result would have been a spectacular engine fire.  This could be caused by the fact that maybe my cheap low-pressure fuel pump is "stronger" than the mechanical fuel pump - or the fact that it is mounted in the engine compartment instead of next to the fuel tank.

2. Every time I try to force a quick start after the truck has been standing for more that 12 hours, nothing useful happens until the fuel pump quiets down after being primed.

3. It works for me despite any operational quirks.

and most importantly -

4. I don't have to worry about my engine being destroyed by the failure of the mechanical fuel pump.


I will be more than satisfied to know that three of the four above statements probably have a basis in fact.

 
A college education is truly a wonderful thing.  I actually have one!  But being a showoff just for the delight of seeing your big words in print isn't going to pay off your college loans - nor is it going to impress (or help) all the hard-working folks among us in the Zukin' Universe who don't have the benefit of that level of education.

I sincerely hope, somehow, that this helps!

Ack - if you're happy with the way your Samurai works, by all means leave it as it is - I just know that based on over three decades wrenching on old cars, that's not the way it should work - personally - I like to be able turn the key and get rolling if & when I need to.

My point on locating the pump in the engine compartment was clearly stated in my first post - the only thing that dictates that the pump be placed low down and near the tank is the design of the particular pump chosen - both types of installation have design compromises and from my point of view, neither is inherently better.

By the way - for what it's worth - college educations are hard to come by in third world countries, seat of the pants experience however, coupled with a lot of reading, is a wonderful thing.

Any air leaks between the tank and the pump will reduce the fuel flow.  Also, old rubber hoses in the fuel line may collapse from the pump sucking fuel rather than pushing it.

Fun fact, a cracked fuel line on top of the gas tank is a real pain to diagnose.  Especially if you use a 'testing' tube that you push inside in order to do some quick testing to find why you aren't getting any fuel and it ends up patching where the break in the main line is...

1. If I hadn't fixed the overpressuring problem by connecting the return line, I could easily imagine the rubber fuel line bursting. 

You see, I got around that problem by using a really weak (cheap) pump.    If I let it sit idling for more 5-10 minutes it will start to overheat and cavitate though...

1.3 88.5 mostly stock-replacing stock carb with brand new weber 32/36.  Can someone tell me exactly what type of pressure regulator I need?  There are topics and replys that mention a jeep filter, some say use a pressure regulator.  I cant find the right post that has this answer.  Just not clear which regulator to buy.

WHat is this about mounting the carb backwards?

Thanks a ton,
Jesse

Jesse!
hendrixautospeed a seller on eBay sells the Spectre fuel regulator kit 0-5# for $22.99 shipped - buy it now!
Check it out!

Hope this helps!

Riverrat

ACK,

Now on the pressure relief without any formulas or theory.

Check to make sure the parts house gave you a LOW PRESSURE fuel pump
with a built in pressure relief .

Check on Riverrat's post a good source!! and the right psi range.

CAPT

Getting ready to replace my old Weber 32/36 with H2O chole on my '87 Samurai with a new 32/36 with manual choke. I'm also going to install a Holley 12-804 pressure regulator. The previous owner never hooked the carb up to the vent hose on top of the valve cover. I replaced the fuel pump last week with a new stock mechanical pump.

Does anyone have pics showing how the air cleaner vent line is hooked up to the line out of the top of the intake/valve cover. Also, pics of where people have mounted their fuel pressure regulators.

Thanks in advance,

Rick