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post #16 of 28 (permalink) Old 06-18-2006, 10:56 AM
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the basics

OK..if the conventional wisdom is that the syphon pump is superfluous, then fine. Make sure that the main pump isnt drawing vacuum, as I had experienced at times, when my syphon pump was problematic.

Just making a point: Positive displacement pumps are stressed when pumping dry. Dry pumping was to have been reduced by the syphon pump. If a syphon pump isn't going back in, try to develop a fuel circuit that avoids dry pumping.

Best of Luck

Mike Pate

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post #17 of 28 (permalink) Old 06-18-2006, 11:12 AM
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The retrofit of a boost pump involved cutting the internal fuel pipe to the tank pickup sump and blocking off the outlet. That means draining/safing the tank and cutting the pipe through the sending unit opening.

If I had a late S2 model, I'd seriously consider retrofitting the boost pump.

John Stewart
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post #18 of 28 (permalink) Old 06-19-2006, 06:56 AM
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at the start

John....in thinking about your description of the circumstances for which the syphon pump would be required...your description makes perfect sense. Should of course have been obvious.

Once the line between the tank and the main pump is full and as long as the tank doesnt run terribly low, then fuel statics will keep the line between the tank and main pump full, without a syphon pump.

Donny: But...When you replaced your main pump..I dont understand how you refilled the line between the tank and the pump. Its easy to see how the main pump would draw vacuum, at lease for a while. Fluid doesnt like to flow against gravity. The vacuum drawn from the main pump might be enough to eventually draw fuel up the line, but totally at the expense of the main pump lifetime. Physics says you don't need the syphon pump most of the time. It, of course was added to fix a periodic problem.

Good Luck;

Mike Pate
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post #19 of 28 (permalink) Old 06-19-2006, 07:18 AM Thread Starter
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Mike,
You are right, I had no way to re-fill the line bewtween the tank and pump after replacing it. And I think you are right that is causing a vacuum now. Any idea's how to fill that line now without adding a boost pump? I think adding the boost pump would definately be a prudent thing to do, I just can't do it right now.

Would this work to prime the system and get the circuit flowing properly again: disconnect the fuel line at the SPICA inlet and then momentarily turn the main fuel pump on, then once fuel is flowing put it back on the SPICA?

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post #20 of 28 (permalink) Old 06-19-2006, 08:24 AM
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I don't think you should be having a hard time getting the main supply pump to prime itself. I haven't heard of this being a problem before. Try disconnecting the fuel outlet at the tank and filling the hose with fuel, then reconnect it. There will be a little air in the system but certainly not enough to cause a problem.

I'm thinking you have something else going on here.

Confirm that you have the supply pump installed correctly with the inlet and outlet oriented correctly.

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post #21 of 28 (permalink) Old 06-19-2006, 08:36 AM Thread Starter
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Thanks RT, I was thinking the same thing about disconnecting and manually filling the fuel line at the tank, always looking for a new way to use my wife's turkey baster!! I will get under there tonight and take some pics of the pump setup, I put everything back they way it was so I am pretty sure it is oriented correctly. I think I will also blow the line between the pump and front filter incase it is clogged (Akitaman's idea). Oh yeah, I now have 12.66 volts at the battery after charging it up.

Thanks again to all for wracking your brains with me on this one!!

Donny
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post #22 of 28 (permalink) Old 06-19-2006, 11:56 AM
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be careful out there

Donny...it looks like you have a plan. Use care. I would suggest getting the car out of the garage, while disconnecting/connecting the fuel system. Make sure the car is sufficiently elevated for emergency egress, if you must get under it. Make sure the battery is disconnected prior to starting work.

Best of luck

Mike Pate
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post #23 of 28 (permalink) Old 06-19-2006, 07:55 PM Thread Starter
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Sweeeeet Humble Pie!

So this one was totally my mistake. Tonight I first tried disconnecting the supply line at the tank and used the turkey baster to fill the line, still nothing. Then I disconnected the line from the SPICA inlet and tried turning the pump on to see if I was getting any fuel at all, still nothing. Then I disconnected the line at the front fuel pump inlet and tried turning the pump on, still nothing. So then I get back under the car and how about that, I had the wires backwards. It doesn't work so well when you are pumping the gas OUT of the engine!!! Swapped those puppies and obviously she fired right up, even took the wife for a semi-victory lap. Anyway, the humble pie I ate tonight still tastes sweet since she is back to perrring again. I learned a few things along the way and I am sure things could have been worse than they turned out. Thanks again to those who pitched in with idea's, and my appologies for dragging it out with a simple wire swap. RoadTrip, you seem to always be right on, thanks!

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post #24 of 28 (permalink) Old 06-19-2006, 09:20 PM
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Here is a pic of the boost pump/sender assembly from my 81 Spider.
I believe that this car was Spica Injected, but there was no engine in it.
Hope it helps.



EDIT..... I guess I should read the last post before I post! Doh!
Here it is anyway!

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post #25 of 28 (permalink) Old 06-20-2006, 05:45 AM Thread Starter
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Keyspider,
Thanks for the clear picture.

Does anyone know where to get one of those. I think I can get the pump from IAP, but not sure about the rest of the setup. Mine sending unit does not have the fuel nipple on the flange.

I do think that adding the in-tank pump would be a good thing to have someday. Now that I have the car running like it was before, I am going to re-connect the inertia switch that was by-passed by the PO.

Thanks again!

Donny
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post #26 of 28 (permalink) Old 06-20-2006, 07:18 AM
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Just for information . . . See that black hose that connects the pump at the bottom with the outlet pipe that goes up through the flange? That rubber hose can get cracks in it and leak back into the tank. That will slow or stop the feed to the main supply pump. To check it you can put a fuel pressure gauge on the outlet fitting of the tank flange and make sure you're getting 3.5 psi. If not, you may have a bad boost pump, or more likely a cracked hose. BTW is OK to deadhead test the in-tank boost pump. It is NOT OK to deadhead test the main supply pump (because it can produce VERY high pressure when deadheaded).

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post #27 of 28 (permalink) Old 06-20-2006, 07:27 AM
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Quote:
Originally Posted by Donny
Thanks again to those who pitched in with idea's, and my appologies for dragging it out with a simple wire swap. RoadTrip, you seem to always be right on, thanks!
Indeed....nice remote analysis, John

Mike Pate
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post #28 of 28 (permalink) Old 06-20-2006, 07:47 AM
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Call APE, I am sure they can fit you with a good intank pump assembly for a pittance. You will need a 12v source at the tank to run it. See if you have a 3 wire setup going to the fuel guage. One is 12v, one is ground, and the other goes to the gas tank guage. That I see new pumps on Ebay all the time for the intank pump. I just sold a couple a few weeks ago that I didn't need anymore.

Christopher

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