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Bird-in-the-bush
04-22-2017, 11:01 PM
I'm sure this subject has been presented numerous times, and I did try and research an answer before posting.
Can I get schooled on why the vacuum for the wiper motor is ran from the fuel pump? Was wondering if it has a intermittent vacuum purpose maybe? Or perhaps it can be run off of straight manifold vacuum?
The reason I ask, is I'm chasing a vacuum leak, and would like to start weighing options for conversions, i.e. fuel pump, electric wiper install and switch. I believe in diagnosing problems before just throwing parts and upgrades at it. It may be an OCD of mine, but I won't sleep until I know what the problem was to begin with, even after I upgrade haha...much thanks in advance. I researched the library, but couldn't find an explanation on why the vacuum is pulled from the pump to begin with. Thank you,
Audie.

jopizz
04-23-2017, 12:00 AM
Manifold vacuum will rise and fall as you accelerate and decelerate which will cause the wipers to speed up and slow down. The vacuum from the fuel pump is much more consistent. You can certainly run the wipers off of manifold vacuum. There are multiple vacuum hoses behind the dash for the wipers and vacuum windshield washers so that's where you may have a leak. Disconnect the pipe that goes from the manifold to the fuel pump and plug it. That will eliminate the pump and everything behind the dash. If your vacuum leak goes away then you know it's either in the fuel pump, wiper motor or the hoses.

John

Bird-in-the-bush
04-23-2017, 12:31 AM
This may be a lot to ask, but would you happen to know what the vacuum in inch pounds should be coming from the pump. I'll measure mine, but i would like to know what it's supposed to be at.

KENN
04-23-2017, 12:38 AM
I Am Running Vacuum Wipers Off Of The Manifold And They Do Slow Down Under Acceleration . Where Is The Best Place To Get Vacuum If You Dont Have A Vacuum Fuel Pump? Will A Larger Vacuum Can Help? Or Maybe A Separate One Just For Wipers? Will I Still Need The Can When I Change Over To 8" Dual Booster Disc Brakes? Thanks Kenn

jopizz
04-23-2017, 12:40 AM
This may be a lot to ask, but would you happen to know what the vacuum in inch pounds should be coming from the pump. I'll measure mine, but i would like to know what it's supposed to be at.

You should be getting between 14 and 18 in. of vacuum from the pump.

John

Bird-in-the-bush
04-23-2017, 04:50 AM
Ok, thanks John. I've seen several people have done, or are in the process of converting to the electric wiper motor. Are they replacing their pump as well, or plugging the vacuum lines to maintain the stock appearance? Which pump will interchange with our 352 pumps? Any FE pump im guessing.

JohnG
04-23-2017, 09:09 AM
I checked mine last Fall and was happy to have 20" of vaccum for the wipers.

If you are trying to debug the system and get your wipers running well, I would suggest first running a line just to the wiper motor itself, by passing the washer switch entirely.

Use new hose, put a little grease on any connections to eliminate leaks.

Whatever performance of the wipers you then get is your "best case" scenario, short of sending the motor out for rebuilding.

The switch is, almost without question, a potential source for leaks and thus reduction in performance. If you decide to keep it, carefully check it out and perhaps use some RTV or other sealant.

Check your hoses for cracks (they could be 60 years old!).

I had my motor rebuilt over 10 years ago by Fricken and it still works really well, with the current 20" driving it.

John

PS should you happen to get a fuel pump rebuilt, a good shop can fiddle with the geometry of the arm for the wiper vaccum and gain some additional vaccum over stock.

YellowRose
04-23-2017, 10:50 AM
Audie, if you are not going to use the vacuum line off the fuel pump, you will want to plug it. I will let John or others answer the other questions.

jopizz
04-23-2017, 12:02 PM
Ok, thanks John. I've seen several people have done, or are in the process of converting to the electric wiper motor. Are they replacing their pump as well, or plugging the vacuum lines to maintain the stock appearance? Which pump will interchange with our 352 pumps? Any FE pump im guessing.

There's no reason to replace the fuel pump if it works properly. Either remove the line from the pump and plug it there or plug it at the T connector at the intake manifold. If you need to replace the pump any 352/390 pump will work fine.

John