The Stovebolt Site Forums The Shop Area General Truck Talk Vacuum Wiper question and update

Now that the rainy season approaches, and I've done all I can about the trucks windshield wiper system (new arms, blades, connector grommets, and supply hose), it still isn't doing its job right. It will get most of the way across the initial sweep, and I'll have to turn it off to return to the down position. So here's my question- The fuel pump doesn't have the vacuum back up, so I'm running on just the vac supplied at the carb base. (This is a rebuilt '56 235 on my '51 3100). The fitting on the carb has a T fitting for the vac. I want to get an electric pump, but the wife is nixing the $220 right now. Would it be worth buying the $90 fuel pump with vacuum? Bad side of this is it has a nearly brand new fuel pump, so I don't really need one. But I sure as hell don't like driving in rain with useless wipers. Yes, I know the electric would be better, but that's not going to happen til Spring is over at my house. Thanks for any input on this, folks! Lee

Dry windshields and vacuum wipers aren't a good mix. Try it wet.

Using Rain X usually eliminates the need for wipers at highway speed.

The vacuum needs to come from the manifold, not the carb. The carb vacuum is strictly for the vacuum advance.

I found with mine, the new wiper arms have a lot more tension than the old ones and the wipers don't work well with them.

thanks, cletis, but the other day when I gave it the first "real" test, it was coming down really good. I had read on here when I first started rehabbing this section, that they were almost sure to not work when dry, so I've waited. Funny thing is, yesterday when the wife got in with me to go somewhere, I had forgotten to turn the switch off and they worked great, like they're supposed to, until I turned it off, and it was dry and warm out. (???) Of course as soon as I turned it back on, it was back to normal. Wouldn't hardly budge.

truckernix- It was from the manifold, just underneath the carb is what I meant. You can see it on the 3rd pic in my signature spot. (Shown the way it was when I bought it. The two hoses were plugged with screws, so I bought new hose and replaced the old one, and put a rubber cap on the forward fitting.)

What I was asking about also is that fitting. When the dual action fuel pump is hooked up, would it be correct for both the wiper hose and the gas pump vacuum tube to both enter the vacuum at a 'T' type fitting on the manifold? Not quite sure I understand the mechanics of hooking up the two on the same T, which seems like it would bypass the manifold.

You connect the vacuum side of the pump to the wipers. The air outlet side of the pump connects to the manifold. At low speed and high vacuum the motor pulls vacuum through the pump. At higher RPM and low vacuum, the pump supplies the needed vacuum. The pump will produce less vacuum then your motor and only helps at high throttle/low engine vacuum situations. In other words it only helps going up hills.

My wipers didnt work Well either before. Unlike you though, i didnt want to "uppgrade" to electric. So what I did was that I took out the wiper "motor", took it apart, cleaned it, regreased it with grease that wasn't to thick and sprayed some wd40 in it. Then I changed the springs on the wiper arms to make sure they really push the whole blade against the windshield. Worked like a charm!

I like the vacuum wipers with the electric pump because you have an infinite number of wiper speeds. I sure don't pay $220 for one but just go to a pick and pull yard and get one from a Mercedes diesel for $10. Not even an electric pump with a steady 20+ inches of vacuum will make a worn out wiper motor work so it's sent off to Ficken first thing. Pump takes 12v negative ground.

truckernix- my wiper motor only has one inlet/outlet, so this is kind of confusing. I noticed in the manuals that there are some with 2, and to be honest, my truck came with two spare pumps, which the PO tells me that one is "in real good working order". (Wish he would have put that one on in the first place!). But all of them only have one hose port. I did spray some silicone lube spray into the motor while I had everything apart, but without it being hooked up, I don't know how much made it in, or the condition of the inside of the pump.

Raoul and coilover- thanks very much for this info. too. It really helps me understand what's going on with it. Think I'll take one of the spares apart and see what's going on inside those things, and try to figure out which one is the "good" one.

So, repeating one of my questions, Do the dual action fuel pumps really help with these wipers? Is it worth buying an unneeded fuel pump? I've read a couple of threads in the search section where guys say no matter how well these things work, they're insufficient when you really need them. And this truck is now my daily driver, which means I can't take any chances on wipers that won't perform if I'm on the highway (or hilly, curvy backroads) in a down pour some day/night. Thanks again, guys! Lee

Are you asking about the pumps or the vacuum motors? Vacuum motors have one hose connection and the pumps have two. If you want good dependable action, go electric.

Here is the theory in the shop manual. Shop Manual Explanation

Thanks, tn, I was asking about BOTH of them. Whether to spend $90 on a dual action fuel pump (is it worth buying an unneeded fuel pump, and will it even work well enough if I do?), or save my money and time and wait out the rainy season (not really an option since this is now my daily driver) till I get the extra $220 for an electric wiper motor, so as not to upset the missus too much at one time. She's been really patient with me spending LOTS of money on parts for both the "new" '51 and the Indian Chief's winter work. Sorry, I guess I didn't make it real clear, there. Sometimes I type faster than I think. Thanks for the link. I have this manual, but never noticed this page until you posted it. Thank you.

I put a new dual pump on my truck, a few years ago. I had trouble with the pump leaking gas and oil. A replacement unit did the same thing and I gave up. I think the name was something like "Airtex". Another point of interest was that the spring tension on the actuator arm was much greater then the ordinary pump. It was so high that the only way I could move it was to hold the pump and push the arm against my work bench. I didn't actually like the idea of that much tension on the cam lobe.

Ok, then, bud, you just answered my question, and I thank you for being honest about your experience with them. I was going to order through classicparts, though I don't know where they get theirs. I was reading through my shop manual last night on the section you referred me to, and it seems like there was something mentioned about one of the actuator arms was 'tighter' than the other, since there are 2, one to operate the air and one to operate the pump. The "eccentric", as they call the arm that rides the cam, has always seemed VERY tight on any I've ever had off, unless it was just shot. I actually have another spare fuel pump (with the original fuel filter bowl), that I thought about rebuilding, if I could find the parts, but it's not dual action, so that would be no help.

The pump I have on now is a new one with no bowl. I can just about work the arm with my little finger. I forgot to mention that the fuel pressure on my dual pump was quite high, around 6psi I believe.

What's it supposed to be? I mean, what is normal for a pump on a 235? Also, what it the normal vacuum pressure?

3.5-4.5 psi at the carburetor