Windshield washer pump troubleshooting and rebuild

abaird269

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Hi guys, finally got my windshield washers working today in my 73 K20! During my research I didn't find much information on how these pumps worked but it sure seems like lots of guys have a similar problem; hopefully my experience will be of use to someone out there. Once you get your head wrapped around how the assembly works, its pretty simple but if you have a piece missing or worn it makes it much harder to figure out what actually does what.

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This is my old gross pump that doesn't work. I'm not sure what years these pumps were used except for 73, but I believe they were fairly common place across General Motors products.

So you hit the switch and nothing comes out of the nozzles, what now? Lets start with the simple stuff because its easy to overlook.

  • The washer pump is actually driven through a mechanism from the wiper motor, so if your wipers aren't working, nothing will
  • Check for crud in the bottom of the washer fluid tank, there's also a little filter on the feed pipe to the pump so that's something else to check
  • I've found the pumps in these trucks are very susceptible to air in the lines and don't bleed themselves very easy, so any kinks, cracks or pin holes in the feed hose, you're screwed. I also found it helpful to blow through the little vent hole in the top of the reservoir to push fluid through the feed line. DON'T suck the other end of the line to try and prime it, mouthfuls of washer fluid aren't cool!...don't ask.
  • If the lines are good all the way to the pump, check the two lines that split out to each jet. Believe it or not, my pump actually wouldn't prime with the output lines to the jets disconnected. Not sure why, I figured the pump wouldn't care but once I connected them, it primed right up. Guess the pump depends on those output lines being full of fluid to pull from the tank.
Once you've checked all of that out, there's 3 major areas your problem can lie.

1. The mechanism that drives the actual pump has stuck or failed. The biggest part of my problem was the 40+ year old grease on the mechanism had dried up and was more of a adhesive than a grease. If your unlucky and the mechanism has failed, it will be pretty easy to spot. Things that used to be one piece...won't be any more :(

2. The pump itself. More on this later....

3. An electrical problem. If the wiper motor is working, there is a little solenoid that actually engages the mechanism that drives the pump. Since the pump is driven off the wiper motor and you don't want to wash your window every time you turn on your wipers, this little guy is necessary. More info on that below.

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Above is my newly refurbished pump assembly. It could have done with a coat of paint when I had it apart, but I didn't have any to hand so a wire brushing had to do. If you were lucky like me, all your pump assembly might need is a clean up and a greasing to get all the parts moving again.

Red circle: This is were the actual pumping happens. As can be seen the washer pump assembly is actually like 80% just mechanism, the little pump that actually moves the fluid is pretty simple. It's just a little piston that works similar to a typical air compressor. When the piston goes down, a rubber read valve in the head of the plastic piece opens and lets fluid from the tank be sucked in, when the piston goes up the valve closes and forces open the two reed valves that go out to each of the jets. Like all rubber parts, the valves and seals get hard and crack over time. Rebuild kits are easily available from places like RockAuto.

Blue Circle: This is the solenoid that actually engages the mechanism to the pump when you hit the switch. When you do it should get 12v and pull the little retaining plate towards it. With your multimeter set on continuity, you should be able to get a reading of a few ohms through this coil. If not, its pooched and will never engage the mechanism.

Brown Circle: This is the connecting rod from the plastic pump. The wiper motor moves this little rod back and forth. The round grey plastic wheel covering it is what actually governs when the rod can move the pump and how many stokes it can do. The wheel is shaped with a little notch on the underside so that in its idle position it holds the connecting rod back, stopping it from moving. When the solenoid is engaged it releases the arm in the yellow circle and lets it fall onto the grey wheel. The arm then starts to turn the grey wheel which in turn moves the notch and releases the connecting rod. The rod can now move freely and move the pump back and forth dispensing fluid onto your windshield. The grey wheel does one complete revolution until the notch on the underside comes back around blocking the connecting rod from moving once more and stopping the pump.

Hopefully once you put it all back together you should have a functioning washer system. Whenever I did, for some reason when I turn my wipers off they park themselves in the proper place instead of freezing mid swipe. No explanation for why but I'll take it as a bonus! Hopefully this load of waffle has helped someone and your pump isn't toast.
 

shiftpro

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Nice post thanks, and welcome to the site.
What part of Alberta are ya from?
 

74 Shortbed

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Welcome aboard, thanks for the info..:favorites13:
 

Honky Kong jr

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Welcome, excellent post!!!
 

abaird269

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Thanks guys! shiftpro, I'm from edmonton. You're in BC?
 

1973c10

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Welcome aboard
 

LateOnTheBrakes

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Any chance of re-uploading the photos? I'm scratching my head to figure out if my truck has the pump or not. It does not have the plumbing.

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Paladin

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2 types of washer motors, the 1 on the right has the pump built into it. Yours has the pump in the reservoir.
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:cheers:
 

LateOnTheBrakes

5.3-Swapped 86 CUCV
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I don't have a reservoir. Not sure if that was not installed on the CUCV or if it was removed over the years. What is the second connector on the bottom of the wiper motor for then?
 

Catbox

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The pumps are pretty easy to find.
We pulled one out of the junkyard and put it in our truck last week.
In the photo you can see we have connected to the original hoses and pump through it.
Wiring is a simple and easy to hook up.

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LateOnTheBrakes

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Thanks for the info. I'm trying to put it together from the butcher that had the truck before me. I actually don't have the washer fluid bottle, power steering fluid reservoir, etc. The main reason I asked about the washer pump is I'm cleaning up the wiring harness right now and I want to remove all the connectors/wire I don't need with my LS swap. I do not know what the connector looks like for the pump.

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