Priming The Pump

[Jetaway]

No question this time, just something that may help someone some time.

My gauge works, and seems at least consistent, however, the markings on the gauge don't correspond with the needle. That is, it never shows (F)ull and I remember going pretty far once when the needle had hit (E)mpty.

The gauge was registering "E" so I thought it would be a good time to drain the tank and measure then resistance of the sender after adding a known quantity of gasoline to the tank. I'll be posting pictures of the gauge and resistance measures in another thread in the next day or two.

My fuel pump is a generic electric "thumpa-thumpa" type installed at the tank, with a filter between it and the tank. The mechanical pump has been removed and replaced with a cover plate.

Drained the tank, all 3 and 1/4 gallons of it (With the gauge on 'E!'), measured the resistance, snapped a couple of shots of the gauge and poured the gas back in. Started right up but by the time I had it out of the garage and down the driveway it coughed and died. Wouldn't restart. My first thought was that the slight incline of the driveway had moved the gas away from the pickup, though my 2nd thought was 3 gallons was a heck of a lot of gas to have unavailable in the tank. I rolled/pushed it onto the level street and tried again. Nope. Took the other vehicle down to the corner gas station and bought 2 gallons, put it in the Z and tried again. Nope.

Thought about what I had done while draining the tank -- that was it, all I did was drain the tank, measure the resistance, then refill and measure again. Maybe inadvertently knocked off the hose to the tank? Nope. A vacuum in the tank? I took off the gas cap and tried again. Nope.

Arggh.. Wasn't planning on car work today. Pulled the fuel hose at the rails, seemed a bit dry, put the hose into a container and turned on the ignition. Thumpa-Thumpa, but no gas. Connected the hose back up, pulled the hose at the entry to the engine bay fuel filter. Plenty of gas there, but when I turned on the ignition, again, no gas. Went a got a big-arse (2 oz, to be technical about it) syringe that I picked up at a scientific supply store, stuck it in the fuel hose and pulled the plunger. It filled with gas. I pushed the plunger back in and was going to ask my wife to come and put her ear to the gas tank to see if she could hear anything but instead decided to test the pump again. Put the line into a container, turned on the ignition and TA! DA!, it had started filling with gas. Connected the gas lines and I was on my merry way.

What I found really interesting about this was that last spring I drained the tank to clean the sending unit and replace the leaking sender gasket. I didn't have a large enough gas can at the time so I had put a couple of gallons into the other vehicle and as a result put, at most, 3/4 of a gallon back into the Z. Started up and ran with no problem, with the same fuel pump. When I installed the pump three years ago, I didn't have to prime it either. Just replaced the old one and was on my merry way.

The only change that has occurred is that the pump has aged a year. (I replaced both fuel filters last summer) When newer, it didn't require priming, now, a little older and no wiser, it does. Seems like a good excuse to get a quieter centrifugal pump come spring.

Chris

[240260280z]

I think that a fuel primer bulb between the tank and the pump would be a good thing.

[5thhorsemann]

Sounds like the check valve in the thumper pump is leaking and beginning to fail.

https://www.pegasusautoracing.com/productdetails.asp?RecID=8674

These are the pumps that were installed on the 240's to eliminate the vapor lock issue. The problem with the cyntrifugal pumps (I've heard) is you need to run a regulator to get that low pressure that the SU likes. By the time you get the CF pump and reg, you're way above the price of the Facet pump. Just MHO.

[Oiluj]

I think that a fuel primer bulb between the tank and the pump would be a good thing.

Have one of those in-line for bleeding the 13 HP diesel in my small sailboat.

[Captain Obvious]

I think that a fuel primer bulb between the tank and the pump would be a good thing.

Yeah, Sometimes Ol' Bessie just won't leave the barn until I give her a quick milking :laugh:

[Jetaway]

Sounds like the check valve in the thumper pump is leaking and beginning to fail.

https://www.pegasusautoracing.com/productdetails.asp?RecID=8674

These are the pumps that were installed on the 240's to eliminate the vapor lock issue. The problem with the cyntrifugal pumps (I've heard) is you need to run a regulator to get that low pressure that the SU likes. By the time you get the CF pump and reg, you're way above the price of the Facet pump. Just MHO.

Yeah, I know that a centrifugal pump run considerably more than a thumper, but man, that thumpa-thumpa annoys the heck out of me.

Chris