Fuel Pump Problems

C

CRAIGTERRY

Member
I have a 36 Series 68 with a 37 Flathead in her. I’ve not been able to get fuel through the mechanical pump and have attempted to do so with several pumps. I’m thinking it’s related to the push rod as I get suction on the pump when manually tested. I’m contemplating a 6v pump a oil pressure shut off switch. Few questions:

1.) has anyone had this fuel problem and how’d you fix it
2.) can I run the electric pump through mech pump and use a dash switch so I can manually turn it off (assuming I get mech to work)
3.) the oil pressure switch has 3 prongs - pump - ignition - solenoid. I’m thinking I run the dash switch to ignition prong and solenoid to the starter wire side of the foot starter button.

Would appreciate any wisdom you can offer.
 
Yes - I’ve replaced with new. I tested the electric pump without the switch and she’s getting fuel and runs. However I need to add some safety with pressure switch. I’d really like to use the mech pump and just use electric for priming and vapor lock. Probably should put a pressure regulator on the fuel line as well. I’m using the airtex 6v pump.
 
I have a 6V electric pump on my avatar. It is mounted back near the gas tank and pumps through the mechanical pump just fine. I only use the electric pump to prime the carb.

You lost me on the oil pressure switch. Apparently it is not stock from your description.
 
Lawson Cox said:
I have a 6V electric pump on my avatar. It is mounted back near the gas tank and pumps through the mechanical pump just fine. I only use the electric pump to prime the carb.

You lost me on the oil pressure switch. Apparently it is not stock from your description.
Click to expand...

It’s a oil pressure switch that only gives power to the pump when there’s oil pressure. See pic, trying to figure out wiring for it though.
 

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I think old Chevy vegas , had oil pressure switchs , you could look up the wiring schematic for them .
 
19Fordy said:
Does your car have the short OEM flexible fuel line on the firewall that goes to the pump?
If so, they eventually deteriorate from the inside out. it is similar to this:
https://www.ebay.com/itm/2645947754...55-0&campid=5338722076&customid=&toolid=10050

It might be a good idea to disassemble the pump and check the mechanical pump diafragham for hairline cracks.
Click to expand...

Check - I’m thinking the push rod may not be operating the pump correct. Just not sure how to verify that’s the problem.
 
CRAIGTERRY said:
Check - I’m thinking the push rod may not be operating the pump correct. Just not sure how to verify that’s the problem.
Click to expand...

With the pump dismounted from the manifold, crank the engine and watch the fuel pump push rod. It should have a stroke of 0.2". If not, it is somehow stuck and not dropping down onto the cam. That can happen if the rear cam bearing is just a little bit to the rear of where it should be. Look down into the hole for the rod; you should see only the shiny steel cam surface. If you see any brass cam bearing intruding into the hole, that is your problem. Depending on the extent of the intrusion, you can turn down the diameter of the push rod to pass by the bearing and rest on the cam.

If you are getting proper push rod movement and the pump is working by hand, that leaves the possibility of vacuum leak or obstruction on the inlet side of the pump, either of which the electric pump might be able to overcome.
 
drolston said:
With the pump dismounted from the manifold, crank the engine and watch the fuel pump push rod. It should have a stroke of 0.2". If not, it is somehow stuck and not dropping down onto the cam. That can happen if the rear cam bearing is just a little bit to the rear of where it should be. Look down into the hole for the rod; you should see only the shiny steel cam surface. If you see any brass cam bearing intruding into the hole, that is your problem. Depending on the extent of the intrusion, you can turn down the diameter of the push rod to pass by the bearing and rest on the cam.

If you are getting proper push rod movement and the pump is working by hand, that leaves the possibility of vacuum leak or obstruction on the inlet side of the pump, either of which the electric pump might be able to overcome.
Click to expand...

Thanks for the insight - I’ll check this out and let you know what I find
 
CRAIGTERRY said:
It’s a oil pressure switch that only gives power to the pump when there’s oil pressure. See pic, trying to figure out wiring for it though.
Click to expand...


Easy wiring! Screw the switch into an oil pressure port. The switch has three wires. One goes to a BATTERY source. Another wire goes to GROUND. The third wire goes to the FUEL PUMP. When engine starts and produces oil pressure, a contact inside the safety switch closes, sending power to the electric fuel pump. DD


483196
 
I don't know much, being an 8BA guy, but aren't there two different fuel pump pushrods for the early engines, depending on the intake manifold?
 
Is the fuel line from the tank clear? If it's blocked, you'll not be able to get fuel delivery with any sorta pump! Blow through it to check.
If you manually operate the lever on the pump, does it suck and blow? If so, hear the noise it makes? right...mount the pump on its mount. Turn the engine over observing the push rod. Stop engine whilst push rod is at top of its stroke. Lower the fuel pump on its mount down over the push rod. The mount should stop higher than the flange it bolts to. If you apply more downward pressure, you should hear the pump make the same noise as when you manually operated it. Indeed, if you now bolt on the fuel line flexible hose, [which you have checked eh?] and line from tank by physically moving that pump assembly up and down, it should in no time deliver fuel. If it doesn't even make that noise, the push rod is not contacting the pump lever.
 
tubman said:
I don't know much, being an 8BA guy, but aren't there two different fuel pump pushrods for the early engines, depending on the intake manifold?
Click to expand...

You are correct. Aluminum valve chamber cover utilizes a rod that is fully one inch shorter than the cast iron cover's counterpart.
 
Kube said:
You are correct. Aluminum valve chamber cover utilizes a rod that is fully one inch shorter than the cast iron cover's counterpart.
Click to expand...


Aluminum manifold takes a 7.87" rod, whereas the iron manifold takes an 8.87" pushrod. DD

.
 
There are different aluminum intakes, some have the lower mounting height, but not all of them. Look at a 34 or 35 'camel back' intake, it has the taller height and takes the longer pushrod.
 
If you want to have an oil pressure safety switch, then these are normally open (NO) and they close when you have oil pressure (usually rated between 2 - 15 PSI - depending on the vendor). This ensures that the pump only runs when the engine is running.

Now, if you want to be able to prime the carb, then you need a push-button bypass switch to power the pump (momentarily) before the engine is started.
 
CRAIGTERRY said:
Thank you V8 - I suspect this is the problem as the fuel push rod came out of a different engine. I’ll check it out today.
Click to expand...

Push rod is 7.90 and it’s too short, will order 8.90 and see if that fixes it.

Fuel pump and oil pressure switch working. Put in a under dash toggle switch so I can turn it on and off. Wiring for oil pressure switch is from pump to oil pressure switch, oil pressure switch to starter side of solenoid, oil pressure switch to under dash toggle and the under dash toggle to battery (with inline fuse). This way the pump is energized by solenoid initially then by oil pressure once started. I will need to put a regulator on it as the pump is putting to much pressure on the carburetor.

Now I have a thermostat issue, thinking they’re stuck closed as radiator dumping coolant from overflow tube. Ugh
 
If you fill the radiator right to the top, it will dump out the overflow tube as the coolant heats up and expands. It will find its own level.
When its found its own level, it'll be full at operating temperature. When the coolant cools back down, the level will drop, normally just covering the top of the tubes. That is normal. Your modern car does exactly the same except the coolant goes into a catchcan, whereby it can syphon back into the radiator. So, you can do much the same with your 36...run the end of the overflow into a catchcan, by extending said overflow with a hose that'll go to the bottom of the can. Make sure your radiator cap seals. Fill the radiator and drive...the expansion will run through the overflow into the can. However, the radiator will still be full. When you allow engine to cool down after switching it off, the coolant in the catchcan automatically syphons back into the radiator. Result; radiator will remain full at all temperatures. I use this exact system in my 35, have done for years. Works extremely well
 
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