PSI output CCKW fuel pump

[Bill_Wolf]

I know I have seen this but can't find it now (of course).

What is the PSI output of a CCKW late war fuel pump?

Bill

[mudflap]

Not sure about late war pumps, but my July '43 copy of TM 9-1802 has this procedure in Chapter 8, Fuel System, Section VIII Fuel System Test and Adjustment:

" (2) Test for Pressure. Connect gage No. 41-G-500 to disconnected fuel line at carburetor end by slipping gage hose over end of line. Start engine and run at speed equivalent to approximately 30 mph vehicle road speed. (Engine will run on fuel already in carburetor.) Observe pressure reading registered by gage. Pressure should be within 2 to 3 1/2 pounds."

Best Regards...

[Gordon_M]

That sounds about right. 2 to 3 psig should be fine.

I've seen a lot of talk about problems with electric pumps that really can't be dialled down to deliver less than 4 psig, and electric pumps seem to be commonly fitted where the real problem is blocked lines, filters, and deteriorating hoses.

[dr deuce]

All mine have electric pumps and have never had a problem. Think about it; the gasoline in the carb evaporates from sitting a few days. That is why they have the primer lever on the pump. Or you can take it out on he starter if you are lazy, or you can use an electric and wait for the clicking to slows down. I almost lost the engine in my GPW from a crack in the mechanical pump diaphragm pumping some of the gas into the crankcase! Do you know what they are putting into gasoline this week? Do you know what it will do to that decades old diaphragm?

[mudflap]

All mine have electric pumps and have never had a problem

Dr. Deuce,

So, do you typically run with just the electric pump and bypass the vehicle's mechanical fuel pump? Or, do you run with both pumps in series?

The previous owner of my truck had set it up with both pumps. I like the electric for priming, but I do think about that old diaphragm in the mechanical fuel pump... I'm thinking about bypassing it, and just running on the electric pump.

Also, the electric pump is fed directly via ignition, so anytime the switch is on the pump is running. I was thinking about putting an oil pressure switch inline with the pump so it stops when the engine is not running - including an over-ride button for priming.

How do you usually setup your pumps?

Best Regards...

[dr deuce]

Mine are set up on the ignition switch. I have no mechanical any more. You MUST have a inline filter BEFORE the pump. If not, it will fail. Keep the pump low on the frame.

My latest system has the ignition run off of the HL switch brake feed. If the HL switch is all the way in, no power to the lever ignition switch. The ignition switch feeds the coil and the Panel Light switch then to the electric pump (I don't do blackout rides anymore, too dangerous. Panel lights come on with the head lights). You have to have all three or no ignition, and/or no pump. Makes it easier to use the lever ignition switch and have decent security.

[Motto]

I use a similar setup to power the coil on my WC63. The BO driving light switch needs to be on as well as the ignition switch.
I had a WC51 years ago that had an Autopulse electric pump fitted back near the tank because the PO had experienced vapour lock. It was powered straight off the ignition switch. One day I was manoeuvring the vehicle up close to the house to get it under the eaves and stalled it. Pushing the clutch pedal down I heard a sputtering noise at the same time as the ammeter went crazy. On investigation I found the battery cable had got between the pedal and the chassis flange and the rubber insulation had peeled off. The frightening part was that the copper (non original) fuel line adjacent also had flash marks on it. If luck had been against me and the line had ruptured the Autopulse would have worked its little heart out until the power was turned off, assuming I had the presence of mind to do so and it wasn't too late. I could have lost the truck and maybe even the house very easily that day.
I understand that modern vehicles with an electric fuel pump must by law have the pump powered in such a way that if the engine stops, the pump stops. Mudflap is on the right track.

David