Help testing warm control pressure
 

In the next few days, I'll be testing system and control pressures in my car.
My question is, is there a way to keep the WUR heating element switched on without the pump working all the time ? some shunt ?

I always pull the plug on the WUR giving me cold pressure then plug it in for the time for warm up.
Bruce

I may be wrong, but I would think you could just pull out the fuel pump relay...should be the red one under the hood.

A 74 doesn't have a fuel pump relay.

On my 75, there is a 2 wire connection to the fuel pump in the left front of the engine compartment, directly below the fuel filter.

FP and WUR........
 

prebordao,

For the '74 & '75 CIS, the WUR's heating element won't get energized until the alternator starts to run or operate. To answer your question, you could make the WUR's heating element ON with the FP shut off but why? How could you test the fuel pressures with the FP shut off? Would you like to share with us your objectives? Thanks.

Tony

To clarify, I want to test the pressure with the pump on !
My idea was to keep it off just while the element is heating... but there's probably no need for that and this way I can see if the pressure starts changing or not.

I had the same thoughts as Tony--it can be done but why? You can do your system pressure and cold pressure tests with the engine not running and it only takes a few minutes.

If you want to check just the wur heating element, you can pull the wur relay (round black) in the engine compartment electrical panel and jump terminal 30 (red/black wire) to terminal 87 (red/white wire). Then, turn on the ignition--fuel pump will run and wur will begin to heat up. Or, you can just start the engine and monitor the pressure change as it is running. (See this diagram for wur relay: http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_1973_CIS_add.jpg

This is simpler than I thought. I'll hook the gauge, test cold pressure and turn on engine and let it run...

I had problems figuring what fittings to use from the ones that came with the gauge...

I admit I was in a bit of a hurry, but I couldn't find a combination that allowed me to insert the gauge between the FD and the 2 lines going to the WUR and the throttle valve. I ended up inserting it between those 2 lines, instead of just by the FD. Do you understand ?

I suppose that's the reason I got 3 bars of system pressure instead of 4-5...
we'll have to look again at those fitttings.

bump

The 74 has a throttle position pressure regulator. It is plumbed in parallel with the wur and is also adjustable.

If i understand it correctly, (which is very unlikely), it richens, (allows controll pressure to lower), just off of idle, as well as at full throttle. So, if it is adjusted to come in too soon,it may provide a false reading as you test the wur.

When i picked up my dad's car, the throttle position regulator was disconnected and the car runs reasonably well??

I need to do some more research on this fine bit of 73.5-74 only CIS magic.

HTH,
chris

On the early CIS, 73.5 and 74, you will need to connect the gauge set between the fuel distributor and the throttle positioner. It sounds as if you put it between the positioner and the wur. You are correct on your reasoning, you will get a low reading on the system pressure.

Ossiblue,
Have you used the gauge kit that pelican sells ? If so, do you remember the fittings used ?

1973.5 CIS Pressure test gauge hook up
 

Where does the gauge go?

Between the FD and WUR?

Thanks

On a 73.5, the gauge goes between the FD port and the throttle positioner and WUR. In other words, be sure the line going to the positioner and WUR are on the valved side of the gauge.

Thanks....sorry for the double post.