Proper Technique-Whitney CIS Fuel Gauge

Paulporsche · 01:48 PM

Thanks to Mark87Turbo, I'm about to start checking fuel pressures on my engine. The JC Whitney gauge is similar to but not exactly the same as the one pictured in the Bentley's.

The instructions from Bentley are to close the valve for system pressure and for residual pressure. The pic shows the valve handle in a perpendicular position relative to the fuel line from the FD to the WUR.

The valve should be open for control pressure testing. The pic has the lever parallel w/ the fuel line.

Is this the same for the Whitney gauge?

Also, if the valve is closed, why doesn't running the engine for 3 min prior to residual testing blow out the dial? If closing means no fuel flow gets to the gauge itself, then how can it measure the residual pressure? Should it be opened again after the 10 and 30 minutes?

MotoSook · 08-13-2008, 02:36 PM

Paul,

The gauge should be between the valve and the FD. (If you posted pictures in your thread I can't see them because of the company blocks. I only see text in some cases).

Generally, valve handle perpendicular to line is closed and parallel is open.

The easiest way to understand it all is knowing that the WUR is a valve itself that modulates the control pressure in the circuit back to the FD. Flow is from the FD to the WUR. So if you want to monitor the control pressure, a gauge between the WUR and FD will tell you what the pressure is (no valving needed really). If you put the gauge between a valve that isolates flow to the WUR and the FD, you are reading system pressure (i.e. the pressure builds up if it isn't bled off by the WUR..and now flow is blocked by the isolation valve.)

Residual pressure is with valve open.

The FD has a relief on it to limit max pressure and a pump can only generate so much pressure before it slips or recirc's.

Does that help?

Paulporsche · 03:46 PM

Thanks for confirming and the explanation, Souk.

Here's the procedure though from Bentley's (paraphrasing pp 240-15 and 16):

Close valve. (OK perpendicular to the fuel line from the FD to WUR)
Operate fuel pump w/o running engine (same as when checking system pressure; look for 65-75psi)
(Turn ignition on w/ jumper wire in place and)
Run engine for at least 3 min, switch off and check residual pressure after 10 min and 30 min. (apparently w/ valve closed, because, next: )
If resid press is OK w/ valve closed you can then open it to check the system pressure regulator. If the resid press drops once the valve is opened check line press regulator for faults and , if none found, check the WUR for internal leaks.

So many posters have used the Whitney gauge. Can anyone for certain state that on this gauge parallel is open and perpendicular is closed? And that the procedure outlined in Bentley's is correct?

Finally, the only fuel line to be used is the one from the center port of the FD to the WUR?

MotoSook · 06:37 PM

If those are the Bentley instructions, get a red marker and cross out that page.

Do this:

Connect tester in series with the fuel line leading from the FD to the WUR.

Close the valve on the tester so that fuel cannot flow from the FD to the WUR.

Place jumper to activate the fuel pump and turn on ignition w/o starting the engine.

The gauge reading should be your system pressure.

Open the tester valve and start the car. The tester is simply acting as an inline gauge at this setting.

With the engine running from cold, you'll see your cold start pressure.

Monitor the rise in "control pressure" as the engine warms up the WUR (along with the WUR heater). It should follow the fuel pressure chart for your car. There is a bit of margin in the control pressure here. I've even driving the car with the test in place, but well secured to warm up the system.

Once at operating temperature, turn off the engine (valve still open) and monitor the pressure. The pressure should drop and them stay steady at the residual pressure. If it doesn't, you may have problems with the accumulator, check valve WUR or FD. Suspect the the check valve , then accum, then WUR then FD...will usually be the check valve. A leaking accumulator (the later ones will drip fuel out the bottom.

MotoSook · 08-13-2008, 04:23 PM

If you want to check the valve, just blow on one end and check that air comes out the other end when it should be open.

Paulporsche · 08-13-2008, 06:11 PM

Thanks a lot for that, Souk.

Your procedure makes vastly more sense to me than the Bentley one. I just couldn't see how fuel under 70 psi of pressure was going to run the engine for at least 3 minutes w/ the valve closed!

Your "blow" method confirms that indeed parallel is open and perpendicular closed.

MotoSook · 08-13-2008, 06:39 PM

You're welcome, Paul. Actually, I'm surprised I remembered as much! I haven't tested a CIS car in over four years...LOL!

Paulporsche · 06:45 AM

Good to have this correct procedure "on the record".

I'm now going to check my presures and report in my "Baffling WUR Behavior" thread.

Note: upon doing the procedure I found that jumping the 87a and 30 terminals was not enough to start the FP. On my 77 chassis and fuse box I had to turn the key to the on position.