WUR Fuel pressure tests

[LFogelson]

Have an '82 SC with cold start rough running for 1-2 minutes. Just bought a fuel pressure gauge hooked it up to the fuel pressure regulator. The ambient temperature is 60F. Bleed air out of system by pushing up sensor plate. I hooked the valve on the side of the pressure regulator (?backwards).

The cold control pressure was 22.
Started the car and the pressure went to 10 and ran horrible. If I closed the valve the car ran fine. Opening the valve and letting it warmup the pressure slowly raised up to 50. It started to idle smoothly after the pressure was at 22 again.

Why is the pressure dropping when the car is started? And the warmup idle is smooth when the WUR is blocked?

[MotoSook]

Where and how are you hooking up the gauge? Sounds like you are by-passing the WUR with that gauge when you open it.

10 PSI after the fuel distributor will make it run RICH!

You're going to have to explain what you are doing in better details for us to help.

[LFogelson]

My pressure guage has a T connector with the guage on the top and an on and off valve on one side. I had the on/off valve on the Pressure regulator.... So the fuel coming out of the fuel regulator was turned off when the valve was closed and the pressure reading was zero, but the car idled better cold.

[MotoSook]

You have the gauge connected to the outlet of the WUR, and the guage downstream of the valve...that's what I can glean form you post. You've got it all wrong. You don't have a traditional CIS pressure tester, but if you connect the gauge-tee-valve correctly it'll be useful.

The WUR is a "back-pressure regulator" so anything downstream of it is not going to tell you what it's doing, unless there is a restriction downstream of it. By downstream, I mean anything after the WUR in the direction of flow. Since you have the guage installed incorrectly, you are sensing tank pressure when you shut the valve...that's why it's zero.

Put the guage upstream (before) of the WUR such that you can isolate the flow to it to check system pressure and residual pressure. With the valve open you should be reading cold to warm pressure as the engine warms up.

[LFogelson]

I have done a little research. I did the test correct for the warm system pressure. Reversing the side the valve is on only tells you the system pressure (I did this on my warm engine 72). To do a proper cold system pressure the engine should be off with the fuel pump turned on by a jumper relay. I cannot do this today because my engine is already warm.
Does anyone know if the initial control pressure (between the regulator and WUR) at startup is near or equivalent to the cold system pressure?

[MotoSook]

Post a picture of the rig is you can...it'll help.

with a warm pressure (I don't know how you got that with the connections..if I'm right) of 50 psig, you should be fine. It sounds like a simple problem of rich or lean cold start up condition...easy fix, and you don't need the gauge.

OK...no more answers (GUESSES) until you post a picture or clarify...DETAILS...

"NO MORE SOUK FOR YOU!"

[LFogelson]

WUR ----------T--------valve-------Fuel pressure regulator
_____________1
_____________1
___________Pressure
____________Gauge

Test 1: Valve open, engine off, fuel pump off = Pressure 22 at 60F
Test 2: Valve open, engine on = 10 cold and increased slowly to 50 as warmed
Test 3: (during beginning of test 2) Valve closed = Idle smooth, Pressure = 0?

Proper configuration

WUR ------Valve----T--------------Fuel pressure regulator
__________________1
__________________1
______________Pressure
________________Gauge


Test 4: Valve open, engine off = Pressure 22
Test 5: Valve open, engine on (but already warm) = 25 increase 50
Test 6: Valve closed, engine on and warm = 72


I hope this helps clarify.

[clevy70911T]

Check out testing on this site.

http://members.rennlist.com/jimwms/

[MotoSook]

Originally posted by LFogelson

Proper configuration

WUR ------Valve----T--------------Fuel pressure regulator
__________________1
__________________1
______________Pressure
________________Gauge


Test 4: Valve open, engine off = Pressure 22
Test 5: Valve open, engine on (but already warm) = 25 increase 50
Test 6: Valve closed, engine on and warm = 72


I hope this helps clarify.

That is correct, and youy pressures look fine. You might want to check out the "It's that time of the year AGAIN (CIS)" thread.

Your "fuel pressure regulator" is the fuel distributor, correct?

[Paulporsche]

LFogelson,

If your control and fuel pressures are correct, then your AAR or your mixture may be the cause of your rough running during startup. Try just enrichening the mix as Souk mentions in that thread for now. It may do the trick. You may have to up your idle speed when you do this and you may have to set it back when next summer rolls around. If your idle hunts then you are set too rich.

[LFogelson]

UPDATE:

Ran fuel pressure tests properly today. Pressure gauge properly oriented. Cold car. Jumpering the fuel pump relay. Heater connection on WUR disconnected. Motor off.

System Pressure = 70
Cold control pressure = 10
Plug in wur heater connection and the pressure increased to Warm control pressure=50

Note: the pressure of 10 when I was checking with the car running was the cold control pressure (ie. initial "starting" fuel pressure with the car running was the cold control pressure)

I tapped the cold control pressure pin in the wur up, and with the fuel pump jumpered and the engine cold knocked it back down to a cold control pressure of 22. The car now starts well cold.

Thanks everyone for the help. Next project....

[Paulporsche]

LFogelson,

Congratulations. Something I don't understand. Back on 6 Oct your test 4 for ccp yielded 22 PSI, but apparently things weren't right (?). Then you pushed the plug up and then down to get 22 again and now it is fine. Was the original test faulty?

[LFogelson]

The pressure of 22 that I was calling the cold control pressure was the pressure with the fuel pump off and engine cold. I think that was actually the residual pressure the system was holding. To get the cold control pressure the pump should be jumpered (or the car started).