jwillman

Just did an intake refresh and resolved my hunting idle.

Car starts immediately but takes a few seconds to establish and stabilize at cold idle.

Warm idle after cold start is ~850 and the car responds immediately to throttle and accelerates smoothly.

Problem is that when shut down and left for 10-15 minutes it starts immediately but idle is low and rough and the responds poorly to throttle sputtering and almost stalling until you open it up a bit at which point everything clears up and she seems to run normally.

Have pressure gauges but have not checked pressures before as the car has run well in the past.

What else should I look at?

Jadz928

Check pressures and leak down and report back.

jwillman

Hooked up the pressure gauges today. Outside air temp was 71 deg.

Cold pressure with pressure gauge valve closed - 75psi
cold static pressure pump off - immediately dropped to 45 and was slowly dropping.
Engine cold running - 35 psi
Engine up to temp - 65 psi
engine shut down - 43 psi and dropped to 39 psi within 10 minutes

Jadz928

http://928classics.com/4/post/2014/0...ide-78-79.html

Cold and warm control are way high. Check for WUR blockage and adjust.

PS. Pressures can be dialed in with engine off.

jwillman

Jim,
Re-reading the process on your site. I did disconnect the electrical connection for the cold reading but did not reconnect nor block off the side vacuum line for the warm test. Do I need to comply and recheck?

Control pressure, cold:

1.2 bar (17 psi) @ 50°F
2.0 bar (30 psi) @ 75°F
3.0 bar (44 psi) @ 100°F

Note:
Disconnect the elect connector on the WUR, to disable bimetallic heating element.

Control pressure, warm:

2.8 bar (41 psi) to 3.2 bar (46 psi)

Note:
Connect the elect connector on the WUR.
Disconnect the side vacuum line on the WUR and plug hose.

Jadz928

^^^
For an engine running test, yes.

Pulling vacuum on the WUR for warm or cold test will raise pressure.

So did you do the cold test with engine not running?
Warm test with engine running and hose connected?

I've noticed I didn't clarify engine running or not running on my website.
Will go back and fix this.

jwillman

I added additional conditions below in red. Since I am already high and pulling vacuum will raise it more seems I still have the same condition.

Cold pressure with pressure gauge valve closed - engine off, power disconnected to WUR - 75psi
cold static pressure pump off/ engine off - immediately dropped to 45 and was slowly dropping.
Engine cold running, power to WUR disconnected side vacuum connected - 35 psi
Engine up to temp, running , power to WUR disconnected side vacuum connected - 65 psi
engine shut down - 43 psi and dropped to 39 psi within 10 minutes

Jadz928

My additions in 'blue'

jwillman

so when you say "do the test not running" do you mean fuel pump jumpered and valve on the test guage open? Do this with the engine cold and then run engine to warm up, shut down and jumper fuel pump and check warm with test set valve open but engine off?

Jadz928

1. Hook up test gauge
2. Close gauge valve
3. Jumper FP relay #17, pins 87 & 30
4. Read system pressure, make note
5. Disconnect FP
6. Check leakdown, make note of pressure and time
7. IR thermometer on WUR, make note of temp
8. Connect FP
9. Open gauge valve
10. Read cold control pressure, make note
11. Disconnect FP
12. Check leakdown, make note of pressure and time
13. Connect FP
14. Turn ignition switch to ACC
15. Read warm control pressure after the pressure rises (give it 2-3 minutes), make note
16. Disconnect FP
17. Turn off ign switch
18. Compare notes to specs LINK
19. Make adjustments as needed
20. Go have a beer

Guy

Just a note.....on my 79, the WUR heating element gets power once the relay is jumped. I disconnect for COLD testing. Just FYI

jwillman

Ok, here are the numbers. Still looks high. Do I need to take the WUR apart?

4. Read system pressure, make note - 75psi
6. Check leakdown, make note of pressure and time - 31psi at 10, 26psi at 20min
7. IR thermometer on WUR, make note of temp - 78deg
10. Read cold control pressure, make note - 54psi
12. Check leakdown, make note of pressure and time - 28 psi at 10, 24 psi at 20min
15. Read warm control pressure after the pressure rises (give it 2-3 minutes), make note - 58psi

Jadz928

Jim,
Leakdown reads good. System pressure good. Control pressures high.

On WUR, pin down lowers pressure, pin up raises pressure (to raise pressure you have to take apart WUR).

1. Have test gauge hooked up (w/valve closed)
2. Disconnect 2-pin connect on top of WUR
3. Connect fuel pump
4. Take temp reading at WUR
5. Then drive down pin on top of WUR to lower to correct cold pressure spec @ temp, make note
6. Once cold pressure is set, reconnect 2-pin on top of WUR
7. Read warm control pressure after the pressure rises (give it 2-3 minutes), make note
8. Disconnect side hose at WUR
9. Start car and let it get up to operating temp, make note of final pressure
10. Stop car... go have another beer.

Guy

Jim and his site are a BIG help for the CIS crowd. I had similar readings as you and found that I could not adjust the WUR properly until it was cleaned, soaked, cleaned, soaked, cleaned soaked and a new O ring installed. If you cant get the readings to jive, you may have to go the same route as I did.

It takes a good bit of hammering to get the pin and body driven down, you will quickly get a feel for the of it. Let the gauge "settle" as you make the adjustments. Too little is better than too much

jpitman2

Before you start moving things in the WUR, I suggest you verify that the WUR is the issue, and not some other part of the system. With the pump jumpered, gauges fitted showing control pressure, carefully (with extinguisher handy, helper with you), crack open the WUR outlet(wrapped in rag) - if control drops, the WUR is NOT the problem - its further down the line from that union to the tank return. If control stays high, and very little fuel comes out, the WUR is blocked at least partly. If the problem is a new one (ie it used to be ok, and is lately gone bad), try blowing some solvent through the WUR while its intact, or dismantle and clean the interior thoroughly. The brass gauze filter in the inlet is easily clogged with lint and debris.
jp 83 Euro S AT 55k