tailpipe

I find a few drops of muratic acid inside the WUR screens for a couple hours makes a huge differance in being able to get your presures to stay consistant. It seems they fill up with sediment under the screens you can't see it but the fuel sure sees it... The acid wont eat the metal just all the crap that is inside it some I have had to do a couple times to get them cleared out. When you drop the acid in the screen side you should see it come up the other side if you don't see it in the other side its still plugged with sediment

LT Texan

How, after all these years, did I miss this tip?

I removed the copper sealing ring and gave it a quick polish with 1000 wet/dry and WD40.

Heated it with a torch, let it cool.

Worked like a charm.

Thanks!

LT Texan

I hate to say it, but might be time to give up on this WUR. It seems the control pressure range is too wide. When the warm control pressure is good the cold pressure is too low and visa versa.

I stopped hammering (almost) and used a vise to press the mounting stud in....



And press it out....



repeat, repeat, repeat, repeat...........

Even wired up the heater to see where the pressure went over time.



But to get the warm pressure in the ballpark range, the car hated the low control pressure.

I'm talking like 12 psi (about 40 degrees) and 47 psi. And then the pressure seemed to sneak up a bit.

I did pop the mounting stud with a hammer a couple times with the WUR in line and the gauges hooked up. I could see the control pressure move. (I settled on 47 psi warm.)

I'll see in the morning.

But the high control pressure keeps leaning it out under light/medium loads.

System pressure is 74 psi - in spec.

Is this my excuse to buy an Unwired Tools WUR?

jpitman2

I would have thought 47pis hot would be OK, but it might depend on where the mixture control screw in thr FD is as well. Same goes for 12psi at 40F. What symptoms are you getting at those pressures that show its not happy ?
I contacted Unwired tools and quoted my 83 Euro which does NOT have an O2 sensor, and they went very uncommunicative...
Have you cleaned out the regulator assembly, replaced the O-ring etc? In the few experiments I have done, the wrong thickness of O-ring can produce odd results.
Have you tried the hot control by assembling without the heater in place, just the springs and pin on the regulator?
jp 83 Euro S AT 55k

linderpat

great thread. This should also be in the 928 DIY section.

LT Texan

I've adjusted the A/F ratio to around 13.5 - 14:1 at idle for now.

Driving with no load, it stays there.

Press the throttle and it leans out dramatically.

When I got it to 47 psi warm control pressure, seemed better, but then I got horrible hard starts and initial poor running for a minute or so until the heater started raising the control pressure to around 30 psi or so.

I'll jump in again today, but my wife is dragging me to a much needed trip to the clothes shop right now.

rjm65

Pushing the pin in/out only adjusts cold control pressure. Turning the hex on the bottom of the diaphragm (where the coil spring is inside the WUR) in the WUR adjusts the warm control pressure. Maybe I missed it but didn't see any mention of making an adjustment on the warm control pressure in the thread.

Raymond

Dennis Wilson

Dan,

Since you were missing the small o ring on the relief valve plunger, it has probably broken up and stuck in the FD return manifold or in the return line. This would cause your high system pressure and cause a bleed off through the decoupler orifices in the distributor which could be the cause of your weird control pressure. I would try removing the access bolt on the side of the FD return manifold and put back pressure on the return line to see if it frees things up.

Dennis

LT Texan

Thanks Raymond. I gave that a try with good results.

The hex screw look out quite a bit, so I thought i'd start with turning it clockwise 2 turns. I then set cold control pressure at 17. Then warm pressure measured:
28psi @ 1 minute
42psi @ 2 minutes
51psl @ 3 minutes
58psi @ 4 minutes

58psi - 17psi = 41psi differential

This compared to 47psi - 12 = 35psi differential

So I turned the hex screw 3 turns counterclockwise and set cold control pressure at 18psi. The measured warm at:
31psi @ 1 minute
41psi @ 2 minutes
42psi @ 3 minutes (topped there)

So, 42 - 18 = 25 differential (now we're talking!)

Running warm control pressure goes up to 50psi with the vacuum connected.

Took it out for a spin, and I no longer get leaning out!

I'll let it completely cool down and measure again.

I don't think I can forget about the FD pressure regulator.

I don't think it is perfect yet, but I'm on the right track!

jwillman

Dan,

I would love to see a summary of what finally worked once your done. Great thread!

LT Texan

Dennis, haven't gotten the plunger out yet. I need to. The o-ring on the needle assemble was missing. (I don't recall removing the needle assemble and it is a rebuild FD from 1995-ish.) Put one on that I had on hand. It is black and "looks right."

Will probably break down and buy the kit. Raymond has given me a link to one on Amazon.

checkmate1996

What was the A/f testing gauge from summit that you bought?

Also, I modded my wur with the screw trick to adjust pressure on the fly. That is very helpful when diagnosing issues. You don't have to take the WUR off every time to make adjustments. That's a real PITA...

LT Texan

AEM A/F gauge kit from Summit. About $325 if I remember right.

LT Texan

Had a bit of time to mess with it today.

I found that the hex screw under the vacuum enrich effects the pressure by increasing or decreasing the range from cold to warm pressure.

Turning the screw counter clockwise decreases the range. And clockwise increases the range.

Of course with the complication of moving the heater mounting pin up or down.

So I unscrewed it a bit. (I ended up turning it about 1 1/4 turns.)

Pressed the heater pin out of the body (so I could tap it back down later.)

Put everything back together and installed the WUR (no wires or vacuum lines).

Jumped the fuel pump and read the cold control pressure (high as expected).

I tapped the pin down with a 1/4" drive extension and a hammer watching the pressure gauge.

I got it adjusted to 15psi (probably good since 17psi is for 50 degrees and it was a bit colder than that).

I then energized the heater and watched the pressure increase. It came up to 40psi.

Finally I used a vacuum pump to hold 15psi on the vacuum enrich and the control pressure rose to 46psi.



I've left everything hooked up and will check again Thursday just to make sure since these readings are pretty much perfect!

jpitman2

Once you have pressures that give you acceptable cold starts and good driveability, up to and including heat soaked right through, then you can tackle the mixture screw under the air intake, preferably with an exhaust analyser on it. that adjustment is SENSITIVE!
I found that idling testing of hot control can be misleading - you think its good (< 50psi), but some real work can lift the temp and the pressure, and you lose power again.
jp 83 Euro S AT 55k