TAREK

'79 sc

Symptoms:
1) Very difficult cold start - backfiring from exhaust - sputtering, etc. Warmer weather makes it easier to start.

2) missing under load - bogs down - as though running on 3 cylinders

3) No issues with restart when warm

I tested the following, using a CIS pressure tester:

Fuel pump pressure (WUR isolated): 68 psi
System pressure (with WUR) : 68 psi (same as fuel pump!!!!)
System residual pressure (upon shut down from warm - with WUR of course): stabilizes around 25 psi

These numbers were different in the distant past. I believe system pressure should be closer to 45 psi if the WUR is doing its job. no?

Is there something I can do to rebuild or adjust the WUR? Any thoughts would be greatly appreciated.

Thanks in Advance
Tarek
'79 sc

TAREK

Correction: System residual pressure upon shut down holds at 25 psi temporarily, but stabilizes longer at 20 psi....and eventually continues to drop very slowly

TIA

tdatk

Tarek,
Try posting this on Pelican technical. A guy named Souk is very good with CIS issues and with any luck he will chime in. HTH

Tim

TAREK

Thanks Tim. I will do that and will post an update

art

The cold control pressure is in the 30's psi,(I don't remember exact value) and the warm is 50-ish, so it seems like your control pressure is too high no matter what.

Do you have the gauge between the fuel distributor and the WUR?

Did you measure cold and hot?

I can check the exact values when I get home if you still need it after looking at PP. They are in the Bentley manual.

TAREK

Hi Art,

yes the gauge is between the distributor and WUR, and both cold and hot measure the same.

Would greatly appreciate it if you can look up the exact values. Thanks a bunch
Tarek

art

I'll check tonight, but you clearly have a problem if cold and warm are the same (too high) value. The good news is that if the WUR is not bad, you can affect the pressure by shortening the pin that actuates the valve by very small increments until it comes into cold spec, and then confirm when warm.

I posted a long summary of my CIS saga not too long ago to help people realize what can be wrong, sometimes without knowing it. Search my posts if you want to, but I think you know at least one thing that is wrong at present.

tdatk

Tarek,
Just popped in Pelican and saw your post there. Looks like you got some good advise. BTW, I met you at mm1 on the BRP in 2003 at the old hotel. I had the white S4 and had a blast. I'll not bring up the gas pump mishap.....just funnin. Great to meet you though.

art

cold control pressure (at 70F) 2.2 bar(32 psi)
warm with vac line attached 3.2-3.6 bar(46-53 psi)
line removed 2.7-3.1 bar (39-45 psi)

All are with engine running, but you can test cold with engine off to see if you are in the ballpark. I drove around for a while with the gauge on just to montior in all conditions.

TAREK

Thanks Tim. Yes excellent advice on the pelican forum as well. Thank you for recommending it. I will post here when I get to a resolution.

..uh oh...did you witness the gas pump incident? I should swear you to secrecy!

TAREK

Thanks Art. Tomorrow is dedicated to working on the car. greatly appreciate the help. Will post progress

Tarek

TAREK

Update:

Weather is nicer and it's warm outside. Starting is not as big of a problem as it was days ago, but still backfiring, sputtering, missing, etc at startup up as well as when fully warm. low on power and running hotter than usual of course.

I removed and cleaned the WUR. There was some sand, but no t too much in my opinion. No changes. Pressure between FD and WUR still reads 68 psi, warm or cold, electrical plug connected or disconnected, guage valve closed or open. All read the same pressure: 68 psi

I verified there was no blockage out of the WUR and in the return circuit from WUR to fuel tank by disconnecting the return line to the tank (plugged the tank) and running the system. Steady stream fuel out of the return line into the jug I setup. Pressure still 68 psi between WUR and FD in that case as well. Should I be looking for a certain pressure in the return line at the tank?

puzzled
Thanks

art

The WUR is basically a controlled pressure bleed device. If you put a gauge on the output it will just read system pressure.

If you feel confident, take it apart and operate the pin by hand with the gauge connected to read control pressure and you will see the pressure rise and fall as you push the pin and release it. If it is fouled in some way, this will not happen and you will need to fullly disassemble to clean it. You could just replace it, but that is admitting defeat. It is a very simple unit to fool with.

TAREK

Art,
I must be missing something here. I've taken it apart once already, but not sure how I would operate it manually. Sorry I'm not quite getting it...yet. And certainly not ready to admit defeat

thanks again
Tarek

art

If you remove the cover, and remove the spring arm that is held in by one nut you will see a pin about 1/16" dia that goes between the bimetal spring arm (it and a small cup and spring will tend to fall out as you remove the arm) and the actual valve. It is about 3/4" long. Use it or a tool to press into the small 'socket' that the pin fits into and put pressure on the valve. more pressure to close the valve results in less bleed and higher control presure. Once you ascertain the the valve can work, it is just a bit of trial and error with the length of the pin to get the pressure right. You can run the fuel pump without the cover on with no problem. They always seem to migrate to the more closed position over the years. I have been doing this mod since the 80's on VWs, Saabs, etc with CIS. It saves a bit of cash.

If the valve does not work, some careful cleaning may be in order. There is really nothing to fail in these, they just go out of adjustment or get dirty.

Use a bit of grease to keep the pin standing up as you reassemble.