Fuel pressure diagnosis readings

[RMG001]

81 SC US. Bought car in rough running condition. Rough idle, would not rev under load, stalling at idle if not manipulated with throttle.
Originally the PO brought to an air-cooled specialist because it was running rich enough that it would not pass a smog test. Due to circumstances with the mechanics health and move to a different shop the car sat for a year. When mechanic resumed work on it he replaced fuel pump, plugs, fuel filter, and drained the fuel tank. Performance was still suffering. Note: only non E fuel was used by previous owner.
Owner retrieved car out of frustration and began trying to tune with the mixture screw. I bought a couple of weeks ago and brought it home on a trailer. Removed plugs, soaking wet after sitting for two weeks.
This weekend started using the CIS for dummies post as a guide along with the Bentley manual.
Have a set of fuel gauges and a multi-meter.
Results of the pressure testing.
Temp at time of testing 70 degrees and stable.
WUR has several identifying marks but I do not see a S/N. See attached photo
System pressure 4.75 bar (with the valve on the WUR closed)
Ohm reading across the two male plugs on the WUR = 3.9 ohms
Opened valve to cold WUR = 2 bar
Plugged in WUR raised pressure from 2 bar to 3.75 in 1 minute 30 seconds.
Residual pressure measurements
1 min 1.9 Bar
15 Min 1.8
30 min 1.6
60 min 1.5
Any insight or interpretation of the results is appreciated. Rob

[boyt911sc]

It looks like you have a -072(?). Could you post the numbers on the WUR? It should be like 0 438 140 xxx. The last 3 digits would identify this particular WUR. Thanks.

Tony

[RMG001]

I do not see any numbers other than this. I have heater hoses out of the way and good light. Do I need to remove to read?
And yes the numbers you are referring to are 072. They are pretty easy to read with good light. Thanks

[T77911S]

I looks like it says 072 on the right side just above the vac line in the pic,

I don't have a chart for the 072 but the pressures look OK for an 81.
I don't know the ohms reading for that WUR but it looks like it is working
good residual pressure

I would pull the injectors and do all flow test on all 6.
the over amount is not important, the balance, spray pattern and no leaking is what you are looking for,
with pump on and sensor plate closed they should not leak.

[RMG001]

Thanks for the feedback! Went to injectors late last night. Really hard to come out, some came out with the entire unit, sorry don't know exact name for the sleeve, others just popped out with the little o ring on them.
Had six clear canning jam jars with the injectors pushed thru a hole in the cap. Turned on the fuel pump with a temp jumper. Only two of the injectors did not leak. Some were dribbling some where spraying.
Pushed up the arm on the intake and got an even spray pattern on all 6. The quantity of fuel in all six jars was visually the same when held next to each other.
So is the initial pressure too high causing the injectors to leak or are the injectors bad and leaking fuel?
Looks to me that they have never been replaced, but I will go back thru the records to confirm. Thanks again - Rob

[Dave Kost]

That would cause the rich running. I knew it would be something simple.

[RMG001]

Dave, would you replace or repair the injectors?

[boyt911sc]

Originally Posted by RMG001

Thanks for the feedback! Went to injectors late last night. Really hard to come out, some came out with the entire unit, sorry don't know exact name for the sleeve, others just popped out with the little o ring on them.
Had six clear canning jam jars with the injectors pushed thru a hole in the cap. Turned on the fuel pump with a temp jumper. Only two of the injectors did not leak. Some were dribbling some where spraying.
Pushed up the arm on the intake and got an even spray pattern on all 6. The quantity of fuel in all six jars was visually the same when held next to each other.
So is the initial pressure too high causing the injectors to leak or are the injectors bad and leaking fuel?
Looks to me that they have never been replaced, but I will go back thru the records to confirm. Thanks again - Rob

RMG,

Unfortunately you just demonstrated that you have a defective FD (fuel distributor). A good working FD should not deliver fuel to any of the injectors when the plunger is down or at rest. If any of the six (6) ports or fuel lines delivers fuel to the injector/s while the plunger is down, you have a defective or leaking O-ring/s located inside the FD. With this FD, you will be lucky to get the engine to start or run consistently. Keep us posted.

Tony

[RMG001]

OK, that is good to know there is a solution for that! I had a feeling we were heading that direction with the amount time it has been sitting. There are some really good posts on here detailing the rebuild and clean process. Drop the engine or try to remove with engine in place?

[Dave Kost]

Originally Posted by RMG001

Dave, would you replace or repair the injectors?

Quick test would be to swap the leaking injectors into the fuel lines that are not leaking. That would determine if its the FD or Fuel injectors.

[RMG001]

Originally Posted by Dave Kost

Quick test would be to swap the leaking injectors into the fuel lines that are not leaking. That would determine if its the FD or Fuel injectors.

Good idea, i read about that and forgot to do that. Sounds like tonight's mission

[T77911S]

could be injectors or fuel head.
the mixture can be set too rich and make the injectors flow with the sensor plate closed,
problem is not all are flowing.

I would send the injectors out to be cleaned and tested.

you could swap injectors that were flowing fuel to the lines that were not and test again for flow with plate closed.

one option you can try, and only do if the mixture screw has been messed AND you can set it back to where it was.
remove injectors from lines, adjust mixture screw CCW, turn on pump then adjust CW to see if all the lines start flowing at the same time and provide the same amount of fuel. but only do this if the same 2 lines failed to flow after swapping injectors.

[boyt911sc]

Rob,

Are you aware that you have the wrong WUR? Unless you have an '80 SC USA engine instead of an '81(?). Keep us posted. Thanks.

Tony

[Dave Kost]

Tony is right. You should have a 090.

[T77911S]

tony, is the 072 vacuum controlled?

[boyt911sc]

Originally Posted by T77911S

tony, is the 072 vacuum controlled?

Ty,

WUR-072 and -090 are used in '80 and '81-'83 CIS with lambda system respectively. These warm up regulators are non-vacuum assisted.

Tony

[RMG001]

Originally Posted by boyt911sc

Ty,

WUR-072 and -090 are used in '80 and '81-'83 CIS with lambda system respectively. These warm up regulators are non-vacuum assisted. Pe

Tony

From my limited understanding... The difference between the two will affect the fuel mixture. Are we that far off western the two?

[boyt911sc]

Originally Posted by RMG001

From my limited understanding... The difference between the two will affect the fuel mixture. Are we that far off western the two?

Rob,

Using the WUR-072 in your '81SC should not be problem at all. As long as the WUR-072 is operating within spec. you will not notice the difference at all. A good working WUR-072 won't be a problem in your engine. They are just referred differently and if you happened to look deeper inside them, you will find the same internal parts. You could call them identical (WUR) twins. The older twin is -072 and the younger is -090. HTH.

Tony

[RMG001]

T77911S, got it we are adjusting mixture screw to reduce pressure. Starting to make sense now. Given the injectors perform as stated

[RMG001]

Lots of diagnostics this weekend. Got the plunger out of the FD and cleaned it with Carb cleaner and polished with a rag. A little spray lube and the plunger is sliding freely. Installed new injectors and now the fuel does not spray with the air plate at rest. Lifting the plate produces a strong fine mist. Volume appears to be consistent with position of plate, raise it and flow increases.
Starts right up but will not take any throttle without bogging and stalling. Backfires out of the exhaust. Does not respond to 1/8 or 1/4 mixture screw adjustments. Turn 1/2 turn to lean and it will not idle or start and 1/2 turn to rich and backfires out exhaust.
Turned attention to the O2 relay.
Checked power at fuse 18, check.
Bench tested relay per Bentley manual, check.
Power to the frequency valve confirmed with probe, and stethoscope on frequency valve confirmed operation.
Checked voltage output on O2 sensor. Confirmed voltage per manual.
Pulled oil cap to confirm change in idle and confirm change in voltage output of O2 sensor, check.
Confirmed voltage at cold start injector when cold, check.
Confirmed no voltage at cold start injector when warm, check.
Built a smoker per you-tube videos. 2 lb of air and copious amounts of smoke. Inserted smoke tube in exhaust and sealed with foam and tape. With all of the heater tubes removed and air conditioning unit removed good visibility at all expected areas, no leakage. Opened pop off valve and confirmed smoke traveling thru engine. No leaks at manifold rubbers, injectors, airbox, or pop-off valve. Used mirrors and plenty of light to look behind engine, nothing. Surprised actually.
Switched out Lambda unit on hunch with a known working unit. No change.

Engine will start right up and happily hold idle at 900 until it runs out of gas or you get tired of breathing the fumes. Absolutely will not take any fuel without bogging to a stall or backfiring out of the exhaust.

Heading to electrical next?