CIS Fuel pressure test results for scrutiny

[mike sampsel]

All tests done with engine not running.
US 1978 SC
WUR no. 911045 (hard to read with scope) sure it’s orig unless changed before ‘84
Resistance of WUR 24 ohms (100 ambient temp)

Bleed the gauge to expel air
All units Bar

System Pressure between 4.6 and 4.7 (Needle shakes between)
Cold WUR (power off) 2.2 (Needle steady)

Add power to WUR

Min. Bar
1 ... 2.55
2 ... 2.7
2-4 ... 2.7

update 8/12

WCP with 16" Hg:
ambient temp 90 deg F; 32 deg C
3.2 Bar at 1,2,3 min

end update


Seems to be right on the cusp of too low, unless those numbers in manual are only for running engine and ambient temps on the x axis.

Shut off key pressure dropped immediately to 2.0 bar from 2.7.

Time (min). Press Bar
5. .... 1.5
10. ... 1.38
15. ... 1.25
30. ... 1.0
40. ... 0.5
60. ... 0

All things considered what’s next if anything?
Seems my WUR pressure is a tad on the low side to me. Should I run the WUR test with or after running the engine too?

Took screw off bottom of accumulator and no leak. I don’t think I have a hot start problem. But after a week of sitting it takes lots of cranking (and some backfire) to get it started. Pretty sure the fuel needs priming.

Thinking I need to test residual pressure after running the engine.

Suggestions welcomed.

[proporsche]

those numbers do not look bad even the leak after shutting the engine is ok ...how is your cold start injector is the Q
How is you sensor plate adjustment??
Tony will tell you exactly what is up..
Ivan

[mike sampsel]

Originally Posted by proporsche

those numbers do not look bad even the leak after shutting the engine is ok ...how is your cold start injector is the Q
How is you sensor plate adjustment??
Tony will tell you exactly what is up..
Ivan

Ivan,

Thanks my CSV is hooked up (but I can double check), not sure it's squirting though.
I wonder if there is a test for the CSV in situ?

Sensor plate height is good, at least it was, I can check.
As you said, Tony is the one who knows more than "all the rest combined" about CIS.
No offense meant to others by my exuberance here.

Hope all is well in Bohemia!

[boyt911sc]

Mike,

I don’t see the value for the WCP (with vac.) in your post. The WCP (w/o vac.) was 2.7 bar (39 psi.). The spec. range is 39~45 psi. Adjust it to 42 +/-(1). You will need a hand vac pump to measure the WCP with vac @ 16” Hg if the engine is not running and using the FP only.

Test the CSV to confirm its operation. A non-operating CSV will cause a cold start problem. Test and confirm. You need to remove the CSV from the motor to be able to test it and confirm that it is spraying sufficient fuel for cold start.

Your fuel pressures (control and system) are still within specifications but at the low end of the range. The residual pressure is good.

Tony

[mike sampsel]

Originally Posted by boyt911sc

Mike,

I don’t see the value for the WCP (with vac.) in your post. The WCP (w/o vac.) was 2.7 bar (39 psi.). The spec. range is 39~45 psi. Adjust it to 42 +/-(1). You will need a hand vac pump to measure the WCP with vac @ 16” Hg if the engine is not running and using the FP only.

Test the CSV to confirm its operation. A non-operating CSV will cause a cold start problem. Test and confirm. You need to remove the CSV from the motor to be able to test it and confirm that it is spraying sufficient fuel for cold start.

Your fuel pressures (control and system) are still within specifications but at the low end of the range. The residual pressure is good.

Tony

Thanks Tony,


Is a hand held vacuum pump (brake bleeder style) accurate enough for the 16" of Hg?
Is another option to test WCP with the engine running at say 1600 rpm?

Guess I'll confirm the goodness of the wires related to the CSV first, before I get the nerve to pull it.

Can the CSV can be removed and installed with the motor in situ? I think found where it can be done with a partial engine drop, the testing of it is another issue, I'll worry about that step when and if I get it out.

[boyt911sc]

Originally Posted by mike sampsel

Thanks Tony,


Is a hand held vacuum pump (brake bleeder style) accurate enough for the 16" of Hg?
Is another option to test WCP with the engine running at say 1600 rpm?

Guess I'll confirm the goodness of the wires related to the CSV first, before I get the nerve to pull it.

Can the CSV can be removed and installed with the motor in situ? I think found where it can be done with a partial engine drop, the testing of it is another issue, I'll worry about that step when and if I get it out.

Mike,

I could remove/install a CSV in situ because I have skinny forearms and weighs less than 140 lbs. soak & wet. Most male adults would have bigger forearms than me and will have trouble reaching the CSV without doing a partial drop. A couple of inches additional clearance would make the CSV removal more convenient.

If you decide to do it, these are some tips to consider:

• Tie a long string to the Allen wrench because once you drop it behind the motor, retrieving it is next to impossible.
• Use inspection mirrors or better a remote camera.
• You could test the CSV using the existing fuel line but will not work for CIS with metal fuel lines.

If you are able to remove the CSV from its mount, I could do the test myself. It takes me less than a minute to do it. I have been doing the testing for several members now.



The top row with X were defective and bottom row passed the tests.


From the lot of used CSV I have accumulated, 50% were bad. It would be prudent to include testing the CSV when you are having a cold start problem.

A Mity hand vacuum pump will do the job for measuring WCP with vacuum.

Tony

[mike sampsel]

I like your string idea, I found it in one of your posts (2010 circa), here is the picture for reference




Thinking a dab of weather strip sealant to the wrench will help me not drop the allen bolts.

[gomezoneill]

You might want to test the thermo time switch.

[mike sampsel]

Originally Posted by gomezoneill

You might want to test the thermo time switch.

Should be an easy test, thanks, I'll get to it.

[mike sampsel]

Bump, I updated numbers in my first post, and apparently an edit does not renew the thread ... voila ...

[mike sampsel]

Originally Posted by gomezoneill

You might want to test the thermo time switch.

Okay, (with both wires disconnected to the TTS) I applied 12.1 volts to the yellow wire side of the TTS and I got 12 volts on the other terminal (red and black wire side), so the loop to ground looks good and the switch is likely okay.

Question:

With both wires connected to the TTS, seems I might apply 12 v to the yellow side and this should activate to CSV. I should be able to smell some gas inside the airbox? If not the CSV has an issue perhaps, connection or other? If so it still might have an issue I.E. lack of atomized fuel. And the easiest way to do this is run the starter with the rotor out of the dizzy so it won't fire (but I need an assistant).

[mike sampsel]

Update on the hard to start after a long sit issue:

Verified the wiring to the TTS comes right off the starter solenoid.
There is 4.3 ohms resistance (between the yellow and the R/bk wire, when taken off the TTS) with the yellow wire off the starter.
This seems to be about right and would indicate the plug is on the CSV.

*** warning ***?
Only measure 9.3 volts at the yellow wire when cranking. The raw spade at the starter solenoid measures 9.5 volts. This seems low as the consensus in the forum is 12 volts.

So perhaps the low voltage to the CSV is contributing to the long crank times after a week long sit without running? There is enough current (amperage) to cause the TTS to open circuit after a few seconds, but maybe not enough to cause the CSV to spray properly?

Might run some tests where I switch 12 v to the W side (yellow wire side of TTS) at cranking with the wire off the starter. To see if this causes better startup after a long sit. I do not want to pull the CSV if it is functional

[mike sampsel]

Car has been hard to start when sitting for a while (10 days or so), now it is also hard to start when hot (after a hot soak on a long hot drive).

So I hooked up my fuel pressure gauge:
with off switch on the WUR side:

System Pressure 4.7 BAR check
WUR wire off "cold": 2.4 BAR @ 32 C

Wire on WUR, start car run for 3 min: 3.4 BAR ambient of 32 C, vacuum line attached

As best I can tell, all good again?

With key off the pressure quickly goes down to 24 PSI
Residual pressure measured with the switch open at the fuel distributor:

2 min 24 psi
7 min 22 PSI
10 min 1.5 BAR
15min 1.4 BAR
20 min 1.3BAR
25 min 1.3 bar
30 min 1.3 BAR
35 min 1.1 BAR
40 min 1.0 BAR

Is it critical to test the WUR with the cable removed and then B+ direct to the WUR?
This is per the "blue" Porsche CSI troubleshooter, page 18.

I guess I need to start car and run for three minutes and

test residual with the pressure gauge switch off

10 min 1.5 BAR
Switched switch open
No change in the residual pressure

Not sure what to do next, everything seems to check okay. It is possible the cold start valve dribbles when it is hot and gets thing rich. But I had the TTS disconnected yesterday when the difficult hot start occurred.

I guess one thing I think I'll do is get the hose made from the bottom of a three connection accumulator and install a "bigger" fuel accumulator with a return line and see what this does. At least it will reduce a fire likelihood.

Keeping you posted.

[boyt911sc]

Your system pressure is too low @ 3.4 bar. Use the correct control fuel pressure chart for motor and set them accordingly.

Tony

Edit: Your system pressure was 4.7 bar not 3.4 bar. Mis-read your numbers.

[Alan L]

Tony - the SP is 4.7 bar - is correct.
WP @ 3 min of running is not very useful as a number.
Alan

[mike sampsel]

Originally Posted by boyt911sc

Your system pressure is too low @ 3.4 bar. Use the correct control fuel pressure chart for motor and set them accordingly.

Tony

You might have seen an older post, where I made the rookie mistake of getting the fuel pressure gauge switch towards the FD and not the WUR, I fixed that error and now the SP is 4.7 BAR.

[boyt911sc]

Mike,

It has been a while since you did the troubleshooting. Could you update us about what has been done so far? What problem/s are you experiencing now? Have you tested and confirmed that the CSV is working when cold? No leak? Thanks.

Tony

[mike sampsel]

Tony,

CSV has not been tested. Maybe it leaks when car gets heat soaked? But a hot start, not super hot, is fine. It’s a start after a long sit, and after a long hot drive that are problem starts. Yesterday all the pressure tests I ran looked okay.

Are you still testing CSV’s? I could send them (CSV and TTS) to you, I’d pay for the service.

Mike

[boyt911sc]

Originally Posted by mike sampsel

Tony,

CSV has not been tested. Maybe it leaks when car gets heat soaked? But a hot start, not super hot, is fine. It’s a start after a long sit, and after a long hot drive that are problem starts. Yesterday all the pressure tests I ran looked okay.

Are you still testing CSV’s? I could send them (CSV and TTS) to you, I’d pay for the service.

Mike

Mike,

Send them to me. It would only take a couple of seconds to do the actual test for CSV. Please include a Return Shipping Label (UPS or FedEx). As for payment, I will accept a small cup of black coffee & a donut from Starbucks (coupon no cash). Will PM my address.

Tony

[mike sampsel]

Originally Posted by boyt911sc

Mike,

Send them to me. It would only take a couple of seconds to do the actual test for CSV. Please include a Return Shipping Label (UPS or FedEx). As for payment, I will accept a small cup of black coffee & a donut from Starbucks (coupon no cash). Will PM my address.

Tony

Tony,

Is a USPS label okay? I plan to ship the parts to you next week, likely Monday or Tuesday. Is this time okay? Oh and if my CSV is faulty, is there a way to get a good one from you, if I need one and you have one, I guess we can determine how many dozen donuts that would be.

Mike