Test Results……….
 

Thomas,

Within an hour after your package arrived at my doorstep, I was able to complete the tests. I usually do the test within a day but never within an hour. Anyway, here are the test results:

TTV………..Defective and leaking. It should be closed at room temp. and could not hold a vacuum reading at all. No good.

WUR-045……………the CCP @ 68°F is within spec. , WCP without vac @ 40 psi. is within spec. and WCP with vacuum @ 48 psi. is out of spec. However, the WUR is still capable of starting and running your motor. While it is out of spec, it is not defective but would need some work to get the WCP set correctly.

Tony

Edited:
There was a typo. 32°F originally written was edited to 68°F. See above.

Stellar work! Thank you.

I just received the WUR. Very pretty. Wasn’t expecting the extra touches. Well done, and Thank you.

I installed it back in the car with the TTV. My garage is a heinous Texas 88° right now per the infrared thermometer directed to the WUR housing.

-System pressure reads 4.8 (4.5-5.2)
-Cold ctl pressure reads low at 2.1 (2.4-2.85) per Bentley chart.

I did not plug in the WUR power connector to test warm yet.

I thought I would check with you before tweaking the new CCP screw.

tw

Start Up……….
 

Thomas,

The CCP was set lower and that was intentional. Install the WUR as received and test run the FP for several seconds and check for any sign of fuel leak. Start the motor and record the control pressures readings until CCP stabilizes to WCP.

Please take note how many attempts before you get the motor to start and idle. If your motor is having trouble starting, do not blame the WUR. We got other problem to identify this time. Keep us posted. Thanks.

Tony

Ok…

-System pressure reads 4.8 (4.5-5.2)
-Cold ctl pressure reads 2.1 (2.4-2.85)
-Warm ctl pressure (ENG off, FP running, power plug installed) in one and a half minutes, it creeps up to 2.75. Once it settled, I hit the starter, it jumps IMMEDIATELY to 3.5

Once the WUR was electrically warm, I started the car. It took at least a half dozen + starter attempts to get it to even try to stay running on its own. The car doesn’t want to idle smoothly and idles very roughly around 500rpm, dying several times.

All of this with the gauge still installed.

Wrong Start Up Procedure……..
 

Thomas,

You are doing it all wrong. Both the WUR and the engine should start at the same ambient temperature. What you did was heat up the WUR and got the CCP to WCP and started the cold motor. WRONG!

You had a cold motor with fully warmed up WUR with 52 psi. and you expected it to START? What were you thinking? Let everything cool down and try again. When was the last time you had the motor running?

Do you have an inductive timing light? Have you checked for vacuum leaks? It is critical that you don’t have any significant source of unmetered air going into the system. They all leak it is a matter how much leak your system could tolerate to affect ignition.

Try it again after an hour or two. Thanks.

Tony

Yep, I wondered about that, and it makes complete sense. I was mentally in ‘lab’ test mode and not being very real world. Lol.

The motor (car) hasn’t been on the road in a couple of months because of these issues, but prior I had put several hundred miles on it.

Yes on a timing light. Have not checked timing on this car.

As far as unmetered air, when it was last running (in the garage) a few weeks ago, warm and idling, I opened the oil cap and the rpms dropped significantly. I took that as a sign that I didn’t have a catastrophic vacuum leak.

I’ll fire it up in a couple of hours and see how she does.

Thanks for the input!

Defective TTV……….
 

Thomas,

Did you install a new TTV? Your old TTV is leaking and don’t use it.

Tony

I am going to log the pressures from cold, but it will be Thurs/Fri before I can do that.

In the meantime…

I did let it cool about an hour and restarted it, and the fast idle came up (1750ish?) and it was smooth. As it started to warm up, the idle began to ease downward, and the fuel pressure easing upward. Then suddenly, after 20-30 secs or so, the idle suddenly plummets (500ish + drop?) and the fuel pressure slams to 3.5. It begins stumbling into a spiral of death. This is puzzling me.

Yes new OEM Porsche TTV is installed.

CIS Troubleshooting……….
 

Thomas,

We will need to test the integrity of your vacuum system. A smoke generator is a very effective tool to locate the hard to find leak sources in your CIS motor. Leave the CIS gauge installed for the meantime and you could drive the car with it installed. Just make sure you secure it away from the alternator fan belt. Something is not right.

Tony

Ok. It was 103° today so I’m going to have to wait for some kind of break in the heat to do this test. I don’t handle the scorchers as well as I used to. :)

While I wait…. if there was a significant vacuum leak, wouldn’t the effect be more linearly present throughout the entire startup vs a dramatic stair-step change as it approached operating temp? What leaking components would likely cause that sudden dramatic change in fuel pressure?

Does anyone have any input as to why the Cold fuel pressure (2.1 bar), upon starting the car, starts to slowly increase, and after a few seconds snaps to 3.5 bar?

Also something else I noticed…

I read 13.5v at the battery. I get only 11.5v at the WUR connector with IGN ON and FP running (engine OFF) When I start the engine, it goes up to 12v plus a little. Not sure what this means.

It shouldn't "snap" up to 3.5 bar. It should move up slowly. Sounds like something might be sticking inside the WUR, but you just got that from Tony, so I'd think at the fuel pressure regulator on the FD.

You should read the same voltage at the WUR connector as at the appropriate pin on the 14 pin connector (should be pin 10). If it reads lower, you have a poor connection somewhere. And that pin should also read normal system voltage.

Thanks for the reply! Yes, it shouldn’t snap. Just haven’t figured out what’s happening. Yes, fresh from Tony. Not sure how many heat cycles he put it through though. I’m not sure a 1978 has a “fuel pressure regulator”? Other than the WUR.

What 14 pin connector are you referring to?

The fuel distributor has a fuel "system pressure" regulator on the back of it. That's what sets the approx 5 bar SP. I don't see how it would cause a "snap" from a lower CP to a higher CP, but I'm trying to think of something other than the WUR that might be implicated.

Maybe your gauge is hanging and then releasing?

Let's wait and see if Tony has seen that previously.

Thanks again Pete.

The system pressure has been a solid 4.8 and the needle never pops when the gauge set is in system pressure mode. When I open the valve into CP mode, as the WUR bimetal strip warms with engine running between 2.1 and say 2.3 then snaps to 3.5, the needle stays rock solid at 3.5 as the engine slowly dies. If I warm the WUR with only the WUR power cable (no engine running) it only gets to 2.75 and the gauge never pops.

Whether the needle pop has anything to do with the motor dying, I don’t know. I just know it’s not supposed to do it.

CIS Troubleshooting……….
 

Thomas,

Based from the data you provided above, the fuel pressure readings are NORMAL. What was the ambient temperature in your garage? These are your collected data:
SP = 4.8 bar (70 psi.)
CCP = 2.1 bar (30 psi.)
WCP (no vac) = 2.75 bar (40 psi.)
WCP (with vac) = 3.5 bar (51 psi.)

The popping noise you have observed was probably the TTV opening after starting the motor (delayed opening). If your motor is starting and stalling after the initial start, do not blame the WUR. There is something wrong with your CIS and you need to investigate the culprit/s. They could be unmetered air or the fuel mixture. Test and confirm.

Tony

At first I thought the TTV made sense if I had not seen this phenomenon before installing the new TTV. But I checked my notes and I mentioned the sudden pressure increase in POST #8 of this thread with the bad TTV in place.

Moving on to the next stage of testing, looking at vacuum leaks. Must be a big one or a combination of things because the engine won’t run. Thank you for your input.

Supplemental Tests……….
 

Thomas,

If you disable the TTV by unplugging the electrical plug, the cold motor would start and run a bit longer but would stall later(?). With the CIS pressure gauge installed, observe at what control pressure the motor would stop running. Keep us posted. Thanks.
NOTE:
You should not have a cold control pressure spike during this test.

Tony

Well you’re right about the lack of a fuel pressure spike with the TTV unplugged.

Ambient temperature 93°. It warmed up decently smoothly from 2.1 bar to 2.7 until about 1:15 in and it began its stumble to death. Highest pressure I achieved with this test was 2.75 where it stopped climbing. It never reached the 3.5. I made a video of the gauge face with sound. Video length 2 mins, from START to DEATH.

Thomas,

The motor stalled @ 2.70 bar (39 psi.). Theoretically, this motor should be idling @ 3.6 bar (52.0 psi.). So it means that the mixture is LEAN. There are two ways to interpret this condition:

• LEAN because less fuel.
• LEAN because too much air.

I would bet my money on the second scenario. LEAN due to air leaks or unmetered air. You need to locate the sources of these air leaks and fix them. The good news, a smoke generator could easily identify where these leak sources in your CIS.

You could buy or borrow or build a smoke generator. If you build yourself a smoke generator, you are are not saving much $$ considering the time and effort you will spend making one. But some people enjoy building things. Keep us posted.

Tony

Sounds logical. For the sake of my edification, in the test above, the gauge actually stopped climbing at 2.7 bar, before the car really began stumbling. It didn’t die while the gauge was still climbing to 3.5. Why is that?

Also, when the TTV was plugged in, gauge showed 3.5, but it died similarly. Trying to wrap my head around this stuff.

Also, any suggestions on a good, cheap smoke kit?

Thomas,

Repeat the test experiments you just conducted:

• The TTV plugged “IN”.
• The TTV plug disconnected.

NOTE:
Both tests should be done with the engine cold (at least 2 hours rest). Record the total time from start to stall time. Start the first test (TTV disconnected) and allow the motor to sit for 2~3 hours. Then do the second test (TTV plugged IN).

We will discuss the test results (total running time) for both tests. Do not forget to monitor the control fuel pressure versus time. A 30-sec intervals would be great.

There are two (2) EVAP Leak Testers that caught my attention namely:
Auto Tool for $77
Romodes SM601 for $80

They look impressive than my home-made 1-gallon paint can contraption. But my smoke generator has been very effective and proven over the years.

Tony

TTV UNPLUGGED:

Ambient temperature 94°.
Started with a CCP of 2.0 bar which moved steadily up to 2.7 and stopped.
:30 - 2.3
:60 - 2.6
:75 - 2.7 (where it stopped increasing)
At 2:15 in, it began to stumble and spiral into a hard, sputtering death at 2:34.

TTV PLUGGED IN:

Ambient temperature 86°.
Started with a CCP of 1.9 bar which moved steadily up until the needle pop at 2.3
:30 - 2.1
:60 - 3.3
:90 - 3.5 (where it stopped increasing)

AT :49 seconds in, gauge pops from 2.3 to 3.2 but continued to creep up to 3.5
At 2:20 in, it began to stumble and spiral into a hard, sputtering death at 2:55.

I PM’d you the links to videos of the two tests.

Most Likely Culprit………
 

Thomas,

You need to test and verify the absence of significant sources of unmetered air going into your CIS. Without performing this test, it is quite difficult to identify the culprit and get this motor to run.

Tony

Will do! Thank you.

Praying for something simple, and an intact airbox :)

I went through an issue w/ a hot start problem, that morphed into similar behaviour. Learned a lot about the CIS system through this forum and JIM's CIS site, (past posts and individuals who responded). Did all the pressure tests which was an awesome learning experience. Results were in spec (well CCP was a little low, but ok).

I was going to take it to a shop, but in looking at maintenance records, the cap/rotor were last replaced in 2004, and no record of the spark plug wires being replaced (they were berus, so were at least replaced once since 1981). Cap was pretty pitted, wires were definitely "ratty". I figured, I should replace these items, rather than have a shop replace as part of a "let's replace parts and see what happens strategy". Long story short; it's been 2k miles since I replaced the components and the issues have disappeared.

Might be something worth looking into especially if those components are old, although this should have nothing to do with the spike cp.

Thanks for chiming in. Probably a good idea to check those out. I know it’s been a long time and I have a brand new cap on the shelf.

Waiting on the smoke tester to show up to get back into the car.

Let me clean up something I said earlier. I didn't realize you were running the engine when the CP "snapped" up. After Tony said that was due to the TTV opening, I realized that occurred while the engine was running, which explains it. Usually, you do the CCP and WCP testing with just the fuel pump running, then attach a vacuum pump to test that the TTV is closed, then open, and that the CP rises a certain amount with a certain amount of vacuum applied. I missed that your engine was running. So once again, Tony got it right! :)