CIS Pressure Testing - Cold start problems

[strictly]

I have a few basic questions. I'll describe the problem first.

Car drives great warm and cold (1978 SC). The issue is cold starting, takes about 10 cranks. Then kicks over and idles around 1000 rpm. It dosent ever go to 1500 rpm when cold then settle down - that maybe a clue? AAR is working (ive checked it warm and cold). Generally drives very well, plenty of power, good warm starting, no backfiring, just hard to start if I leave it overnight

Okay so how to test?

I have allready checked the TTS and the Cold Start valve. I have also checked the AAR.

I have just purchased a CIS pressure tester and going to test the warm and cold pressures. I suspect that maybe the cold start valve is leaking overnight or maybe an injector.

Should i go straight to trying to test this, or start with the warm/cold system pressures?

I have a thermovalve, but im not sure how to test it? Check its getting 12v and vacuum connections are attached?

I think i need to check that the cold start valve is getting fuel at start, im thinking the best way to do this is is take it out, put it in a bottle, disable the CDI, then first thing in the morning, crank the car and see if i get a spray of fuel out of the valve? Ive allready confirmed it works by hotwiring the fuel pump relay, and the TTS connections. I have also confirmed i have power to the TTS at "start" on both sides, etc

Thanks in advance...

P.S. I will also check ignition timing, and CO im going to do that first

[Vereeken]

Pressure test the WUR and System first and report values and WUR type number. If not your not going to get much love from the board.

Most likely cause is they are off at cold. Although if you look on my user name you will find that eventually the cause of my issues was a freak occurence with the AAR.

Leaky CSV....maybe but slim chance. Leaky injector...maybe....

The thermal valve is tested in the morning. If you can not blow through this is good. Next apply 12 V for 30 seconds. If you can blow through this is good. They work or they do not. I have one that is lazy in the sense that it takes 50 seconds to open up while everyone claims it should be 30 or less..... All this assuming you do not live in a place where it is 30 degrees in the morning....if it is kaput go to breakers yard and look for Old Mercs, VW, SAAB, BMW, ...or pay 180€ to a dude behind a counter.

Testing for fuel on the CSV is hard work. Go the lazy way first.

[strictly]

great advice, thanks really really helpful.

Ive just ordered the pressure test kit. Dont worry i'll post those pressures. Thanks for the steer, i wasnet looking forward to taking the CSV back out! Im going to check the TV as you described 2moro.

I think realistically i'll have some results on pressures early next week, so will report back!!

[jason2guy]

once you get the gauges you will find that the WUR will most likely need to be adjusted. not difficult but it helps if you can wrap your mind around exactly what the WUR's function is and how it performs it. after that gets handled, the cold start issue, if it still is present after proper WUR adjustment might be a loss of fuel pressure when the car is off. i would check the fuel pump check valve, the accumulator or the system pressure regulator oring. that oring is on a small piston in the FD accessible by a bolt on the side of the FD. the WUR can also leak residual pressure. i would replace the check valve and the oring just because they are a hundred yrs old and they are cheap. as far as the 1000rpm when cold, i think that is perfect. i dont like when the car idles really high when cold.

[boyt911sc]

Originally Posted by strictly

I have a few basic questions. I'll describe the problem first.

Car drives great warm and cold (1978 SC). The issue is cold starting, takes about 10 cranks. Then kicks over and idles around 1000 rpm. It dosent ever go to 1500 rpm when cold then settle down - that maybe a clue? AAR is working (ive checked it warm and cold). Generally drives very well, plenty of power, good warm starting, no backfiring, just hard to start if I leave it overnight

Okay so how to test?

I have allready checked the TTS and the Cold Start valve. I have also checked the AAR.

I have just purchased a CIS pressure tester and going to test the warm and cold pressures. I suspect that maybe the cold start valve is leaking overnight or maybe an injector.

Should i go straight to trying to test this, or start with the warm/cold system pressures?

I have a thermovalve, but im not sure how to test it? Check its getting 12v and vacuum connections are attached?

I think i need to check that the cold start valve is getting fuel at start, im thinking the best way to do this is is take it out, put it in a bottle, disable the CDI, then first thing in the morning, crank the car and see if i get a spray of fuel out of the valve? Ive allready confirmed it works by hotwiring the fuel pump relay, and the TTS connections. I have also confirmed i have power to the TTS at "start" on both sides, etc

Thanks in advance...

P.S. I will also check ignition timing, and CO im going to do that first

Strictly,

Now that you have a new fuel pressure gauge kit, this would be a good time do some practice. First learn how to test run a FP without running the engine. Next, is to measure the control fuel pressures versus time. A 30 sec. intervals would be ideal no more than 5 mins. Post these numbers when get the chance to do the test. Make sure you have a fully charged battery. The first data point @ zero sec. (electrical plug to WUR is disconnected). Then connect the plug and start the count. And record the pressure readings.

Tony

[strictly]

Thanks for the replies guys, soooooooo appreciated. I am going to redo my pressure testing today, as i didn't do it with the WUR unplugged etc. I will post the results (at first glance pressure look okay (1.5 to 2.1 bar control cold, 4.8 bar system cold and 3.2 bar control warm, also test system warm?)

One thing i have noticed this morning, when i went to bed last night the gauge was at 1.5 bar (cold control pressure - valve open). When I came in this morning. The guage was at 0 bar. So im not holding resuidal pressure.

I checked for fuel leaks before I went to bed and it was okay. My tester was leaking slightly at the valve, but i took it apart and fixed it before I started again (I might take the valve out of the line to be sure).

So I need to do the same residual test on the system pressure (valve closed) to isolate the WUR? If the system residual pressure is okay (more than 1 bar?) then does that confirm that the check vave, fuel accumuator and system pressure o ring in FD are all ok?

I am going to resist fiddling until I have done a residual system check, I think that is wise.

Thanks again, and I will follow up with all of my pressures in 5 or 6 hours (not that your hooked on this thread lol)

=)

[strictly]

EDIT

I'll update in a bit, i noticed my cold system residual pressure failing, but could be my equipment...i'l be back

[strictly]

Ok, It seems my system residual pressure is a problem

BUT

maybe im not testing it right (I havent had the engine running for the residual test?)

I have been testing the system pressure with engine stone cold. I have connected my guage directly to the FD, hot wired the FP (87a to 30) to run the pump and bled the guage of air. I also have the WUR electrical connector diconnected, but not the AAR (i'll do so now).

So ive tested the system pressure to be 4.8 Bar with engine off, and FP running. I then turn off the FP, and watch the guage, it drops immediatly to about 2.4 Bar and then over an hour or so it slowly goes to 0 over about an hour or so.

BUT

I havent run the engine, and the bentley manual says to do this for 3 minutes before testing system pressure, who am I to disagree...does this really matter?

I only ask, as i have plumbed my guage direct to the FD (i.e to elimiante my leaky tester valve from earlier), so i would then have to run the engine, and then disconnect the FD to WUR fuel line, so to reconnect my guage.

I'll move on to testing FP and accumulator (Before and after) and come back to the FD.

[Vereeken]

You need to test cold first (engine stopped for 8 hours at least).

This is your fill-out test:

1. Outside ambient temp at moment of test
2. last three digits of your WUR type eg.....089
3. Disconnect CSV, AAR, WUR TTV electrical.
4. Jumpwire fuelpump relay
5. Check system pressure = bar
6. Check WUR pressure = bar

All the rest is irrelvant at this point. I also do not think you have a residual pressure issue. It is normal to drop suddenly after engine/pump shut-off and then got to zero over an hour. It is only an issue when it goes to zero in 10 or 15 minutes.

[strictly]

Ah ok. I thought the system/control was supposed to stay pressurised all the time, even overnight

Ok in that case, im barking up the wrong tree. I'll disconnect all components you mentioned
And put the list together. I did find a corroded electrical connection on thw WUR, ive cleaned that up

thanks for your help!

Luke

[boyt911sc]

Originally Posted by Vereeken

You need to test cold first (engine stopped for 8 hours at least).

This is your fill-out test:

1. Outside ambient temp at moment of test
2. last three digits of your WUR type eg.....089
3. Disconnect CSV, AAR, WUR TTV electrical.
4. Jumpwire fuelpump relay
5. Check system pressure = bar
6. Check WUR pressure = bar

All the rest is irrelvant at this point. I also do not think you have a residual pressure issue. It is normal to drop suddenly after engine/pump shut-off and then got to zero over an hour. It is only an issue when it goes to zero in 10 or 15 minutes.

Luke,

Michael has given you a good advise and agree with the above suggestions except #3. There is no reason to disconnect the other CIS components except the WUR because they have no effect on checking your residual, control, and system fuel pressures. If you could find out the fuel pressures in psi. I could easily interpret your results. I have not memorized the pressures in bar and very familiar in psi. for all my tests. You don't need a running engine to do these pressure tests. Keep us posted.

Tony

[strictly]

Hi Tony,

Thanks bud, will do. I should have it all 2moro, I got carried away with chasing residual todayL

Luke

[strictly]

Right, I have the info. Im guessing my stone cold control pressure is too low (too rich?). I also pulled a few injectors (1,4, and 5). I noticed all were wet, when wiped dry, #5 didnt drip, but continued to look wet, i did this during the residual testing. 1 & 4 stayed dry. I didnt check the others, or look at spray patterns, etc

Car : Porsche 911 1978 (built September 1977) ROW (UK spec) - 180 Bhp
Temp 17-19 C (62-65 F) - I used two mutimeters both were 1 degree different
Electrical : WUR, AAR, TTS (CSV), and TTV all disconnected
Fuel Pump running (30 to 87a), Ignition on

WUR Part Number : 0 438 140 045 - (the 045 is different lettering to the 140). It has a 2 vac lines on it. One on side to TTV, and one on top to throttle body

Control Pressure (COLD) 1.2 Bar (17 PSI) -
System Pressure (COLD) 4.8 Bar (70 PSI)

AAR, TTS, and TTV connected, fuel pump still running - no change in either pressures above

WUR now connected, fuel pump still running, Control pressure increased to approx 2.2 Bar (32 psi) over 5 minutes. It took maybe 30 seconds for it to move. I can retest this more accurately if you need me to too. I also could have left it and recheck it after 10 minutes with ignition on?

Engine started and left to run until control pressure increased from 2.2 bar (32 psi ) to stabilised to 3.4 Bar (50 PSI), engine shut off, control pressure drops as follows :

Immediatly after disconnecting the fuel pump : 2.2 bar (30 psi)
10 Minutes : 24 Psi (1.6 Bar)
20 Minutes : 22 Psi (1.5 Bar)
30 Minutes : 20 Psi (1.4 Bar)
50 Minutes : 0 (I didn't monitor it after 30 minutes, except to see if the guage still had pressure)

I will check warm system pressure, and remove WUR to get number as well.

Im guessing WUR pressure needs some adjustment? I'm slightly nervous about doing it it, as they are $1000 here if i break it (£600 in the UK). How do you do it, flip it over and tap the recessed thing with a center punch and hammer. Seems impossible to do with a guage attached, do it on the bench?

I also checked my ignition timing during warm up, looks okay, maybe 1 -2 degrees slightly more advance (than 5 BTDC at 950rpm), but normally that would help starting, car runs preety well otherwise, except idle which never changes.

[Vereeken]

I will let Tony deal with exact numbers but the control pressure at this temp should at least be around 1.6 bar.

So it looks like you will get comfortable with the inside of a WUR.

To me system pressure and residual pressure are all fine.

[boyt911sc]

Luke,

Pretty good test results and there is nothing seriously wrong except some slight adjustments for the cold control and system fuel pressures. Based on the results:
a). The cold control fuel pressure (CCP) is low. Minor adjustment needed.
b). Warm control pressure (WCP) OK but slightly low.
c). The system pressure is within spec and could need a slight bump up (+ 2 psi.).

You don't have to remove the WUR to find the ID numbers. Clean the top side of the WUR or use a wire brush to read the numbers. Like to see that too. Could you also post the Bosch number of the fuel distributor? Keep up the good work.

While you're there, check the six (6) fuel injectors for spray pattern and drip. A uniform and symetrical V-shaped mist pattern is ideal. And minimal drip after the FP stopped. So what problem/s (if any) are you experiencing now? Keep us posted.

Tony

[strictly]

Michael, Tony

Thanks again guys.

ok it looks like im going to get intamite with my WUR.

Im going to research this, but at a glance - how easy it is it to adjust (mine ends 045). I have read about some people tapping a plug, and some people using an allen key. I need to take it apart and see, i guess - any tips? Can i reuse the big gasket at the base - be very careful with the spring etc? I'll work it out, but just thought i would ask before I get too deep!

A quick question on the injectors, how do i test them?. Do i hot wire (like before) the fuel pump, put the valve on the tester open, like for control pressure testing, and then one injector out at a time, and gently push up on the airflow plate to get it to spray?

Im away for a few days, so I will update monday/tuesday. TC

[boyt911sc]

Originally Posted by strictly

Michael, Tony

Thanks again guys.

ok it looks like im going to get intamite with my WUR.

Im going to research this, but at a glance - how easy it is it to adjust (mine ends 045). I have read about some people tapping a plug, and some people using an allen key. I need to take it apart and see, i guess - any tips? Can i reuse the big gasket at the base - be very careful with the spring etc? I'll work it out, but just thought i would ask before I get too deep!

A quick question on the injectors, how do i test them?. Do i hot wire (like before) the fuel pump, put the valve on the tester open, like for control pressure testing, and then one injector out at a time, and gently push up on the airflow plate to get it to spray?

Im away for a few days, so I will update monday/tuesday. TC

Luke,

This how you bench test a CIS fuel injector/s. Search some of the posts about how people do their test and pictures help a lot. Since you know now how to test run a FP, you could test the fuel injectors using your set-up.

1). Pull out the six (6) fuel injectors and place each or three of them in suitable container to collect the gasoline coming out during the test. Make sure the collection vessels are secured during the test.
2). Bridged terminals #87a & 30 (FP relay). The FP is now running but the FD is not delivering fuel yet.
3). When the FP is running, slowly and gently lift up the AFS plate or arm causing the FD plunger to move up and deliver fuel to the six (6) injectors.
4). Quickly take a look at the injector. Do it one at a time so you have more focus and observe how the sprayed fuel looks like.

I use this similar procedure for cleaning fuel injectors but I use a small delivery tank (2 gallon capacity) with concentrated fuel injector cleaner and an optional pressure gauge to determine the opening pressure of the injector.

Tony

[Vereeken]

A 045 was a WUR for UK delivery I think. But Tony will know for sure.

If you want to make an adjustable WUR do a search on this board for "I made an adjustable WUR". Frankly I would no longer bother any more.

You open it up and assuming the OHM measurement of the bimetal stacks up you knock the pin flush with the body. close it up and mount your WUR and pressure gauge again. Next you carefully knock the pin in until you reach your desired bar setting for the outside temp. All this on a cold cold engine with the FP hotwired and the 12v disconnected to the WUR. Ofcourse if you hammer too far you can start all over
But the graph shows quite some bandwidth for each temp setting.....


For all specific specs I kindly point you to Tony. I have the memory of a goldfish and its attention span.

[Walt Fricke]

Looks like you are being pointed in the right direction. Residual pressure readings mainly have to do with avoiding hot start problems. No direct tie to cold start problems, since they drop to zero after an hour or more, and should. The fuel pump builds up the pressure almost instantaneously when engine is cold.

So you want to be using the cold start diagnostic tree.

You are lucky that you have the flexible plastic injector lines, so it is easy to stick each one in its own plastic bottle. If you have a graduated beaker, you can check to see how even fuel delivery is from each injector, as well as watching the spray pattern. Bosch says it should be a nice cone spray, but other manuals say it is OK if it is at least half of a cone.

And the injectors certainly should not dribble under residual pressure, which is what is there with the engine off. Nor should they dribble with the throttle fully closed with the engine off.