my submission for "CIS/Running problem" of the day
 

I've now lived with my car long enough to note the following pattern(s), I'm hoping this relates to one of the gurus enough to say "oh yeah, that's X, Y or Z...(or X, Y AND Z). I've been remiss in not managing to get fuel pressures so I'll take that lashing up front.

'78 3.0 Engine, in a '75, recent accumulator swap (old definately tested bad) didn't change the hot weather starting issue, I don't believe I have vacuum problems as there is major suction and big change in idle (but doesn't die) when I check the oil. I have plugged then re-attached the Decel Valve without any real changes in the narrative below.

Hot Weather (80-95°) best starting method requires "priming" the flapper in the air-box for 3-4 seconds. Twist the key usually 3 times with a "vroom"....then dies before it catches and settles quickly into a smooth idle. If I don't let her sit there and warm up for 3-4 minutes I get bucking and complaining and bad behavior, after this idle is steady about 900+, running behavior is smooth and strong, no backfire, no hesitation.

If I leave the car and re-start in say 15 min-1hr I don't have to do the flapper tickle but I have to give a bit of throttle to stay lit for a few minutes of running till it's fully warm again and then all is well.

Leave the car till lunchtime and I have to do the tickle again. If I don't do the tickle I can twist the key repeatedly till it floods and I have to open up the pop-off valve for a few min before it will start.

Cool Weather: (50-75°) I have had my car sitting for 2 weeks working on things, twist the key 4-5 times and it catches and idles (roughly, small amount of backfiring in the air-box here and there) for 2-3 minutes till it smooths out. Let it warm the 4 or 5 minutes and it's smooth as a baby. Now after it's fully warm (trip down the interstate or 6 or 7 miles away) my idle will climb to ~1800 and want to hang there.

I recall having to lean out the mixture when the weather got hot and richen it when it cools off. I am sitting here trying to remember which affect I got on what by adjusting for the warm high idle (I think it made the starting a bear if I brought it down). Tapping the AAV (?) will bring the idle down somewhat and a while back I sprayed some pb blaster on it and want to say it worked for a while....or maybe it got warm and I moved into the above state?

Obviously I have issues, probably in several areas (I appreciate sticking to the car related ones :) )

I agree that you may have several issues with your car, given your description.

First, as you already know (here it comes), you must test your fuel pressures!, all of them--system pressure, cold control, warm control, and residual. Your warm start problems smack of lack of residual pressure which is most likely from a faulty fuel pump check valve since you've already replaced the fuel accumulator. You don't want to throw money into random parts without diagnosing correctly and that requires a fuel gauge set. Do that first!

The cool weather hard start could be related to fuel pressures too. The hanging idle sounds like an air leak from a faulty device as you've indicated. The fact that you've messed with the fuel mixture to compensate for warm/cold conditions really complicates the situation.

Bottom line, IMO, you've got a problem with residual pressure, a problem with control pressures, an unknown fuel mixture setting, and a possible intermittent air leak. You need to get a set of fuel gauges and perform the basic system tests. Report your findings and go from there.

Without a gauge you will be tossing parts at it.

But, there is a cheap check valve in the neck of the fuel pump. It helps keep residual fuel pressure from falling below required starting pressure when the engine is warm and the cold start valve is out of the loop.

Last time I had one fail it was, 20 bucks.

I cave! have been stubbornly putting off buying that gauge set (I can't explain why... ordered the cheaper version last year from JC and it never came) for well over a year now but I just this minute placed an order for it from our host.

I will get it and some real facts and report back to this thread.

I replaced the odd Volvo fuel pump (with absolutely no check valve) with a good used [proper 911] pump and a brand new check valve last year. I have a long long set of stories on my sadly franken-porsche'd baby.

It's so frustrating that I have an "OK" running car but not a great running one. I have an all out refusal to drop it off to someone I don't know in [doubtful] hopes they know any more than I don't and a shoestring budget to work with, but a severe love for this cantankerous beast that puts a smile on my face every day I drive it.

Hey Travis,

Any luck with the pressure tests?

Shawn

I have the gauge set on my workbench, but work has been in the way for a couple of weeks. Need to research just what the he!!/where the he!! to take measurements :)

at the warm up regulator (WUR), remove the line going to the fuel distributor (FD). connect the hose with the shut off valve to the WUR, the other hose goes to the line to the FD. remove the power connector to the WUR.
find the fuel pump (FP) relay and jumper the relay so the FP runs witout having to start the car.
turn on the FP. with the valve open, that checks control pressure, closed checks system prssure.
once you have cold control pressure (CCP) and system pressure, connect power to the WUR and start the car. if you still have the thermo time valve (TTV)and if it is working, you should see a pressure jump about 15 seconds after starting, then it should continue to rise to around 3.6 bar. to test the vacuum circuit, you can remove the vacuum line to the WUR and the WCP should drop about .8 bar to around 2.8 bar.
to some up, you need to check:
system pressure
CCP
WCP with vacuum
WCP without vacuum

it would not hurt to verify timing and make sure the advance is working. also, check the condition of cap, rotor and plugs and wires.

Thank you so much for the detailed explanation, I knew I could find it on here somewhere but that's very helpful.

? - My fuel pump "talks" to me from the moment I hit the detent before start on the key, does that mean I don't need to fuss with the jumper bit?

- I do have a new cap, rotor and [good used] new plug wires. Plugs were new about 3k ago (I should check them). Timing is the one thing I've left absolutely alone on the car in fear of messing with one more thing that was working.

I'll perform the tests in the next couple days and report the readings.

Over come your anxiety.......
 

Just remember most of us here knew very little about CIS troubleshooting years ago. Today, with the advent of Internet, diagnosing the problems become easy and convenient. It would help a lot in your familiarization with the 911 engines if you have and read reference manuals. A digital camera is a plus.

Try to slowly overcome your anxiety or fear. The more you asked questions, the more you'll get educated about 911 engines. There is no such thing as 'stupid questions', but there are 'stupid answers'. Whatever problem/s you are having with your engine, it has been diagnosed and fixed a hundred times before. So it is not something new that would need research to fix.

You have been given sage advises and you are in good hands. These guys could help you with any CIS problems you could imagine. Whatever you do, for goodness sake, don't have a fire on your engine!!!! Oooops!!! I might have added another fear factor. Just joking.......go ahead and don't worry too much. It is easy and fun.

Tony

I would try bumping the idle up to 1000 and see if that helps. you will need to check the timing after and may have to adjust it slightly. The "flapper tickle" sounds fun.


quote

If I leave the car and re-start in say 15 min-1hr I don't have to do the flapper tickle but I have to give a bit of throttle to stay lit for a few minutes of running till it's fully warm again and then all is well.

The 75 did not use a fuel pump relay so you will not need to do the "jumper bit."

You are on the right path. Begin with the pressure tests and don't deviate or mess with anything else until you have completed them and posted the results. One thing at a time.

thanks ossi, i forget about that one.

i did not mean to imply to change timing, just check it and make sure the advance is working. its always good to get the basics out of the way.....like air leaks.

bumping the idle up could be a cover up. check EVERYTHING you can before making any adjustments.....or buying anything.

Ok, Hopefully you guys are still paying attention, here's my book report including videos.

Details: Car has been sitting for 3.5 days, started this morning out at ~55°.

Key on, nothing touched aside from connecting tester:
-Cold Control Pressure = 5.0-5.05 bar (oscillating that little bit)
-Cold System Pressure = 5.1 bar

Reconnected WUR, Started car, when it's this cool my "flapper tickle" (yes, it is fun, moreso inside the house :) ) doesn't seem to have the same affect so I didn't do it.

[Car Startup [see video]: MVI_2624.MOV - YouTube

post 15 minute warmup (car running):
-Warm Control Pressure = 5.1 bar (with Vac. line on)
-Warm Control Pressure = 5.1 bar (with Vac. line disconnected, no discernible change)

Turned car off after 20 minutes:
-Off, open valve = 2.6 bar
-Off, closed valve = 2.85 bar
(left the valve open at this point)
20 minutes later:
-Off, open valve = 1.6 bar

Key On Pressure test @ 20 min (still warm):
-(open valve) Control Pressure = 5.1 bar
-(closed valve) System Pressure = 5.1 bar

[Car Idled for 15 minutes (see video)]:
Fully Warm Runn - YouTube

shut off car, valve CLOSED:
pressure = 2.7 bar
Off @30 minutes later = 1.5 bar

4.5 hours later:
Off pressure reads 1.5 bar
Key On:
-(open valve) Control Pressure = 5.1 bar
-(closed valve) System Pressure = 5.1 bar

Note: Started car at this point (65° outside), just as hard to start as early morning, multiple key turns, ~5 minutes of bad idle and backfiring through intake and exhaust. After this it smooths out and is fine as in 2nd video.

so I'm open and grateful for suggestions, I have not touched the timing, I haven't adjusted the fuel mixture (slight richening reduced all the backfiring last winter when the air cooled off from our usual steam bath)

Travis

If your control pressure is the same as your system pressure, your WUR is not working. (moving the valve seems to not change anything in your results)
The high idle is most likely due to running the fuel head really, really rich to overcome the lean condition that your control pressure is trying to induce.

BTW.. where are you in Mobile? I go there a lot! Never see any air-cooled P-Cars though. I just figured they weren't' allowed west of Fairhope :)

You need to clean the filter in the Wur. It is plugged, giving you those pressures. If I recall is it below the fitting in the wur where the line from the fuel distributor enters the wur. Take the fitting out and it is a bronze looking thing in the wur. You can try some carb cleaner on it, you want to make sure it flows. Listen to what ossiblue has to say. That man saved me tons of time by reading his old posts. I had the same problem with my pressures when I started. Once you get it set up right the engine behaves so much better. Mine went from a hunting idle, popping, and generally poor performance to wow! Good luck!

Cold control fuel pressure...........
 

Travis,

The first few seconds of the first video confirmed my suspicion. The cold control fuel pressure is too high!!!! That's the reason you are having difficulties getting it to start COLD. I can't read the gauge (if that is 0-100 psi) and it should be around some where in the 20% - 25% of the gauge. The video shows more than 50% at the very start of the warm-up. Another culprit that would cause this very high reading at cold start is a clogged or restricted flow of fuel through the WUR and return line. Your cold control pressure is almost like the system pressure. That's definitely an anomaly.

The cold control pressure should be lower to allow the air flow sensor plate to rise up immediately upon START. And the system should start RICH not LEAN for cold start. Your fuel pressure at the very start is for LEAN condition already.

Getting the fuel pressure gauge kit is the best expense you'll have since owning this car. It will pay for itself after a couple of times using it. BTW, the air mixture setting is not changed when the weather changes from fall to winter. Good job.

Tony

It's reading 74-75 psi (yes 1-100 gauge), really through everything I've done so far as long as the key is on (running or not).

So my first step is to try and clean out that filter in the WUR and report back (before I touch anything else)?

No idea how much I appreciate the help.

WUR cleaning.........
 

Travis,

Dismount the WUR from the engine. Blow compressed air to the outlet port not through the inlet port. Why? You don't want the debris sitting on the micro mesh to get inside the diaphragm valve. You could blow air to the inlet after several passes of compressed air to the outlet. Do not attempt to remove the micro screen and do the cleaning in situ (micro screen).

http://forums.pelicanparts.com/uploa...1319982830.jpg

Tony

OK Guys, so I take a look in the WUR...daaaumm (see below)

http://forums.pelicanparts.com/uploa...1320531818.jpg

I find a big glob of rusty, mucky yuck. I cleaned it out, then I tried to blow back through as directed (that didn't work a bit). So I took it off, took it apart, finally after much carb cleaner and blowing through the tiny inside hole I do get [some] air coming back through the carb cleaner.

I have the feeling it's still clogged up though.

So I put it back on, reset to last week and start over. I still have exactly the same results (~75psi/5.1bar) on or off, WUR electrified or not. I start the car with same complaining as always. She's idling to warm at the moment just so she's been run this week but I still hear her coughing outside (after 10 minutes....it is colder today).

Is there further I can take that WUR apart to clean it out? Is it toast? What happens next, can I eliminate it?

Thanks for continued help,
Travis

That is nasty. You may end up doing a couple iterations of the cleaning once you get it going and get some volume of good gas through there.

I have never done this but did you take the four screws off of the base of the diaphragm from the inside to clean? This may be the absolute wrong thing to do. I don't know.

I do know if I blow in one hole or blow in the other hole on my spare WUR nothing comes through the open side. I think without pressure you will not get it to flow freely between the two. Edit - I am not saying to add pressure with an air compressor - I mean the fuel pressure opens it.