Starting problem - WUR?

[s_wilwerding]

Lately, my 911SC has been having starting problems. When you first try to start it, it will nearly kick over. Then, repeated attempts at starting have no effect - the starter just spins and the motor doesn't catch. The last few times, I've taken the airbox off and pushed the float up and down a few times. The car will then start and idle at 2000 for around 5 minutes until it warms up. The car runs fine after it's been started, and, if the car is turned off for only a few minutes, it will start right up.

Any ideas? Could this be a WUR problem? I'm pretty sure it's not a fuel pump issue, since once the car starts you can drive it without problems.

[Jbabic]

Trust me on this, you will need to invest in a fuel pressure gage. see what what your system pressure is, then your WUR pressure cold and then as she warms up. otherwise your guessing on what the WUR is doing. also, a CO analyzer to know where your CO content is. With these tools and a timing light, I have solved all my problems. there are many threads on this bulletin.

oh also, fuel holding pressure after you shut off....the price on these are cheaper than if you went to a mechanic....unless of course your not the do it yourselfer....but then again, when you be on here if you weren't ? don't know...I thought most of us were..

good luck

[Jim Sims]

You may have lost your cold start valve. At least check to see that it is still connected and getting power (check through thermal time switch too) when the starter is engaged (turning). Then you could check to see if it is providing fuel when energized. Then you will need to do as Jbabic suggests. Good luck, Jim

[scphelps1]

Can you elaborate on test procedures? I have the fp tester and a gunson on the way. I'm not sure I'm exactly clear on how to measure/adjust fp. I also have a WUR modified to be adjustable.

Thanks for any tips/insight.

Clayton

[azasadny]

S_wilwerding,

My car starting problems sounds almost excactly like the problem you were having. I've got a 1974 2.7 with CIS. What was the evtual outcome? Was it the WUR? Thanks!

[Doug Zielke]

Originally posted by scphelps1
Can you elaborate on test procedures? I have the fp tester and a gunson on the way. I'm not sure I'm exactly clear on how to measure/adjust fp.

Clayton,
Buy the Bosch FI book by Probst. All the testing details for CIS are contained within.

[john walker's workshop]

see if both wires are still on the thermo-time switch. it's on the left chain cover, under a boot, if the boot is still there. then see if the yellow/blue wire is still attached to the starter solenoid.

[s_wilwerding]

The problem ended up being a bad fuel pump check valve. I replaced it (an $18 part) and it seems to have fixed the problem. I was also having hot starting problems, so that led me away from thinking the WUR was the source of the problem. And, I did check the connections and functioning of the thermotime switch - it works fine.

[azasadny]

Steve recommended that I replace the fuel pump check valve, but I checked on Pelican Parts and there isn't one for the 1974. Can I use one for a later model car (1980) and install it on my fule pump assembly or won't that work? Thanks!

[john walker's workshop]

'74 style check valve, #1 587 010 001.

[azasadny]

John,

Thanks! I'll get it ordered! I just checked the hand throttle because it didn’t seem like it was doing anything and I found that it’s not connected to anything! There is supposed to be a plastic piece connected to the lever, but it’s not there. I’ve got one on order right now and that may explain some of my problems. I still need to get the idle and mixture adjustments correct.

[azasadny]

I checked and the cold start relay was "missing" from the rear electrical tray in the left rear of the engine compartment. I installed the cold start relay but the car still won't start. I have more than a few wires hanging out that aren't connected and I really need to get the wiring figured out because I think the cold start components (trermotime switch, WUR and cold start valve) aren't getting any power, but I'll put a meter on it and check tonight. My hand throttle isn't connected to anything so I have to fix that, too!!!

[azasadny]

I tried a few things last PM. I checked my wires to/from the WUR and there is a ground wire to the engine shroud bolt and a beige wire going to one side of the middle fuse in the rear fuse carrier. I tried pushing the float up a few times to see if I could coax the car into starting, but no luck. I did notice a slight hissing sound coming from the CIS unit after trying to crank the car, is that normal???

[azasadny]

Turns out my WUR went bad. It was replaced and now the car starts fine, although it's a little sluggish when cold because the hand throttle isn't working. I bought a new hand throttle lever and I'm struggling to replace it (it's a tight fit in the tunnel), but I'll get it done this weekend. The WUR was my problem. I bought a few Bosch CIS books and the fuel pressure gauge set so I can troubleshoot any future issues.

[azasadny]

The original starting problem has returned. I managed to start the car after about 50 cranks and several loud backfires, then it started and ran great. I drove it about 60 miles to a Porsche event and I stopped at a gas station. Restarted the car with the first crank. After letting the car sit for 30 minutes, it's extremely difficult to start again. I'm goint to test the pressures using my recently acquired gauges. I'm going to search the PP archives for the testing procedure and take it from there. I'm not going to start replacing parts again and evidently my mechanic didn't fix the problem, so I don't think I'll be taking it back to him.

[azasadny]

Turns out the fuel pump check valve that I ordered is wrong for my fuel pump, on mine the check valve is inside the banjo fitting on the side of the fuel pump, so I'm stuck...

[ruf-porsche]

Is the check valve the same number as JW gave you in a previous post?
Perhaps the check valve that JW gave you is for use in lieu of the internal check valve?

[azasadny]

Ruf,

I'll double-check the part number, but this particular check valve won't fit on the fuel pump. According to my mechanic, the banjo fitting incorporates the check valve and I saw it myself, there is a small spring in the banjo fitting "bolt" type piece that screws into the side of the fuel pump.

[azasadny]

Many of you have followed my intermittent "cold starting" problem that eventually became a constant starting problem that caused my to have to crank my car 20-30 times, with several loud backfires, prior to the car starting. Once the car started, it ran great but the starting problem was driving me nuts. Needless to say, I replaced alot of components (fuel filter and accumulator, cold start valve and thermotime switch, throttle microswitch, plugs, CD unit, rotor, coil, Pertronix unit, WUR, etc...


Each replaced item improved the situation temporarily, but the problem still persisted. The cold and warm pressures were within acceptable limits and I had good spark at plug #1, but the car just cranked and refused to start. To make a long story short, this is what the mechanic found:

- The plugs were improperly gapped (too wide) even though I followed the instructions on the PermaTune CD unit for spark plug gapping specs.

- The plug wires and their "boots" are bad and I will replace them

- The "new" throttle microswitch that Jordi Riera sent to me worked perfectly and the old one was bad

- One of the wires coming off the Pertronix unit had rubbed until the insulation was off and bare wire was showing.

My mechanic "fixed" these things and the car starts on the first crank, idles at 950rpm and runs great. I REALLY appreciate all of the assistance so many of you have provided. I have learned alot from you kind folks. I'll post this update on the other posts that I have been on so that anyone with a similar problem may be helped. I had checked the spark at plug #1 and had a nice spark, but my mechanic showed me that others were weak. I hope this helps others out there....