Cold start problem on 1974 911 2.7L CIS

[ruf-porsche]

Art

Read this thread on check valve, don't know if it applies to your car since your is a 74. I don't remember replacing the check valve on my 74 when I install a new fuel pump, perhaps it is like bigchillcar said the check valve is internal.

Warm start problem

[azasadny]

Ryan,

Thanks! I have replaced the hand throttle and confirmed that it's engaging the accelerator rod in the tunnel. I always lift up on the hand throttle when I start the car, but it really doesn't seem to help. My mechanic said that pressure testing indicated the WUR was bad and it was replaced. Prior to replacing it, I could spray starting fluid in the airbox and it did not make any difference. Now, the starting fluid trick works! I replaced the thermotime switch the same time I replaced the cold start valve last summer. Each time I replace something, the problem goes away leading me to believe it's fixed, then the problem returns again....

I hope I don't have to replace the fuel pump, I've spent quite a bit of $ on this problem and it wouldn't be so bad if I had actually fixed it, but this is so frustrating. If my check valve is internal, then is it hopeless? I ordered a new check valve and wanted to replace it this week. I have to find the fuel pump first, I don't even know where it is although I can hear it "buzz" when I turn the key.

[azasadny]

Ruf,
I read Mark Wilson's post and I'll keep that in mind when I look at my fuel pump. I haven't seen the pump yet, so I don't know what I'm getting myself into...

[azasadny]

Ryan,

I forgot to mention that I can smell gas, but the car acts like it's not getting fuel. I spray starting fluid in the airbox and the car starts right up. This works when the car is cold or warm. When the car is hot (shut off less than 30min) I just turn the key, like "normal" people do and the car starts right up. Once the car starts, it idles at 1000 rpm, smoothly and always runs great, no missing or lags. That's what makes this whole thing so frustrating...

[mperkins]

Originally posted by azasadny
Mperkins,
I just checked, my 1974 doesn't have a fuel pump check vavle, that's for 1980 and newer engines, so I guess I'm starting from scratch again... Thanks for the help!

so now, you've realized, indeed, you actually do have a fuel pump check valve?

2nd - seeing you're in MI - are you by chance using fuel w/ ethanol?? which is commonly found in the mid-west. if so, you should stop - as this could also be causing you problems.

a higher percentage of alcohol in the fuel - will lead to air pockets in the pressure system and adversely affect the CIS.

Maurice
'80 SC Coupe

[bigchillcar]

Hi Art,
I'm almost certain that the '74 has the check valve internal to the fuel pump. The fuel pump is under the car, driver's side, just in front of the rear tire. It has a metal shield underneath it kind of to protect it and rubber shock absorbers to hold it steady in the mounting. It should only be really noisy if it's drawing air from an empty tank, adding fuel you'd hear it to start to gurgle and then go to a pleasant 'whir'. I think new or maybe rebuilt pumps cost around $300-$350. Maybe we should ask how to troubleshoot and rule out or confirm this check valve question.
Ryan

[ruf-porsche]

Originally posted by mperkins

2nd - seeing you're in MI - are you by chance using fuel w/ ethanol?? which is commonly found in the mid-west. if so, you should stop - as this could also be causing you problems.
Maurice
'80 SC Coupe

Only problem is that all the gas in this area has ethanol.

[azasadny]

Hi Ryan and Ruf,

I use premium, unleaded gas and the car seems to run very well on it. Like I've said, the only trouble is getting the car to start, once it starts, it runs smooth and steady, no misses or lags. I'll check the fuel pump tomight, but i really don't know what I'm looking for now that I have found out the check valve is internal to the fuel pump. Can it still be replaced without replacing the fuel pump?. I don't want to buy a fuel pump unless I can absolutely determine this one is bad. All the $ I've spent so far hasn't gotten me very far, except that now I can use the "starting fluid trick" and get the car started, whereas before I replaced the WUR, that trick wouldn't work. I wish I knew what was causing the fuel problem. It's weird to me that once the car is running, the engine isn't bucking or otherwise indicating an insufficient fuel supply. What do I know? Thanks again!!

[ruf-porsche]

Try this post

http://www.pelicanparts.com/911/technical_specs/911_cis_troubleshoot.htm

and this one also

http://www.ncr-pca.org/tech/tech-cis.htm

[ruf-porsche]

Hey Art and JK911

The follwoing is an excerpt from one of my previous posted thread.

Starts hard cold- This is almost always the warm up regulator. High cold control pressure will make the mixture very lean. The cold start valve will still spray and you will likely fire up for a second or two and then die. In order to see what your control pressure is you will need a set of special gauges which are available at most auto parts houses. Keep in mind that you have fuel pressure at all times, even with the engine off, so be careful when attaching fuel pressure gauges.

Now does any of your car starts and run for a little while and than stall and is hard to start afterward?

If you car doesn't even start at the very beginning I think the cold start valve is not kicking in at the beginning. I think that when you spray the starting fluid into the airbox you are imitating a cold stat valve.

The cold start injector unlike the the regular injectors has a solenoid built in to pull the nozzle back to allow fuel to flow, the other injectors doesn't have a solenoid once the thermotime switch kicks in, the power to the solenoid is shut and the nozzle closes so the engine won't be flooded. Even though you replace the thermotime switch and the cold start valve, did you check to see if the cold start valve was getting current at the very beginning?

[jk911]

Originally posted by azasadny
Ryan,

I forgot to mention that I can smell gas, but the car acts like it's not getting fuel. I spray starting fluid in the airbox and the car starts right up. This works when the car is cold or warm. When the car is hot (shut off less than 30min) I just turn the key, like "normal" people do and the car starts right up. Once the car starts, it idles at 1000 rpm, smoothly and always runs great, no missing or lags. That's what makes this whole thing so frustrating...

That is my problem exactly !

As for the buzzing of the pump when I start up Im not talking about the buzzing sound of the pump working Im talking about a very load buzz ,clunking and a whoosh sound you can hear 10 meters away for a second or two (random 1-3 seconds) then it buzzes qiuetly normally continuously.

In the 1974-75 the fuel pump pumps continuously as soon as the key is in the ignition part turned regardless of whether the engine is running or not.

[azasadny]

JK911,

I just removed my fuel filter and it was in the rear of the car, just forward of the rear wheel. My fuel pump buzzes loudly, but I have never heard a gurgling or "whoosh". I've had the car since June 2002 and I had an intermittent starting problem that became progressively worse over time. Each time I replaced something the problem went away for a few weeks only to return.

I'm going to take the fuel pump to my mechanic to have him test it tomorrow, they're too expensive to just replace on a whim.

[jk911]

azasadny


I don't think you have a fuel pump problem as it runs fine !

Maybe a checkvalve problem!

My problem and probably yours is a leak or drain back of fuel somewhere ! The problem is identifying it !

[azasadny]

Gentlemen,

I removed my fuel pump last night (located exactly where Bigchillcar said it would be) and my new check valve will not fit. I took the fuel pump to my mechanic and he looked at the banjo fitting (which he said was also a check valve) and said it looked good to him and recommended that I reinstall the pump. Based on my symptoms, he believes the problem is in the cold start valve or circuit to the cold start valve and has offered to look at it next week. In the meantime, I'll try to get my fuel gauges hooked up. I can't loosen the nut at the top of the WUR or the fuel line connection at the top of the fuel distributor because I can't fit a wrench on either location. Looks like I'll have to make a trip to the tool store to get some offset metric wrenches to do this.

[azasadny]

Ruf and BigChillCar,

I'll take your very wise advice and test the cold start circuit this week after I reinstall the fuel pump. When I checked the circuit prior to taking the car to my mechanic, the cold start valve wasn't getting any power and I told him that. He said that the "throttle microswitch" was bad and bypassed it and said I could replace it later but that it would start fine, which it did for a few days, then the cold start problem started again. I'll check to be sure the cold start valve and thermotime switch are getting power and let you know what I find out. Thanks again for all the help!!!

[jk911]

azasadny

You may have a cold start valve issue and you should sort it out.
Does your car always start easily when the engine is still warm? Mine doesn't and as you know the cold start valve does not operate when the car is warm.

[azasadny]

JK911,
My car only starts easily when it's "hot" (not started for less than 30min) or if I spray starting fluid in the airbox. I haven't seen anything in the CIS troubleshooting guides that covers that....

[ruf-porsche]

Originally posted by azasadny
Ruf and BigChillCar,

I'll take your very wise advice and test the cold start circuit this week after I reinstall the fuel pump. When I checked the circuit prior to taking the car to my mechanic, the cold start valve wasn't getting any power and I told him that. He said that the "throttle microswitch" was bad and bypassed it and said I could replace it later but that it would start fine, which it did for a few days, then the cold start problem started again. I'll check to be sure the cold start valve and thermotime switch are getting power and let you know what I find out. Thanks again for all the help!!!

Hey Art

I think once you fix the cold start valve so it operates as it was intended your cold start problem will be over. Not quite sure why your mechanic didn't fix the microswitch but bypass it. Could be his bypass setup isn't working or came loose.

[azasadny]

Ruf,

That's one of the things my mechanic suggested. Possibly the wires came loose or something happened that is breaking the cold start circuit. I'll take a look and be sure I'm getting power to the cold start valve when the ignition is on. I'm going to replace the throttle microswitch as soon as I can find a replacement. I didn't see one in the PP online catalog for the '74.

[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....