What's your engine "cold start" routine?

[wckrause]

I think some people disconnect the switch just so the fuel pressure comes up a little quicker and the engine starts a little sooner. One of my previous mechanics told me it would help my cold start problem (it didn't, it just backfired sooner).

Leland -- with your switch connected, can you raise the sensor plate and get the fuel pump to come on? Maybe the resting position of your sensor plate isn't correct.

The switch is located directly behind the airbox. It can be hard to find if you don't know what you're looking for. I think one of Leland's engine pics showed the location pretty well. I like those pictures of the front side of the motor. It's kind of like looking at the dark side of the moon. You'll also need to find the disconnected cable end. It is a similar connector as the one on the WUR and the aux air regulator.

[Jamul74]

On my 74:
- parking brake on
- neutral, no foot on gas
- hand throttle up
- turn key wait about 1 second
- turn to on, car starts right up
- adjust hand throttle to 2000 rpm
- warm up for 3 or 4 minutes
- hand throttle off, drive off to the club

[9XI]

I was taught way back when that letting a car sit for a while with the fuel pump madly pumping away, without cranking it over, was not a good thing. The reason being that it would pit your points. Not true? Or is it that the 5 second wait we are talking about here is not enough time to do anything to the points?

Long and short of the story is that I only let the fuel pump bleat away for a while when the car has been sitting for more than a couple of weeks (winter) and the gas is clearly gone out of the lines.

Anyone know the answer, either anecodally or technically?

[racemor]

You mfi guys are forgetting the most important thing. Close the door before starting any of these to keep the smoke out of the cabin.

Tom

[RarlyL8]

SC owners:

The CIS system should hold pressure when the car is off. You should not hear the fuel pump run when you hit the first key detent.

If you DO hear the pump run it could mean the check valve for the fuel accumulator is leaking. That would bleed off pressure when the car is at rest.

[Brian993]

My start up procedure is the same as Jamul74. The p.o. told me the engine was a recent rebuild and thus far she fires right up.

[jluetjen]

For my '69E with MFI; my experience it similar (with a twist).

1) Pull up hand-throttle as far as it will go.

2) Crank the car (about 10-15 seconds) until it starts. Sometimes it take 2 tries.

3) As soon as the car fires, (usually slowly) back off on the hand throttle a little (which helps it pick-up because it is starting lean) and then keep the rev's between 1000-2000 RPM. I hate to hear a cold engine rev'ing higher then that.

The twist?
The cold start enrichment device on the MFI was "modified" by the PO. He removed the part of the system that dumped fuel in the back of the air box. Then he had the fog light switch on the dash wired into a relay that was supposed send 12V to the enrichment solenoid on the MFI. It worked great and the engine would kick-off within a couple of seconds every time --- until it was hot. Then it would just never start at all until it cooled down. After much thinking and checking I finally figured out the problem: The switch leaked voltage which meant that the cold start solenoid was ALWAYS kicking in. When I removed the wire from the solenoid: the car would hot-start immediately. So I permenantly removed the wire which is the current state of the car. I'm going to rewire what the PO did and this time ensure that there is no voltage leakage.

[Jim T]

Nothing so dramatic with my SC.

Turn key, car starts, put seatbelt on, take off.

Drive easy until warmed up.

[9XI]

Racemor, that is FUNNY. I ALWAYS remember to close the door first or you get serious eye burn from the first puff of exhaust. Porsches are not good for the planet, but they sure are fun.

[wckrause]

Rarly, and other SC owners

Whether or not the fuel pump comes on has nothing to do with risidual fuel pressure. If the wiring is per factory, the pump will be on only when the Ignition is in the START position, or the engine is running. (unless the alarm, or rev limiter is grounding the fuel pump relay).

Warren describes this circuit very well in this thread

http://www.pelicanparts.com/cgi-bin/vb/showthread.php?s=&threadid=59329



The spec for holding residual pressure is only for about 30 minutes. This is just to prevent vapor lock, and has no bearing on cold start.

[cmsteed]

Expatriot98,

The starting procedure for my 79SC is identical to yours. I have noticed that my fuel injectors are relatively loose in their sockets and can be rotated back and forth by hand with little resistance. I am wondering if this causes a lean condition upon start up, hence the stall? I plan to replace the o-ring seals in the near future and hope this will cure this two crank start action.


Chuck

[RarlyL8]

Bill - are you certain that '78SCs are wired in that manner?

The fuel pump on my car does sound at the first detent when it has been sitting for better than a week. It has always done this. If driven more frequently the pump will not sound.

I noticed all of this AFTER replacing the leaking check valve when I first got the car together. It sounded every time I went to start the car.

[wckrause]

Perhaps it is just the SOUND of the fuel pump that is different.

I'm certain the pump is wired that way. I've seen it in all of the wiring diagrams that I have on SC's, and I've had to trouble shoot that part of my wiring until I found the disconnected air flow sensor.

[Leland Pate]

I didn't know I could do that Bill!

I'll try it tomorrow!
Plug it back in and lift the sensor plate and see if the pump runs... humph... never thought of that.

I know exactly where the switch is... and you're right... if you don't it would be a bear to find.

So, if I do this and still get nothing... how do I trouble shoot it?

[cab83_750]

My ritual is DRAMATIC!

Open the door for my lady. Close it for her.

Open my door, close it, key in, immediate turn to Start, buzzing sound starts, and then she and I argue as to "who pushes the red 'aux' start button."

Car fires up right away, all the time!

The longest time of the day is between 5:30 a.m. (this is the 'cold' point) and 180 deg. I JUST COULD NOT WAIT for the full warmup so I can push the car to its limit!!!!

PUSH THE CAR TO ITS LIMT!......of course, might as well enjoy every penny I spend on syn oil (3K interval).

HAR! HAR! HAR!

[wckrause]

So, if I do this and still get nothing... how do I trouble shoot it?

I'm not sure. I have an exploded parts diagram in my Haynes manual that shows the connector. It looks like the contacts of the switch are the sensor plate arm, and the small leaf spring it is suppose to rest on when the engine is off. The leaf spring is insulated from ground by two plastic insulators. When the sensor plate arm is at rest, it grounds the leaf spring, and when it raises up, it's open.

I guess you could check that when the sensor plate arm is up, nothing is grounding the leaf spring.

I'll scan the diagram and post it as soon as I can.

[gaijinda]

Originally posted by 9XI
I was taught way back when that letting a car sit for a while with the fuel pump madly pumping away, without cranking it over, was not a good thing. The reason being that it would pit your points. Not true? Or is it that the 5 second wait we are talking about here is not enough time to do anything to the points?

Long and short of the story is that I only let the fuel pump bleat away for a while when the car has been sitting for more than a couple of weeks (winter) and the gas is clearly gone out of the lines.

Anyone know the answer, either anecodally or technically?

The points in a 911 with electronic ignition act as a "trigger" only and dont have that much juice in them.. that is what I have been told. Besides, new points are cheaper than starters..
Why dont you guys with MFI (who seem to be spending a long time cranking) try my technique - ignition on for five seconds - then starter. Good luck.

[wckrause]

Here's the pic,

#18 is the connector. It is bolted to #21 (insulator), and is elecrically connecte to #24 leaf spring. The sensor plate arm #40 rests on the leaf spring, and serves as the electrical path to ground.