Poor starting, looking for ideas, Problem Solved. Another win for the World Board. Options

[Gudhjem]

I've been trying to avoid posting this, since I figure everyone's tired of "my car wont start" posts. But, I've reached the end of my rope, I'm out of ideas, and I need some new ones.

I've got a '73 2.0, stock FI, except for a Crane x700 ignition.

Sometimes it starts right up, but often, about half the time now, it wont. The starter cranks, turns over the engine very quickly, but the engine just wont "catch." It just keeps cranking. It acts as if I forgot the rotor or am out of gas (I didn't and I'm not). Happens warm and cold (though possibly more often warm). I can't think of anything I've done to the car that coudl cause this (no engine tinkering to speak of), and it seems to be getting worse. Today, it did the same thing and after cranking for about 15 seconds, seemed to backfire from inside the case. It blew off the little rubber fitting that sits next to the oil filler cap (the one I'm pointing to in the pic). This happened twice.

The kicker is that once it starts, it runs like a champ. I mean really well - smooth all the way thorugh the range, plenty of power, no smoke out the exhaust, relatively smooth idle at about 800, etc. That forutnatly (or maybe unfortunatly) eliminates most of the reasons why a car wont start. I don't need to worry that my plug wires or injector leads are crossed, or that my plug wires are bad, or my coil is bad, or my Fireball isn't working, or my injectors are not squirting, or that I have no compression, or that I have no fuel pressure, or that my timing is way off, that I have a bad connection or ground somewhere, or that my dizzy is in backward.

Here's what I've tried:
checked timing
checked fuel pressure (set it to 29lbs)
verified spark at the plugs
removed cold start valve wires
replaced spark plugs (0.028")
replaced coil (bosch blue)
replaced spark plug wires
replaced cap and rotor


Seems to me that since it runs so well once started, the MPS and temp sensors or brain could not be the causes. It does look wet when I pear down the throttle body (inside the air distributor thing the throttle body sits on), and although the plugs I pulled were black and a little bit moist, they were not really fouled. So I have spark, I have timing, and I have fuel, I am suspicious that it must be a mixture thing, but don't know where to go with that, and again, it runs so well when it starts.

Any ideas?

--Steve

[underthetire]

Possible ignition switch, seems to be a rash of those lately. Next time, if you haven't tried it yet, push the gas pedal to the floor and try it. That should be flood clear I think. Thats how Porsche wants you to start it from the operating manual, not that I do it that way.

[TheCabinetmaker]

You have gas in the throttle body? The cold start valve shoud not enguage till outside temp gets below 30. Take it out of the loop. Sounds like your flooding.

[pbanders]

You have gas in the throttle body? The cold start valve shoud not enguage till outside temp gets below 30. Take it out of the loop. Sounds like your flooding.

I agree, that's a strong possibility. Try this to see if your poor start is due to a rich condition. Next time your starting it cold, before you turn the key, push the throttle to the floor (FWIW, believe it or not, this is how Porsche tells you to start the car in the owners manual). Turn the key and crank it. If it starts right up, it's likely you're running rich, as the extra air from the open throttle is helping to lean out the mixture.

If it were me, I'd check the cold start valve and circuit, the CHT cold resistance, and the MPS vacuum integrity.

BTW, what's your gas mileage? When everything is set correctly, you should be getting at least 24 MPG in mixed urban driving with a 2.0L. If you're getting under 20 MPG, you're probably running rich.

[markb]

I'd start with the ignition switch.

[Gudhjem]

Thanks for the replies.

The ignition switch was replaced about a thousand miles ago. Anyway, even if bad, I don't understand how that could explain my symptoms. The solenoid engages and the starter cranks with no problem whatsoever. The ignition switch has done its job then hasn't it? What involvement does it have in actually having the engine "catch?" Once the engine does start, it never dies, such as if the ignition switch were losing contact.

I have tried starting with the accelerator pedal depressed all the way (before turing the key on to avoid the TPS squirting in fuel). I think this migh tbe helping a little bit, and so that's the way I've been starting the car ever since this problem started appearing. It definitely is not solving it though. It can still crank away until the battery starts to die even with the throttle wide open.

I have disconnected the cold start valve. It's still plumbed in, and the thermotime switch is still connected, but the wires to the CSV are not connected, which I would think does the trick, doesn't it? I don't want to hassle with actually having to remove it and plug the hole in the air distributor that would leave.

As for CHT cold resistance, I have a new CHT sensor I can swap in. I'll go ahead and do that.

I have not checked the MPS vacuum integrity. I suppose that's my next step (never done this, but I'm sure a good explanation is on this site somewhere).

Again though, the car runs well once it goes. I didn't think that would be possible with a bad CHT sensor or bad MPS. Maybe it is?

I do suspect a rich mixture, and yes, although the car's spent lots of time idling in the garage lately, it does seem that my gas mileage is crap.

Can a rich mixture make the car hard to start and yet allow the car to run well? Is it unusual for the air distributor (the thing below the throttle body) to be wet inside?

[76-914]

I'd start with the ignition switch.

(IMG:style_emoticons/default/agree.gif) The fact that your getting voltage to the starter doesn't mean your getting voltage at the coil.

[SirAndy]

I have tried starting with the accelerator pedal depressed all the way (before turing the key on to avoid the TPS squirting in fuel). I think this migh tbe helping a little bit, and so that's the way I've been starting the car ever since this problem started appearing. It definitely is not solving it though. It can still crank away until the battery starts to die even with the throttle wide open.

That's not what he meant. Don't keep your foot on the throttle. Simply press the throttle all the way down once before cranking, then release, then try to start. Don't keep your foot on the throttle while cranking the engine.

A leaking cold start valve could cause your engine to flood. Disconnecting the wires may not prevent it from leaking fuel. You need to disconnect the fuel supply to the valve.

(IMG:style_emoticons/default/popcorn[1].gif) Andy

[TheCabinetmaker]

what andy said.

[pbanders]

I have disconnected the cold start valve. It's still plumbed in, and the thermotime switch is still connected, but the wires to the CSV are not connected, which I would think does the trick, doesn't it? I don't want to hassle with actually having to remove it and plug the hole in the air distributor that would leave.

As for CHT cold resistance, I have a new CHT sensor I can swap in. I'll go ahead and do that.

I have not checked the MPS vacuum integrity. I suppose that's my next step (never done this, but I'm sure a good explanation is on this site somewhere).

Again though, the car runs well once it goes. I didn't think that would be possible with a bad CHT sensor or bad MPS. Maybe it is?

I do suspect a rich mixture, and yes, although the car's spent lots of time idling in the garage lately, it does seem that my gas mileage is crap.

Can a rich mixture make the car hard to start and yet allow the car to run well? Is it unusual for the air distributor (the thing below the throttle body) to be wet inside?

If your CSV is stuck open, it won't matter if you have the TTS connected or not. Do you have a fuel line clamp (cheap item from your FLAPS)? Clamp the line to the CSV and see if it makes any difference.

Before you swap the CHT, use a DMM and measure the "cold" resistance of it. I have no idea of what temp it is where you are, but it normally reads about 3K ohms at 70 deg. F. If yours is way high (e.g. 10K ohms), it's bad. Otherwise, it's probably OK. Should read under 100 ohms when the motor is fully warmed up.

Check my web page for instructions on how to test the MPS (just do the basic tests I outline, ignore the other crazy stuff).

From what I can tell, a T4 motor will run if you pour liquid gas down the intakes, it loves fuel. Yes, it's possible to have the basic mixture be so rich as to affect starting and have the car run fine.

[736conver]

The ignition switch has done its job then hasn't it? What involvement does it have in actually having the engine "catch?" Once the engine does start, it never dies, such as if the ignition switch were losing contact.

Iginition switch provides power to the starter and to the coil. Both are different circuits.

I could never figure why my 2.2 6 would only catch when I stop trying to start it in the start position. Turns out, I only had the switch hook up to run in the on position not the start position.

You might just have a loose power wire, especially if it just got replaced.

[underthetire]

No andy, actually you put the pedal to the floor while cranking. One shot before does nothing on a FI car. That is supposed to put it in flood clear mode, or at least lean out the mixture. Modern FI is for sure flood clear, gives no pulses to the injectors.

[SirAndy]

No andy, actually you put the pedal to the floor while cranking. One shot before does nothing on a FI car. That is supposed to put it in flood clear mode, or at least lean out the mixture. Modern FI is for sure flood clear, gives no pulses to the injectors.

Are you sure that's how D-Jet works?

The one time down has always worked for me on my D-Jet motors ... Maybe i've just been lucky?
(IMG:style_emoticons/default/idea.gif) Andy

[pbanders]

No andy, actually you put the pedal to the floor while cranking. One shot before does nothing on a FI car. That is supposed to put it in flood clear mode, or at least lean out the mixture. Modern FI is for sure flood clear, gives no pulses to the injectors.

Are you sure that's how D-Jet works?

The one time down has always worked for me on my D-Jet motors ... Maybe i've just been lucky?
(IMG:style_emoticons/default/idea.gif) Andy

underthetire is right, the owners manual actually tells you to put the pedal to the floor while cranking. Personally, when the car is set up correctly, I've never had to do this, in fact, it starts fine with the throttle completely closed.

The reason I suggested opening the throttle with the igniton off, then cranking, is that if you open the throttle with the ignition on, you're shooting 10 ms worth of fuel into two of the intakes, due to the action of the TPS and the ECU. You can hear the injectors click as you do this in a quiet garage. If the car is already rich, more fuel isn't going to help.

I think the reason Andy's method works is that many 914's are too lean on starting, so the extra fuel helps out.

[tradisrad]

Have you checked the trigger points that are on the dizzy? perhaps a loose wire?
You can also take the computer connector off and probe all of your circuits with an ohm meter. Just DON'T probe into the computer from a component to the computer.
My car starts w/o any pedal pressing; I let the fuel pump prime the system then crank it over and its starts real quick.

[Gudhjem]

Problem solved.

Turns out it was...

...


The ignition switch!

I discovered I could start the car consistently by jumping a wire directly from the battery to the coil +, and then cranking with the key. The ignition switch was giving power to the coil in the "on" position, but not when in the start position. New switch = perfect starts.

The oddest part is the "old" switch was only about a year old, and when I dissected it, I could see nothing wrong inside. I'm thinking maybe these switches aren't very good quality or maybe not exactly the same design as the original, which probably lasted 30+ years. (IMG:style_emoticons/default/blink.gif)

Thanks for the replies and the help (still sorting out my mixture to see if I have that right, and figure out why it's wet inside the throttle body, but all is good now). (IMG:style_emoticons/default/beerchug.gif)