Could this be my problem?, Anybody else old enough to remember "Heathkit"? Options

[Porsche Rescue]

I posted last fall about my problem: '70 D-jet, extremely hard to start, requires much throttle goosing to keep it going. Once it is fully warmed up it runs great.
I assumed FI problem and have checked everything. All seems OK. Bleysing and others suggested weak spark. Good enough for warm engine, but inadequate for cold. (Frankly, ignition is the weakest category in my 914 skillset). I have checked all connections, grounds etc. All seem OK.

Then, a light bulb! My car has a Heathkit, vintage capacitive discharge ignition (I have no clue how it works or what it does, see skillset deficiiency above). I do know it is over 30 years old. Could that be my problem? Can I just disconnect the 4-wire harness from the coil? Or do I need to do some other re-connecting.



Here is the earlier thread on my problem:

http://www.914world.com/bbs2/index.php?sho...p;hl=hard+start

All ideas welcome!

[jmill]

I've got a Heathkit dwell meter and AFR meter. If your thinking weak spark that would be the first place I'd look. That coil looks like it has some years on it too.

The coil is a transformer. It takes 12 volts and turns it into thousands of volts. It does this through windings and inductance. It appears that the heathkit is hooked to the positive and negative side of your coil. I'm assuming that it's supposed to ensure you get max voltage to your coil. If it's bad your coil might not be seeing 12 volts.

[70Sixter]

You can check the spark visually by removing plugs and cranking the engine with the plug grounded to the engine. I don't know why it would clear on warm-up. Did you pop the distributor cap? Points could be pitted or dirty.

Sounds more like a fuel enrichment problem to me.

BTW I had a Heathkit radio kit as a kid. Never knew they made anything like yours.

[GeorgeRud]

I used to love building the Heathkit electronics. I think I did a stereo receiver back in highschool, and have loved electronics ever since. I just wish that my kids would get the same kind of kick from having built something like that! It just doesn't seem to interest them at all, just turn on the computer and vegetate.

Next to my Erector set, these were the best toys I remember! Now I play with larger, more expensive, German toys!

[Porsche Rescue]

I have done a thorough "Brad Anders" FI check and have replaced the head temp sensor (old one was ok but did it anyway). Replaced the points also. Didn't help at all. I did not replace the condensor but I think that is a "go-no go" item. I guess it won't hurt to eliminate the CD box and see what happens. I suppose the ECU could not be doing its thing when the engine is cold but I'm told those are the last place to look for a problem.

[markb]

If the coil is in question, replace it.

My Dad built a few of the Heathkit kits. Home amplifier comes to memory right off. (IMG:style_emoticons/default/smile.gif)

[Bartlett 914]

I have done a thorough "Brad Anders" FI check and have replaced the head temp sensor (old one was ok but did it anyway). Replaced the points also. Didn't help at all. I did not replace the condensor but I think that is a "go-no go" item. I guess it won't hurt to eliminate the CD box and see what happens. I suppose the ECU could not be doing its thing when the engine is cold but I'm told those are the last place to look for a problem.

Make sure you have the correct ECU. Using the wrong one will cause the problems you described.

[Porsche Rescue]

I checked Anders chart and I have the original engine and correct ECU. I haven't checked MPS # to make sure it is compatible, but the car runs near perfect when warmed up. It is a one-owner 105K car so is very original in all respects. Previous owner said he installed the CD in the early '70's as it was supposed to provide a hotter spark.

[r_towle]

I posted my thoughts in the other thread...

RIch

[Porsche Rescue]

Well damn, I disconnected the CD.......no change. I then decided to buy a new coil (if you can't fix it, throw money at it!). Again, no change.
I can't understand why the car will run perfectly after about 10 minutes of driving, yet it is very hard to start, won't idle and will hardly run, spitting and coughing, until it is fully wrmed up.

[r_towle]

Did you read the other thread?
Its about your FI questions.

Rich

[Porsche Rescue]

Thanks Rich. I will have a look at the TPS next, then move to the rest of your list. I think I have seen a TPS adjustment method using an ohm meter on Pelican.

But, the car idles just fine when it is fully warm. It is just getting it there that is the problem! It won't idle at all for the first few miles. I have to work the throttle to keep it going at a stop sign.

[r_towle]

lean idle condition.
Lean makes it run like crap when cold.
Lean means vacuum leak.

Picture putting 400 holes in your house about the size of a dime.
Now add all those holes up...they look like an open window..wide open.

From what I have found...and its just me...there are alot of vacuum leaks on these motors just due to age or the rubber, and age of the intake gaskets.
When those are added up together, its one big huge vacuum leak.
So, it does take time, and if your methodical, it works.
I resealed my intake runner last year...made a world of difference.

You can use an ohm meter...or just look at it...the TPS can only be set in one position.

[Porsche Rescue]

TPS, then I will follow your vacuum check procedure. Last fall Bleysing suggested vacuum leak that healed itself once hot. Such as the seal beween the runners and head as you describe. The engine was rebuilt less than 5000 miles back, but that was at least 10 years ago!

[r_towle]

I chased this same thing on mine..
I did the intake runners process...increased the fuel pressure...problem gone..

Rich

[underthetire]

Hey, im looking at the same thing right now. Sitting on my coffe table. You want it?

[Gint]

I remember. Next thing you know you'll have me digging through a pile of boxes and find my TRS80.

[Spoke]

Cold problems could be head temperature sensor. Have you checked resistance at room temp & hot temp? A low resistance from the CHT sender will make the ECU think the engine is warm.

r_towle wrote:
_____________________
Lean means vacuum leak.
_____________________

I though with D-Jet that vacuum leak will make it run rich since the MPS sees low vacuum making the ECU think the throttle is open and thus widening the injector pulses.

[effutuo101]

I remember. Next thing you know you'll have me digging through a pile of boxes and find my TRS80.

Gint, I haven't thouight of them in years! (IMG:style_emoticons/default/pray.gif)
I remember getting my first PC. My buddy had a TRS80 and thought it was the cats meow. Mine could heat my rooom up in about 20 minutes on those cold San Diego mornings...

[Joe Bob]

LIGHTLY spraying carb cleaner or Qwik Start in suspect areas will show vaccuum leaks....the idle changes.