924Board.org

[maybeoneday]

Hi everyone,
I added a 924 to the garage about 6 months ago. It was a car that belonged to a friend of a friend. It needed a new head gasket when I got it but besides that it looked pretty good.

Since then I have replaced the gasket and completed a full head rebuild (head cleaned and inspected, machined, new valves, etc, etc). I thought it should be pretty easy to get going wow was I wrong. It seems like the injection system is going to be a little difficult to work out and a few other issues have raised their head.

First after a little cranking I started to see the alternator smoke. Some investigation showed new wiring I had a quick look and it appears to be not quite right and the cause of the smoking. So I have sent the alternator off to have the regulator and diodes checked, and will rewire it corectly. Also when playing around the brakes felt really spongy. I bleed the system, but no better. It appears to have a very new MC, so I adjusted the drums but still spongy. It looks like this problem was also identified by the last owner as almost everything in the brake system is new. The only bits that are not new are the rubber lines from the calipers. So thinking that swelling under pressure could be the cause I removed these for replacement.

Without the alternator in I tried starting a bit more but no good. Spark is good, and fuel meters the correct rate when plunger is pushed by hand. So I replaced all the vac hoses while I had the time now to save me looking for leaks later. I also drained about 20 liters of fuel from the tank because I know that it is at least 6 months old and i am assuming it could be much older. Our fuel can have up to 10% Ethanol in it so I figured it was a good idea if I ever wanted to get it started. I also replaced the dizzy with a stealth electronic ignition (not really replaced more converted, it just replaces the points, I hope you guys understand what I mean here).

So there is a quick run down I just wanted to let you guys know who I am and what I have (oh I think I forgot to mention that it is a late 1977 model with an auto trans), before I start asking for some help with this injection system and getting it going (I have ordered the injection system book to get a better idea about it). I also wanted to ask if there are any other things I should do while I am waiting for the alternator and brake lines to be done. I probably wont get these done for about a month because I am off to Japan for a month in a weeks time and I cant see them getting done before then, unless the alternator is ok to go back as is.

Please ask anything I missed, even though this is my first post this board is a great resource and has helped me heaps. Thanks again.

[larchie]

For spongy brakes, you might also check brake booster and vacuum check valve -- this page from online Hanes Manual (scroll down page for info as the anchor links are flawed).

[SilverGhost]

As has been stated many times before on this forum, fuel injection system fault diagnosis attempts are an exercise in futility unless you have the correct fuel pressure measurement rig.
I have one. I'm in Melbourne. PM me if you'd like to use it.
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"Priscilla" 1981 924 NA RoW auto, metallic blue

[staticsan]

I'd discard the fuel that might be tainted with Ethanol. There is a risk to the fuel system from the added Ethanol because it absorbs water and that makes things rust from the inside. The engine was designed for Premium petrol, anyway. I've never put anything less in mine.

Wade.
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'82 British NA - Which I think I've been very lucky with!

[maybeoneday]

Great thanks guys for the replies.

All that advice noted and I may have to get in touch about that fuel system pressure tester.

[larchie]

Here's useful information (beside that in the Hanes Manual (for access use links in left-hand column)) from ideola on testing the CIS: How to connect & operate the Hoffman CIS Test Kit

[musicalannette]

just a thought, I had the wiring go from the battery to alternator/starter.
I think its pretty common, a couple of the other guys mentioned it. runs near the exhaust, not sure if effects you, but if your fitting a new alternator I WOULD look intoitandreplace thewirewith something more heat resistant,its a weekspot and it might save you problemsin thelong term.

I think mynewUSB keyboard isrubbish, spacedoesnt seemto work too well andi'm not going back to edit, sorry.
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I KNEW white wall tyres were invented by Americans .....just not at Boeing.... to be fitted on the 737.....

[maybeoneday]

[924RACR]

Shielding is an absolute must; stock has a fiberglass sleeve, and they often deteriorate with oil exposure, plus there's much better options available now. DEI in the US makes some excellent protective sleeves for racing, but there's probably equivalent sources/products available in the UK/EU more conveniently for you guys:
http://www.designengineering.com/catalog/design-engineering-inc/line-hose-protection


The gold foil is particularly lovely stuff, I use plenty of it (the tape can be used to spiral-wrap oil hoses etc), but probably overkill unless you have a modded turbo or a racecar.
http://www.designengineering.com/category/catalog/design-engineering-inc/heat-sound-barrier/reflect-gold


_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[musicalannette]

erm,

well what you trying to do there is build a dam to stop the water getting to you house;

i.e. stop the heat from getting to the crap plastics covering the wire which will melt and then allow the wire to short.

It's better if you can live on a boat in the firstplace!!

No need for extra dams!!!

What I would suggest is P.T.F.E. coated wire, it's just wont be effected by the heat in a way most insulators would be.

The standard heat shielding will be plenty good enough.

By the way, if the car was fitted with this wiring and you had a short, the insulator probably wont be the thing to give up the ghost first.

It might seem expensive but might be actually cheaper than fancy heat shielding. It will probably be able to melt paint before the insulator goes.
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I KNEW white wall tyres were invented by Americans .....just not at Boeing.... to be fitted on the 737.....

[musicalannette]

Found this, looking at the specs its good to 260deg C
So *9/5+32

Is 500deg F



http://uk.farnell.com/brand-rex/spc00443a002-25m/wire-ptfe-a-black-7-0-2mm-25m/dp/1184020

I think you would need a thicker wire but a quick search give you an idea of the temp it can handle and quite frankly the 500 degF looks conservative , not too much more and the solder melts!!
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I KNEW white wall tyres were invented by Americans .....just not at Boeing.... to be fitted on the 737.....

[924RACR]

Not actually; you are better to keep the heat out of the wire, since of course the resistance of the metal conductor increases dramatically with temperature. Eventually, the battery won't charge adequately and the starter will be unable to draw enough current to crank. Note that the protective sleeve should include the battery cable to the starter, which is like 2 or 0 GA...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[musicalannette]

Don't get me wrong, i'm not saying I wouldn't use heatshielding with this wire, or for that matter your heatshielding if I had some to hand, it looks very nice, what I am saying is, once you have seen this wire you will wonder why they produce ANYTHING else unless you need something extra flexible say.

tbh you are right about resistance increases with temp, but the reality is the failure will occur from the insulation breaking down and the wires shorting inside the heatshielding, not from increased resistance due to being raised 500 deg C from absolute zero.

Remember, with a short you are talking arcing which is really at temperature that melt the wire material. An awful lot higher temp than 260 deg C. You know, it can melt steel quite happily.

Once this happens the material resistance then probably changes altogether as there will be carbon and oxidised crap in there from the arc and the value of roe change, the result could eventually become something as bad at conducting electricity as an insulator.


If you are AT ALL worried about internal resistances fit silver wire instead of copper or better still fit larger diameter wire as resistance will dramatically reduce.

This is not strictly true for all cases though, as when you start to add high frequency oscillations in current flow to the mix only the outer edges of the wire carry the current, called skin effect, then things like bends in cables can cause problems and if you keep turning up the frequency you have to think a bit more outside the box, hence microwave waveguides.

No BS, this stuffs bombproof, far too good for the motor racing industry.....I doubt the McLaren F1 was wired with it, it should have been, either that or with just the supply wires of this stuff and then just a coax for serial buses, the defence industry was on that path in the mid 80's.

I bet F1 didn't catch on until USB became the norm. I some ways motorsport spends the money on NEW NEW NEW and lifestyle and instant results, otherwise the sponsors won't pay. Not actually on taking a radical departure from the norm and throwing all the money into what they are making.

The rules changing to keep a level playing field kinda scuppers the creativity of the engineering staff, along with the fact three bad years to get a technical leap forward would have most sponsor driven teams going to the wall. As a consequence this stuff will never hardly be used in their environment, they aren't brought up with it, and that knowledge will never filter down to the club or back into there engineering departments.

I would say it's down to cost, and probably on the 924 it was. But on an dedicated motorsport car? just lack of knowledge, or should i say, more importantly lack of craft skill. You could probably come back after a minor fire and the wires be ok.

Honestly the standard Porsche heat-shield (which i hate to say, looks like it may be made of PTFE) works fine with better insulation on the wires. Has done since all the wires melted and took out the alternator.

This is one the wife will love you for, its also PTFE or non stick as most people know it made of similar stuff. If you look at it after use it looks remarkably similar to the original protective heat-shield material.

http://www.agacookshop.co.uk/bakeware/bake-o-glide?gclid=CMTMv_OBmrwCFTCWtAod7U4ApA

You never have to buy or more importantly run out of tin foil again!! Just wash and re-use!!

Were probably taking used and/or developed for Saturn 5's. I am guessing, it is that good, i know for a fact when you solder it your fingers' melt before any sign of insulator damage!

So after me going on and on and on, if you have changed your alternator change your wires from the battery to the alternator/starter.

You can probably guess what wire I would use. As for heat-shielding with it, as long as it isn't touching or will move about and touch the exhaust, turbo, ridiculously hot bits of the engine, i doubt you even need a heat shield! As I think the insulator its the same material as the heat-shield itself, and how long had that been there......
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I KNEW white wall tyres were invented by Americans .....just not at Boeing.... to be fitted on the 737.....

[924RACR]

No, I have way too much experience with heat-soak and hot starts in these cars to agree. Sorry. You're making some very big assumptions regarding how much heat builds up in that area.

Sure, better wire is great, but it's not enough...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[musicalannette]

i don't doubt that something which is racing round or has an engine pumping out 300 hp upwards isn't going have it very hot under the bonnet when is stopped and there is no airflow, or indeed, in the boot as were talking porche.

Especially if it has been racing round a track and comes to a halt, What i was trying to say is that for an unmodified 924 n/a, where that wire where it runs (asumming its all neatly routed and doesnt flap about) that type of wire would be ok on its own. Perhaps important if you heatshield material is a bit weathered or is isnt there!.

Spend a bit more money on the right wire and you might be supprised what you don't need if you cant find it.

Of course if your unsure, buy a couple of meters and run a couple of wires OUTSIDE the heatshield where it gets hot dont connect them to anything, then after a few runs look at the state of the insulation and carryout some resistance measurements to see if there shorted.

The best quality stuff will be manufactured to a DEF STAN or defence standard, they will be a traceable item for quality purposes or for failure investigations and as such you will pay a premium, but if its a smooth skin of insulation your probably on the right track.

I not too sure about the turbo as I dont know where they put the turbo, but again, a couple of meters to have a test with might surprise you.
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I KNEW white wall tyres were invented by Americans .....just not at Boeing.... to be fitted on the 737.....