Initial Start-Won't Run-Ignition?

[H/O Driver]

Alright Brain Trust, maybe you can provide some insight here:
Just finished with the rebuild of my 1976 930. I get it to start, but it won't continue to run. I can get get it to run with someone giving it throttle AND me pushing the CIS plunger down slightly and not letting it completely close. Even then it won't run for very long (<1min).
I'm thinking the timing is just way off so I pull up the timing light to check and adjust. My timing light is very sporadic and at times doesn't even work. I then connect it to two other spark plug wires and still no timing light. So now, thinking I have a bad timing light, I take it outside and hook it up to my pick up and it works fine.

Does the metal braiding around the plug wires interfere with the operation of the timing light? Can my spark be too weak to run the light and hence causing the engine not to be happy?

When it was working the timing appeared to be way off and I was able to get it closer by pulling the distributor and moving the rotor one tooth in the retard direction. Seemed to help some, but still doesn't want to keep running.

Here's some background:
Engine was in boxes when I purchased. Hadn't run in over 20 yrs.
First time Porsche engine build for me, so don't assume anything is 100% correct! I used Wayne's book to do it, and believe I made all of the necessary changes to make the assembly work for the '76 turbo.
All fuel lines replaced from front tank to FD.
FD was rebuilt by CIS Flowtech.
WUR rebuilt by Tony.
I checked fuel pressures using the guide here in the forum-all seem good.
All fuel injectors are new, but I did NOT flow check them. Felt that I probably didn't need to since WUR and FD were rebuilt and assumed to be tested.
Purchased the CDI from a fellow Pelican. He said it worked.
I replaced the blue distributor coax wire (it was shorting). I actually spliced it in using a good section of the old one and reversed the leads in one of the connectors so that the polarity remained correct (i.e. ground on outer wire for a CW rotating distributor). I feel decent about this repair, but there is about a 1" section where the splice is that isn't shielded.
I would appreciate any insight. If you need more info, I'll get it to you.

Here's a short video so you can hear her struggle: https://youtu.be/COdWHByenNs

[1979-930]

Not firing on all cylinders. You’re going to need to get the gauges and go through checking fuel pressures.
But I think getting a good green wire from Timmy2 is the first thing to do.


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[dannobee]

Yes, the braid affects the signal of some timing lights. An old trick is to hook up the inductive lead of the timing light to the coil wire. The light will be brighter and you'll figure out the correct mark.

Spark plug wires are all installed correctly? None are crossed?

[lite75]

Both fuel pumps running?

[H/O Driver]

Today:
Verified both fuel pumps running.

Removed and re-secured plug wires to connectors at distributor cap and really had to bear down on pushing them into the distributor cap. They don't want to go in there! Thinking that I may have had some that were not inserted far enough.

Tried to start again. Sill won't run without me pushing down on the plunger. But I did get it to run longer and when it did, it sounded MUCH better (smoother).

Also connected timing light to center wire seemed consistent. Also had the timing light inductive pick-up attached to the non-shielded portion of the plug wire adjacent to the distributor cap and it was consistent too.----Conclusion: shielded plug wires DO affect timing lights (at least mine).

Tomorrow night I think I'll hook up the fuel gauge again and recheck pressures as well as trying to screw the idle screw down to hold the plunger open a little more.
That plunger isn't hard to move, but has anyone heard of them being too "stiff"?

[Alan L]

When you get it briefly running, let it die after 30 secs.
Put your hand on each of the headers - that will tell you if you are missing some cylinders, or have a complete misfire across all 6 - ign/valve timing etc. If you have one or two cold(er) headers - then go looking at those cylinders for fuel/spark. One issue I have found is putting the plug caps on - they can feel right but often are not. They should 'snap' firmly on.
Alan

[smurfbus]

Could one cam be off? You are 100% sure of your plug wire order?

[T77911S]

if the timing is off and it starts it should keep running.

sounds like the fuel mixture is not correct.
remove the connector on the rear of the AFM so the pumps run with the key on.
adjust the mixture CW until the injectors start to flow then CCW to where they don't flow.
adjust the idle up, large screw on TB. that way you don't have someone controlling the air into the engine while you manipulate the sensor plate as you did before. you need steady air in. pushing down means it is too lean, lifting up means too rich.

another issue could be power to the CD unit.
verify the CD unit is "whining" after shuts off is an easy way to check for power.

[H/O Driver]

1- I know the wires are in order coming off the distributor.
2- Could one cam be off? I wish I could verify. After completing that part of the build, I felt good that I had it right. I do remember early in the build getting confused with the cylinder numbering (I'm a GM guy). One of the things I have been thinking about, but, again, I believe I got it right.
3-I'll do the fuel mixture/idle screw tonite.
4-I too thought I had a bad CDI because of no noise. Bob Ashlock (the "CDI guy" on the forum) said the 8 pin units on these early turbos don't whine because they aren't on all of the time-only when the signal is received from the distributor. I am prepared to send it to him so he can evaluate on a 'scope.

r/
Bob

[T77911S]

then just check for power TO the CD. make sure it is constant with the key on for at least 2 minutes.
I don't think you have the time delay relay on there but I did see capacitor on the power side to the CD unit. don't know if that could cause an issue with power to the CD.

cams? seems funny that it would start but not keep running due to cams.

if one cam is off, depending on how much, you could bend a valve. if you did the damage is done. cam timing is not hard to check. just pull the upper valve covers and put the dial gauge on.
don't want to scare you or start sending you down different roads but since you brought it up, I f you did bend one you can check with a leak down or compression test.

you might also consider checking the firing order of the plug wires. I have put them on wrong and it ran, but no power. with that and bad mixture it would not keep running,.


with someone else working the gas like you are doing it can be hard to coordinate the how much you need to push on the sensor plate and how much gas the other guy is giving it.

the wires coming off the dist CAN cause a BIG change in timing. IE, if you set it up with the engine off so that it is close, it will be way off when you try to start it. this is a problem when guys put on the MSD box and yes I looked to see if you put one on.

I did not think about this until now but "IF" they are backwards the timing will retard as you rev the motor. just a thought. don't run down this road unless your other checks don't help you.
you can only cross them up if you take the connector apart or splice the wire.

[H/O Driver]

T77911S,
I don't believe I understand your last 2 paragraphs about the wires and setting up with engine off. Also about the "backwards" do you mean for CCW rotation?
Can you explain further so I understand?

Thanks

[H/O Driver]

Here's the results of my fuel pressure tests:
System Press: 7.1 bar (spec=6.0-6.7)
Cold Control Press: 2.7 (spec=1.5-1.9 @ 27C)
Warm Control Press: 3.3 (spec=2.6-3.0) got there in 1:40m
Residual: 5m=1.95; 15m=1.7; 30m=1.5; 60m=1.2
Control Circuit Flow: 285ml @ 1min (spec=160-240ml)
Fuel System Flow: 1900 ml @ 30sec (spec=1170)

I removed all plug wires and made sure they were all inserted as deep as possible into the rotor cap and double checked firing order vs plug wire orientation. I think I had issues with the insertions of more than one.

Got the car to start again. Still won't run without me holding the plunger down, but when it did, it sounded the best so far! Here's a link to the run video so you can hear:
https://youtu.be/sGCBM8FIt94

As soon as I let go of the plunger, it dies.

So please confirm or not with me that I think it runs without missing, and decent given that the air to fuel is jacked up.

If I have to hold the plunger down then that means it is too rich. Can my high pressure readings above be off enough to cause this problem to this degree?

My plunger is all of the way up when off. When I unscrewed the access screw, I didn't see anything in there to adjust the plunger downward. Stuck my allen wrench through the hole and can reach the plunger.
Haven't figured out how to adjust FD press. Do I buy a shim for a spring somewhere?
I think I can figure out how to adjust the WUR, but the FD adjustment may fix this???

I really appreciate your help!!

[H/O Driver]

oh yeah..... All of the exhaust headers are hot.

[Alan L]

Ok, then it is a general condition rather than specific cylinders - based on the headers not showing any difference in heat.
Your system pressure is easy - you are too high, so to get in to spec you remove shims. Take a medium sized one out - if there is a range of them.
You undo the nut on top RHS of FD. Carefully remove it - be careful - there can be some pressure behind there and stuff flying out - spring lost etc. Then just take a shim out and re insert. That will drop the system pressure.
Your idle setting sound suspicious. There should be a 3mm allen head knob between the FD head and the airplate? It should be sticking up about 1/2". You insert the allen key, and depress until you feel it engage - then rotate slightly, it should lock into a special housing in the airplate arm. Then turn it - anticlockwise - as previously suggested until there is no injector squeal. That is a different noise than the pumps whining. When you depress the airplate you will hear the injectors open/squeal. Let the airplate rest and that should stop and only the pump whine - cycling fuel thru the FD back to tank. This will occur when you disconnect the airplate sensor switch on the back of the airplate - pull the plug (key on). That should get you close to a base idle setting - the injectors should squeal as soon as you crack the airplate open slightly (1-2mm).
Then when warm you can tweek the idle mix until the engine runs happy. Anticlockwise is lean. 1/4 turn is a big adjustment - very sensitive.
Your Cold WUR pressure is quite high = lean cold start.
Alan

[Alan L]

I think you are chasing a leaness problem on a cold engine - which is why you are having to crack the airplate open. The TB butterfly stays shut (no gas pedal action) so no more air going in, but you are opening the metering slits in the FD (almost randomly) to let more fuel in to adjust the mixture.
Alan

[dap930]

Another possibility is that the o-ring on the FP regulator piston has swollen due to exposure to ethanol in the gas, causing the piston to stick. It happened to me before I converted to EFI. Also, on the early cars, the mixture screw is adjusted using your own allen wrench or a special CIS tee-wrench if you have one.

[Alan L]

There is no O ring on the FD metering piston - but good point. It must be able to move freely.
The airplate should be able to move easily thru full travel - best checked when no residual pressure in the system.
Alan

[H/O Driver]

Yeah piston moves freely. Well, I can't actually see the piston, but the plate moves freely and "feels" like the piston is riding on it and following. Also, I'm able to keep the car running by manually pressing the plate down (which in turn moves the piston).
Recall, I had the FD rebuilt by CIS Flowtech. When I got it back, the piston moved freely.
I'm concerned that the allen screw that is used to adjust the resting position of the plate at the uppermost point is not correct. There's only a screw and a washer and it doesn't appear to touch the arm of the plate.

[Alan L]

Your early engine may be different to the later ones for the idle adjust screw. But the principle is the same. Maybe post a pic for others. Sounds like the piston is free - you would feel it sticking, and if it follows the plate back to rest it must be free.
You did not state the temp you measured your Cold Pressure at. But if it was close to 27deg C or colder, it is a fair bet you issue lies here (as well as perhaps idle mixture adjust).
Regards
Alan

[Alan L]

"System Press: 7.1 bar (spec=6.0-6.7)"
Having just adjusted mine, I may have put you wrong which way to shim - mental picture was back to front. You will probably need to add a shim - about 0.5mm thick. Any appropriate size washer will do it if thickness is right. D 5.5mm, OD 9mm.
Alan
EDIT - sorry to muck you around - you do need to remove shim to reduce. It is a bit confusing looking at the way it shims. You will need to remove 0.5mm of shim - either by dropping an equivalent shim out, or a combo that adds to approx 0.5mm.