69's MFI cold start problem...now ignition issue ?

[SFE]

Another post for probably another issue

Thanks to Mr Edmayo, I've already checked fuel cold start devices :
1/Solenoid attached to the pump : clicks when 12V is applied directly on it and about 11V (during 1 or 2 sec) when turning the key all the way to the starter cranking position. The round black relay is brand new and works with the horn.
2/Solenoid on top of the fuel filter : fuel coming out when cranking is ok. This was working at about +6°C (it should only work at -10°C and below I think but it works...and when temp was about +10°C it was not spraying any fuel).

So apparently plenty of fuel (confirmed by the smelling !!!).

And the engine cold start is still a PIA ....but after many many attempts, it eventually starts with a lot of fuel smell and smoke.

Our analysis is a lack of ignition.

Is it possible the BHKZ is faulty and don't give enough power the spark plugs ?
Could it be the ignition starter switch ?
A faulty ignition transformer/coil ?

What do you recommend ?

[lopena]

SFE:

Start with the basics:

- Check your points for condition and dwell angle (38 degrees +/- 3 degrees).
- Check condition of rotor and distributor cap, especially the little carbon button in the center.
- Pull a sparkplug and check for spark by grounding it while cranking.
- Check condition of all plugs…clean and tan or sooty and oily?
- Measure the continuity of your ignition wires end to end.
- Is your gasoline fresh?

Start there and let us know if you find any anomalies.

Good luck,
Alan

[edmayo]

Took the words out of my mouth Alan!! In addition check ignition timing, is the battery cranking the engine strongly, if battery is weak it will lessen voltage to the ignition while cranking. What spark plugs are you using? Pull the wire off the solenoid on the fuel filter, you don't need that fuel spray since you say it smells rich. Are you holding the throttle at least half open during cranking?

[SFE]

SFE:

Start with the basics:

- Check your points for condition and dwell angle (38 degrees +/- 3 degrees).
- Check condition of rotor and distributor cap, especially the little carbon button in the center.
- Pull a sparkplug and check for spark by grounding it while cranking.
- Check condition of all plugs…clean and tan or sooty and oily?
- Measure the continuity of your ignition wires end to end.
- Is your gasoline fresh?

Start there and let us know if you find any anomalies.

Good luck,
Alan

Thanks for your reply Alan.

Actually we just finished tuning the engine after having changed the throttle body and other component around the air intake system.
The engine is now perfect under partial load and still a little bit rich at idle (but it is probably the best the pump can give us before I decide to send it for a complete overhaul someday).

So the only issue regarding your list is the spark plug are a little bit sooty but that shouldn't be the problem. Everything else in your list is brand new (with NOS or new Porsche parts) or has been checked.

The engine was completely rebuild and compression numbers are "as per the book".
When it is started it really runs fantastic with a very smooth +/- 900 rpm at idle when warmed up.

This is why we now plan to inquiry around peripherals component such as BHKZ, starter switch, ignition coil,.... but maybe it is a wrong direction ?

[SFE]

Took the words out of my mouth Alan!! In addition check ignition timing, is the battery cranking the engine strongly, if battery is weak it will lessen voltage to the ignition while cranking. What spark plugs are you using? Pull the wire off the solenoid on the fuel filter, you don't need that fuel spray since you say it smells rich. Are you holding the throttle at least half open during cranking?

Hello Mr Edmayo,
I will definitely disconnect the fuel filter solenoid because in my country I shouldn't need this device.
Bosch Batteries are new (pretty much) and seems to crank the engine firmly but it is true that the main symptom we feel is as if there was not enough ignition during the start.

For exemple when we measure the voltage at the enrichment solenoid on the pump, sometimes we have 10V, sometimes 11V or a little bit more when cranking the starter. Is this enough I don't know.
Since the engine start problem seems to occur only when it is cold, I still have a doubt with this solenoid, maybe the thermo time switch connected to it is not telling him to stay rich ?
On my car there is 2 thermo time switch, I guess one for the fuel filter solenoid and one for the enrichment solenoid on the pump. Since the fuel filter solenoid send fuel even above the "supposed to be" -10°C, maybe the wiring are inverted on those thermo time switches ?

So it is still a fuel issue or now an electrical/ignition problem.....?

We are quite lost on this side of the Atlantic

[SFE]

After some investigation we found out the connections on the 2 thermo time switch were inverted.
The 2 yellow + red wires where on the rear switch and the 1 yellow + 1 red/black wires where on the forwards switch.
Start was looking better but I will have to check again when the weather will be colder !

Also the batteries are 7 years old and even if the voltage looks acceptable (12.7V at rest), they might be a little bit weak in order to take care at both the starter and the ignition.....?

[SFE]

Still very difficult to Start when cold

So I decide to change the batteries....same problem

Next step I will change the 6 spark plug.....

[edmayo]

What spark plugs are you using?

[SFE]

What spark plugs are you using?

I don't remember what's installed but I plan to try those one :






Regarding the 2 thermo time switch the rear one shows +35°C....that may explain why the fuel filter solenoid is spraying fuel even at +10°C...anyway it is disconnected now.
The forward switch which is supposed to be the one connected to the injection pump solenoid has no temp indication on it...??? Maybe the injection pump solenoid itself is not working even if it "clicks" with 12V on it ???
Anyway when the wires where inverted on those thermo time switch the car was difficult to start either...

[edmayo]

May not matter too much for current problem,,but those are too cold. I use the 7 heat range, but you may still have other issues. Try a temporary jumper wire to the enrichment solenoid from one of the fuses on the relay board. See if that helps the start, but don't leave for more than a few seconds.