'79 911 Turbo issues?

kerNol · 02-11-2011, 05:08 PM

So I just got my hands on a 79' 911 Turbo and have a few questions. First off the car is in decent shape, only 40k original miles, but it had been flooded slightly in the interior due to the previous owner leaving the car outside for some time with the windows slightly cracked. So the carpet is junk but besides that my main questions revolve around the engine.

Now on to my problems, while putting the car up on the lift and doing a once over I noticed there is a line missing from the wastegate. The line right off the top of the unit is non-existent. I'm looking all over the engine following the charge pipes etc. and haven't found any location that seems to be the connection for this. Where should I be looking to hook this up to, I'm assuming just as in any other turbo system it should go to a vac/boost source.

Now my next question is that I found what seems to be an auxiliary fuel injector down below the fuel distribution block. Is this suppose to be wired? as there is no connector attached to it and I can't find any loose wiring that would hook up to this injector.

My last question revolves around a misc. 2 pin connector I managed to find floating around on the right side of the engine compartment under the airbox. Any ideas what this is for or if it should be hooked up?

Thanks in advance, I'm sure more questions will follow. This car has no begun its transformation into a stock'ish track car, cage, modified suspension and stock engine for now.

mooney265 · mooney265's Garage

The last item is the plug for the thermal time switch, i believe...

jwasbury · 05:58 AM

First off, welcome the forum

Regarding your first question. The top of the wastegate is simply vented to atmosphere in stock configuration. It does appear that you have some non-stock fitting at the top of your wastegate because from the factory there would be a hard line that goes up through the tin into the engine compartment and vents to atmosphere there, presumably to prevent dirt and other debris from clogging up the orofice.

Its the lower line (I added red arrow to your pic) that should be plumbed to a boost source to open the wastegate. This will be connected to the intercooler in a stock config

Regarding question 2, that is the cold start injector, part of the Bosch CIS fuel injection system. There should be a connector off of the main harness that plugs into it. It should only fire when called for, based upon an engine temp sensor that is screwed into the left side chain box cover on the front of the engine.

As for the 3rd item, I second Mooney's thoughts. That looks like a thermo time valve connector. On a USA '79, there were two thermo-time valves. 1 was plumbed into the distributor vacuum lines (blocked engine vac to distributor for the first minute or so of cold start, to advance ignition timing). The 2nd thermo time valve was plumbed into vacuum line running to the AAV (Aux air valve). The AAV is not to be confused with the AAR (Aux air regulator), but it performed a similar function of allowing some intake air to bypass the throttle body at cold start. In my '79, the thermo time valve was missing for the AAV, effectively disabling it. I have subsequently removed the AAV entirely and my car starts fine hot or cold.

kerNol · 02-12-2011, 07:40 AM

Ok, so now I just have to dig for the injector wire off the harness. The thermo time valve connector I have yet to find a mating counter part but I'll keep looking. The car itself actually starts fine cold so I'm not to worried at this point.

Maybe you can clarify but the cold start injector does that do any supplemental fueling during boost situations or is that only a cold start thing? If its only cold start I might just leave it unplugged as everything cold, even down to 20F starts and idles well.

My last an final question is that the boost gauge tends to reads full boost at idle, is there something I'm missing here or is that suppose to be a vac. reading?

Thanks again.

jwasbury · 02-12-2011, 07:47 AM

The cold start injector is only there for cold starts. Its not involved in fuel enrichment on boost, at least not in stock configuration.

Boost guage pegged at idle is not right. Probably an electrical issue, bad sender or the wire to the sender is unhooked.

jwasbury · 02-12-2011, 07:52 AM

#14 on this diagram is the boost pressure sender.

Sam Matthews · Sam Matthews's Garage

If the charging pressure gauge in the tachometer fails, check all wire connections on the tachometer or charging pressure sensor against the wiring diagram.
Pull off wire on charging pressure sensor.
Turn on ignition.
The charging pressure gauge needle must deflect fully.
Hold the disconnected wire against ground. The needle must return to zero.
If the instrument meets these requirements, the cause of trouble will be found in the charging pressure sensor.
Otherwise the gauge would be defect, and the tachometer would have to be replaced.

Note
The resistance of the charging pressure sensor (measured between the connecting lug and
housing) must be between about 5 and 13 ohms at 200 C and atmospheric pressure.

spuggy · 02-13-2011, 12:28 AM

Quote:

Originally Posted by jwasbury

The cold start injector is only there for cold starts. .

What he said. I think it's intended for folks going Ice Racing or something; my car starts just the same as it does in summer with ice on the windshield and the TTS completely disconnected.

The cold start valve circuit is powered from a terminal on the starter solenoid. The thermo time switch (on the chain case) completes the circuit by providing ground whilst the car is cranking on the starter, if it's cold enough (doesn't close until it's below the cut off temperature).

That injector is plumbed into the regulator return side and just dumps raw fuel into the manifold as long as it is powered and there is fuel pressure - however, there's a heater in the thermo time switch so it'll only do that for a few seconds, to prevent flooding.

kerNol · 02-13-2011, 06:24 PM

Thanks for the info and diagram. I'll have to check out the sending unit to find out if that or the gauge is bad. I'm thinking sending unit as the gauge does zero when the ignition is turned off, but who knows.

On another note, adjusting the clutch on this car appears to be adjusted both under the trans and at the pedal. What is normal for the amount of free play before engagement. Like I said the car has 40k on it and it hasn't been run hard and it seems like I have 3 inches or so off the floor before the clutch engages.

Also what might you guys suggest as budget friendly upgrades or free mods to do to this car to make it more track happy. The basic idea behind this car is that it will be a track car with very limited street use but I don't wanna go full race prep as it might be street driven once and a while. I don't want to go crazy as this is more or less a car just to take out and beat around on the track, primarily for my brother or friends as I have another car I run regularly.

Thanks again.

kerNol · 02-14-2011, 03:57 AM

Well I found the pressure sensor, or what remains of it. It looks like someone drilled the guts out of it and brazed the body shut. So now it's just a plug, the issue now is wiring for a new sensor. Any chance I should be lookin for a wire from the rear left of the engine compartment? I found a blue 2 conductor cable with a white or white & yellow pair of wires. 1 looks tampered with and it's ground out to the engine. The other is just cut off. I tried pulling the one off ground and nothing. There's just something weird about this car.