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Join Date: Dec 1999
Location: Milpitas, CA
Posts: 2
Flashback valve & more problems.

Ok.. Well I was thinking of selling my 914 (recently acquired) in favor of a motorcycle.. but I went on a date the other night with a great woman that mentioned to me that she liked old Porsches. *smile*



It runs really rough right now. I'm sure it could really use a rebuild.. but I'm just going to try and get what I can out of it before I get it rebuilt. The guy I bought it from appeared to know what he was talking about. I found Dave Darling's hose diagram and I decided to dive in and make sure everything was hooked up the way it should be.

Some questions.
What is the flashback valve? I can't seem to find it! There is a screw hole or two in the location where it looks like it should be..

On the far top left side of this picture, where are the two green hoses going?

When the car is running, exhaust seems to be coming out of two of the hoses. One is the hole with the green hose coming out of it on the lower-right hand corner of this picture, and the other is on the opposite side of the engine (upper left).. both are coming out from the bottom, not from a valve of some sort. (I hope you can get what I'm saying here..)

After the car is started, it will stall until it runs for about 10 minutes. The auxiliary air regulator appears to be sucking in air while the car is cold, so I don't think that's the problem. Any other quick things I can check?

Thank you all for your help.. Hopefully, I'll get this thing running well enough to not be embarassed to show up at a Bay Area 914 gathering!

Kris L.
74 2.0
Old 12-22-1999, 03:15 PM
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Join Date: Oct 1999
Location: San Ramon, CA
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Hey Kris,

I am in San Jose and I have a 74 2.0 as well. Ill try and answer your questions if I can remember them...

The 2 green hoses come from the front of the car and connect to the charcoal filter I think they are important for smog or something...

I don't know what the flashback valve does, but I do rtecall a recent conversation about it on this list...do a search of recent posts.

The other hoses do need to be hooked up for vacuum purposes as well as emissions.

I have followed that diagram closely and know that if certain connections aren't made, the car won't start or has idle problems.

Post more questions if this isn't enough. I'll check it daily over the holiday.

PS glad to hear you'll be at the meet...I hear there may be a door prize...
Old 12-22-1999, 03:34 PM
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I reread your 1st post...

The 2 holes from the bottom are nipples from the top of the valve cover chamber and I believe are part of the PCV system. I'm not sure why you see exhaust from there...I never pulled mine off while the engine is running... If exhaust, it would have to slip by the cylinder rings and valve guides, or maybe the exhaust valves are out of adjustment...maybe what you see is gas/oil vapors of uncombusted fuel?
Old 12-22-1999, 03:40 PM
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I'm pretty sure I do have valve guide problems.. The car burns oil like crazy.. especially when >3000rpm with my foot off the gas when the engine is in gear. (Engine braking is pulling oil in past the valves into the cylinders?)

Thanks for your help.

Old 12-22-1999, 03:51 PM
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Join Date: Dec 1969
Location: Dade County, FL.
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The flashback valve is a safty device of sorts. Inside is a fine wire mesh that works as a flame arrestor. Reason for this is that the vapor you see coming from the heads is oil vapor (if you run VERY rich it may also be fuel vapor that has diluted the oil) this vapor (being a petrolium by-product) is flameable. The flash back valve is ment to keep a back-fire in the intake from causing this vapor to ignite. I don't know if the explosion would simply blow out gaskets or split the case, either way it would be bad.

For the most part the only harm I can see leaving these hoses open (as far as I know) is 1. Oil vapor all over the engine, cloging not only the air filter but also insulating the engine with dirt causing it to run (a little) hotter. 2. Polluting the air. 3. Allowing water egress into the engine. A used flashback from Pelican must be cheap, I'd to it the right way.

Cold stalling could be a low idle (should be at 900-1000, use a tach dwell meter the dash tach won't do). Or the dwell is too small, or the points are bad, or the timing is retarded. Also see if the idle fuel adjustment is set too rich (little knob on top of the ECU) , or if the cold start valve is leaking causing a rich mix follow this link for more info.
http://www.914fan.net/

Step one: Get a tune up. New plugs,points, condensor, wires, set dwell (dwell meter $15-$25), timing ($20-$50 but most good timing lights are >$35), change the oil and add a snake oil to stop the oil burning, check the fuel mixture at a gas station. Make sure all the vac hoses are not leaking, if they are cracked at the ends chop them back until it is plyable rubber or replace them.
Old 12-22-1999, 04:48 PM
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Join Date: May 1999
Location: Burlington, NC
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You might want to check the resistance of your Cyl. Head Temp. Sensor. When cold, it should be at least 2500 ohms. My 2.0L started and stalled a few times before it finally started and ran. The head Temp. Sensor could be your problem.

Pritchard

[This message has been edited by Pritchard (edited 01-03-2000).]
Old 01-03-2000, 10:00 AM
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