Another sportomatic queston; no clutch action

[caproader]

Guys,

Just rebuilt and installed the S engine in my 73 Sporto. Engine runs great, but......

Sporto trans does not work. Any attempt to shift into any gear produces monster grinding noise (appears to be no clutch action). I checked/replaced fuse in engine compartment. No change.

During rebuild process I removed the MFI and associated sporto vacuum lines and switch, but did not replace vacuum lines. Anybody had this problem before? Where to start looking first? Electrical signal at vacuum switch? Vacuum at tank on fire wall?

I plan to tackle the problem with my son, johannes356, this week end and would appreciate any trouble shooting list that might be out there.

Thanks

John

[edmayo]

John, the first thing I'd check is to see if you're creating and storing vacuum. After running the engine turn it off and find a vacuum line that you can easily pull off, see if there is that hiss of air indicating indicating air is trying to fill up the vacuum in the reserve tank. Or better yet see if you rig a "TEE" into a vacuum line so you visually see if the system is tight enough to create a vacuum. Check the obvious areas like the plugs that go to the neutral and safety switches on the side of the trans for good and proper connection, same with the plug to the vacuum control valve on the engine.

[caproader]

Ah, Ed. Glad to see and hear that you are still out there. I checked the electrical connection at the top of the vac switch for a good connection (seems to be tight). The engine starts fine but only in P or N. I tried to start it in R but no luck. which seems to tell me that the safety connections on the side of the trans are good.

Can I put a volt meter at the wire at the top of the vac switch to see if I get current when some one wiggles the shifter? Also, the top vac line on the switch goes to the tank on the firewall, and the bottom one goes to diaphram on top of the trans, right? I hope that I did not cross the vac lines.

meantime, the vac test is next. As I mentioned, I did not replace either the hoses or clamp in the interest in authenticity. Is there any commercial available vacuum lines that will stand up to the vac pressure? The line is not available from Porsche. Do I need reinforced line or will any serious rubber hose do? I don't want to have the vacuum suck the line shut.

John

[edmayo]

John, my shop manual shows the "single" hose on the control valve (which faces down) goes to the intake manifold. Of the two adjacent vacuum fittings on the valve, the one closest to the electrical connection goes to the vacuum reservoir. Hope it's this easy.
However I'm looking at a early carb setup, your control valve is in a different position. I'll look in the later book tomorrow.

[JT912]

Could be something with the microswitch on the shift lever?

[caproader]

jt912,
Thanks for the thought. I was thinking the same thing. Maybe the electrical connection popped off when I re attached the shift linkage at the transmission end. I plan and diving into the trans tunnel when I get home tonight.

Ed,
All hoses are connected as you outlined. I am hoping that this is an electrical issue as I do not want to replace a bunch of hoses and clamps.

John

[caproader]

OK, now the thinking out loud portion of the process:

When I apply an exterior 12v source to the contacts on top of the vacuum valve/switch, I can hear the vacuum valve cycle. However, I do not know what the normal state is for the valve when running; power to the valve or no power to the valve until a shift is inititiated.

When I pull the connection from the top of the vacuum switch and put a test light on the wiring harness at the valve, the test light comes on until I put a strip of paper between each of the two contact points on the shift lever. Without the paper between the shift lever contacts, pulling the ground wire at the shifter does not put the light out.

Do I understand correctly that this means that the normal state of the vacuum switch is no power and only when power gets to the switch does it activate? When I run the engine and try to activate the vac switch by an external power source, there seems to be no clutch action even though i can hear the switch try to cycle.

And if there was a vacuum leak in the lines coming off of the intake manifold, wouldn't that screw up the engine running? Right now the engine runs fine.

John

[Bullethead]

John and Raj are probably right. Provided you've found no vacuum leaks, the accumulator tank is good, the clutch servo isn't toast, the electrical connections aren't compromised between the shifter and servo... there are really only two things left to check. Which happen to be the most common problem with the Sporto, but an easy fix. Address the microswitch first, clean everything and with the shifter in neutral, be sure there's a 0.4mm gap on all contact points. Next, remove the two valves from the left intake mainfold (don't know if they're same side for MFI, but probably are) and unscrew the caps. If the springs are shot, the only option is to replace the valves. Still available from Stoddard... just recently got a set as completion of a full restoration on one of my Sportos approaches. Good luck!

[edmayo]

John, the easiest way to do this is to send me your e-mail, I can send to you the shop manual pages describing the clutch action. It would be far easier if you have these and can diagnose better than doing it with back and forth e-postings.
send me a PM with your e-mail.

[dporsche74]

I think it is shifter microswitch, In a quite place... car off, move the shifter slowly until to hear the ping of the slave cylinder working the clutch ,
that microswitch is sensitive and has to be right on the money to work well,
good luck