TY Tony!

Andy

Thomas, thank you, somehow I either missed or didn't understand this comment from you from two days ago.

I just grounded the W cable as you suggested while the engine was running and there was no difference in the engine rpm, so I do not think the CSV is working (in addition to the TTS not working as the previous tests showed).

[edit] I also just put a test light on the G/yellow/smaller TTS cable and it does have power when cranking.

Andy

Hi Tony, thanks, my old TTS fails #2 procedure, the new TTS should arrive late today.

Andy

Wrong Test Procedure…..
 

Andy,

Grounding terminal W while the motor is running will NOT activate the CSV. For the cold start valve to spray fuel, you need to energize the (+) terminal of the CSV and the (-) terminal grounded. That’s the reason I offer free assistance to people like you to help your troubleshooting done quicker.

Tony

Thanks Tony, that makes perfect sense.

I did just now attach the probe of my test light to the G connector on the yellow wire and grounded the alligator clip to the engine, and cranked the engine, and the test light did light up.

So that tells me the yellow wire is supplying power to the TTS during cranking as it should.

I should be getting the new TTS tonight.

Question: With a working TTS and a cold engine, if I put the yellow G wire onto the G terminal, and put a test light between the W wire connector and the W terminal on TTS, the test light should light up during cranking for some seconds, right? And that would indicate that the TTS is providing a ground, right?

And please understand that I am very, very grateful for all of your help and your offer to test my TTS and CSV. I also am one of those guys, probably like yourself, who likes to figure things out and fix things.

If I can't figure out whether the TTS & CSV are working myself, I will gladly and thankfully throw my hands in the air and send them to you and let the expert take over! :-)

Andy

Andy,

Do the test and share your result.

Tony

Well, the new TTS is in and the test light lit up during cranking just like I had hoped. So that should mean the new TTS is providing the ground for the CSV as it should.

And there is no light during cranking with the old TTS. RIP.

So I guess now I just drive it around and hope that the intermittent no-start is fixed?

Fingers X'd, but I'm not getting my hopes up too much!

Andy

On my ride home tonight the car simply shut down while driving. It then cranked, but did not start. There was no fuel injected when I lifted the AFS arm in the airbox. I pulled the connector off the AFS switch but the fuel pump did not run when I turned the key to "on."

My car has an old-style 25A ATO fuse jumpered to the fuse block by the previous owner, I think near the #16 fuel pump fuse (it was too dark to see exactly). Anywho the 25A fuse was blown. So I bought a handful of 25A ATO fuses, switched out the burned fuse for a new fuse, and the engine started up immediately, but only made it about 2 miles before the new fuse blew. I put another 25A in and was able to limp the car back to my office.

So that was my day and now I am reading Tony's procedure on testing/checking the FP...

https://forums.pelicanparts.com/porsche-911-technical-forum/550098-fuel-pump-fuse-1983-911sc-cab.html

Sorry to hear.
If your FP is bad, definitely check the fuel tank. It's supposed to be corroded. Replacing the FP without checking - and if necessary cleaning or better replacing - the fuel tank is stupid.
Replace the FP with a original one. Mostly Bosch. They deliver 210l/h and a pressure of up to 6bars.

https://forums.pelicanparts.com/porsche-911-technical-forum/1125870-fuel-pump-question.html#post11790041

I installed an inline fuel filter between the tank and the pump in my car. That will prevent crap from the bottom of the tank getting into the fuel pump, which should make it last longer.

Got the same idea but not yet done. Which filter did you used?

Thanks guys. So fuse holder #16 is empty (and looks like it got cooked during a previous ownership) and the jumpered-in ATO fuse replaces it. It's pulling power from the top of fuse #11 and delivering it somewhere underneath the bottom of #16. Hard to see.

That bottom wire seems a little loose where it connects behind the fuse block, but it holds continuity while I move the wire around so the connection seems secure.

Andy

Tony posted this many years ago, at the link I included in my comment above (#88).

I did test #1, running the pump for several minutes. The fuse seemed fine as it did not heat up at all, and the fuel pump sounded normal too.

I'm reluctant to do test #2 as my multimeter can only handle 10A. And from googling around it seems most MMs limit out at 10A.

How do you guys measure >10A?

Andy

Either with a MM that can handle this high current or more likely use a clamp meter. They can handle much higher currents and you don't need to break the curcuit... And in earlier days they used a shunt resistor...still an alternative...

Thomas

Thanks Thomas, I guess a clamp meter is in my near future. Looks like a super useful device!

Andy

Well, my brand-new clamp meter read 6.7A at the fuse doing test #2. Measured it several times, turned the meter off and on several times. No where near the 25A fuse rating.

I'm completely at a loss.

Andy

I then did test #2 with the engine running to see if the other engine/CIS components that pull power from this fuse (Like the FPR, WUR, AAR, TTV. Are there others too?) would overload the fuse, and the meter read 7.6A.

So, I'm completely at a loss as to why the fuse was blowing yesterday.

Unless, is it possible that the "looseness" in the fuse wire connection that I mentioned above allows the wire to ground out intermittently?

Andy

[edit] Can I just remove the fuse block screws to be able to see the back of the block, where it looks like the loose fuse wire is mounted? Disconnecting the battery first, of course.

Just did test #2 with the engine running and with the fuel pump relay instead of the 87a/30 jumper, in case that was necessary to get the engine/CIS components energized, but got the same 7.6A draw.

And tried to see behind the fuse block but it didn't seem possible to pull the block away from its mounting bracket with all the wires connected to it.

Maybe tomorrow I can try taking just the top wires off the fuse block to see if that will allow me access to the back side of the block to investigate the loose lower wire on the fuel pump jumper.

Andy

Thomas, here's where I mounted the filter. Note, this is on a a 1973, so the pump is in the rear of the car, and that's where I put the filter.

See this link to a discussion about replacement pumps, response #6:
https://forums.pelicanparts.com/porsche-911-technical-forum/1142734-bosch-fuel-pump-upgrade.html?highlight=fuel+filter+1973

Well I think I figured out what caused the 25A fuse to blow! lol. This is the power cord to the WUR.

And why the amperage was way below 25 by the time I tested it.

I took all the heating/AC ducts, etc., off the car the other day, just hours before the 25A fuel fuse blew, and I believe the WUR's power cord went over a plastic heater shroud that I removed, so maybe the cord got damaged when I removed the shroud? I tried to be careful but it was a bit of a struggle to wiggle the shroud out from under the various wires that were over it.

http://forums.pelicanparts.com/uploa...1729364463.jpg