My '77 convertible...

[john walker's workshop]

Could the airbox be blown? Sucking so much air it won't stay running? Seems the sensor plate arm moves and activates the injectors, so the fuel distributor piston is moving. Potential fire hazard if it is.

[ZeroHecksGiven]

Tried disconnecting the safety switch on the back, still no dice. Here is a video of current situation..

https://youtu.be/UzuQJxyU2fY

Airbox seems fine, though I haven’t tested it.

[ZeroHecksGiven]

Okay, watched the CIS video on youtube last night and added some things to check and work on. Also got my fuel gauge set from amazon, hopefully that's all good and can test accordingly.

Last night we tried a TSS from a running '75 911. Also tested the CDI, but the one from my '77 did not allow his 911 to start up, so not sure if there is an issue there or not, his battery was low as well. They look the same physically, but may not be the same inside. WUR is different, so couldn't give that a go.

Up next checklist:
•check WUR for power
•check AAV for power (both seem easy enough)
•test basic system pressure
•try basic DIY airbox test
•replace fuel filter (pelican order showed up)
•trace/replace some vacuum line (pelican order showed up)

[ZeroHecksGiven]

Up next checklist:
•check WUR for power - GOOD
•check AAV for power (both seem easy enough) - GOOD
•test basic system pressure - couldn't get the hose tight on the FD side, buying a shorty 14mm tomorrow.
•try basic DIY airbox test - didn't attempt
•replace fuel filter (pelican order showed up) - I couldn't get my adapter thread pieces to fit on one side, of course. It's like the threads are a little deeper in the filter on one side...
•trace/replace some vacuum line (pelican order showed up) - didn't work on this



Feeling a little frustrated tonight. Didn't make much progress. It's becoming clear there seems to be one little thing stopping me from actually completing most of these tasks. Trying to be patient and not cut corners, but having to order things and wait multiple days between each step is mildly infuriating, lol. Going to try and find an adapter to fit the fuel filter so I can actually get that replaced. Will buy the wrench and see if I can get the pressure tested tomorrow or this weekend...

[ZeroHecksGiven]

old filter left, new filter right

[PeteKz]

Yep, they are different. Some filters come with the fittings, some don't. Take the fittings off the old filter, and see if they go into the new filter (they are locktited in, so it will take some effort and heat will help). Hopefully, the fittings from your old filter will screw into the new filter, otherwise, you will need to order one or two to make it work.

After doing the same thing you are about to do, I have decided on a different approach for my next filter: Get the filter that goes on Carreras, because that filter is common across multiple models and I think different brands of cars. And you can get it at some FLAPS. I also think it comes with fittings, which will make backfitting easier.
https://www.pelicanparts.com/More_Info/92811025307.htm?pn=928-110-253-07-M45&SVSVSI=911M&KeepHeader=Y&cat=https%3A%2F%2Fwww.pelicanparts.com%2Fcatalog%2 FSuperCat%2F911M%2FPOR_911M_BASFLT_pg4_fuel-filters.htm

[ZeroHecksGiven]

Originally Posted by PeteKz

After doing the same thing you are about to do, I have decided on a different approach for my next filter: Get the filter that goes on Carreras, because that filter is common across multiple models and I think different brands of cars. And you can get it at some FLAPS. I also think it comes with fittings, which will make backfitting easier.
https://www.pelicanparts.com/More_Info/92811025307.htm?pn=928-110-253-07-M45&SVSVSI=911M&KeepHeader=Y&cat=https%3A%2F%2Fwww.pelicanparts.com%2Fcatalog%2 FSuperCat%2F911M%2FPOR_911M_BASFLT_pg4_fuel-filters.htm

Thank you for that tip. I might just grab one. Yeah, only one fitting seemed to work. I’ll swing by my local Napa or VatoZone and see if they have something that will work, but finding a standard filter would be ideal. I’m led to believe the one that was on the car is now NLA, so that’s sweet, hahah.

One step at a time I guess.

[ADDvanced]

The fact your CDI made his car not start sets of my alarm bells. Keep at it, you'll get it. I bet she'll run fine when you figure it out.

[ZeroHecksGiven]

Originally Posted by ADDvanced

The fact your CDI made his car not start sets of my alarm bells. Keep at it, you'll get it. I bet she'll run fine when you figure it out.

His wouldn't allow mine to start though. But you're right, it's something I've thought about since. Might try and get his battery charged up a bit more and then try it again.

But you're right, it'll work out eventually. It feels like it's sooooo close, so frustrating to feel like I'm not making any progress. But, plenty of other vehicles on these forums that were in MUCH worse shape and are now beautiful running vehicles.

[ADDvanced]

You've read everything on Jim's CIS primer, right?

https://jimsbasementworkshop.com/CIS/pages/test_troubleshoot.html#TS_chart

So I had a similar problem, could not get my fuel pump to turn on with I turned the key, you can sift through here (lots of good electrical troubleshooting of the CIS system)
http://forums.pelicanparts.com/porsche-911-technical-forum/1128356-fuel-pump-wont-come-no-ground-85-a.html

It wound up being a connector near the fuse area.... unplugged it, plugged it back in, works now.

[boyt911sc]

A fuel injection pressure gauge kit is a MANDATORY tool for fuel injection troubleshooting. Without one, you are wasting your time. And invest on a good set. Get a S&G Tool 33800 or similar model. You are not saving by buying the low priced gauges in RED Box from Amazon or HF.

From watching some of your videos, I would say you have to test and identify the sources of your air leaks. Use a smoke generator to locate them. Nice car.

Tony

[ZeroHecksGiven]

Thank you both. Got the gauge hooked up this evening and tested pressure. It climbed to 74psi and then wouldn’t go higher. I felt good about that for the time being and wanted to move onto some other tests, so we pulled it off and got everything set back up.

We cleaned some connections at the rear of the car, moved relays around and cleaned those connections. We cranked car with our hand on the pump and it did run while key was ON and turned to RUN.
Pulled an injector. Small little mist of spray when they key turned to ON and then sprayed mist when it was being cranked. Nice strong spark during cranking as well.

I suppose this leads to air, right? Fuel/Spark seems good.
I will follow your advice and head down that path next.

I will look up some ways to test and work on replacing vacuum lines that I can.

[PeteKz]

One other tid bit: Please have a fire extinguisher handy while working on the fuel system.

[ZeroHecksGiven]

Always a fire extinguisher nearby, both of the other cars nearby have them as well.

Finally got around to doing a smoke test. This proved more difficult than it looked on YouTube, lol. There was a little bit of smoke coming out of the pop off valve inside the air box, but not much. Even less coming from somewhere near the AAV I believe. Right side of the engine. I’m going to rebuild the smoke machine and try it again. To me, it didn’t seem like there was any massive air leaks present, at least what I would think that would prevent a car from starting.

Is there anything I could have missed up to this point? So weird how it seems to run so well for those three seconds and then just not be able to run.
I rechecked spark, that continues to spark until the car sputters and dies (from pressure air plate)
When turning key to on, there is a small squirt of fuel. If we DONT raise air plate, it does not send fuel through the injector during cranking. What is stopping the injector from misting during cranking?

[boyt911sc]

You need a CIS fuel pressure gauge to determine your control, residual, and system fuel pressures for your troubleshooting work. It is a MANDATORY tool whether you are an amateur or a professional. Without one you will have too many unknown variables to help you solve your problem/s.

Borrow and use the correct tool/s to help you diagnose what is wrong with your CIS. There are numerous things that could cause your NO START namely:

• Presence of unmetered air going into the system.
• Out of spec fuel pressures.
• Ignition timing.
• Defective CIS components.
• Defective cold start components.
• Etc.

Tony

[ZeroHecksGiven]

Originally Posted by boyt911sc

You need a CIS fuel pressure gauge to determine your control, residual, and system fuel pressures for your troubleshooting work. It is a MANDATORY tool whether you are an amateur or a professional. Without one you will have too many unknown variables to help you solve your problem/s.

Borrow and use the correct tool/s to help you diagnose what is wrong with your CIS. There are numerous things that could cause your NO START namely:

• Presence of unmetered air going into the system.
• Out of spec fuel pressures.
• Ignition timing.
• Defective CIS components.
• Defective cold start components.
• Etc.

Tony

Thanks Tony, I did test pressure, measured 74psi. I only did pressure from FD to WUR, but will go back and do the other tests to see where those land.

I did end up pulling the WUR last night and spotted some grime inside the side connected to the FD. I did NOT open it up or move past removing it from the car, I will see about cleaning that up, re-installing and checking the other pressures.

[boyt911sc]

Since you have the gauge, you might as well measure the following:

• Cold control pressure.
• Warm control pressure without vacuum.
• Warm control pressure with vacuum.

This is how to do this simple test. Install the CIS gauge between FD and WUR (valve closer toward WUR). Disconnect the plug to WUR and test run the FP. With the valve open, you are measuring CCP (cold control pressure). Record the pressure reading. Next step is to plug the connector back to WUR. As soon as you connect the plug back to the WUR with the FP running, the WUR will begin to heat up and the control pressure will gradually increase until it stabilized. This is now your WCP (warm control pressure). It is also helpful to record the transition time from CCP to WCP. A 1-min. interval up to the time WCP maxed out (4~5 mins.).

If you are just running the FP (engine off), you will get the WCP without vacuum. To measure WCP with vacuum, use a vacuum pump and apply 5” Hg. Keep us posted.

Tony

[unclebilly]

ZeroHecks… John Walker, who is one of us, and a good guy, knows your car and has chimed in twice to be helpful…

At least give him the courtesy of replying. That’s how this community works.

[ZeroHecksGiven]

Originally Posted by unclebilly

ZeroHecks… John Walker, who is one of us, and a good guy, knows your car and has chimed in twice to be helpful…

At least give him the courtesy of replying. That’s how this community works.

I didn’t quote him directly, but I did respond to his inquiries. I’ll do better about quoting folks. I’m very appreciative of anyone who is responding here and I’m doing my best to take each bit of advice seriously, but also within my budget, time and general knowledge.

His last comment asked about the airbox and I responded in the next post saying it seemed fine and also attempted a smoke test and it also seemed fine with that one. My apologies.

[ZeroHecksGiven]

Originally Posted by john walker's workshop

Looks like Oscar's ride.

Missed this. I bought it from an older Asian guy named Elmer. He’s worked for King County Metro the past twenty years, though not sure where he worked prior. Though, maybe he went by Oscar. I could see that, lol. Super chill guy and it felt dang near wrong to drive away with his baby. I think there were legit tears happening as we drove away.
The car is pretty dang clean overall, though quite a bit of grime around the engine, so it may have been a bit since you or anyone else saw it :/
Anxious to get ‘er running and then dive into some of the detail work that I love.