Intermittent No Start, how to test?

[PeteKz]

It just unplugs with a little force. Pull on the connector, not the wire.

[boyt911sc]

Originally Posted by acorad

Pete, thank you, will do. I should be able to disconnect the safety switch tomorrow and the fuel injection test set should arrive on Friday.

Question, does the safety switch connector have a specific method to release the connector? Or does it just pop out when you pull on it?

The electrical plugs for WUR, AAR, CSV, & air sensor switch are identical except for the color and wires connected to each one. The plug/s is secured in place by a spring wire. Pull out the plug by grabbing the body and gently wiggle it out. Practice removing the plug for the WUR which you could see better than the AFS plug. Practice makes perfect.

Tony

[acorad]

Thanks Pete and Tony.

[acorad]

Safety switch unplugged, starting fluid in hand, waiting for next no-start event to see if the fuel pump is running.

[acorad]

Just had a no-start event, FP was running.

[mysocal911]

Originally Posted by acorad

Just had a no-start event, FP was running.

Then use the starting fluid! Maybe now a spark problem.

[acorad]

Thanks Dave. I lifted the air sensor arm which primed some gas into the engine, and then it started right up, as it always does. tbh, I was preoccupied with something at the time and forgot all about the starting fluid, lol!

I will hit it next time with the starting fluid, but I don't understand what the difference is between priming it with gas by lifting the air sensor arm vs priming it with starter fluid?

[mysocal911]

Originally Posted by acorad

Thanks Dave. I lifted the air sensor arm which primed some gas into the engine, and then it started right up, as it always does. tbh, I was preoccupied with something at the time and forgot all about the starting fluid, lol!

I will hit it next time with the starting fluid, but I don't understand what the difference is between priming it with gas by lifting the air sensor arm vs priming it with starter fluid?

Using starter fluid is the absolute test! You know fuel has gone into the intake. Remember, you don't always know whether there's fuel, or enough pressure to open the injectors, when "priming".

[acorad]

Originally Posted by mysocal911

Using starter fluid is the absolute test! You know fuel has gone into the intake. Remember, you don't always know whether there's fuel, or enough pressure to open the injectors, when "priming".

Thanks Dave, I'll use the starting fluid next time. I have some errands to do, so another no-start might happen later today.

[acorad]

Hi all, just had a no-start event and then it did start after a couple squirts of starter fluid.

Are we thinking the results of this test indicate fuel delivery during cranking?

[boyt911sc]

Originally Posted by acorad

Hi all, just had a no-start event and then it did start after a couple squirts of starter fluid.

Are we thinking the results of this test indicate fuel delivery during cranking?

That is why a fuel pressure tester is a mandatory tool for any fuel injection troubleshooting. Without one, you have too many unknown variables and identifying the culprit/s is more difficult. Test and verify the following:

• Fuel control pressures (cold & warm)
• System pressure
• Cold Start Valve
• Fuel injectors spray pattern
• TTS
• Vacuum leaks
• Ignition signal during cranking.
• Fuel pump delivery volume per min.
• Etc.

Tony

[acorad]

Thanks Tony, the fuel pressure tester shows up tomorrow, so today I'll work on testing stuff that doesn't need the tester.

[acorad]

Well, some progress on a different front!

I found that one of the wires on the TTS was a little loose, so I tightened it up. When I started the car after work the engine leapt instantly to life, instead of dragging to life with me having to floor the gas pedal.

So, that seems better anyway.

Of course, though, it no-started again after I stopped at the Albertsons on my way home, just to let me know who was boss. lol.

But hey, small steps!

Andy

[boyt911sc]

Originally Posted by acorad

Well, some progress on a different front!

I found that one of the wires on the TTS was a little loose, so I tightened it up. When I started the car after work the engine leapt instantly to life, instead of dragging to life with me having to floor the gas pedal.

So, that seems better anyway.

Of course, though, it no-started again after I stopped at the Albertsons on my way home, just to let me know who was boss. lol.

But hey, small steps!

Andy

Andy,

For CIS, you don’t need to step on the gas to get it started. If you did, you have already found the problem. Put the car in neutral and just reach for the ignition switch through the driver side window. If it takes multiple attempts to get it running, check the things I suggested above. Do not press or touch the gas pedal. Keep us posted.

Tony

[acorad]

Thanks Tony. It looks like Amazon shipped my fuel injection test set to Boston, MA, while I live here in the LA, CA area, so I'm not sure when the test set will arrive.

So I've been looking at smoke machines for leak testing, how does this one look does it have all the fittings, etc., that we need?

https://www.amazon.com/Automotive-Smoke-Leak-Detector-Motorcycles/dp/B0CYQ1YFTV/ref=sr_1_5?dib=eyJ2IjoiMSJ9.NR7mYrzqRzhF5Gg4u1MCT_ EzZIeir_kOccHDWRGqtxuAvRfIXrbX7nKD6zTNaVuLlXZfijy8 CWiU4JxxjyqU8GVqFhEXYYqOOYU7yhlOsMAbe3CprJOLRzslow f8f8mf8tYEdv46i60sF7vYG61AIWXS2qclnUX24XGveOxrR1OG d5rKlgwnw7RKvdIoqfzjp_wZVQ1pZ8sF5qiRxIm-vPoH9VHK66nCuKWFAMetFHuqsmMELHfWD6YQ-uodqll9dNJHkDwXCHTng9Q_D1cemMMSGZqYSc6pM_5ek1u2EPE .79-ssvHA8phIPDkTifKje7UO6AzDJAE3Lrt9e5LNRy8&dib_tag=se&keywords=smoke+leak+detector&qid=1728080726&s=automotive&sr=1-5

Andy

[boyt911sc]

Originally Posted by acorad

Thanks Tony. It looks like Amazon shipped my fuel injection test set to Boston, MA, while I live here in the LA, CA area, so I'm not sure when the test set will arrive.

So I've been looking at smoke machines for leak testing, how does this one look does it have all the fittings, etc., that we need?

https://www.amazon.com/Automotive-Smoke-Leak-Detector-Motorcycles/dp/B0CYQ1YFTV/ref=sr_1_5?dib=eyJ2IjoiMSJ9.NR7mYrzqRzhF5Gg4u1MCT_ EzZIeir_kOccHDWRGqtxuAvRfIXrbX7nKD6zTNaVuLlXZfijy8 CWiU4JxxjyqU8GVqFhEXYYqOOYU7yhlOsMAbe3CprJOLRzslow f8f8mf8tYEdv46i60sF7vYG61AIWXS2qclnUX24XGveOxrR1OG d5rKlgwnw7RKvdIoqfzjp_wZVQ1pZ8sF5qiRxIm-vPoH9VHK66nCuKWFAMetFHuqsmMELHfWD6YQ-uodqll9dNJHkDwXCHTng9Q_D1cemMMSGZqYSc6pM_5ek1u2EPE .79-ssvHA8phIPDkTifKje7UO6AzDJAE3Lrt9e5LNRy8&dib_tag=se&keywords=smoke+leak+detector&qid=1728080726&s=automotive&sr=1-5

Andy

Andy,

That’s a nice looking smoke generator and the price is good.

Tony

[acorad]

Thanks Tony.

Also, it turns out that the fuel pressure tester I ordered a week ago from Amazon is not certificated for sale in CA, or something like that. It got delivered to MA. lol.

Does this one look ok for our needs?

https://www.amazon.com/gp/product/B0CQCWXT68/ref=ppx_yo_dt_b_asin_image_o00_s00?ie=UTF8&th=1

[PeteKz]

Yes. It's the same kit, different name. Cheap Chinese stuff, but good enough for DIY.

Re your troubleshooting. So far it's pointing to a failure to deliver fuel at start. If it starts every time you either prime the engine by raise the arm, or by using starting fluid, then I really doubt it's related to spark (although, keep that hypothesis on the list somewhere). If you never get stumbles during normal driving, that points even further away from ignition problems.

The hypothesis that the fuel pump isn't working right seems to have been ruled out, because the pump runs whenever the key is on, and you can hear it running even when it doesn't start.

Since you know you can get it to start either by priming the engine or by using starting fluid, and it runs normally after that, I recommend that you keep driving it and see if you notice any other abnormal behavior. Otherwise, you need the pressure gauge set to do further troubleshooting. The smoke test is good to have too, but I don't know why a vacuum leak would be intermittent.

Keep us posted.

[Schulisco]

Here's a manual to build it on your own:
https://cis911primer.com/pages/test_pressures.html

Also there are some shops providing some, also our host provides one:
https://www.pelicanparts.com/More_Info/TOLSGT33865.htm?pn=TOL-SGT-33865&bc=c&SVSVSI=0572

Almost 200 bucks seems a bit pricey to.me, I paid less than 100 bucks in 2018, it's still available for 108€ here in Germany, very good quality.
There's no 911 version, all pressure gauges fit the same.

Thomas

[acorad]

Thanks guys, I should be able to do some testing later this week. I'll let you know what I find out.

Andy