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-   -   Voltage @ Injectors? (http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/161441-voltage-injectors.html)

ae1969 05-07-2004 06:16 AM

Just tell your wife you can put her on ebay as well.... :)


Well if all your readings are correct .....

The only last thing you havent checked out of the 13-14 steps for no start....Is the signals sent by the reference and speed sensor. We need an oscilloscope or a meter than can read voltage peaks.

By the way did you check the clearance on the sensors ?

sneed21 05-07-2004 06:24 AM

HA! that would be a no reserve auction ;)

I have not checked the clearances on the ref and speed sensors. They were tight and I haven't messed w/ them, (other than testing the outputs) because I was told that I'd most likely not have a spark if they were bad. I will check the clearances this afernoon (gotta find my feeler gauge). I'll dig up that Fluke One Touch here at work and see if I can't educate myself on how to use it. I'll let you guys know how I make out, and thanks.

ae1969 05-07-2004 08:18 AM

hehehe no reserve....... I would think you would just go with a LOW buy it now feature.

You are right that if the reference sensor was not picking up the signal you would have no spark or injector pulse.... but

The thing I am not sure of (socal can pipe in)..... if the speed sensor is not picking up the signal from the ring gear what are the symptoms? The dme reads it to keep the car running (injector pulse length)..... but not 100% sure of what other symptoms would appear if it began to fail.

I had to use an oscilloscope on my last adventure with these sensors.......

The only other thing I have ever done to confirm if the speed sensor is bad is to swap it with the reference sensor........... Thus when you cranked.... you would then have no spark/injector pulse with the bad one now reading the reference pin.

We can assume the height on the sensors is correct since you are getting spark..... but it may be worth your while to just swap them. If you then get no spark/injector pulse then you must have a bad sensor even though the ohms checked out on your previous tests......

?? did I make any sense ?? hehehe :)

SoCal Driver 05-07-2004 08:35 AM

Quote:

Originally posted by ae1969
The only last thing you havent checked out of the 13-14 steps for no start....Is the signals sent by the reference and speed sensor. We need an oscilloscope or a meter than can read voltage peaks.

By the way did you check the clearance on the sensors ?

He used a noid light on the injectors and got a signal on all four.

He's tested and found spark at the end of a plug wires on all four.

He's jumpered the fuel pump and it runs.

He's cranked the car with the injectors out to see the spray pattern.

This is a good one.

The reference sensor has to be sending a correct signal to the DME as there is injector pulse and spark. No broken cam belt either as the spark would not be distrubuted to the plugs.

The fuel pump is working so the DME relay is pulling in the second contacts. Remember this is only possible IF the first set of contacts close.

The engine should start or attempt too.

I wonder if it's getting sufficent fuel to start let alone continue running.

ae1969 05-07-2004 08:47 AM

Socal .. what happens if the speed sensor fails by itself? The things you listed above are only affected by the reference sensor?.... but what if anything can we see if the speed sensor goes kaput......



Now I am really going to start pulling at straws hehehehe.... I am starting to think you have something loose...........Did you check the wire to the starter.... I once did not tighten the little wire to the starter and it would intermittently start. It would fire up and stall as the wire shook itself....

sneed21 05-07-2004 09:02 AM

I can check the connections at the starter. When I pulled the plugs they were real wet, and each gave a hot spark. The injectors are spraying, this I now know, but I don't understand why, when it starts, it will run like it's on 2 or 3 cylinders then die after about 2 seconds. When I had the injectors pulled, and cranked the engine...they were all spraying on and off. All the plugs spark while cranking the engine....yet only semi or no ignition. Running the spark test, I didn't pull the plug wires off the others I wasn't testing. When the engine cranked, it started running rough on 3 cylinders, but wouldn't die until the switch was off. I put the spk plg back in and it would just kick over a little and die. Almost like it's flooding itself out?? I changed the damper and fpr though....

SoCal Driver 05-07-2004 09:17 AM

According to the experts and a few technical documents, the speed sensor only comes into play after the engine starts -- when you stop cranking the engine. This sensor supposedly keeps the fuel pump running and provides refined engine rpm data to the DME to determine injector pulse width. But the temp sensors and the AFS do this too.

I'm thinking fuel delivery as the reported failure was a limit of about 2,000 rpm then a total failure. Now there is a spray pattern but is it of sufficent quanity to start the engine.

He's replaced most everything that is related to this.

You can over ride the speed sensors control of the fuel pump by using the bificated jumper to replace the DME. Don't use pin 30 to get the power from as this is straight from the battery. Use pin 86 as this is switched through the key.

Another random thought: Check that the rubber boot between the AFS and the throttle body is tight and not cracked.

SoCal Driver 05-07-2004 09:19 AM

Does sound like an over pressure situation. Pull one of the injector wires off and see if it starts and runs a bit smoother all be it with a known dead cylinder.

SoCal Driver 05-07-2004 09:21 AM

Another random thought: Check that the wires to the battery are clean and not corroded. Should have the stock type connectors where the wire is soldered into it. Also check the grounds to and at the engine.

SoCal Driver 05-07-2004 09:27 AM

Is the HV wire between the coil and dist new?

sneed21 05-07-2004 09:41 AM

OK, I'll have to try and overide the speed sensor. The Boot has been changed out (forgot to mention that)..no cracks. Pulled one injector wire off and the car will run on 3 cyls for a little while then die. When I try it again, the car acts like I never took it off to begin with...ie, stutter start die. This happens no matter which injector I disco. Checked grounds to engine, cleaned w/ a wire brush. Connections tight at the battery. Both sides still have sodered connections. Yes, the HV wire between the coil and dist is new...done the same time as the plug wires. When the car starts, and it's stuttering and shaking like Rick James in rehab, there is no backfire....and it's super quick. Turn key, 3 turnovers, kick, hicup, 3-4 turnovers, kick, hicup,.over and over again. Grief SoCal, Why do you and AE have to be over a thousand miles away! :)

ae1969 05-07-2004 09:45 AM

What happens if you try and start with one fuel injector disconnected? and the temp sender was in spec as well ?

sneed21 05-07-2004 09:49 AM

It will start on 3, shudder like mad (obviously) and die after about 2 seconds. If I try and restart, it will just kickover, fire, and die. I have to wait a couple of minutes to try again before it will start and run for another 2 seconds. Yes the temp sender was w/in spec, but I changed it out anyway.

sneed21 05-07-2004 10:03 AM

When it first happened, while trucking down I95 doing 75mph, it happened suddenly and wouldn't rev over 2k. I coasted off an exit and into a parking lot (by the way, it all happened on my birthday...what a great gift, and it reminds me that I've been working on this since 3/11) I turned the car off, popped the hood, etc... The car would restart instantly and idle perfectly, only dieing and falling on it's face if I went over 2k. I started checking the normal things, pulled the cap, put the cap back on, started the car, and it drove fine, reved above 2k. Started going home and the person following me said, your blowing black smoke when you give it gas.....at that point, it started happening again, I had to coast into another lot. The car would always restart instantly and idle fine. I had to let it sit in a retirement home parking lot overnight. When I came back the next morning w/ the flatbed, the car wouldn't start.....just acted the way it's doing now.

ae1969 05-07-2004 10:16 AM

OH man ...it just sounds like you blew an intake hose.....

Take a look at the hose under the intake....

YOU ARE GOING TO KICK YOURSELF.

sneed21 05-07-2004 10:36 AM

Don't toy with me!! :) Are you talking about the one going to the aux air reg? That makes sense. I can hear a loud hissing sound while the engine is running/stuttering. I had checked all my vac lines and intake boot, but couldn't find anything.

thanks! I'll check.

sneed21 05-07-2004 01:02 PM

Checked/changed all hoses running to/from aux air reg, intake boot, etc.. no change.

ae1969 05-07-2004 01:39 PM

are you referring to the aux air reg (I am assuming you are talking about idle stabilizer valve)? Underneath the intake...... the one hose connects to a large ~1/2 inch opening under the intake

It really sounds like a bad intake problem as you describe it........ You know what I tried once is to blow air through the rubber boot and go over it again.... looking at the sealing surfaces.... sometimes the intake gets caught up and does not seal properly....

Uhmmm you also did not put the intake gaskets backwards.... by doing so you block the injector from spraying properly as well

.....You obviously know what you are doing... I just think its something you are overlooking. :(

It would be nice if someone in your neck of the woods would give it a second look.

I would fly over but I have a head to pull tonight. :)

SoCal Driver 05-07-2004 01:46 PM

There are a few more places that you can have a serious vacuum leak. Follow the large hose around. Brake booster diaphram, connections at the rubber duct between the AFS and the throttle body, idle valve.

Have you checked the AFS? Could have moisture in it. Flap could be sticking. Remove the air filter and push the flap with a wood dowel. Check the resistance curve to see that is is smooth and not jumpy.

sneed21 05-08-2004 10:21 AM

Check all hoses/seals under intake. Nothing is cracked, split, or loose. Replaced intake boot, no change. AE, your right, it's something simple that I'm overlooking....I need another pair of fresh eyes to look at it. Socal, I checked the AFS and performed the test as described in the manual. All values were correct. Just in case, I switched it w/ a known good one. I traced all the vacuum lines, and air hoses, to and from the booster, intake boot, etc... All checked out. Also, this morning I swapped fuel pumps.......grasping at straws......I know.....


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