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A Novel

 
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toast54  



Joined: 08 Sep 2014
Posts: 78
Location: Oklahoma City OK

PostPosted: Tue Jul 25, 2017 6:37 am    Post subject: A Novel Reply with quote

I have been working on this hobby car for what seems like forever. I have an 87 924S that I just put front struts on. Per instructions, I disconnected the negative side of the battery for about 2 weeks while I worked on it. After finishing the struts, I fired the car up and backed it out..everything fine. After an hour or so, I tried starting it. It fired once, then just turned over without firing. I watched for "tach bounce" and saw nothing. I did hear a chattering coming from one of the injectors. I bypassed the DME and the fuel pump worked fine. I then started it again and this time it started, ran about 15 seconds, doggedly but WITH tach bounce, and then died again. I could smell gasoline .I then opened the fuel rail at the end cap and there was a drop of fuel and no pressure. I did notice a vacuum line disconnected from the temp sensor that goes to the valve by the left of the brake master cylinder, reconnected the line and the car then started, but still acts like it isn't getting any gas and dies on any acceleration. Then, just to make matters worse, I think the starter solenoid is fried. What might I start looking at once I get the starter and solenoid replaced to troubleshoot this non-start? Thanks for any help
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toast54  



Joined: 08 Sep 2014
Posts: 78
Location: Oklahoma City OK

PostPosted: Thu Jul 27, 2017 7:13 am    Post subject: Update Reply with quote

Whine was just me, I suppose..Starter is strong and the injector no longer chatters now that I have a very good battery connection. Turns over great, but still no start, I've jumpered the DME relay socket and I have good pressure at the fuel rail and I have spark at the coil. Odd thing is (well, one anyway) when I attempt to start it I'll have tach bounce on the first try...let the starter cool down a bit, try it again and this time NO tach bounce. It alternates between showing 1/16" bounce one try and nothing the next. I can smell gas fairly quickly. I replaced the plugs, wires, disty cap and rotor bug a few months ago. Ill check for spark at the plugs and go from there, I suppose
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ganz924S  



Joined: 31 Oct 2015
Posts: 16
Location: Idaho

PostPosted: Thu Jul 27, 2017 12:29 pm    Post subject: Reply with quote

I did my foes last month and when I started my car (88 924S), it did the same thing yours is and it was the the vacuum line under the intake was not connected. Be sure and check your vacuum lines.
_________________
1988 Porsche 924S Guards Red
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toast54  



Joined: 08 Sep 2014
Posts: 78
Location: Oklahoma City OK

PostPosted: Sun Jul 30, 2017 2:07 am    Post subject: Sensors Reply with quote

I tested both the position and speed sensors on the car. The reference sensor (BG) measures 1062 ohms (within range of 600-1600)- across terminals 25 and 26.I get no measurement across terminals 25 and 78. I pulled the ref sensor to have easier access and tested again. Same result.I have no tach bounce, which is why I pulled it to start with. All of my vacuum hoses are now connected after finding the temp sensor disconnected. Not sure how that happened anyway. I did notice quite a range in cost of the sensors, from $30 to $250. Wish me luck testing the speed sensor. Perhaps I will soon be driving this "hobby" car
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toast54  



Joined: 08 Sep 2014
Posts: 78
Location: Oklahoma City OK

PostPosted: Mon Jul 31, 2017 6:05 am    Post subject: Reply with quote

OK, I re-installed the reference sensor, hooked everything back up. Still no start no tach bounce, but I pulled the DME relay, used the 3 terminal lug jumper and THIS time I DID get tach bounce and it did start ...for about 5 minutes doggedly and with a lot of smoke. So i pulled the jumper and replaced it with the DME relay a couple of times just to see a pattern. As long as the jumper's in it TRIES to start.....DME in and nothing. I'm going to test the fuel pressure at the rail per Clarks and see what I get> I'm beginning to think it's the FPR
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toast54  



Joined: 08 Sep 2014
Posts: 78
Location: Oklahoma City OK

PostPosted: Tue Aug 08, 2017 8:22 am    Post subject: Reply with quote

Well, I should have pulled the regulator BEFORE ordering in the
replacement . Information was wrong and now I have a later model regulator, but I think I can adapt it using a 14mm 1.50 to 8 mm hose Barb adaptor. They're both 2.5 bar. If it doesn't start after changing it out, I'll be nearly out of ideas from Clarks
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toast54  



Joined: 08 Sep 2014
Posts: 78
Location: Oklahoma City OK

PostPosted: Mon Aug 14, 2017 9:02 am    Post subject: Back to it Reply with quote

...I've sorted through the "no crank" issue so that's a start. It turns over BUT, with the DME relay in I get no tach bounce and no coil spark. Once I pull the DME relay and replace with the 3 pin jumper, the fuel pump kicks in, I have tach needle bounce and I have spark at the coil, but still it won't start. Is it time to start looking at the DME computer itself?
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toast54  



Joined: 08 Sep 2014
Posts: 78
Location: Oklahoma City OK

PostPosted: Mon Aug 14, 2017 10:01 am    Post subject: Reply with quote

Addendum. With the DME relay in, I get no voltage on either pin on the injectors
With the 3 -pin jumper, I get 13V on BOTH pins and according to Clarks, I should only get it on one side
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toast54  



Joined: 08 Sep 2014
Posts: 78
Location: Oklahoma City OK

PostPosted: Tue Aug 15, 2017 11:12 pm    Post subject: Reply with quote

I've pulled the connector off of the ECU after dropping it for easier access and here's what I have found. I have 12V coming from pin 1, nothing for 19 (not listed on my sheet) and NO voltage to either pin 18 or 35 with the DME relay in. If I pull the relay and use the 3-way jumper, I do get voltage on 18 and 35 ECU but still a no-start. I guess I'll check the injectors tomorrow with the DME in and out and see what I get.
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toast54  



Joined: 08 Sep 2014
Posts: 78
Location: Oklahoma City OK

PostPosted: Thu Aug 17, 2017 1:36 am    Post subject: Reply with quote

Both of my DME relays test good
Now. more baffled than ever. readings of 0.01-0.02 across the terminals when the relays are energized(including the one I kept 3 years ago) yet neither one energizes the ECU or anything related to it when they are plugged in. The Clarks 3- wire bypass does....losted. NOW, the starters dragging so I'll have to replace it this weekend.
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toast54  



Joined: 08 Sep 2014
Posts: 78
Location: Oklahoma City OK

PostPosted: Sun Aug 20, 2017 1:22 am    Post subject: Help! Reply with quote

I've replaced the dragging starter and now I'm getting it to rotate. Still won't fire though.With the DME relay in, I get no fire from the coil, but if I replace it with the 3 wire jumper, ( per Clarks garage)then I get coil fire,. But still no start. Anyone have a next step in mind? I've tested the flywheel sensors and they come up good. If I open up the throttle body all the way, it will doggedly start,rolling black smoke from the tailpipe, but it won't stay running
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