Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > Porsche 928 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Network Native
 
Danglerb's Avatar
 
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
Ljet brains rarely go bad, happens, but rare.

12v directly to the coil might have fried it, I would check resistance on it, maybe just replace.

What can be measured easily with a meter to verify the green wire signal is getting where it needs to go? Fuel pump continues to run maybe?

Old 03-21-2012, 03:41 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #21 (permalink)
Registered User
 
Join Date: Feb 2012
Location: Philadelphia, Pa
Posts: 38
Garage
After being unsuccessful with the timing light I took a spark plug out, hooked it up to a ground, and tested for spark. Though weak and faint, there is spark! I am under the assumption that if there is any spark at all, the ECU can be ruled out of the possible problems. If the ECU was bad, would weak spark still be possible? If so, is there a way to test the ECU to make sure it is working properly? Also, a friend who has been helping me with this project stopped by a little earlier to hear the cranking difference and thinks the car is finally cranking the way/ at the speed it should be. Any thoughts? Thanks for the replies. And I just updated my profile, I'm in the philly area.
Old 03-21-2012, 04:20 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #22 (permalink)
Network Native
 
Danglerb's Avatar
 
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
Are you sure your timing light works?

Have you checked your plug and coil to dist wire resistance?
Old 03-21-2012, 07:19 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #23 (permalink)
Registered User
 
Join Date: Feb 2012
Location: Philadelphia, Pa
Posts: 38
Garage
I am sure that the timing light works, I tested it on my other car. As for the coil, I will try another coil this coming weekend in hopes of that being the problem.
Old 03-22-2012, 11:08 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #24 (permalink)
Network Native
 
Danglerb's Avatar
 
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
Coil on my 84 Euro measured ok, car ran bleh, bought a used one from 928Intl, ran much less bleh, on to next problem.
Old 03-22-2012, 12:03 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #25 (permalink)
Registered
 
Maleficio's Avatar
 
Join Date: Mar 2010
Posts: 1,217
Garage
So the car does not run, right?

I recommend buying a "noid" tester. It's a light bulb apparatus that plugs into a fuel injector connector. If your ECU is commanding the injectors to pulse, then the light will pulse rapidly. You can see it in plain daylight. Verifying that your injectors are pulsing or not will save you LOADS of time. You say you have spark, you say it's weak, but it's there, so next up is verifying injector pulse. If you do have injector pulse, time to verify fuel pressure/flow.

There's not much else to it. Save for one thing: cold start injector. If the injector is not plugged in, or has a broken wire, the car will never light off. At least my 82 would never light off with the cold start injector disconnected, even after warm.

The cold start injector operates off of battery power.

I bought one of these, brilliant design. Stick it to your windshield and watch while you crank.

http://compare.ebay.com/like/270553691729?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar
__________________
1982 Porsche 928, Auto, 4.5
http://i72.photobucket.com/albums/i166/hethaerto/928Mist2.jpg?t=1305333945
Old 03-22-2012, 06:01 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #26 (permalink)
 
Registered User
 
Join Date: Feb 2012
Location: Philadelphia, Pa
Posts: 38
Garage
Thank you for the help! I was definitely running out of ideas. The car has not run in seven years. I bought the car in hopes of learn how to work on porsches and sure enough, this has proven itself to be a challenge, though fun. I will try swapping out the coil and seeing what happens but I will definitely look into a noid tester and report back with my findings.
Old 03-22-2012, 09:18 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #27 (permalink)
Network Native
 
Danglerb's Avatar
 
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
Noid light is handy and cheap, 928 uses Bosch injectors with same connector as older Fords.

Usually you get so you notice the clicking sound the injectors make, but there are several diagnostic tools that target injectors because they are troublemakers.

With spark its a simple system, start at the plugs and move back up the chain until you find where good signal goes to bad output. Used to be you could hook a meter to the primary side of the coil (low voltage) and see whats going on, but I haven't a clue if that is still done.

When this is all sorted out should make a nice addition to Leo's common fixes thread.
Old 03-23-2012, 12:02 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #28 (permalink)
Registered
 
Maleficio's Avatar
 
Join Date: Mar 2010
Posts: 1,217
Garage
I wouldn't bother replacing the coil. You've already proven you have spark.

Buy a couple of cans of starting fluid, spray a BUTTLOAD into the intake, crank and see if it will start. If it starts, and idles, but finally stalls after the fluid is all used up, then you have a fuel delivery issue. Replace filter, verify pressure, keep going up the chain. Use the noid, too.
__________________
1982 Porsche 928, Auto, 4.5
http://i72.photobucket.com/albums/i166/hethaerto/928Mist2.jpg?t=1305333945
Old 03-25-2012, 03:24 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #29 (permalink)
Network Native
 
Danglerb's Avatar
 
Join Date: Jan 2007
Location: SoCal
Posts: 10,349
Spray was already tried, no luck, so ign needs sorting. Used coil is like $20, pretty cheap diagnostic.
Old 03-25-2012, 05:59 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #30 (permalink)
Registered
 
Maleficio's Avatar
 
Join Date: Mar 2010
Posts: 1,217
Garage
Quote:
Originally Posted by Danglerb View Post
Spray was already tried, no luck, so ign needs sorting. Used coil is like $20, pretty cheap diagnostic.

He said he had (weak) spark, and he said he sprayed "gum cutter', not starting fluid.
__________________
1982 Porsche 928, Auto, 4.5
http://i72.photobucket.com/albums/i166/hethaerto/928Mist2.jpg?t=1305333945
Old 03-26-2012, 12:30 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #31 (permalink)
Registered User
 
Join Date: Aug 2011
Posts: 55
Quote:
Originally Posted by Maleficio View Post
I wouldn't bother replacing the coil. You've already proven you have spark.

Buy a couple of cans of starting fluid, spray a BUTTLOAD into the intake, crank and see if it will start. If it starts, and idles, but finally stalls after the fluid is all used up, then you have a fuel delivery issue. Replace filter, verify pressure, keep going up the chain. Use the noid, too.
This is where you need to check. Maleficio is right. You have no fuel .Check pressure at the injector rail.Should be 38psi. If no pressure go back to tank ,tank fuel filterscreen, check valve ,fuel filter,lines etc. If pressure then pull the injectors ,wash with acetone.I had this problem from gummed fuel 15 yrs old. Purchase seals and injector screens and rebuild them. Go to the wreckers and get a set of 4 electrical connectors that fit.I think old jeeps and vws have them. I got 4 with clips and about 10"leads for 10.00. Make up a test rig and with a battery charger or old battery to power open the injectors.With a compressor apply 30psi to acetone or paint thinners filled line and watch each injector spray.Once your satisfied reassemble.Acetone will clean the whole sytem fast and not hurt anything if not left more than a day or two.Paint thinners works too but slower maybe 3 or 4 days to clean tank. You may have to remove the tank. If so check the procedures on the forum as we have all done it with varying experiences.


Last edited by waynestrutt; 03-27-2012 at 01:13 PM..
Old 03-27-2012, 12:26 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #32 (permalink)
 
Reply


 


All times are GMT -8. The time now is 07:26 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2025 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.