Jump to content

Server Lease Renewal/Software Licenses

Our yearly server lease, software licenses, as well as hardware operating costs, ARE due Dec 6th, 2021. Our current donations have fallen far short of the funds we need to renew. Please remember the RennTech.org community is Member supported so please consider a donation to help...  THANK YOU!

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)

Fuel pump will not run.


lib

Recommended Posts

Hi

I wonder if anyone has any ideas on this.

Yesterday I drove my 1986 911 coupe out of the driveway into the road where it stalled, I tried to start it, the engine was turning over but it would not run.

After some time spent checking I found the fuel pump was not working. If I fed it direct and it ran and the car started.

following many hours of tracing the circuit I found that the supply came from one of the relays in the DME relay. This particular relay is given a negative return through the DME.

What I do'nt know is what sensor tells the DME to activate the DME relay by providing the negative return to energise the relay coil.

I would be very grateful for any help on this subject.

Thanks lib..

Link to comment
Share on other sites

the speed sensor gives an AC voltage to the DME which in turn grounds the DME relay to power up the DME and the fuel pump.

common failure the DME relay, carry a spare! I don't know how many cars got towed in and started when they came off the rollback.

Edited by magcuda
Link to comment
Share on other sites

You did check the fuse in the front trunk? Panel 1 (center panel of 10 fuses) fuse 3 -- should be 25A

Hi Loren. Thank you for your response to my problem. Yes I have checked the fuse and it was ok but there was no supply current to the feed in side of the fuse.

Regards Lib.

Link to comment
Share on other sites

the speed sensor gives an AC voltage to the DME which in turn grounds the DME relay to power up the DME and the fuel pump.

common failure the DME relay, carry a spare! I don't know how many cars got towed in and started when they came off the rollback.

Hi Magcuda. Thank you fpr your reply to my problem. I have checked the DMI relay by feeding the windings separatly and both relays in the DMI relay do function and there is continuity through the contacts and out to the pins. So it is possible that the speed sensor is at fault. Would this be the sensor that detects the crankshaft is rotating? Or is there another sensor elswhere? although the engine does run if I provide a separate ground to the fuel pump relay that's inside the DMI relay.

Regards Lib.

Link to comment
Share on other sites

yes that is the sensor that reads the flywheel speed. did you try another relay?

they can look and test good but are bad, wish I had a dollar for every one I replaced.

to test the sensor you really need a scope but an analog volt meter set on AC voltage can give you a reading.

Link to comment
Share on other sites

yes that is the sensor that reads the flywheel speed. did you try another relay?

they can look and test good but are bad, wish I had a dollar for every one I replaced.

to test the sensor you really need a scope but an analog volt meter set on AC voltage can give you a reading.

Hi maguda Thanks, I will try that and let you know

Regards lib.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.