Won't run unless I pull the fuel pump fuse - Page 3 - Rennlist - Porsche Discussion Forums

Notices

Won't run unless I pull the fuel pump fuse

Old 10-04-2018, 11:51 AM
  #31  
Jacob AbuKhader
User
 
Jacob AbuKhader's Avatar
 
Join Date: May 2018
Posts: 155
Default

Awesome. Iím get my fuel rail back together and try to charge up the battery.
Jacob AbuKhader is offline  
Old 10-05-2018, 07:10 PM
  #32  
Dan Martinic
Addict
Rennlist Member
 
Dan Martinic's Avatar
 
Join Date: Aug 2017
Location: Toronto, Ontario, Canada
Posts: 1,118
Default

Jakob, my apologies; I forgot about this. Just went out to see. To my surprise, both sides of my injector plug show 12volts key on engine not running!

Chris.. if you're reading... is this correct?






Dan Martinic is online now  
Old 10-05-2018, 07:24 PM
  #33  
Jacob AbuKhader
User
 
Jacob AbuKhader's Avatar
 
Join Date: May 2018
Posts: 155
Default

Dan that reading is correct. The reason is because you left the other four injector harness plugs connected. The circuit needs to be floating in order to track the short. I went and did the same thing again but with the 3 injector plugs still in and also got 12V on both sides.

If you try it again disconnect all 4 injector plugs and then youíll be able to see 1 side 12V and the other side should have no voltage reading
Jacob AbuKhader is offline  
Old 10-05-2018, 08:07 PM
  #34  
Dan Martinic
Addict
Rennlist Member
 
Dan Martinic's Avatar
 
Join Date: Aug 2017
Location: Toronto, Ontario, Canada
Posts: 1,118
Default

Here ya go: both sides show voltage, albeit one side less so







Dan Martinic is online now  
Old 10-05-2018, 08:13 PM
  #35  
Jacob AbuKhader
User
 
Jacob AbuKhader's Avatar
 
Join Date: May 2018
Posts: 155
Default

Lol damnit thatís really annoying hahahaha. Our numbers are nearly the same. Except Iíve got 12V and 8V. Man I was so hopeful this was the issue. I knew it had to be too good to be true.
Jacob AbuKhader is offline  
Old 10-05-2018, 08:23 PM
  #36  
Dan Martinic
Addict
Rennlist Member
 
Dan Martinic's Avatar
 
Join Date: Aug 2017
Location: Toronto, Ontario, Canada
Posts: 1,118
Default

Hopefully Chris will chime in.. maybe we're missing something here; he's usually on the ball!
Dan Martinic is online now  
Old 10-05-2018, 08:24 PM
  #37  
Jacob AbuKhader
User
 
Jacob AbuKhader's Avatar
 
Join Date: May 2018
Posts: 155
Default

Dan out of curiosity did you measure continuity? Iím assuming that if you have voltage on both sides, you must also have continuity. My logic there is the wires have to be able to carry a charge continuously otherwise there would be a break in the circuit and you wouldnít be getting any reading at all.

Jacob AbuKhader is offline  
Old 10-05-2018, 10:41 PM
  #38  
Dan Martinic
Addict
Rennlist Member
 
Dan Martinic's Avatar
 
Join Date: Aug 2017
Location: Toronto, Ontario, Canada
Posts: 1,118
Default

Sorry, didn't check that. Got company tonight and was rushing
Dan Martinic is online now  
Old 10-05-2018, 11:03 PM
  #39  
Jacob AbuKhader
User
 
Jacob AbuKhader's Avatar
 
Join Date: May 2018
Posts: 155
Default

Originally Posted by Dan Martinic View Post
Sorry, didn't check that. Got company tonight and was rushing
No worries! These two tests have saved me sending out my injectors and buying an ECU so far so lol. I went back and reread the LJET thread entirely. I still believe thereís an electrical issue somewhere but probably not where Iím looking we will have to see what Chris says to confirm.

Theres an issue happening thats being distributed to all 4 cylinders. The mechanical components of the fuel and ignition systems are working. Leak down test was successful. Each injector physically works and isnít stuck. The car only runs when the pressure is fully bled from the system and that can only happen two ways. The injectors fire and bleed the pressure, or the car bleeds pressure over time after sitting.

Carbon on the plugs and raw fuel out of the exhaust means too much fuel. So itís definitely something thatís either not talking right to the DME, or the DME isnít talking right to the injectors. Their could be a short in any of the other circuits that control the AFRs either in the harness or the computer.

Narrowing down it seems like at least.
Jacob AbuKhader is offline  
Old 10-10-2018, 06:24 PM
  #40  
Droops83
Addict
Rennlist Member
 
Droops83's Avatar
 
Join Date: Feb 2003
Location: Santa Barbara, CA
Posts: 1,144
Default

Hey guys,

Sorry for the delayed response, I have not had much time to browse the usual forums lately . . . .

Anyway, +12V at both injector connector pins with the ignition switched on and and while unplugged is normal. Remember, voltage is a measure of the difference in electrical potential between two points. If there is 12V on both sides of the injector coils, there is no difference in potential and therefore no current will flow when the circuit is completed. If one side is switched to ground, that will complete the circuit and current will flow.

The fact the Jacob has ~11V on one side and 7V on the other side (open-circuit voltage) means that there IS a difference in potential between the two sides of the circuit and current will flow when the connector is plugged in. Plug in an injector and it will likely click open (partially).

I think you have a bad DME, but unplug it to see if your voltage readings change (injector 12V+ is provided by the DME relay, not the DME itself). If they change, DME is the culprit. If not, it is a wiring issue.

Send in your injectors anyway if they've never been cleaned, it is well worth the effort. I recommend RC Engineering in Torrance, CA.
Droops83 is offline  
Old 10-10-2018, 06:41 PM
  #41  
Jacob AbuKhader
User
 
Jacob AbuKhader's Avatar
 
Join Date: May 2018
Posts: 155
Default

Chris, thanks for the input. Since testing the injector harness I went through every single sensor harness plug yesterday and tested looking for any shorting or signs of an issue and couldnít find one, even with the disgusting shape the harness for the speed and ref sensors the numbers are still bang on.

I physically pulled each injector and tested them direct to the battery and they each clicked.

Half of the sensors are new or replaced and the others have outputs within spec so if it is electrical I agree with you and Dan that itís gotta be a DME.

I didnít know that unplugging the AFM makes the DME run a different air fuel map. Even with my new one unplugging it helps the idle. So if it runs good on one map, their could be internal damage in the DME circuitry on the regular map.

I finally found someone whoís got a DME they are willing to lean me to test out so that should be a pretty definitive test.

Once the cars running, Iíll treat her to an injector cleaning lol and a new set of tires since mine are now lopsided from sitting.
Jacob AbuKhader is offline  
Old 10-10-2018, 07:34 PM
  #42  
Dan Martinic
Addict
Rennlist Member
 
Dan Martinic's Avatar
 
Join Date: Aug 2017
Location: Toronto, Ontario, Canada
Posts: 1,118
Default

Wow cool info Chris, thanks.

Curious... when testing one injector connector while the others are plugged in, my reading is even +12V both pins. With all plugs disconnected, the same plug drops to 10V on one side; not as drastic as Jakob's, but a drop nontheless. Normal?

I'm chasing a long-running issue that is slight but... perhaps the infant stages of something Jacob is getting.

Looking forward to the DME swap test!
Dan Martinic is online now  
Old 10-10-2018, 07:38 PM
  #43  
Jacob AbuKhader
User
 
Jacob AbuKhader's Avatar
 
Join Date: May 2018
Posts: 155
Default

Originally Posted by Dan Martinic View Post
Wow cool info Chris, thanks.

Curious... when testing one injector connector while the others are plugged in, my reading is even +12V both pins. With all plugs disconnected, the same plug drops to 10V on one side; not as drastic as Jakob's, but a drop nontheless. Normal?

I'm chasing a long-running issue that is slight but... perhaps the infant stages of something Jacob is getting.

Looking forward to the DME swap test!
Dan what is the issue youíre having with your car?
Jacob AbuKhader is offline  
Old 10-10-2018, 07:46 PM
  #44  
Dan Martinic
Addict
Rennlist Member
 
Dan Martinic's Avatar
 
Join Date: Aug 2017
Location: Toronto, Ontario, Canada
Posts: 1,118
Default

Jacob, it's a long-running issue of cold-start first 2 minutes hesitation with recent occasional popping in exhaust off-throttle upshift (not sure if related).

New-ish spark plugs are already carbon fouling. All else running well. Over the past year, I have improved upon lots of things and changed out many of the parts that could be related. I seem to fix everything but this stubborn issue just won't die!

It's mild enough to ignore but don't we all prefer to have a period of "zero-issue" lol
Dan Martinic is online now  
Old 10-10-2018, 07:49 PM
  #45  
Jacob AbuKhader
User
 
Jacob AbuKhader's Avatar
 
Join Date: May 2018
Posts: 155
Default

Lol I genuinely donít think that exists with these cars 😂
Jacob AbuKhader is offline  

Thread Tools
Search this Thread
Quick Reply: Won't run unless I pull the fuel pump fuse


Contact Us Advertising Cookie Policy Privacy Statement Terms of Service

© 2018 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: