Intermittent Spark
05-25-2020, 10:39 PM
#16
Two things that fixed problems like this on my car: Test your DME water temp sensor - car won't start when they fail. Also, check the terminal wires on the coil to see if the nuts are loose.
05-25-2020, 11:37 PM
#17
Banned
Progress has been slow, but I have finally had a chance to start looking into my intermittent spark problem again, and have been able to run a few more tests. I hooked an o-scope up to the speed and reference sensor just to rule them out and they were well within spec per Clark's garage. I also checked the new to me, tested DME/KLR for cracked solder joints or any other signs of damage and they looked prestine, so I cut the necessary resistor and swapped the chips. I thought this solved the problem I got a solid 15 minutes or so back and forth down the road, which is the longest I've been able to drive. Then right as I was about to pull out for a longer test run the car lost spark. Since, then I've pulled the wiring harness apart a bit more and confirmed the installation of the wasted spark on the DME/VRPB side. I also verified all of the grounds to the DME and went through about half of the VRPB wiring. I am thinking my next steps are to go through the engine bay wiring harnesses and finish checking the installation of the VRPB. However, part of me thinks that maybe there is something wrong with the Vitesse wasted spark computer with the way the red LEDs flash. Even when the car is running the LEDs do not flash as it says they should in the instructions. I included a video of the LEDs while the car is running and while the car is not consistently sparking to see if anyone familiar with wasted spark has any thoughts. If someone knows a way to test the computer I would love to know how, if not I'll get in touch with John and see if he can help me test it after I have ruled out all the wiring. Finally, while going through all of my Vitesse docs I found some info about the coding plug and about how out of the box a removed coding plug is for pump gas and an installed plug is for race gas. However, after installation you can make the plugged/unplugged tune whatever you like correct? So, my car, which has the plug installed and has only ever been run on pump gas, could still be running a safe tune with the plug installed, right? I am also going to hook up the VRPB to my computer next time I test drive it to see if maybe the piggyback can give me any insight into what the problem may be.
Set the PB to factory spec. I don't believe it has the ability to alter timing. Just the fuel maps.
Sounds like you may have an issue with the wasted spark. Is there a way for you to reinstall a factory coil as a diagnostic and see if the problem goes away?
05-26-2020, 12:54 AM
#18
Take the thumb screws out and pull your fuse block up out of your fuse box. Look at all those fancy connectors, for cracked insulation or bad repaired wiring jobs by mechanics not understanding the dme relay. Get a electrical schematic and trace your wiring from the ignition coil backward, check continuity. Could be something simple like a badly spliced wire from a previous owner. And I second and Third that a dme, even a supposedly repaired one, could be bad. I went through 3 of them in 2 years.
03-14-2022, 10:56 PM
#19
Racer
Thread Starter
Due to some personal stuff with Covid I never ended up moving to the same city as the car or bringing the car to me, so the closest I have lived to it is over 300 miles. This has lead to very slow progress, but over the last 2 years I have spent 40+ hours messing with this problem and countless more researching the issue, and I think I have finally found my issue.
Here is a comprehensive list of what I have done in the approximate order I have done it, but I am sure I am forgetting some things:
Anyway, I have decided to buy new sensors and will hopefully be installing them next month and will report back on whether or not that works.
Here is a comprehensive list of what I have done in the approximate order I have done it, but I am sure I am forgetting some things:
- Fixed cracked solder joints in DME and KLR and Vitesse Wasted Spark
- New used tested DME/KLR
- Bypassed alarm
- Bypassed DME Relay
- New Coil
- New DME Temp Sensor
- Oscoped Speed and Reference sensors many times both while the car would and would not start, and every time they tested in spec according to Clark's garage
- Tested Ignition switch
- New Fuel Injector Harness
- While installing I discovered the shielding was done improperly, so I fixed this with the new harness
- Installed another brand new, never installed Vitesse Wasted Spark
- Thoroughly went through the whole DME harness and much of the engine bay harness cleaning all corrosion and redoing/checking all splices for mods
- Checked the shielding for the newly installed (couple months prior to my ownership) Speed/Reference sensor harness and discovered the shielding was done improperly, so I corrected this.
- Installed new FTech9 Diagnostic DME Relay and OBD+ Sport DME
Anyway, I have decided to buy new sensors and will hopefully be installing them next month and will report back on whether or not that works.
Last edited by Type65; 03-14-2022 at 11:00 PM.
