Won't run unless I pull the fuel pump fuse
11-07-2018, 05:40 AM
#61
Regarding a leaking vacuum line, it will cause a lean issue up until a lean misfire happens. Then raw fuel dumps into the exhaust and tells the O2 sensor it’s running rich when it’s really lean. Then the DME will try to lean it out more creating more of a lean missfire issue. Also what injectors are you using? Stock 4.5 ohm injectors? If your using low impedance injectors you’ll want to use two 1 ohm resistors for each batch fire fuel injector harness. If you use low impedance injectors without resistors it will eventually overheat the DME drivers (there are only two) and basically destroy your DME. Not that this is your issue but you want to rule that out.
Thanks again for everyone clearing up the vacuum leak symptoms I had them backwards in my head thinking the car would run rich due to overcompensating for fuel. Had a duh moment and realized the car won’t add fuel if the air is unmetered.
Even though testing was good with the meter for the harnesses I pulled back every boot and inspected the connections and they look remarkable compared to what I’ve seen on other posts giving me extra peace of mind that aside from the corrosion on the harness for the speed/red sensors the wiring harness is in great shape and doesn’t have any shorts. The DME is testing fine too so I’m about 90% sure the injectors are my issue but I won’t know until I can get them tested at a speed shop. I can’t crank them on the car but when they flow test them they will be able to tell me if they were leaking/ have screwed up nozzles or worn springs. Whatever the case may be.
11-19-2018, 07:53 PM
#62
Hi guys.
Finally knocked out the injectors. 3/4 needed to be replaced they were so bad.
You’d think my troubles would be over but no. Same symptoms. Car refuses to start/ run.
pull the fuel pump fuse and same result, car runs until it dies. It won’t start at all unless I pull the pump fuse.
Fuel pressure is still normal.
Disconnected the AFM and the idle smoothed out beautifuly and ran for a few minutes until it died. Keep in mind AFM was replaced already it’s not the issue. Now what?
Finally knocked out the injectors. 3/4 needed to be replaced they were so bad.
You’d think my troubles would be over but no. Same symptoms. Car refuses to start/ run.
pull the fuel pump fuse and same result, car runs until it dies. It won’t start at all unless I pull the pump fuse.
Fuel pressure is still normal.
Disconnected the AFM and the idle smoothed out beautifuly and ran for a few minutes until it died. Keep in mind AFM was replaced already it’s not the issue. Now what?
Last edited by Jacob AbuKhader; 11-19-2018 at 08:09 PM.
12-16-2023, 12:57 PM
#64
I did it turned out to be the DME module itself. In fact just the other day it hit me why the DME failed in the first place.
i had gone to put gas at a different station and I used 87 rather than my usual chevron 91. I figure the ignition circuit overheated trying to compensate the ignition timing for the lower grade fuel unlit the aging chip overheated and failed.
if the car can run without any added fuel (ie) removing the pump that means it’s over fueling so much that spark or weak spark is enough to operate the engine for those few seconds.
the only way to really test this is to try a known good DME unit in the car
if you find out that’s the case I recommend going with a focus 9 dme to replace yours.
