/2019: Issue with hesitation on cold start;
Issue with hesitation on cold start
(1/23/2023 update: this post began an investigation the resolution of which took a couple of years to work completely thru. First thing was to understand exactly what i had, & climb the learning curve to begin to troubleshoot an EFI system. As i'd mentioned before, the GW has an AFI (Affordable Fuel Injection) system installed by the previous owner. At this point, in my
mechanic career, i'd never messed with EFI, wiring, pulled EFI logs, set timing myself, or pulled & replaced the distributor - took a while to get over that fear of all of that. Tried to use a couple of local shops to boost me off, but no one wanted to touch it. The wiring under the hood was terrible looking, especially given the EFI box was under the hood, with a lot of extra wiring exposed that should have been under the dash. Eventually(Spring 2022), we worked thru timing, rotor phasing, a new chip from Bill Hamilton & replaced the entire EFI harness, and finally got it how it should be. In hindsight, i shouldve started with replacing the harness given how hacked up it was; the learning from troubleshooting it increased the knowledge of how things work.
Here's a pic of the ALDL connector where you can see the mess of EFI wiring going around the master cylinder reservoir.
To begin the troubleshooting/tuning work, we picked up a Bluetooth OBD1 Monitor from 1320electronics.com, an Amazon Fire tablet & a copy of ALDLdroid, and proceeded to build a virtual dashboard to see what was going on with the engine. This enabled me to work my way thru the myriad of configuration & wiring issues, finding countless voltage drop issues & tracing out wiring to find bad connections/bad splices, a broken fuse. Eventually, we work with Bill Hamilton at Hamilton Fuel Injection to figure out that the tune is too lean, & rotor phasing is incorrect. Once we get that the rotor phasing & tune right, we make the move to totally replace the harness & move the EFI box under the dash. After tremendous travail between 2020 & 2022, am finally daily driving the GW. More on this later...
Right now, the ECM is in mounted in a box under the hood, on the driver's fender where the rear window washer bottle should be. Given the hacked up nature of the EFI harness, am planning on getting a new one & moving the ECM to inside the Jeep - but wanted to get it running properly first.
Here's an example of a digital dashboard you can build with ALDLdroid. If i had a VSS, the Vehicle Speed would also report.
When we started with ALDLdroid, the ECM was reporting Battery Voltage at ~12.5V; along with severe drivability issues (hesitation at cold start, intermittent dying when going into gear, and high speed backfire when letting off the throttle at 70mph, coasting to 60 & getting back in it.
Over a couple week period, i broke apart the wiring harnesses (factory & EFI) & ran voltage drop tests, finding a myriad of bad splices/ connections along the way. As part of that, ive cleaned battery terminals, cleaned all the grounds i could find, found and connected a previously unconnected 'green' 12-ga ground wire that was connected to the negative battery post - stuffed in the headlight hole. All of this got me from ~12.5V measured at the ECM to ~13.2.
After reading & re-reading posts, and talking to AFI & Bill_USN1 on binderplanet, i worked my way to the ECM itself, the main relay & fuel pump relay & began cleaning connections there with DeoxIT D100 contact cleaner. Corrosion was pretty amazing, as evident from the bubbling. That's when i found a major cause of voltage drop - the ECM fuse. The mix of corrosion & cracked connection was responsible for ~1V.
Cracked fuse - responsible for ~1V drop
Battery voltage as reported by ECM jumped from 13.2 to 14.2, after cleaning ECM & relay connections and replacing the cracked fuse.
DeoxIT D100 electrical contact cleaner - highly recommend
Learned a tremendous amount during this exercise. From posts & conversations on forums like:
- binderplanet.com (Fuel Injection section)
- Gearhead-efi.com
- JeepForum.com (JeepHammer's Wiring Guides)
- chevytalk.com
- gmt400.com
- theamcforum.com
- pirate4x4.com
along with phone calls with Bill Hamilton @ Hamilton Fuel Injection, & rang-a-stang on ifsja.org who got me over the fear of diving in. Though it took a couple of years to get there, today (2/10/2023), we have a nice running engine.