This may be a long shot but I am going to try anyway...
I just got done replacing the main wiring harness in the engine compartment. This included the harness that connects to the PCM as well as the harness that connects to the sensors on the intake manifold. I started this project by removing my wiring harness and placing it on the work bench next to the new one I pulled from an older truck. Most of the wires were in the same places, I went wire by wire and found a few differences that I fixed.
After I installed the new harness I did some tests to make sure the lights worked (which they did), I can hear the fuel pump coming on when I turn on the key, my dash lights come one, and when I pulled the codes I didn't get anything I didn't expect. The new harness also has the grey, remote-mounted TFI module just like the original harness.
When I first tried to start the motor, the starter would turn over but it was definitely struggling as if it didn't have enough power to turn over the motor (truck has only been sitting for 1.5 weeks). Occasionally I would also get the clicking sound as if there wasn't enough current, but the motor would turn over a few times. After the truck didn't start I poked around to see if I was getting spark by taking off the coil wire from the cap and setting it next to ground. I have done that a few times and each time I can't see any type of spark at all.
While it is true that I am not getting spark, I am not sure if this is a wiring issue or just low current. I have the battery out of the truck while I work on it so to get power to the system without installing the battery I set the battery on the floor and use jumper cables to go from there to the battery terminals and the battery is just about as charged as it could be. So far I have checked a few connections at the TFI module and they are OK but aside from the weak spark or me not getting enough current from the battery to the harness...just not sure so I thought I'd ask here to see what the first troubleshooting steps would be for determining why I have no spark.
I obviously have something not right, did I miss something obvious?
RIKIL - Colorado Chapter Leader
-------------- Red, 1992 F150, 351W, E4OD, Vortech V-2 Si trim blower, Snow Performance water/meth injection system, custom cam, Edelbrock Performer intake, Twisted Wedge 205cc heads, shorty full-length headers, MASS Air (converted), tuning with QuarterhorseRT, 4x4, short bed, 33" tires
Also check your grounds, both to the engine and chassis. Install the battery if you can, since the less wire you have the lower the resistance will be. Make sure it's able to crank at full speed, I've seen a no start due to too low of a cranking speed (Nissan).
Progress but still not starting. I installed the battery and it now cranks over as I would expect. It also produces spark from the coil but I think it's a weak spark. My timing light can't detect a signal in the #1 wire or When I connect it to the coil wire. Could this be a bad coil? Or poor grounds? From what I remember there is a stock wire going from neg of battery to the block just below #1.
Got it started, I had the plug wires off by 2 on the rotor.
I may be premature in this because the truck hasn't been run in a couple of weeks, but if I had an incorrect position for a couple of my 8 injectors (with my MASS Air system), could that be the cause of me smelling a rich exhaust? I wasn't able to let the motor fully warm up today but it seemed fine When running. However, when starting I need to crank for 6-8 seconds before it'll catch. Seems something is still off.
Assuming the MAF trucks have sequential injection, odds are you'd have a dead miss if the incorrect wire went to the incorrect injector. The injectors themselves aren't cylinder specific though. Does the oil smell like fuel at all? You could have loaded it up pretty badly when trying to start it before. Also, it will run rich until the ECT hits a certain point, and it eventually goes into closed loop.
Nah, it'll still run with the injector wires on the wrong cylinders. The factory batch fire system fires against closed intake valves anyways.
It might be somewhat hard to start, and idle quality won't be great with the injector wires incorrect though.
That's what I thought too but what threw me off was the idle was pretty steady. Today it won't start but it almost wants too, it's also 20-30 degrees colder. I'm thinking about pulling the plenum and checking the injector wires, but for some reason I don't think that'll be the problem.
I'd check your ECT wiring and verify you have no intake leaks.
ECT wiring is correct. I had all but 2 of the intake bolts on, I doubt those missing bolts could cause this behavior.
So i decided to remove the intake to test injector connectons. Smelled a lot like gas when I removed the intake. I have verified the injectors each have one individual wire and one connected to vpwr. But When I probe the injector harness, I get a one to many relationship. I then tested the injectors and each connector on the injector has continuity and a resistance of 11.5ohms. Is this right? I didn't think the injector connection would be like this and it makes me think something is wrong with the injectors. This is a new injector harness I made.
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