[Disco2PC]

I’ve been searching the forum and trying a few things for a few weeks off and on, but I’m officially stumped. I have a 2001 D2 with 135K miles on it that won’t start. I started to get an occasional rough idle while stopped at traffic lights a few weeks ago that became more and more frequent. It would run perfectly for 30 minutes or so, then the rough idle would begin to happen at traffic lights. After a few days of this, it wouldn’t start at all one morning. I put my scanner on it, and saw that I was getting misfire codes. I had new 8mm sparkplug wires that I had been meaning to install, so I installed them with new plugs; still wouldn’t start. After searching the forum, I decided the crankshaft position sensor must have failed. I replaced it; still wouldn’t start. I checked spark, and I found that I wasn’t getting spark on 4 cylinders, so I replaced both ignition coils. Though it didn’t start on the first attempt, it did start on the 3rd or 4th and ran perfectly… for two or three days. On the third day, the rough idle came back at the last traffic light before getting home. It hasn’t started since. I had my father-in-law look at it with me this weekend and he thought the spark looked weak and erratic. We also determined the fuel pump was not priming when the key is turned. We unplugged the fuel pump relay, jumped it, and the fuel pump does run, so I don’t think the pump bad. The relay is fine too. I replaced the crankshaft position sensor again just to make sure I wasn’t given a bad part, and still no go. After pulling the fuel pump relay, it pitched a code having something to do with the fuel pump relay failing or something, so that leads me to the think the ECU fine. I’ve tried resetting the inertia switch. Like I said, I’m stumped. Any ideas would be helpful.

 

[Disco Mike]

First, never ask a question with out giving us all the fault code Numbers, otherwise, we are left guessing.
Have you considered the coil pack, have you tested the fuel pressure?
If you want some help with this, send me your number and lets talk.

 

[Disco2PC]

After some more tinkering, I'm still having no luck getting this thing started. Per Mike's advice, I've cleaned the CKP wire harness to make sure it wasn't contaminated with oil. I've checked compression, and I have 160- 170 PSI across the board. I have spark, but I must not be getting it at the right time, since spraying starting fluid makes no difference. I've checked continuity between pins 1,2 & 3 on the CKP plug (C0168) and pins 32, 46 & 45 on the ECM plug (C0636) and it checks out. I'm on my second CKP from the local auto parts store, but I'm starting to wonder if they've got a bad lot of these things. I've unhooked the CKP from the truck and put an oscilloscope on pins 1 & 2. When I turn the engine over, I get a sine-like waveform with roughly 1 Vpp. Does this sound right or is that too low? Its kind of hard to extrapolate engine RPM from the chart on page 18-2-15 of the workshop manual with such a low Vpp, so does anyone know roughly how fast the engine is turning over during starting? I realize this will vary with battery CCA and starter condition, but I'm just wondering about ballpark RPM.

 

[Disco Mike]

Sounds like we should talk.

 

[killerkaw]

MASS AIR FLOW.....I'd bet money

 

[Disco2PC]

I considered the MAF some time ago since it was pretty filthy and it was 6-7 years old. I replaced it and my rig still won't start. The SES light is on now, but no codes are present. Anyone have this happen before?

 

[Disco2PC]

I read a post about remobilizing a demobilized Disco, so just for fun I turned the key in the driver's door in the 1515 sequence like the post said. Truck still wouldn't start. As I was stepping out in disappointment, I remembered reading something about trying to start the truck in neutral. I put the rig in neutral and it fired right up. It will also start in park now as well. I've driven it a few times since without issue. Not sure what to make of this...