Figured I'd try here as a last ditch effort before having the British Boneyard take a look at my 97 Disco. It's had an intermittent no start condition since buying it in April as a project but recently it seems to have given up the ghost, it now cranks but won't start at all.

Recent work:
Fuel pump
Crank sensor (seeing rpm on scan tool when cranking)
Repaired crank sensor wiring (insulation had failed at the sensor)
Resurfaced heads, ARP head studs, Elring headgaskets, all engine gaskets/seals except rear main, all rubber hoses --> This was done 3-400 miles ago
Plugs
Plug Wires
Oil pump gears
Full exhaust from manifolds back
All 02 sensors

Diagnosis:
Fuel pressure is 38psi at the rail, bleeds down to 20psi after a few minutes
Compression is in the 160's across all cylinders. RAVE says 170-180 but for 156,000 miles 160psi is fine by me.
Has spark
Has fuel (plugs all came out wet with fuel)


All through this the intermittent starting issue remained, usually it was when hot but the past few times it occurred when cold. Any other ideas here? The truck came with an old cam sensor in the seat back pocket so my guess is someone has been chasing this for a while.

Two things come to mind but neither should cause a cold start issue, right?

• Occasional coolant temp sensor circuit code - Have a new sensor, just need to swap it out.
• Fuel temp sensor - Again, shouldn't cause a cold start issue?

 

It looks like I've narrowed this down to sticky lifters and/or rocker arms. During the head gasket job I did my best to clean the gunk and crust off everything, especially the rocker arms and ensure the oil passages were clear. Who knows what happened but during more diagnosis yesterday I got the following compression on the driver side bank...

120-60-50-60

Added some oil to each cylinder, go the same results. After pulling the rocker shaft for that bank an retesting the results aligned with the other bank (all cylinders around 160psi). Each rocker arm moved smoothly with no abnormal wear so my guess is oil sticky lifters causing the valves to hang open a bit. After putting everything back together the truck fired right up and ran smoothly leaving me scratching my head. At this point I might try an ATF flush or seafoam to hopefully free things up before replacing any parts.

 

crank no start - sticky lifters

dont think so

likely a failing CPS

 

Well, it seems like you’ve definitely been investigating the right parts. Even delving in to the engine!

My crank no start was a combo of some bad fuses and bad CPS wires.

I’m assuming you’ve checked if your fuel pump relay is still good? And inertia switch? And your fuel pump wiring harness is still good?

 

Just bumping this thread as the Disco continues to have intermittent crank but no-start issues. The worst is sometimes it's no fuel, other times no spark... sometimes both. It's actually with Randy at British Boneyard and he's having a heck of a time with it too. Just when we think it's good he'll drive it for a few days and it does it again. Once it's started it runs perfectly fine and the problem occurs randomly whether the truck is cold or hot.

Additionally we've done the following:
Fuel pump and pigtail wiring - the Airtex pump I installed wasn't providing good pressure when running and bleeding down too quickly. The pigtail was somewhat burned up as well.
Replaced all of the CPS wiring along with the sensor
Coil was weak, replaced that

Not sure where we're going from here.

 

Check the ECU under the hood for corrosion. They have a vent hole in the ECU case and depending on your climate they can get wet and then corrosion starts and will make your D1 do crazy crazy crazy things. When I first got my 97 XD it refused to maintain any kind of idle and it ran awful especially at a cold start up. Finally came upon a scenario in which it ran decent and maintained idle which was VSS unplugged, and A/C on. If I didn't do those two things it ran awful. Finally pulled the ECU opened it up to find one main section of the PCB was ruined. Tracked down another ECU slapped it in and she's been good to go ever since.

 

They actually tried two ECUs today and same things. Truck starts/runs perfectly when cold but has no spark when warmed up. You'd think it was the CKPS but we've been down that road and many others. At this point they're not billing me for any of this as they just want to figure it out.

I pulled my hair out for 6 weeks troubleshooting this until it died one day at a light and wouldn't start. Had AAA dump it with the Boneyard for a bit.

 

so you did replace the cps ? did you replace with a Lucas part ? did you check all grounds ?

 

pb,
Looking at the thread starter, it has two clues regarding occasional coolant temp and fuel temp faults. That reminded me of the repair I had to do to solve coolant temp from bouncing around when driving on bumpy roads. There is a common sensor splice (S502 in the '96 Electrical Test Manual) at the front of the engine taped up inside the wiring harness. The coolant and fuel temp sensors are connected there, along with Intake air temp, throttle position, MAF, and Cam position sensor. That splice grounds to pin 36, connector C507 of the ECM. If splice S502 is subjected to movement (think off road or front cover maintenance) it is liable to come loose.

On my truck, the S502 splice was only partially loosened up, so that caused the ECT to bounce around (and probably all those other signals). So I took it apart, cleaned the wires, then soldered them all together. Now I have solid signals. Thanks to 96sd suggesting ground checks for helping jog my memory.

I think you should take a close look at that splice. It is easy to get at and all those signals taken together might cause a no-start condition.

Good luck. You'll need it. Intermittent wiring faults are a real bear to track down. You may need to check every sensor circuit, or at least the crank sensor circuit, very carefully.