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97 Discovery I - Diagnostic Nightmare - Cranks, Won't start, Won't link with ECM
1997 Land Rover Discovery I SD, GEMS V8i engine, Advanced Evaporative Loss (fuel system)
Symptoms:
Car cranks, won’t start. Appears to have fuel but no spark. Check engine light does not come on as soon as ignition is turned on (as it is supposed to), OBD II scanner can’t link with the car’s computer.
When the key is turned to position III, the car does nothing, until about 3 seconds of holding the key in position III, when it suddenly starts to crank strongly. The car never starts, however. After several previous attempts, the car will start cranking as soon as the key is turned to position III, but still will not start (the cranking delay goes away after repeated attempts). I don’t know what this delay means.
(Portable power used for all these cranks to make sure battery power is not an issue.)
Background:
Car running perfect, left it in the airport parking lot. Picked it up 10 days later, the car barely started, would not go above 10 mph until I drove it around the parking lot a few times. The longer I drove it, the stronger it got. I managed to get it up to 65 mph on the highway, drove it 25 miles home. Every few minutes I would feel the engine misfire, and twice the car lost power entirely on the drive, forcing me to slow down on the side of the highway to 20 mph; as soon as the car hit that speed, both times, the engine instantly got its power back and accelerated to 65 mph. After that, the car sometimes started, sometimes didn't, for 3 days before finally dying while idling in my garage. The car would turn on every time if the engine was already hot, but leave it for several hours (overnight) and it would be very difficult to start again.
Tests:
Using a spark wire tester, there is no voltage through the spark plug wires.
When the valve on the fuel rail is depressed, fuel always comes out very strongly, haven’t checked the pressure yet.
Right before the car died, the check engine light code was on for a random misfire.
Recent Work:
After the no-start issue happened: New DieHard battery, New OEM ground cable. Positive battery cable is original.
6 months ago: Oil change, transmission fluid change, new power steering pump, belt
2 years, 10,000 miles ago: New spark plugs, plug wires, fuel filter, air filter, Sea Foam in gas tank, crankcase.
Thoughts:
I would assume a bad Crank Position Sensor, except that the lack of check engine light/computer interface makes me think either:
The ECM is bad, the Relay Module is bad, or some other electrical problem prevents the ECM from receiving power.
If anyone has any ideas about what is wrong, or knows whether a bad Crank Sensor can prevent the ECM from turning on at all, I would appreciate it. The next steps I plan right now are 1. Check the fuel pressure with a gauge to confirm that the pressure is good. 2. Change spark plugs, (time to do it anyway). 3. Change multifunction relay module. 4. Change Crank Sensor. 5. Swap in a used ECM
Do items 1, maybe 3, and maybe 4. But first get power on ECM (check all fuses, plug/unplug connector on ECM). Start with F3 in satellite fuse panel 2 (the smaller sub panels next to main panel under dash). That runs the OBDII connector.
If ECU is not working, you may not get fuel pressure either as it controls fuel pump relay.
97 Disco 1 178K "Frankenstien" brought back to life with parts from the dead ones
Shade Tree Mechanic Second Class - no charge for worthless opinions, all info presented as academic discussion. Not affiliated with any vendor mentioned.
Just had a similar problem and it is now solved. I had to replace the ignition module next to the coil. This module communicates with the ignition system. If you fit it yourself (Failrly easy) make sure that you apply a jointing compound to the rear of the module where it mounts to the coil bracket. The metal backplate on the module provides the earth and if you leave this step out, it can provide problems later.
As for the cutting out, my problem was solved by unplugging the throttle idler module on the rear of the engine. The plug is locatged at the back of the engine at the top close to the throttle control. I had a dry joint and after 2 years of diagnosis and hundreds of dollars spent replacing the ingnition components, it turned out to be a dry joint in this connector.
Possibly unrelated, but if the Alarm ECU is acting up, then there is no communication to the ECU from the OBD, but more telling, the check engine light does not come on when you turn the key.
I just went through this in the middle of some mechanical related issues and it was a nightmare to diagnose.
The crankshaft position sensor is the most important
sensor on the engine. It is located in the left hand side
of the flywheel housing and uses a different thickness
of spacer for manual and automatic gearboxes. The
signal it produces informs the ECM:
- the engine is turning
- how fast the engine is turning
- which stage the engine is at in the cycle.
As there is no default strategy, failure of the
crankshaft sensor will result in the engine failing to
start. The fault is indicated by illumination of the malfunction indicator light (MIL) on North American
specification vehicles.
That said, we have a lot of people on here that can't crank and no spark and it turns out to be CKP.
As for the OBDII port and alarm system, the alarm module is connected to pin 8, but that doesn't do much on generic readers.
97 Disco 1 178K "Frankenstien" brought back to life with parts from the dead ones
Shade Tree Mechanic Second Class - no charge for worthless opinions, all info presented as academic discussion. Not affiliated with any vendor mentioned.
97 Discovery I - Diagnostic Nightmare - Cranks, Won't start, Won't link with ECM
