I have benefitted greatly from the accumulated knowledge/experience of this forum - Unfortunately, I'm running low on probable causes on this one.
- 98 LandRover Discovery LSE
- 115,000 miles
- Currently not illuminating a "fault"
- Symptoms
- Initially, vehicle would occasionally not run well when parked at operating temperature and then restarted while still hot/warm - extremely rough idle / difficult to raise RPMs
- Later, vehicle would not start at all when hot/warm. After vehicle cooled down, vehicle would start and run fine.

After reviewing LandRoverForum posts, all indications seemed to point to Fuel Temp Sensor or Crankshaft Position Sensor. I checked parts availability and cost - Fuel Temp Sensor was most expensive so with my luck, I chose that. After replacing Fuel Temp Sensor, problem persisted and proceeded to get worse. Experts on this forum warned that Disco would likely stall in near future.

I ordered the Crankshaft Position Sensor - Before it had a chance to replace, the vehicle stalled. Towed it home and replaced the Crank Position Sensor.

Started the vehicle - ran fine (it was cold when I test started it). My son drove the vehicle today and after about 10 miles, the vehicle stalled.

I have not changed the fuel filter yet - That's the only other thought I can come up with.....

Any ideas from the LandRover Gurus?????

 

Mine did that before the fuel pump failed. Filter might help though.

 

After changing the Fuel Temp sensor and then the CKP - with no resolution - I changed the fuel filter and the disco seemed to be running OK - made several short trips around town with no problems......until today.

Vehicle was driven about 10 miles, parked for 5 minutes, when tried to start the vehicle ran very rough at low idle and then died. After that, it would not start (engine will crank, just won't start). No engine fault codes.

I have not checked fuel pressure at fuel-rail - Any reason why the fuel pump would cut out when vehicle is hot?

Any suggestions???

 

That's when they die. Check the pressure at the rail. It would not be unheard of for your fuel pump to go out. I got mine at Advance Auto, Airtex 3270 for under $100. But, I believe yours will be different. There are AEL and pre-AEL, something about emissions stuff. There is a bunch of stuff in the archives on fuel pumps. It's really not as bad as a lot of vehicles where you have to remove the tank.

 

Slight possibility your relay ma be shutting down when hot.
Pretty much has to be that or the pump. If it is the pump, just replace the motor as mentioned above, don't replace the entire pump housing.

 

Let the vehicle sit overnight....Vehicle started right up and drove great the 7 miles home in 98 degree heat. Pulled it into the garage and shut her down - Waited five minutes and went back out and tried to start - very rough idle, unable to increase RPMs, vehicle died.

Checked fuel pressure at the fuel rail (with a tire tester as this is all I have). Shows about 10 lbs. When I switch ignition to position-2, I do not hear the fuel pump coming on.

My current thinking is the Fuel Pump Relay. When the vehicle is cool, relay is functioning - When vehicle is running, usually enough cooling air inside engine compartment to prevent relay from failing - When vehicle is parked, heat builds up under the hood and fails the relay (I don't know if this makes any sense, just grasping at straws). I'm leaning toward the relay because I'm thinking that if the fuel pump was bad, it wouldn't start when the vehicle is cold. (anyone feel differently?)

Anybody else have any ideas and/or suggestions??

Planning to order a new Fuel Pump Relay unless one of you guys has a better idea

 

You can try squirting hot relay with brake cleaner (which is like circuit board cleaner and will chill it). That is an old TV repair trick, you would spray each componnet until the picture changed. Could also be bad inertia switch, which is in series with pump. Or waco fuse

 

After letting the vehicle sit overnight:
- Turned ignition switch on - could not detect fuel pump running
- Started the vehicle and it started fine
- Shut vehicle off, checked fuel pressure at the fuel-rail with a tire pressure tester and it was 10 lbs
- Checked the fuel tank for pressure - slowly opened the fuel cap - did NOT hear any air escaping.

Questions:
1) Does the fuel pump run continuously when vehicle is running or does the ECU cycle the pump to maintain fuel pressure in the system?
2) Does a properly functioning fuel system maintain observable pressure in the fuel tank (when you open the filler cap, should you always hear some air pressure escaping?)
3) IF my tire tester is reasonably accurate and shows 10lbs of pressure at the rail when both hot and cold - Why will the car start when cold but not start/run when hot?

My son is driving this vehicle on his short commute to work (less than 10 miles) all city driving. Not sure what would happen if vehicle was started cold and run at highway speeds.

Is there any way to test fuel relay and/or fuel pump without installing a replacement?

 

1. Yes the pump runs continuously (when the engine is running)
2. No, it doesn't pressurize the tank
3. If you actually had 10psi of pressure the truck would not run, a tire gauge is not an accurate means to determine fuel pressure.

Your last description of symptoms makes me suspect a pressure bleed down in the fuel system, there is a check valve in the fuel pump that maintains system pressure for a time after shutdown to facilitate hot restarts, over time all this pressure bleeds away but when the engine is cold the ECM enrichens the fuel mixture (kinda like a choke operates on a carburettor engine). But, when I look at your initial description it doesn't match this pressure bleed down scenario, this pressure bleed down will not affect running once you actually get it started and running for a few seconds, a good fuel pump will repressurize the system almost immediately once the truck is running. The fuel pump only runs for 10 seconds when you initially turn the key on, if the ECU doesn't detect the engine running (from the crank sensor) then the fuel pump is shut down until the key is cycled. If you don't have the RAVE manual, I would suggest downloading it, all this stuff is detailed there. Good luck.

 

Quick Update - Secured loaner fuel pressure tester from auto parts store - adapter was broken so waiting on a replacement.

Definitely has fuel pressure at the rail, (obviously since vehicle will start cold). My plan is to confirm approx 30lbs of fuel pressure (static and while engine is running) - run the vehicle until it is at full operating temperature and anticipate that vehicle will not start - check fuel pressure when vehicle is hot and won't start. I'm thinking this will confirm if the relay is opening and thus shutting down the fuel pump.

To Gale's post - I did notice that the fuel pressure at the fuel rail diminishes very quickly after the ignition is turned off, (within 1 minute). Not sure if this is a clue. I do have the Rave