You need to check fuel pressure. Im pretty sure Land Rover discovery fuel pumps don't do anything until engine is turning over (cranking). I just went through this scenario on a friends disco, the fuel pump was only putting out 25 pounds pressure.

 

I'm as surprised as anyone that the fuel pump energizes with the key on, but that's what the BOSCH manual says it does in this version of Motronic.

"The ECM energizes the fuel pump relay when the ignition is first turned to position II. It also energises it during engine cranking and when the engine is running."

It may be just that it's worded poorly. It does say "first turned" and "also energizes during engine cranking", which could mean that it de-energises it until it sees cranking at the CKPS. I certainly can't hear any pump running with the key on. I'm equally surprised that there's so much misinformation about this, as if no one's ever checked to come up with a definitive answer. In any event, I let the truck sit all weekend and it started right up this morning so until something changes I don't plan on doing any more troubleshooting. If the problem returns I'll put a meter on the pump and solve this fuel pump eneregizing mystery forever.

Also, 25PSI is not enough to run the truck so that's clearly not my problem, once it does start it runs fine.

 

The way I remember it working is like this:

As soon as you turn the key to position 2, fuel pump comes on automatically.
If it does not see crank position signal (engine start / running) within 30 secs, pump shuts off.

If the crank position signal (attempting to run / crank) is seen after the 30 secs goes by and the pump is off, then it turns the pump back on.

Should show 53-ish PSI. I have heard of this kind of hard starting behavior with a dying (but not yet dead) fuel pump.

 

The local indy mechanic here tested my friends hard starting disco and diagnosed a bad pump at 25 psi. It's been starting hard for a few years....Maybe the indy mechanic is just trying to get money? idk...I do know that Im replacing the fuel pump for him. We'll see if the hard start goes away.

 

Keep us posted. After you disconnect the electrics and before you pull the pump out, maybe you can put a meter on the connector and see if the harness get power with the key sitting in Pos II for any length of time. My guess is you may see voltage for a split second, and then nothing until you start cranking the engine. I'd love to know the real answer there.

 

I will do that ahab

 

This is my understanding also, l'm pretty sure the Dll doesn't activate fuel pump relay until ECM sees rotation. Even read it somewhere, but don't remember where. It would be easy enough to verify, pull fuel pump relay, find ground signal wire from ECM in relay terminal plug and use a DVM to see if she goes to 0.00 ohms once key is turned to second position.

And then this age old question would be answered...lol. l'd do it...but not today.

 

OK, we have an update here. After almost a week of driving the truck with no more cranking issues, I took it in for safety/emissions inspection yesterday and she passed with flying colors. This morning I went out and it finally happened. Cranked for 3 or 4 seconds and no fire so I shut it off, turned the key to position 2 and waited. After 10-15 seconds I tried it again and still just cranked away. Finally after another 5 plus seconds of cranking it fired up. The driver's door was still open and this time the smell of fuel was a little more pronounced so I walked over to the filler door and looked around under the truck. I took a video but that seems a bit overkill, fuel was dripping from the frame rail at a good clip. I shut the truck off and watched it drip rather profusely while it bled off the pressure. With it still dripping, I jumped in the other truck to run an errand and came back home.

A few hours later I went out to check and saw this.



I rolled under the truck and the stain is directly below the area where the fuel EVAP canister lives. There are a few connections in that area that were completely dry although there was evidence of past wetness so I knew I was in the right area.



I turned the key to position 2 and waited a bit, then rolled back under the truck and it looked exactly the same, dry. However when I cranked the truck for a quick second and checked again, the area was dripping wet.



This leads me to believe unequivocally that the pump does NOT come on until the ECU sees the engine turn.

Upon closer inspection I saw what looks like the o-ring visible on a connection in the primary feed from the pump to the fuel rail. I have no explanation for the course of events that led up to this over the last month, but it looks like this is why the rail has been bleeding down when the truck sits, sometimes. I think it's losing enough fuel at this point that there would be running problems.