DII- ECM Not Grounding Fuel Pump Relay

[group captain mandrake]

I bought a '03 DII with a wasted engine. I built an engine for it and am finishing up the install. This thing sat for who knows how long, so I decided to drain the fuel tank to put fresh fuel in it. I did this by jumping the FP relay pump power wire, worked great. I thought I'd better make sure I had good fuel pressure so I don't spin all the lube off the bearings & cam. Key in on position=no fuel pressure. I checked inputs at the relay and the ECM wasn't providing the ground input. Then I remembered when they unloaded the truck off the flatbed the hazards were flashing when we hooked up a jump pack to shift into neutural, so I thought the engine might be immobilized. I locked the truck with the fob, then unlocked it and turned the key to the on position and got 50 lbs on the fuel pressure guage. I thought all was well and called it a night.
The next day I was back to no fuel pressure. I tried locking/unlocking again with no joy. Dash LED is not blinking indicating immobilization. Fuel cut switch is not tripped.
Right now I'm puzzled. I'm digging into RAVE, but haven't found an anwer yet.
Any ideas?

 

[jafir]

Any codes?

 

[group captain mandrake]

No codes.
And I should clarify; dash LED functions normally when armed, ect.
I'm really puzzzled why I had proper function one night and not the next day and thereafter.

 

[Hugh166]

Crank sensor? Check if you have spark. Or if you have a scanner see if you see a crank signal

 

[group captain mandrake]

Did some searching. Looks like PT had the same problem a couple years ago; crank sensor. I've got a spare I'll try tomorrow. Although I can't see how that would have an affect on key on engine off fuel pressure prime, but it is easy enough to try, and it fixed PT's customers truck.

Edit: I have not been cranking this thing, just checking for key on fuel pressure prime. I still have to install the plenum, bleed the cooling system and finish priming the oiling system. So I do not know the status of spark, yet.

 

[KyleT]

BECM ground trigger might be bad. mine did this when it sat for a long time. i grounded the wire to eliminate this. i cant remember what wire but it was on the pass side footwell.

 

[Hugh166]

When my crank sensor went bad it did the same thing you are describing. It won't give ground to give fuel until it sees a good crank signal. So my advice would be to finish everything up and replace the crank sensor, because if it doesn't see the engine turn n it won't allow fuel. The fact that it wouldn't prime the fuel system threw me for a loop too

 

[listerdiesel]

Remember that the fuel pump runs for 5 seconds only when you turn the ignition on, then it's off until the engine has fired and the ECU sees feedback on the crank and other sensors.

You haven't knocked the inertia switch? Just thought it worth mentioning....

Peter

 

[group captain mandrake]

Remember that the fuel pump runs for 5 seconds only when you turn the ignition on,

That is exactly what I'm trying to get: key on fuel pump prime.

I thought I was on track with this thread:

http://www.discoweb.org/forums/showthread.php?t=76789&highlight=fuel+pump+relay+ground
PT had very similar symptoms and a crank sensor fixed it. Although I couldn't see how a crank sensor could prevent non-cranking fuel pump prime, I tried it anyway, with no change. I have never had to change a crank snsor in one of these yet and I read someone said you had to leave the key on for 10 minutes for a relearn. That did not help either.

seventyfive suggested to someone with similar symptoms to swap engine compartment fuse blocks. I did this also with no luck.
I wish and Rover had diagnostic flow charts like a lot of other manufacturers do (did).
I mentioned earlier the immobilizer system was working as it should. I'm not so sure about that anymore. I think that may be the area I'm having a problem with. I am going to read up some more on that system.
Oh, and tomorrow I will check to make sure I checked all the grounds.

 

[crown14]

So you arent even turning the key to START position at all? Finish up the oiling system, plenum, and then try it.

 

[jymmiejamz]

I may be wrong, but I thought the fuel pump in a DII will only run whilst starting or running, not just when the key is in the on position.

 

[Hugh166]

Have you finished assembling the rest of the engine so you can crank the engine yet? If you haven't actually attempted to start the engine you are wasting your time trying to figure out an issue. The ecu cuts off fuel supply and spark until if sees a crank signal from the sensor. If it doesn't know where's the engine is in rotation it won't give fuel to protect from flooding. Without getting the engine cranking you really can't make an accurate diagnosis, you might not even have a problem at all

 

[group captain mandrake]

I thought when the key was placed in the on position, the ECM energizes the fuel pump relay for a few seconds then shuts off until it sees a crank sensor signal and then re-energizes the fuel pump relayas long as the crank signal is present.

Is that not correct?

 

[crown14]

I think it does that a few times, then it will stop until it sees an complete key cycle. Finish putting your truck together and give it a shot.

 

[jymmiejamz]

I thought when the key was placed in the on position, the ECM energizes the fuel pump relay for a few seconds then shuts off until it sees a crank sensor signal and then re-energizes the fuel pump relayas long as the crank signal is present.

Is that not correct?

According to RAVE the fuel pump will is energized for 2 seconds, but will time out until the engine is started. I interpret that as once you cycle the key to position II, and the fuel pump times out, it will not be energized again until the engine is cranking.

 

[group captain mandrake]

Well done Jimmy & Joel. You guys were more right than anyone.

All the vehicles I have checked fuel pressure on energized the pump for a few seconds at key "on", then off until the engine cranks. I always expect a few seconds of fuel pressure prime at key "on".

I pulled my '04 into the shop to verify how a properly operating Disco's fuel pump operates:
At key "on" the ECM energizes the fuel pump relay for two seconds; only 2 or 3 cycles in a row, then not again until the engine is cranked. After that, key "on" fuel pump 2-second prime only occurs after a successful engine start.

Now that I am done spinning my wheels on this non-existent issue, I'll try to get this thing buttoned up and running this weekend.

Thanks for the input guys.