RR 1995 TD: engine stops but fuel pump doesn't!

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Grrrrrr

Grrrrrr

Technician, Bodgit & Scarper Ltd
Full Member
Posts
18,980
Location
Buckinghamshire, UK. ('95 DT)
Bought a RR P38 TD yesterday. Drove it back. No issues! Woke up this morning: battery dead. Recharged battery. Refitted and then noticed a humming sound. Followed it to rear of car and then underneath. To cut a long story short, pulling the fuse for the fuel pump stops the humming.

Car starts fine, runs fine, stops fine. But even after an hour the damn fuel pump is happily whirring away to itself and draining the battery.

Is there a usual suspect? Fuel pump relay (#12)? ECU? Or is this a pull parts until it sorts itself job?
 
MrGorsky has just posted on the same issue...

I suggested looking at Relay 12 ... pull it and test the switching pins (diagram should be on the relay as to which pins are the coil and which are the switch)...

My guess is its stuck closed...
 
Saint.V8 said:
MrGorsky has just posted on the same issue...

I suggested looking at Relay 12 ... pull it and test the switching pins (diagram should be on the relay as to which pins are the coil and which are the switch)...

My guess is its stuck closed...
Click to expand...


Yeah, didn't realise he was doing that! Same car, same issue! Thanks, I'll try and have a look tomorrow if I get a chance before it gets dark.

J
 
Saint.V8 said:
MrGorsky has just posted on the same issue...

I suggested looking at Relay 12 ... pull it and test the switching pins (diagram should be on the relay as to which pins are the coil and which are the switch)...

My guess is its stuck closed...
Click to expand...

Progress (or lack of) report. Charged battery last night. Battery held charge during the day at 12.8V. Not perfect but not catastrophic.

Pulled relay #12 (fuel) and compared to relay #4 (heated screen) as it looked the same. Both have pins 1 & 2 connected but none of the others show any connection between them. That kind of make me think the relay might be OK.

Reconnected the battery this evening and pump whirred away immediately so pulled the fuse again. Will see if battery discharges overnight.

Oh, no odd smells from the fusebox - well, none odder than usual.

There was one odd thing, after reconnecting the battery and getting in the car and turning the ignition, it came up (along with warnings about windows not set etc) with Alternator Fault. I assume this is normal when you turn the key but don't start?

Cheers,

J
 
Grrrrrr said:
Progress (or lack of) report. Charged battery last night. Battery held charge during the day at 12.8V. Not perfect but not catastrophic.

Pulled relay #12 (fuel) and compared to relay #4 (heated screen) as it looked the same. Both have pins 1 & 2 connected but none of the others show any connection between them. That kind of make me think the relay might be OK.

Reconnected the battery this evening and pump whirred away immediately so pulled the fuse again. Will see if battery discharges overnight.

Oh, no odd smells from the fusebox - well, none odder than usual.

There was one odd thing, after reconnecting the battery and getting in the car and turning the ignition, it came up (along with warnings about windows not set etc) with Alternator Fault. I assume this is normal when you turn the key but don't start?

Cheers,

J
Click to expand...
Not normal - no....

Did you swap the Fuel Relay for a known good one.....can't remember the colour, but swap out a relay of the same colour into the Fuel pump relay socket and see if it still runs - if it doesn't, relay is at fault, if it still runs, then there is a wiring fault or fuse box problem...

With the battery connected, pull the fuel pump relay out, does it click when you take it out and put it back...if it does, there is a fault causing the relay to be permenantly switched....if after removal and no relay in place, and the fuel pump still runs, there is a earth leak somewhere causing the fuel pump to run, or the fusebox is tracking....
 
Grrrrrr said:
There was one odd thing, after reconnecting the battery and getting in the car and turning the ignition, it came up (along with warnings about windows not set etc) with Alternator Fault. I assume this is normal when you turn the key but don't start?

Cheers,

J
Click to expand...

You should not see an alternator fault message, but it can be caused by low battery voltage.
I would still bet on the fuse box being the source of the problem.
 
Quote: "Did you swap the Fuel Relay for a known good one."
No, just compared resistance across pins to #4 relay. The guy I bought the car off is sending me a replacement relay which is good of him.

Checked battery this morning. Down to 8V and that was with fuse out and after stripping out after-market radio. So, put battery back on charge.

Looks like I've got a short somewhere. Sounds like the fusebox is a likely source. I'll try a parasitic drain test at the weekend and hope that homes in a little more. So far we have:

Fuel pump doesn't stop.
Drivers door lock doesn't respond to blipper (rest of car does) but works with key.
Losing charge from battery from some sort of parasitic drain (on top of fuel pump issue.) "Brain" not going to sleep? Alarm system fault?

Hopefully I'll know more when I can work out which circuits are drawing current after I shut her up. Need recharged battery and a free day though!

Thanks for all the suggestions!

J
 
Grrrrrr said:
Quote: "Did you swap the Fuel Relay for a known good one."
No, just compared resistance across pins to #4 relay. The guy I bought the car off is sending me a replacement relay which is good of him.

Checked battery this morning. Down to 8V and that was with fuse out and after stripping out after-market radio. So, put battery back on charge.

Looks like I've got a short somewhere. Sounds like the fusebox is a likely source. I'll try a parasitic drain test at the weekend and hope that homes in a little more. So far we have:

Fuel pump doesn't stop.
Drivers door lock doesn't respond to blipper (rest of car does) but works with key.
Losing charge from battery from some sort of parasitic drain (on top of fuel pump issue.) "Brain" not going to sleep? Alarm system fault?

Hopefully I'll know more when I can work out which circuits are drawing current after I shut her up. Need recharged battery and a free day though!

Thanks for all the suggestions!

J
Click to expand...

Sounds like you may also have the RF receiver problem burning lock motors and keeping the BECM awake:eek:
 
RF issue interesting. Reading on here it is around 433MHz, exactly the same as my weather station transmitters that are 12 yards away. Disconnected the RF antenna (breaking 3 fasteners in the process) but still no joy.

The car is drawing (parasitic) 3.5A with fuse 39 removed. So, I removed relay 12 as well and now it is losing over 5A! The fuse box looks all right but maybe you are right and it is cooked.

I believe the BeCM draws about 1.2A so we're way about that. A big messy problem looms.

J
 
Grrrrrr said:
RF issue interesting. Reading on here it is around 433MHz, exactly the same as my weather station transmitters that are 12 yards away. Disconnected the RF antenna (breaking 3 fasteners in the process) but still no joy.

The car is drawing (parasitic) 3.5A with fuse 39 removed. So, I removed relay 12 as well and now it is losing over 5A! The fuse box looks all right but maybe you are right and it is cooked.

I believe the BeCM draws about 1.2A so we're way about that. A big messy problem looms.

J
Click to expand...

When the BECM goes to sleep, the current draw should drop to around 30ma.
Even with the aerial disconnected, your weather station may be stopping the BECM going to sleep if you have the early RF receiver.
 
It is a '95 model so fairly early but BeCM should only draw 1.2A or so.

Had another play. You can hear the relay click as you push it in. Swapped it for a few other relays in there and same story so I think the relay is safe. As you look at the relay from the front there is a horizontal pin hole and then 3 vertical. The vertical one on the lest (5?) is permanently at 10V with the car shut and the key in my pocket. Is that correct?

Also, there was a black box bolted behind the BeCM (or the box behind the battery which I assume is the BeCM) and it has 2 wires that go into the BeCM box. Opened the top as they're definitely not original. 1 wire seems to be linked into a glow plug feed wire in the BeCM, I think. Any idea what it could be?

My only thought is that maybe the ignition switch might be sticking a bit, or something like that?
 
The BeCM sits under the drivers seat, the box behind the battery is the Engine ECU.

The little black box is no doubt one of the hot start fix devices (this thing fools the ECU into thinking the engine is cold and as such put the glow plugs on to help the hot start issue).

I attach the wiring diagram for the fuel pump relay....looking at it there is a permenant Live (30) one side of the switch to Pin number 3, when the ignition is switched on power is fed through line (15) to pull in the relay contact by sending power to pin 1 and earthed through pin 2, this send the permemnat live power from (30) on pin3 through to Pin 5 then onwards to the inertia cut-off switch and then onto the pump.

If you are getting 10V on pin 5 with the relay out, there is a fault in the wiring or more than likely a dodgy fusebox (which I think many have mentioned previously).

I am not an auto-electrician but I can't see how else you can have voltage at pin 5 with the relay out unless there is a short in the fusebox somewhere.
 

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Saint.V8 said:
The BeCM sits under the drivers seat, the box behind the battery is the Engine ECU.

The little black box is no doubt one of the hot start fix devices (this thing fools the ECU into thinking the engine is cold and as such put the glow plugs on to help the hot start issue).

I attach the wiring diagram for the fuel pump relay....looking at it there is a permenant Live (30) one side of the switch to Pin number 3, when the ignition is switched on power is fed through line (15) to pull in the relay contact by sending power to pin 1 and earthed through pin 2, this send the permemnat live power from (30) on pin3 through to Pin 5 then onwards to the inertia cut-off switch and then onto the pump.

If you are getting 10V on pin 5 with the relay out, there is a fault in the wiring or more than likely a dodgy fusebox (which I think many have mentioned previously).

I am not an auto-electrician but I can't see how else you can have voltage at pin 5 with the relay out unless there is a short in the fusebox somewhere.
Click to expand...

As above, ant beat me to it this time:D
 
Are you sure you have the correct pin. There should be power to pin 3 at all times. Pin 5 is the one that is contrary in orientation to the other three. It is the one used to supply positive power to from the battery when doing the fuel flow test. If indeed you have the correct pin and there is voltage to it, then you as others have said, look at the fuse box.
 
No, not certain on the pin. The one that is permanently live is the one on the left of the contrary pin (nice turn of phrase that one.) If I try and draw here ...

|
| |
_

What I hope has turned out bold and red is permanently live without the key even in the car.

J
 
How interchangeable are these fuse boxes? It is a '95 model yet an awful lot of documentation seems to mention from '96 so I'm guessing some sort of major revision went on in '96?

Are the diesel and petrol fuseboxes the same?

Cheers,

J
 
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