Unusual electrical problem- diesel P38

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kapilamuni

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Hi
About a month ago, I replaced the fuse box with a new one from Rimmers. This was not due to any issue but considering it's the original factory fitted one and just changed. It was okay for about two weeks and then ABS pump gave up with 3 dash lights ON permanently. Removed relay 17 and direct linked , the pump started. Assuming it's the normal fault with the pressure switch ordered a used one from bay E..
Yesterday when I started it ( done on every other day to avoid battery going flat as I do not use it with low brakes) the ABS pump started and all seems okay. After running it for a while stopped the engine. There was a whirring noise which appears from the in-tank pump. It's running even without IGN ON. Replaced the relay with a known good one but still it's running. Thinking that a bad diode pack in the alternator could pass current to the pump relay checked the alternator but the electrician says no issues with the alternator but pointed that alternator small wire too shows a supply without IGN ON. Also observed that dash light for battery would not come On when IGN ON.

Is this a problem with BECM?
 
kapilamuni said:
Hi
About a month ago, I replaced the fuse box with a new one from Rimmers. This was not due to any issue but considering it's the original factory fitted one and just changed. It was okay for about two weeks and then ABS pump gave up with 3 dash lights ON permanently. Removed relay 17 and direct linked , the pump started. Assuming it's the normal fault with the pressure switch ordered a used one from bay E..
Yesterday when I started it ( done on every other day to avoid battery going flat as I do not use it with low brakes) the ABS pump started and all seems okay. After running it for a while stopped the engine. There was a whirring noise which appears from the in-tank pump. It's running even without IGN ON. Replaced the relay with a known good one but still it's running. Thinking that a bad diode pack in the alternator could pass current to the pump relay checked the alternator but the electrician says no issues with the alternator but pointed that alternator small wire too shows a supply without IGN ON. Also observed that dash light for battery would not come On when IGN ON.

Is this a problem with BECM?
Click to expand...

Check if either relay 15 or 19 are stuck shut.
 
Checked both are fine. Replaced with known good ones, yet the same results.:confused:
As per RAVE, RL 12 can get power from glow plug-6 and Alt charging light wire. Checked glow plug inputs when IGN off no power but the Alt charge light wire has. Even when that wire disconnected from Alternator, power is still there. Also, the charge light does not come ON whether IGN ON or OFF. yet the battery gets 14.2 V when idling.:confused::confused:
 
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have you tried pulling the relays one by one kapil until you possibly come across a duff one, with the ignition off of course..
it does sound like something in the fuse box is still making a circuit with the ignition off??
how much hassle would it be if you tried the old fuse box..
why dont we have a little face scratching his chin??:p
 
Relays 15,19, 12 & glow plug relay are enough. Other relays have no link with the in tank pump.
Bit of hassle to put the old fuse box back. Was there any situation where new fuse boxes gave trouble?
Wonder it's the BECM connection to Alternator.
 
kapilamuni said:
Relays 15,19, 12 & glow plug relay are enough. Other relays have no link with the in tank pump.
Bit of hassle to put the old fuse box back. Was there any situation where new fuse boxes gave trouble?
Wonder it's the BECM connection to Alternator.
Click to expand...

You never listen then go off on a tangent. Refit the old fuse box and see if it changes anything. If it doesn't then start looking elsewhere. There are diodes in the fuse box circuit that feed relay 12 at certain times, two in the early fuse box and three in the later fuse box, to put lift pump on whilst cranking. One connects to D+ on alternator sounds like diode D2 has blown. So power is going back to D+ when ignition is turned that would put charging lamp out.
 
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kapilamuni said:
Thinking that a bad diode pack in the alternator could pass current to the pump relay checked the alternator but the electrician says no issues with the alternator but pointed that alternator small wire too shows a supply without IGN ON.
Click to expand...

That's what I had. In-tank pump was running all the time. Replaced the alternator and that fixed it. I had a post on it soon after I joined.

https://www.landyzone.co.uk/land-ro...t-fuel-pump-doesnt.192773/page-2#post-2047949
 
Grrrrr- Alternator was checked & found okay by an electrician. Part of the issue is Alternator D+ wire has power without IGN ON (checked after disconnecting from the Alternator) . That wire coming from BECM and spliced n connected to Rly 12 via diode D2.
 
Fitted the old fuse box, no change.
BECM ?
C114-15 is the line that supplies to Alternator D+ and also the RL12 - 1
 
Good news guys.
Removed the C114 connector at BECM. Checked continuity from C114-15 to D+ and RL12 -1.
At the C114-15 too there is +ve voltage. Hence assumed that between C114-15 and D+ , some additional thing happening..
Started from D+ end and removed rubber cover & voila, some one had joined the D+ wire and that joint touching the B+ .
Removed and put everything back in order. No free running intank pump.
Now incidentally, ABS pump too started running after a while but the charge light remains on. Give a direct +ve from battery momentarily to D+
and got the battery charge light off. Checked charging voltage with DM and it's 14.4V
Now the problem is why is not D+ getting power when IGN ON?
Also noted that RL6 & 7 are too hot to touch without blower fans running, seems there is a small current flowing through and making both relays hot..
Temporarily removed both RL 6 & 7.,
 
kapilamuni said:
Good news guys.
Removed the C114 connector at BECM. Checked continuity from C114-15 to D+ and RL12 -1.
At the C114-15 too there is +ve voltage. Hence assumed that between C114-15 and D+ , some additional thing happening..
Started from D+ end and removed rubber cover & voila, some one had joined the D+ wire and that joint touching the B+ .
Removed and put everything back in order. No free running intank pump.
Now incidentally, ABS pump too started running after a while but the charge light remains on. Give a direct +ve from battery momentarily to D+
and got the battery charge light off. Checked charging voltage with DM and it's 14.4V
Now the problem is why is not D+ getting power when IGN ON?
Also noted that RL6 & 7 are too hot to touch without blower fans running, seems there is a small current flowing through and making both relays hot..
Temporarily removed both RL 6 & 7.,
Click to expand...

Well if it was running ok then went tits up it can only be you or whomsoever fitted the alternator that did that. You may have blown something. When ignition is switched on 12 volts is sent to D+ and charge lamp lights. When the alternator starts to charge 12 volts is applied to D+ by the alternator a polarity change takes place on D+ and the charging lamp goes out.
 
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Charge lamp cct & D+ cct are two different ccts, as per RAVE.
BECM senses voltage reversal from D+ cct and then shuts the charge lamp , otherwise the charge lamp will continue to glow.
 
RL6 and 7 are the main blower motor feeds.

If they are getting hot, then worth checking the wires from the fuse box, through the 2 way connector in the RHF footwell, behind the kick panel and on to the blowers.

I cut out my RHF footwell connectors awhile ago as 'preventative' measures as the pins were starting to look pretty green in all of the connectors (though didn't have any faults, just didn't want to wait until I did!). My connector with the main power feeds to the blower motors was looking pretty green, and there is signs of corrosion internally in the wiring itself, which will cause higher resistance in the wire, and more current to be drawn.

I plan (when it's a bit warmer) to replace the sections of internally corroded wire right the way from the fuse box to the blower motor connectors with new wire, and that should hopefully help with RL6/7 too.

Might be worth checking those wires, as it could be causing at least part of your issues with the relays getting hot - especially if you have a new fuse box in.
 
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