Help needed!

[lotus160sport]

So I've finally got my car transported to the garage due to what appeared to be an issue with my fuel pump not working anymore after checking all the relays etc which appeared to be ok. Now bare with me on this as I'm not technical so this is what has been said, on inspection the mechanic has found some burnt wire leading to the pump which he has cut out and has been trying to diagnose why this has happened, on reconnecting the wires the fuel pump primes but doesn't cut out like it normally would after about 3 seconds when you turn the key, now here's the weird part, when he dropped the car down on the ramp thinking the keys where in the ignition, they weren't and were on the seat? In turn it appears that for some reason maybe when I had the initial problem and tried to charge my battery a few weeks ago, it wouldn't take a charge and it sounded like there was something clicking the following day by the fuel pump (updated bosch) so don't know if this caused the burnt wiring somehow? So he now thinks maybe it could have something to do with the ecu? Can you guys tell me if the ecu controls the fuel pump or have any ideas of what could be causing this issue, sorry it's all a bit vague and I appreciate it's hard to tell of my poor description of the issue but he and I figured that someone may have an idea on here of where we should be looking before buying a new ecu etc.

[J50NWA]

when you upgraded the fuel pump did you do the fuel pump wiring mod, or do you know if done already? Its possible the new pump was drawing too much current on the old wiring. The standard fuel pump wiring is not really up to the job. If the wiring mod is completed the perhaps the pump is faulty (again drawing too much current).

if the keys were on the seat and the car ran it sounds like the ignition has been bypassed.

[lotus160sport]

Good point, as far as I was aware when I had the exhaust done the fuel pump had been done and I was told that the wiring had also been upgraded, how would I know what the modified loom would look like over the standard? Cheers

[TuxMan]

Yes ECU controls fuel pump but I would say your bulk head relay is knackered and stuck on !!

You need to fit a power relay at the pump and use the old wires to switch it !! The std wires are rubbish and get hot when under heavy load !

[lotus160sport]

Excellent ok I'll forward this info on, hopefully he can get it sorted 🙏🏻 Thanks guys

[lotus160sport]

Ok so here is the message I got from forwarding on the information to the garage.

"There’s no problem with any relays.
The issue is the live feed from the ecu which goes to the pump relay is permanently live even with ignition off.
If I had an ignition problem the dash lights would be on."

Sorry about this does this shed any light as to where to look next?

Cheers

[D_G]

I would disconnect the ECU next, see if the live to the switch side of the relay stops. Then do a quick short to ground / live check on the wire, if ok then plug the ECU back in and see if the live returns. All with the key off and relay removed of course.

[TuxMan]

Sorry still think it's a relay problem !!! Ecu sends a live feed to the relay which switches the relay and put power to the pump , need to check too see if there is a permanent power into the relay , if so ecu is knackered !

[Craighb]

Don't know if this will help you check wiring. This is the fuel pump wiring upgrade.

[lotus160sport]

Thanks for the replys, before you sent these messages I spoke to him last night and he told me he's checked the relays and what's happening now is that if he unplugs the ecu and the relays behind the drive and even Ines in the passenger footwell the ignition is still live with the keys removed? Could this be an immobiliser issue or ecu? Also if it's the ecu where do I get a new one from?

[lotus160sport]

Sorry this is what he said.

"Ecu and all relays disconnected with ignition off and fuel pump still runs"

[Blu3R]

OK with the greatest of respect...

1) You had an issue that caused some wiring to become damaged. Up until this point I'm going to assume that everything was working as it should, i.e. the fuel pump primed and then stopped if the ignition was switched on but car wasn't started - can you confirm that?

2) You then took it to a garage, someone repaired/replaced some key wiring to the fuel pump and you now have an almost impossible situation regarding said pump.

Can you see where I'm going with this...?

[lotus160sport]

I can indeed, I think an auto electrician maybe the next port of call which the garage has also mentioned but was trying to see the various options before calling him. I'll let you know the outcome fingers crossed.

[Jim O.]

Most of the fuel pump wiring upgrades that I’ve seen are DIY jobs, very inconsistent from car to car. Sometimes, they are done by adding a relay to the row of relays behind the bulkhead on the right side of the car, sometimes the relay is placed in the compartment on the left side of the car where the fuel pump is located, and sometimes the relay is put in some random location that looked like a good idea to the person doing the mod. What I would do is follow the wiring back from the fuel pump itself - my guess is that there’s another relay near the fuel pump that’s gone bad.

[lotus160sport]

Hi Jim, it turned out that the company that did my mod with the new exhaust had wired the relay up back to front or something meaning that even with the ignition off the pump was live, which eventually after a good few years burnt through the wire, it could be why my battery wasn't particularly good at holding a full charge for long. Anyway all sorted now and running like a dream. Now time for a full respray, and some other mods but nothing too exciting as I'm looking to keep the car relitavly standard for now.