Fuel pump not working can i bypass immobiliser

[Andy_J_G]

Fuse ok, swapped over relays to test, and fuel pump still not coming on with ignition. Hardwired the pump and it spun, is there a way of bypassing or turning off the immobiliser to see if that sorts the problem? Will it be safe to hardwire the pump if i need to get it going to get to a garage?
Cheers (4.0 Pre Cat with Gemini alarm)

[5.0ltr]

My understanding is that both fuel pump relays need to be working. 1 is for the ecu the other the pump so if one has gone and you swap over it still will not work, certainly that happened when one of my relays went. Replaced both which sorted it out.

[Andy_J_G]

Fuel pump relay position is clearly marked in my manual, but no mention of ECU relay, will it be down by the ECU and is it a normal relay, or one of the electronic version i have read about?

[Aussie John]

The pump and the ecu relays are on the flying part of the loom but also a fuse on this part of the loom had blown causing the pump to stop, I dont know if the fuse controlled the ecu relay or the pump relay but this solved it; my griff is a 94 pre-serp; good luck!

[5.0ltr]

If I understand the question...On the spaghetti atop the battery are two square grey relays, sometimes with a red stripe on them. When I suffered similar to you I went to David Geralds for replacement relays. They told me that you need two good ones to get the car running, one is the fuel pump, one does something to the ecu, so if one has gone it dont work. I held each of them and turned the key, you need long arms! The working one will click which is easier to feel in your hand, one of mine did not click so I changed both and it primed and fired. I now have a spare but I dunno which of the 2 I have is the good one! HTH.

[Andy_J_G]

Thanks for that, i will check both relays, and the fuse, tomorrow.
Cheers

[Pupp]

IIRC the 'other' relay of the pair is actually the source for the +12v feed to the injectors (the -ve being switched by the ECU)

In response to the question that was actually asked, the answer is yes but not going to tell you how exactly on a public forum, although doing it won't help you if the actual relays (or one of them) are on the fritz

[Andy_J_G]

Ok, just tried putting 12v across the relays, 30 being the + and 85 being the - and no clicking on either, assuming the test is correct they are both kaputt, what are the chances of that? Can these be sourced at local autofactors?

[spend]

Quinny said:

Mmmm Pretty sure thats how I tested the last ones.... Maybe someone could clarify that I've got it right??


As for the relays, they need to be the Bosch metal cased ones... Cheap plastic ones won't do...

I'm sure someone like Steve Heath will be able to supply

Any suitable twin/double make/break relays will do to get you home or for testing.. You can also 'hotwire' the relays by linking the 3 pins down the middle.

Test the fuses and don't get fooled by the way the ecu controls the fuel relay - it only flicks it on momentarily (priming) until the engine spins up.

The Bosch ones have a diode so which way you connect to test is important, just reverse the test connection to make sure.

VWP have nice illustrations of relays to help you identify the terminal locations if in doubt

[Andy_J_G]

Right, just put the 12 volts across pins 85 and 86 and i get switching! Also get continuity between pins 30 and 87, tried the second relay and nothing, no continuity either across pins 30 and both 87s, which i believe switch when power is supplied to 86. So it seems one is kaputt.

[Andy_J_G]

Quinny said:

You mean I've just been out into the cold garage to figure out which way to test and you've figured it out for yourself

Well thanks alot

Sorry..... but thanks all the same

[Andy_J_G]

Power has been restored! New relay ordered from local Land Rover Dealer for pick up tomorrow but have put in a pattern part from Europarts for now and we are up and running. Thanks for all the help, glad that the problem was a simple relay and nothing to do with the alarm system.
Cheers

FYI Europart number is 450110050 "5 pin motronic relay" and is £9.70 plus the dreaded. One third the cost of the one from the Landie dealer (£28.12 for genuine bosch version)!

Edited by Andy_J_G on Tuesday 29th December 15:14

Edited by Andy_J_G on Wednesday 30th December 15:57

[5.0ltr]

[brd1984]

Andy_J_G said:

Fuse ok, swapped over relays to test, and fuel pump still not coming on with ignition. Hardwired the pump and it spun, is there a way of bypassing or turning off the immobiliser to see if that sorts the problem? Will it be safe to hardwire the pump if i need to get it going to get to a garage?
Cheers (4.0 Pre Cat with Gemini alarm)

How did you hard wire the pump mate, I’ve having same issues and I’m about to set it on fire 🔥 lol

[Loubaruch]

To check the pump just run a +ve lead from the battery to the +v terminal on the fuel pump.

It could be that your immobiliser has failed but there are many other possible causes that prevent the pump running.

This may help:

http://www.bertram-hill.com/fuel-pump-schematic.ht...

A prime suspect is the plug/socket behind the passenger B post ( under the carpet) these are quite often corroded.


The two relays dangling in the passenger footwell are also troublesome

If your pump is OK you do need to test the circuit systematically.to make progress.

[Penelope Stopit]

Fit an in-line fuse into any cable you use for jumping any circuits, better be safe than sorry

[brd1984]

Loubaruch said:

To check the pump just run a +ve lead from the battery to the +v terminal on the fuel pump.

It could be that your immobiliser has failed but there are many other possible causes that prevent the pump running.

This may help:

http://www.bertram-hill.com/fuel-pump-schematic.ht...

A prime suspect is the plug/socket behind the passenger B post ( under the carpet) these are quite often corroded.


The two relays dangling in the passenger footwell are also troublesome

If your pump is OK you do need to test the circuit systematically.to make progress.

I ran a wire to the positive on the pump and to the pos on battery and still nothing.

I’m getting 12v up to the pump though.

[Loubaruch]

The fuel pump only has two connections +12v and earth, if you have a true +12v at the pump and the earth is OK then the pump is faulty.

It depends how you measured the +12v, readings on high impedance meters can be deceiving that is why I suggested running a wire from your battery. No argument then.

[brd1984]

You don’t think it could be immobiliser?

[Loubaruch]

If you ran a wire from Battery +ve direct to the pump and the pump earth is OK how can it be the immobiliser?

If the pump does not run when wired directly then the pump is faulty. Have you checked the pump earth?