Fuel pump experience to share

[Jeff Miles]

A dry sunny morning in Lancashire is not to be missed. Turned key in the P reg 400 and that re-assuring sound of the pump powering up was not there - aaaargh. Head down feet up in the well trying to identify fuses and relays from the bible, ears pounding and 62 year old blood pressure going off the clock as none of the layouts quite match the 'bible'. Work out it's not a fuse. might be a relay - which one? Deduction and elimination point to two Bosch 12v 30A on a spur off the loom but no positive ID. Swap them over thinks I (you have to understand I am pre-electronic age - Lotuses in the 60s). No go. Phone the very helpful team at the factory service - replace them both says the man, which I do and vroom vroom Mr Toad has a smile back on his face. At leisure fiddle with the two 'dud' relays and a tester to find only one dud and one live,which cached as a spare with the fuses. Seems these two relays drive pump and injectors and appear to be interdependent - one goes down and you lose both functions. Might help someone out there one day. Otherwise car continues to delight.

[M@H]

Hi Jeff.. welcome

A good first topic and a far from uncommon problem. I always have a couple of these things "spare" as for some reason the Chims seem to knacker these relays on a fairly regular basis (normally when you're not using it ). Unlike for the S Series.. now there's reliability for you

Cheers
Matt

[GreenV8S]

There should be two metal cased Bosch relays on flying leads. One is the main power relay for the ECU, the other supplies the fuel pump and lambda sensors. On mine the one for the fuel pump has a blue socket. If either relay fails the car will not run, so swapping them doesn't tell you much!

[M@H]

Here they are on the left:



Any ideas what the blank flying relay connector is for in the picture..?

Cheers,
Matt

[griffter]

M@H said:

Any ideas what the blank flying relay connector is for in the picture..? Cheers, Matt

Golf Buggy charging socket.

(Actually I think it's redundant - for some luxury item on the RR loom).

[Jeff Miles]

Hmmmm

Yet another layout - As I thought, many variants, each car unique, interesting and slightly ideosyncratic - rather like the contributors to these forums, which I have been happily browing this morning as a newcomer. The 'yellow peril' resides in Blackburn and will be weaving and wandering its way to Southampton and The South tomorrow and the weekend, whatever the weather.

[M@H]

Jeff Miles said:

Hmmmm Yet another layout - As I thought, many variants.

Not too many actually.. this is the "early" battery/wiring setup on 93/94 cars. Note the battery is above the relay plate rather than below it. IMO this is a "better" design than the later one in the respect of being able to remove the battery, as its a more simple operation than compared to the later cars.
Cheers,
Matt.

[wolosp]

GreenV8S said:

There should be two metal cased Bosch relays on flying leads. ...... If either relay fails the car will not run, so swapping them doesn't tell you much!

Swapping will help in the diagnosis Peter - if your 'fuel pump' relay has gone, swapping it will make the pump work (you'lll be able to hear it) and the engine will start but will run only briefly....a fellow Wilts member had this experience recently.
On the other hand, if the ECU one has gone, swapping over will mean you won't hear the fuel pump.

[GreenV8S]

Sorry, I meant taking the two relays out and putting them back in the other way round wouldn't help because a faulty relay in either socket will prevent the fuel pump from running. (Or are you saying that the fuel pump will run without the main power relay? I haven't tried but wouldn't expect it to work.) I agree that swapping a faulty relay for a known good one would give useful information.

>> Edited by GreenV8S on Friday 21st January 17:32

[wolosp]

GreenV8S said:

Sorry, I meant taking the two relays out and putting them back in the other way round wouldn't help because a faulty relay in either socket will prevent the fuel pump from running. (Or are you saying that the fuel pump will run without the main power relay? I haven't tried but wouldn't expect it to work.) I agree that swapping a faulty relay for a known good one would give useful information. >> Edited by GreenV8S on Friday 21st January 17:32

My fellow Chim owner had the fuel pump relay go, so we swapped them over...the fuel pump hummed into life and the car started, but would not run continuously....but it was enough to diagnose the relay as being faulty.
So, if the pump runs but the car won't start, or won't run continuously, I'm saying you could swap the relays to see if the pump ran or not - confirming the ECU relay was duff.

[tlewthwa]

Although I have never met or spoken to Jeff Miles (the originator of this thread) I owe him a massive debt of gratitude. Like others (so I now understand) I went to start my Chimaera 400 last week but on turning the key the familiar whoosh behind my head did not arise. I went through the standard route of checking fuses, inertia switch, immobiliser etc including swapping the 2 Bosch relays over to see if the fuel one had gone. Imagine my suprise when I stumbled across this thread. I had not appreciated the interdependence between the fuel and ECU relays (obvious now) but what I can state is that in my situation swapping over the relays did not cause the fuel pump to work. I have since replaced both (I checked them and found one had gone but thought it prudent to replace both and I now have one spare) and 30 mins ago put the new relays in. Whoosh was followed by Vroom. Great post - and yes Jeff your post did help someone out about a week later. I am now left with a huge grin on my face.

Thank you.

TOM

[jem]

nice,

can you publish the source/part numbers for the relays?

Ta - in anticipation of a problem, and having spares.

J

[mongoose]

jem said:

nice, can you publish the source/part numbers for the relays? Ta - in anticipation of a problem, and having spares. J

the part no. is on the relay(0 332 014 112) if you go the sensible way and buy from a bosch agent.the agent will charge you about 7 or 8 pounds,whereas tvr/landrover will charge up to £20!! i always carry a spare now also,after suffering a similar fate and a very ruined day out!

>> Edited by mongoose on Monday 7th February 16:01

[spend]

I just carry 2 twin make/break relays these suffice as spares for all my relays. They may run the battery flat if left in the fuel/main ecu relays but are perfectly good for diagnosis / emergencies. My fuse box and aux relay panel (under the dash) is not wired to use any of the central terminals (changeover or twin/double 87(ii) 87a/b) of the relays, so this type of relay is ideal to carry as a spare. In fact relays 8 & 11 in the MO264 fusebox are the only ones that even have support for these terminals.

HTH, Dave

[Bob the Planner]

tlewthwa said:

...(I checked them and found one had gone but thought it prudent to replace both and I now have one spare) ...

How do you test them to find out if it is faulty ? I have a non-starting fuel pump and only one spare and wish to find out if it is the relay.

Bob

[GreenV8S]

Change the fuel pump relay, if that fixes it the old one was knackered.

[M@H]

And ironically I had to change my fuel pump relay this weekend (I used a Lucas SRB521 (cost £5.26))

Can someone please clear up this "electronic" relay vs "standard" relay thing please for the fuel pump. As far as I am aware, the immobiliser circuit cuts the power to the fuel pump circuit before the relay, accordingly how does a "standard" one flatten the battery when there is no current available?

Cheers,
Matt.

[GreenV8S]

There's nothing special about the relay except that (a) it is a high current relay, (b) it is a dual output relay not changeover, (c) it is in a metal case (presumably to improve heat dissipation. Internally it looks just like any other relay and does *not* have any clever electronics in it.

Edited to add:

The reason that fitting a standard changeover flattens the battery is that it leaves the lambda sensor heaters powered up when the ignition is off.

>> Edited by GreenV8S on Monday 7th February 09:28

[mongoose]

GreenV8S said:

There's nothing special about the relay except that (a) it is a high current relay, (b) it is a dual output relay not changeover, (c) it is in a metal case (presumably to improve heat dissipation. Internally it looks just like any other relay and does *not* have any clever electronics in it. >> Edited by GreenV8S on Monday 7th February 09:28

i hate to correct you on this,but there is a little something special about these two relays,and its why they dont look like simple black plastic 5 pin std relays.theyre different because they have a diode built in which i imagine is to prevent backfed current screwing up the ecu.i certainly wouldnt replace it permanently with a 'normal' 5 pin.but i have temporarily used a std relay,which incidently was only 20amp 4 pin! just to get me moving again.ive always beleived to stick to original spec if in doubt,and in this case i beleive it to be sound advice.there are other makes out there though that are also 30A,5 pin with diode.a company called,i think,'vehicle wiring products'(on the web somewhere)also sell these.

[M@H]

Ok.. the one I have as a direct replacement for the original from Lucas is the SRB521. Its in a plastic case not metal, and to a layman like myself it looks like an ordinary relay. All the pins match the metal one that came out, and it works fine.

Without casting aspurtions, I'm lead onto this path by the passage in "the bible" that says:

Chim/Griff V2 p244 said:

A particular case in point is the fuel pump relay located in the wiring loom with the ECU in the passenger footwell. This can be replaced with a standard relay but the original is electronic and the difference between them is not immediately apparent. That is not until the car is left overnight and the battery is flat. The reason is that the standard relay will energise the fuel pump and this load flattens the battery. The electonic version switches off the pump automatically. These are available from TVR or Range Rover dealers

..hence my first confusion/post regarding the immobiliser circuit.

Have I (and doubtless others) got the wrong relay fitted to the car then

Cheers
Matt