I like elastic trickery.........

[york33]

..........NOT

So, I starts off with one relay that's buzzing. Fine, it's broke, I'll replace it, so I does. Hmmm, no longer buzzes, but still no fuel pump action. Can't figure it out and am very puzzled.

Anyone know their relays?

It's a 5 blade changeover type. As far as I can work out, you shove 12V up terminal 30, and either get it out of 87 or 87a, depending on whether terminal 85 gets 12V up its backside. Sound about right so far? So why doesn't it do this. 12V comes out of 87a continually, regardless of what I do to 85.

Am I missing something? I thought my elastic trickery wasn't too bad! Go on give me a clue!

cheers
Dave

PS What made me move on to disturbing the next relay I don't know, but that's another story
PSS Handbrake works, not driven it to test though due to above

[jeff m]

Dave,
Are you aware that there is a safety module that only allows the fuel pump to run when motor is turning.
IE no pulses to safety mod no 12v to fuel pump.
Fuel pump should op during starting, easy to check with two people.
Jeff

[streaky]

+V on 30, 0V on 85/86 gives 0V on 87, +V on 87a
+V on 30, +V on 85/86 gives +V on 87, 0V on 87a

Anything else and either the relay is broken, or the relay is broken.

Your description of +V on 30, 0V on 85 giving +V on 87a indicates that the relay is stuck in the normal state. It suggests one of three things: either (1) the coil is duff, or (2) the contacts have welded themselves together - typically through excess current, or (33) there is a short inside the relay.

Does the relay 'click' when you apply voltage to 85/86? If so, then the coil is OK and the relay is changing over - at least to the extent that it makes a noise. In this case it is likely that there is an internal short, or that the c/o is not affecting the contacts. If there is no click but there is current flowing 85/86, then the contacts are likely welded together. If there is no clikc and no current flow, then the coil is duff.

Of course, I could be wrong!

Streaky

[jchase]

I have a black wiring loom 280i, the one with the relays under the bonnet. I've just been playing with Relay 3 and Relay 4, which together act to energise the fuel pump. Relay 4 only activates when a switch inside of the fuel delivery system is closed (presumably a safety feature), then relay 3 sends power to the fuel pump. (see wedge bible for wiring loom)

I had the buzzing noise, and it was caused by my replacing the change-over type relay(number 4) for one where 87 and 87a were internally joined in the relay. These relays are much cheaper than the change-over ones, and number 3 can be substituted for one, but not relay 4. so if you get them mixed up, you get a buzzzz, or if you are unlucky it might energise the starter motor...makes you jump a bit.

Hope this helps.

[streaky]

jchase said:

[snip]I had the buzzing noise, and it was caused by my replacing the change-over type relay(number 4) for one where 87 and 87a were internally joined in the relay. These relays are much cheaper than the change-over ones, [snip]

That sounds like a 'twin make or break (MoB)' rather than a 'Change-over (C/O)'. The terminals on this should be marked 30 / 85 / 86 / 87 / 87 - not '87a'.

If the terminal is marked '87a' it should be a C/O relay. [Edited to say that I have now seen one example where the terminals were labelled 87 & 87a, but it was NOT a C/O relay. Kinda bers up the standard that!]

If two terminals are marked '87' it should be a 'twin MoB' - where the two circuits are normally joined (and are joined in (or on) the relay (I previously referred to them being 'shorted' - this does not necessarily indicate a fault with the relay).

If the terminal is marked '87b' it should be a 'double MoB' - where the two circuits are normally isolated but are jointly energised by the relay.

Dave (york33) - I've assumed that you've been testing the relay out of any socket and out of the wiring loom. If you have been testing it in a socket but out of the loom then there is further possibility. There are two types of blade configurations for 4 blade relays that swap the 30 and 86 pins. I haven't seen a 5 blade relay with those pins swapped, but it's worth checking your 5 blade relay. If swapped, it could lead to some confusion. Again, listening to the relay whilst applying current can be informative.

If you have been testing it in the loom, remove it for testing as voltages already on the wires connected to the relay can distort your findings.

Hope this helps. Please let us know the outcome - Streaky

>> Edited by streaky on Sunday 14th September 07:46

[york33]

thanks for the detailed replies people, shall print out and go armed with that, wiring diagram, multimeter, coffee and a bacon sandwich

Hmmmm, definitely a changeover relay that I have bought to replace the old one which I'm 99% sure is the right type The two which have issues are the ones going by name of "control relay" and "power supply relay". They look like they've been fettled in the past as they were all done with dodgy looking crimped spade connectors, which I'm now soldering.

I'm puzzled about the safety switch, my fuel pump always has run as soon as you turn the ignition on. Although perhaps it was bypassed in the past?! Hmmmm, I didn't even try starting it as I couldn't hear the familiar fuel pump bzzzzzzzzz! Any ideas where or what form it takes

There does appear to be 2 different pin layouts going on with the rest of the relays.

I'll have a 'play' with a relay away from the car and see what happens, incidentally, I could get the fuel pump to run if I tapped the relay, but that may be cheating

thanks so far, I'll hopefully let you know a +ve outcome......
Dave

PS I don't want to start on my new headlights, side/indicator lights, new cooling fan and thermo-switch, not to mention all those new switches......

>> Edited by york33 on Sunday 14th September 08:47

[streaky]

jeff m said:

Dave, Are you aware that there is a safety module that only allows the fuel pump to run when motor is turning. IE no pulses to safety mod no 12v to fuel pump. Fuel pump should op during starting, easy to check with two people. Jeff

My fuel pump runs for a second or two as soon as the ignition is turned on (no starter) - I guess to ensure the rail is primed. Mine is the 4.0lt hot-wire engine - if that makes a difference.

[streaky]

york33 said:

[snip]I could get the fuel pump to run if I tapped the relay[snip]

It could just be a sticky relay. Check if it clicks when power applied across 85/86. If not hold the power on and tap the relay with a piece of wood. If the relay clicks (that's why a piece of wood so there are two distinct noises), or you see a change of state (87a>87) with power applied to 30, then teh relay is sticking and needs replacement.

Good luck. Just had a bacon butty myself (sort of canibalistic that ) - S

[york33]

Hoorah

Well, armed with my coffee and wonderful advice I attacked it. She burst into life and into a lovely fast tickover, not bad after x weeks sitting looking upset with me!

I'm sure the wiring of those 2 relays is different now!

The fuel pump now does as before and always runs when the ignition is switched on. So either I don't have the safety switch or the switch is unwell? Still not found it though.

Either way, she works now, thankyou lovely people On with the rest of the wiring now, I may be back when something else stop working.......

I'm replacing all the rest of the relays too. Bought a pack of 10 as the originals are suffering now, after 20 years. The rest are just plug in affairs, don't worry, I'll check the pin layouts as I go

>> Edited by york33 on Sunday 14th September 11:36

[wedg1e]

The safety switch is in the airflow meter. There should be a 2-pin connector coming out of the meter, next to the wing.

Ian

[streaky]

wedg1e said:

The safety switch is in the airflow meter. There should be a 2-pin connector coming out of the meter, next to the wing. Ian

The 'bible' covers this for the Ford V6, but doesn't seem to mention for the V8. Is it the same?

Certainly something runs when I turn on the ignition - for about 1-2 seconds then stops.

[york33]

Hmmmmmm, seemingly none of these safety devices on my air flow meter, oh well, c'est la vie.

In any case, I said I'd be back

Good news is my new headlights, sidelights and indicators work, woohoo

Bad news is my engine cutting out and not restarting problem is still there. Now she did this on the way back from my failed MOT too

OK, it's a little bizarre, after about 15-20mins she cuts out. When you try and restart she cranks over very slowly and after a few seconds refuses to even do this. Now, you'd think alternator, battery or maybe both. So, I checks my charging voltage, 13.8v at fast tickover, hmmm now 14.4V is normally quoted but I reckon on it being close enough to be charging OK? Battery, well it could be this, but how come it'll hold charge for weeks and still crank the engine over?

What say you?

cheers
Dave

PS I keep meaning to buy 'the bible' but never do

[jmorgan]

Normally I would check a battery by charging, measuring the voltage then leaving for a few hours and re checking the voltage. Also check the voltage whilst cranking under these conditions.

[danny hoffman]

I have just had to change the battery on my other car. It would always start from cold 1st thing in the morning, but would die later on during the day. On one occasion I has only turned it off for a couple of minutes after a long run and it would hardly crank the motor.

It had all the syptoms of a faulty starter/bad connection somewhere - but turned out to be the battery.

Danny

[wedg1e]

streaky said:

wedg1e said: The safety switch is in the airflow meter. There should be a 2-pin connector coming out of the meter, next to the wing. Ian The 'bible' covers this for the Ford V6, but doesn't seem to mention for the V8. Is it the same? Yes, I think Dave (york33) has a 2.8. The V8 airflow meter also has a kill switch in it. I think I have a description of how the electrics work on the Lucas EFI system somewhere if you get really bored... Ian Certainly something runs when I turn on the ignition - for about 1-2 seconds then stops.

[jeff m]

streaky said:

jeff m said: Dave, Are you aware that there is a safety module that only allows the fuel pump to run when motor is turning. IE no pulses to safety mod no 12v to fuel pump. Fuel pump should op during starting, easy to check with two people. Jeff My fuel pump runs for a second or two as soon as the ignition is turned on (no starter) - I guess to ensure the rail is primed. Mine is the 4.0lt hot-wire engine - if that makes a difference.

Yes it makes a difference.
This is a Tasmin, it has Bosch CIS same as 73.5 + 911 it starts from residual fuel pressure, pump starts on engine rotation. That's the reason the safety mod has to be bypassed to check fuel pressures with engine not running.
Jeff

[streaky]

wedg1e said:

The V8 airflow meter also has a kill switch in it. I think I have a description of how the electrics work on the Lucas EFI system somewhere if you get really bored...

Sad that I am, yes please - Streaky

[york33]

there will be a delay before I pursue this prob as I feel awful today and will soon go to bed. Thanks for ideas so far though...........

[york33]

oh well, will find out in the not too distant future if it is the battery, just wobbled my way back from shop with a new one strapped to the back of the m'bike Well, it's an improvement in capacity at least, 60Ah instead of the 35 of the current (ha ha) one.

[wedg1e]

Dave:
Slightly off-topic: I should be in your vicinity sometime in the next few days if you're up for a jar? I have a service job near Elvington; I could also wield meters and stuff at your electrics if you still have problems...

Ian