fordsteve77

Ok chaps pictured below is the radio suppressor
Bosch part no. 0 119 910 002 - ford no. 86GB17K499AA

At the INLET wire to this is 12.15 - 12.30 ish Volts reading on multimeter...

On the outlet of suppressor going to the wiring loom which ends up at Speed Sensing Module is 1.60 Volts

Is this normal procedure to take it from 12.30 Volts DOWN to 1.60 Volts...?

And if not what voltage does the Speed Sensing Module need to activate/work

1st photo is Suppressor - 2nd is Speed Sensing Module

stevos

I'm no auto electrician but the speed sensing module has a 12v badge on it. Now I'm sure the way a modern car takes it speed readings from the abs sensors and it reads resistance in ohms as I'm sure that's how you check if an abs sensor is faulty. But anyway this isn't helping you out but maybe your speed sensor will work in the same way and although it has a 12v supply maybe the speed is determined by resistance if that makes any sense as I said I'm no expert and may be wrong on all accounts.

Rob_DOHC

iTrader: (4)

http://www.rhocar.org/index.php?showtopic=380

If it is what they say it is, a capacitor in a box then these can break down and fail after a while which would fit your symptoms.

Rob_DOHC

iTrader: (4)

And PS, if it is just a capacitor in a box it will only pass AC so doing a DC volt check will not highlight it as a fail.

fordsteve77

To stevos, its on an XR3i MFi 1988

When I disconnected it and plugged the 2 ends together the car started and ran and the voltage was 13.50 all the time the car was running, which was only 5 mins...?

What voltage should the outlet of the suppressor be around the 12 volt mark...?

fordsteve77

Here's diagram of wiring to and from suppressor

stevos

I'm really not sure mate as I said I'm no auto electrician but if you bypassed it and it ran fine then I think you may have found your problem.

fordsteve77

It didn't run fine is was lumpy running 'BUT' it ran, but only for about 4-5 mins then cut out...
I have been having starting problems, well it starts over then cuts out after 2 seconds..
But every time I bypass this suppressor it will not run, say out of 10 times ive tried about twice it will run but again only for 4-5 mins then die,

I have severval other posts on here regarding other parts that make up to start/run system on me XR3i, just trying to pin point through the lot

Rob_DOHC

iTrader: (4)

The box is a series capacitor looking at that link. This BLOCKS DC ie, steady voltage so the output of the box will be close to zero. However! It will pass a pulse (AC Voltage) such as a flyback pulse needed to trigger the tach or other tach equipment.

fordsteve77

so me bypassing would let dc voltage through...?

and it should send pulse signal to the speed sensing relay then onto tach...?

Rob_DOHC

iTrader: (4)

Yes. the DC won't bother you but the AC pulse will/should trigger the tach etc.

fordsteve77

so the alternating current sends pulses to the speed sensing module ( bosch call it electronic control module see pic) then on from that to the tach.... so if the radio suppressor or ignition module or speed sensing unit are foocked or all 3 this would cause no tach working and running problems...?

iansoutham

If I am not mistaken, wasn't that little black box meant to be used to alter the voltage for the coil when starting as some coils ran @ 9v when starting and 12v when cranking (or the other way round). Gave more power for starting the car or something similar.

It has been a while and my mind is a little foggy.

Rob_DOHC

iTrader: (4)

You might have more than one problem don't assume the tach has anything to do with the bad running. But yes any of the above being faulty can mean no tach and or bad running. Remember that no spark also mean no tacho and no running (obviously lol). Do you 100% have a spark?

I will have a look in a ford wiring manual I have somewhere to check.

But, from what little I can remember! The ignition coil flyback is routed to the tach via a green wire, I didn't know that it also went to the speed sensing module (but it makes sense) to provide one or both of the ecu's with an RPM pickup.

What is in the chain first? Ie what is closest to the ignition amp/coil, the radio suppressor?

fordsteve77

Some diagrams from bosch on the system

Rob_DOHC

iTrader: (4)

http://vwts.ru/injector/k_and_ke-jetronic.pdf

After a quick read of that, I think they also refer to the speed sensing module as a safety module.

Does your fuel pump run when you first turn the key and when you are cranking the engine. It looks like the speed sensing module is used to disable the fuel pump relay if the engine stalls.

fordsteve77

It primes with igniton on I can hear it,
then go to start fires up for 1 -2 seconds primed fuel runs out it stalls

But other day when I bypassed the radio suppressor it ran for 3-5 mins very lumpy could not accelerate with the pedal or it would go to die then it cut out and could not strat agin only for th 1-2 seconds after priming

Rob_DOHC

iTrader: (4)

Those pictures don't really help

1) check to see if you have spark.
----If you do not then nothing else will work as the high voltage flyback mentioned in your pictures as "pulses from terminal 1 of ignition coil" will not be present.

2) If you have spark then the ignition amp is ok, so move on to the next part in the chain, (radio suppressor?)

3) with the radio suppressor removed and shorted perform a continuity check from the coil term 1 to the back of the tach and then from coil term 1 to speed sensing module.

Tell us what you find.

Rob_DOHC

iTrader: (4)

Can you also give some history on the car? Is this a very recent problem? Or have you just got the car etc.

fordsteve77

I will check, I just assumed I did as I changed :
spark plugs
ht leads
dizzy cap
rotor arm
ignition coil
but will try....
cheers rob

fordsteve77

Purchased at the end of September
was running and driving started all the time
there was no Fuel Pump relay present
there was a ignition live to where the fuel pump should go
I removed that and the dodgy Moss alarm there was no immobilser
I changed everything above and fuel filter and oil change
then this started

Rob_DOHC

iTrader: (4)

No worries mate, the more info the better


Was the tacho working when you bought the car? I'll have to do a bit more reading, the book I have is for the RS Turbo which apparently?!?! Has a different ignition system to the XR3i... I've never owned an xr3i so am working partly on assumption. The good news is that the XR3i ignition system looks much simpler than the RS Turbo!


Still 100% check for good spark to begin with. If the tacho was working when you bought the car it sounds as if the engine speed module may have a big part in this if the original fuel relay was bridged out like that.

s1cosse

It's same ignition system as a mk2 xr2. I've had the same fault quite a few time in my time Bing in the trade and it's all ways been the ingnition module. That cause all sorts of problems. Hence why the pump relay is not kicking in when he is cranking.

fordsteve77

Got an ignition module/amp and radio suppressor both coming today/tomorrow
Brand new at a cost of Ł21 all in so not bad for piece of mind

And too Rob no the tacho was not working either when I purchased, bought it to restore it back to its former glory... weren't expecting to be taking the dash out and chasing wires the engine itself it in mint condition, apart from this electrical problem, just want it running so I can drive it to paint shop

Rob_DOHC

iTrader: (4)

Could well be mate. But a faulty ignition amp means no spark. no spark means no flyback voltage to trigger the tacho or other modules looking for the 'pulse'. Either way the no spark or a very weak spark is easy to check for and would certainly point to the ignition amp as a suspect.

Rob_DOHC

iTrader: (4)

Good luck Steve! I seem to remember something in the past about someone having a faulty tacho causing all sorts of problems where the tach wire was shorted in the tacho its self. This could also mean that there would be no flyback pulse to liven up the speed sensing module and hence fuel pump relay. You can check for this by doing a resistance check between the green wire on the output of the radio suppressor and ground. If its over say 1000 ohms you should be able to eliminate that as a problem... if its under 200 ohms I would be a bit suspicious of anything connected to the tach wire.

fordsteve77

Right I will check that, so NO ignition on...?
Set multimeter to 2000k or 2000 picture below

then between the green wire on the output
and
a good ground?

Rob_DOHC

iTrader: (4)

Correct, just a quick reality check to make sure the tacho wire is not shorted to earth somewhere. Set the multimeter to 2000 NOT 2000K as that is actually 2000 000 (2M).

Ignition off and on the tacho side of the suppressor (ie the side going to the car not the side going to the ignition coil). I am assuming this will be a fairly high value however if it is not it might help you to isolate an issue.

BUT - if you do have spark I suspect the issue may be the suppressor.....

If you do not have spark the issue is likely the ignition amplifier.

Does the car run if you short out the fuel pump relay like it was when you bought it?

Rob_DOHC

iTrader: (4)

PS if the multimeter gives no reading at all set to 2000 ohms (ie just displays 1) then set the meter to 20K

Rob_DOHC

iTrader: (4)

https://www.clubford.ro/documente/ma...01981-1990.pdf

Page 226 is your diagram. Assuming your is after 1986:

Part 138 is the suppressor
Part 133 is the speed sensor relay/module
Part 68 is the Fuel injection relay
Part 102 is the instrument clustor (tacho)

It looks like the speed sensing relay uses the flyback from the negative of the ignition coil to enable the fuel injection relay. The flyback voltage signal goes via the suppressor to the speed sensing relay.

Rob,

fordsteve77

Right green/red wire tested going after radio suppressor to speed sensor relay/then tacho But my tach aint plugged in at mo....?
pic below

fordsteve77

yeah mines the 102 instrument cluster = 15 pins

fordsteve77

Heres my speed sensing module/relay

fordsteve77

Whats the green relay for.....?
in pic its never had relay in it was just wondering

fordsteve77

Yeah here a diagram of suppressor - speed sensor - fuel relay - pump - coil:

Rob_DOHC

iTrader: (4)

That looks believable, at 104K and would suggest that there is not a short to ground anywhere which is a good thing.

If you have spark I would just wait until your suppressor turns up and give that a go. If no spark then exchange the ignition amp and go from there. Good luck! Looks like a good project too btw.

Rob,

slider

did you ever test the continuity of the green wire from the fuel relay to the coil?

although it does look like a component issue as it runs with the suppressor linked out,

on a side note a m8 has a complete mk4 cabby hes breaking if you need any little bits for yours, hes keeping all the running gear etc but theres a set of clocks in it plus some panles and trim, only in iwade so local

slider

ignore that continuity bit just seen youre reply in one of the other posts

fordsteve77

Yeah could do with the door and wing side mouldings/trim/stripes
And weather strips for the doors
and whats his rear ford badge anygood

fordsteve77

has he got the relays slider?
what colour is it