No Fuel, bad relay? but pump can be made to run?

shocker said:

any advance on this ? can you make a self cranking control by fitting croc clips to each end of a cable with a momentary push to make switch in the middle , linking the battery to the starter spade , thus being able to crank single handed ?

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hmm, possibly, but i am going to try and get the GF to help me at some point, but she doesn't like messing with cars.

had all the connectors apart and cleaned (and changed a afew of the spades for new ones for the hell of it) around the coil yesterday, and cleaned the earth strap that fits at the base of the coil too.
no change
next step then.
i need to find this resistor thats been mentioned that is inline from the coil to the ecu. any idea on its location without tearing the whole dash apart?

It isn't under the dash...

It is under the bonnet, near the Mas Air Flow Sensor....small little black rectangle with (iirc) White wires to and from it - or White with Black Tracer.

The resistor is the little black rectangle and the wires should have spade connections on it....I know this sounds vague.

I attach the wiring diagram which shows the resistor....

ok, i have had a look look at things today and tried lots of stuff. just trying to remember everything i have done.
firstly there is no resistor on the wire between the ignition amp and coil! there is a place that looks like there used to be one, but its been soldered together, so is now hard wired by a previous owner!
but, i have found another resistor inline near the ECU. its on the black/ white wire again.
Lucas RD 953066. this had dirty/. corroded connectors, so cleaned it all up. shows resistance of about 7ohms.

i have been trying to check for continuity between pin "39" and the coil, but pin 39 seems to be dead. cold this be the issue? :? strangely i get continuity on about 11 other pins between the coil, but not pin 39

after this i started clutching at straws :?
i also tried cleaning some sensor connections in the engine bay, including the coolant temp sensor. i know on some cars, the ECU needs a signal from certain sensors, before it will fire up. these sensors appear on the wiring diagram too, but i dont know for sure if the ecu needs the signal on this car?

does the ecu need a signal from the "road speed transducer", to fire the injectors? the speedo generally works, but recently it stops working if i travel over 60mph for over 10 minutes. wondering if thats given up the ghost, and could effect this?

with multimeter across the + & - on the coil it reads about 18V? is that right? no idea what it should read?

here follows loads of pictures i have taken at each stage of investigation. quite a few damaged wires along the way, all now soldered.







possibly for the alarm? looks aftermarket.


ecu under drivers seat


fuel pump can be made to run by jumping


injector wiring diagram


relays all look clean and good. opened up and cleaned out the contacts too to make sure.



hidden ignition amplifier


damaged wiring again- repaired





contacts cleaned up on coil


some fo the pins look a bit wonky so straightened them up





pin 39 seems dead!!


wire between coil and ignition amp, where resistor should be, but PO has soldered.


uncovered other inline resistor near ecu


dirty!


cleaned up





continuity between here and the coil


continuity to lots of other pins except pin 39!


cleaned coolant temp sensor



thats it so far! lots of photos so i can try and remember what the hell i have, otherwise easy to forget.

any thoughts?

Saint.V8 said:

The engine ECU takes a signal from the coil through a resistor to let it know the engine is running, if this resistor or wire to/from is bust, the engine ECU will not fire the injectors as it won't know the ignition coil is firing!

Maybe off the mark, but I had similar issues and this was one thing I checked for.....

Click to expand...

so will a ****ed ignition amp-what voltage is across coil?

fanatic said:

so will a ****ed ignition amp-what voltage is across coil?

Click to expand...

He says 18v.....

The emulator looks to be from an LPG system, but could be wrong.....

Some LPG systems use an injector emulator to fool the ECU into thinking the petrol injectors are firing when they aren't to prevent check engine light coming on...as there is no point in firing the petrol injectors when on LPG.

If this is indeed what it is, it could be preventing the injectors firing....just another thought!

Also the engine gets a running signal from the crank sensor, if fitted, and not a road speed sensor... Or the signal from the coil to ECU via this little resistor....

If the ignition amp has failed, it won't fire the coil or in some cases won't allow the coil to charge fully creating a weak and useless spark.

saint.v8 said:

the emulator looks to be from an lpg system, but could be wrong.....

Some lpg systems use an injector emulator to fool the ecu into thinking the petrol injectors are firing when they aren't to prevent check engine light coming on...as there is no point in firing the petrol injectors when on lpg.

If this is indeed what it is, it could be preventing the injectors firing....just another thought!

Also the engine gets a running signal from the crank sensor, if fitted, and not a road speed sensor... Or the signal from the coil to ecu via this little resistor....

If the ignition amp has failed, it won't fire the coil or in some cases won't allow the coil to charge fully creating a weak and useless spark.

Click to expand...

+1

when you switch ignition on fuel pump should run for 4 secs then go off then come back on when cranked,if it doesnt there is an issue with either or both tin covered relays or ecu / wiring to from them ,pump will run with ignition on whether it gets signal from dizzy or anywhere else or not

Where you say the previous owner removed a resistor in the loom between coil and ignition amplifier - NO, this is a factory splice and is correct; look at the ignition wiring diagram, you will see the splice.

18v at the coil is wrong. Check coil resistance. As already said, ignition amp could be faulty. Get yourself in to the V8 section and search for ignition checks, then with your DVM go through the ignition system. Also, be careful sticking DVM probes in to the ECU plug from the front like that, you can break the tabs, the correct way to test is to open up the plug and put probes in from the back. (It isn't difficult, even I can do it).

If the ignition checks out you may need to try a substitute ECU. Good luck.

guys , quick update. not much progress on this as yet.

my multimeter is not auto ranging, so i think i had it on the wrong setting possibly, but anyhow, it seems the coil puts out 180v, not 18v as previously mentioned.
it happens that my jag also runs with the same coil (bosch), so i put the meter on that, and its exactly the same reading, around 180 volts (jag running fine!).
i am kind of ruling out the ignition system for now on this basis, but it is possible this lpg emulator/ ecu/ wiring or immobilizer are still the issues

still need to do some more reading on the V8 section, so will; get back once i have checked out all the suggestions so far.

i was careful not to damage the ecu connector. i only touched the probes upon them, not jabbed them through.

i have not found a second resistor inline between the coil/ amp and ecu. only the one pictured that is next to the ecu, and that one checked out fine.
i was surprised to see a crimp done by a manufacturer. thought they would have a better way of doing it somehow.

jamesmartin said:

when you switch ignition on fuel pump should run for 4 secs then go off then come back on when cranked,if it doesnt there is an issue with either or both tin covered relays or ecu / wiring to from them ,pump will run with ignition on whether it gets signal from dizzy or anywhere else or not

Click to expand...

ok, thats interesting. the fuel pump does not run unless the connector blocked is jumped. and there does not appear to be any voltage at the fuel pump fuse
i swopped the relays around, and it made no difference. i opened and cleaned the contact on them. no difference. i guess its possible both relays have died???

do immobilizers cut the fuel pump or ecu/spark normally, anyone know.
or both?

had a result!

couple of things. i went through and replaced every fuse in the fuse box. after looking again at them, most of them were, lets say old and less than perfect? i know from past experience on other cars a fuse with poor spades on it, can cause problems with higher resistance? i had previously changed the fuel pump fuse, but i know many of these fuse have dual usage on them, so thought it a safe bet.


tried jumping the fuel pump relay block, the pump ran and the car started!!!
swapped the relays around and then it didn't run. thus deducing that one of the relays is duff too! as was suggested by a few of you. so the duff relay was either in the fuel pump block or ecu block when i was testing it. but i think the possibly one of the fuse was casuing an issue too, as am sure i had swapped both relays around before, whilst jumping the fuel pump, and no result.
either way i think/ hope thats it now. no test drive yet.

but this also brings me to realise that i dont actually know the best way to "test" a relay.
i have tried putting 12v on random connectors, hoping to hear a "click" but no sure which ones are +/-.
i tried it again now and got a spark off the battery, so thats not good?

relay in question

can i replace the relay with any 5 pin 30A relay or does it have to be the exact same bosch one? any idea how they differ other than the Ampere rating?

naki said:

can i replace the relay with any 5 pin 30A relay or does it have to be the exact same bosch one? any idea how they differ other than the Ampere rating?

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Replace with the same tin topped relay....

Usualy pins 85 and 86 are the coil connections, unless it has a diode in place (doubtful, but you never know), it will not matter which one is positive and the other negative.

naki said:

can i replace the relay with any 5 pin 30A relay or does it have to be the exact same bosch one? any idea how they differ other than the Ampere rating?

Click to expand...

as long as it is 30amp

ok, thats good to know. thats what i sort of assumed, but its odd when you look online for parts when there are 100s of part numbers for what looks like the same.

you can test efi relay by removing fuel pump one and listening for click when ignitions turned on if it does you can then use other relay in same connector and test it ,fuel pump relay is triggered by ecu once ignition is on ,if efi relay works and fuel pump doesnt either not been triggered or poor feed to it earth etc

i did sort of try this by swapping them around. there are other relays clicking in the footwells though when i turn the key, so have not been able to isolate any clicking under the seat area.
on top of listening for the fuel pump.
would be easier with a helper of course! but not available.

i was hoping to find a way to test the relay off the car, but connecting 12v to specific spade, but not sure which way to do it.

naki said:

i did sort of try this by swapping them around. there are other relays clicking in the footwells though when i turn the key, so have not been able to isolate any clicking under the seat area.
on top of listening for the fuel pump.
would be easier with a helper of course! but not available.

i was hoping to find a way to test the relay off the car, but connecting 12v to specific spade, but not sure which way to do it.

Click to expand...

Saint.V8 said:

Replace with the same tin topped relay....

Usualy pins 85 and 86 are the coil connections, unless it has a diode in place (doubtful, but you never know), it will not matter which one is positive and the other negative.

Click to expand...

As above!!!

you can feel it ,or connect 85 to live and 86 to earth should click if it works