Brain Teaser - EFI wiring issue

Hello all, I am looking for a little assistance.

I am in the process of putting a 4.2 hotwire into my 90, it has been mucked around with previously and had a 3.5 flapper systenm in it that wasnt runnign properly.

I bought the 4.2 complete with the injection and the loom for the injection, it was previously on an auto. I have wired in the loom and have got to a point where I tried to fire her up, but have not managed to get her started.

When i power up the ecu - the fuel pump kicks in to purge the system for about 4-5 seconds, but as soon as the starter motor kicks in the fuel pump stops working.

I cannot get it to fire up at all. Does anyone have any ideas at all as to what could be the issue?

I am trying to get this sorted out before the snow comes this year - It should be a lot of fun un the snow

Cheers in advance for your help

James

Have you studied the pin-outs for the ecu to make sure you've got everything?

I can't think of any particular reason why the pump would stop running, have you picked up the feed from the coil for the injection timing? Have you got the correct resistor fitted?

Have you read Rover 14CUX Hot Wire Mass Flow EFI: Service and Troubleshooting ?

have you got the wire from loom to coil it lets system know it should be running

Thanks for the answers - I do have a lead from the coil, this is wired in to the ecu just to get it running - but the wiring diagram says it should be a white and black, the inly white and black seems to go to the ignition module next to the coil, any ideas where this should be or any ideas on colour at all?

it is causing me a headache

James

coil has two wires from module ,positive feed and ecu pick up cant remember colour

jamesmartin said:

coil has two wires from module ,positive feed and ecu pick up cant remember colour

Click to expand...

The EFI coil negative (RPM Input) is a white and black wire. The Coil positive is a white wire that is connected to the ignition amplifier, the other wire on the coil is a white and black wire that also goes to ignition amp.

To the OP, have you checked the inertia switch (is it fitted??) make sure all earth wires are connected and making good contact. If you get it running make sure you connect the road speed transducer.

James, Where have you taken your ign live from to feed the ecu?

Some go dead when the engine is cranking over, for example, the radio feed.

If this happens to be what you've tapped into, the ecu will think the ign has been turned off.

Dave

Hi All,

I'm helping James with this, so thanks for all the help so far. The ignition feed for the ECU loom has been temporaily connected to the back of the ignition barrel (piggy backed off the white wire powering the rest of the ignition circuits). I haven't tested it with the multimeter, but would think it stays live when cranking ??

Re: the Black/White wire from the coil. Would this run through the engine loom back to the ECU, or is this an additional connection we are looking for? Presumably, if it part of the engine loom then it should all be connected OK anyway?

The engine loom has a seven pin plug rectangular plug by the gearbox. Does anybody know what each terminal should be? None of the colours match up with the diagrams available on the web. I have a rogue Black/Brown wire coming out of this connector which I need to trace.

Thanks again for the help so far

Slim

The big fat orange/brown is your permanent live from battery, purple/white is positive feed to fool pump, white/grey is ign live.

I cant remember off the top of my head what the others are but only these 3 are needed to get you up and running.

The others are stuff like road speed transducer,and heated front screen. The engine will fire up without them.

The coil wire should come out of the loom on the same 'leg' as the plug for the air flow meter, I cant remember if its black/white or just white, and goes to the -ve terminal on the coil.

Dave

If the fuel pump is priming on ignition turn the you must have most of it correct. The rpm input to the ECU is a bit of a 'run around' wire on a 4.2 Hotwire system. 1) You will probably have two wires bound in tape with small resistors on spade terminals .. the black / white wire from the coil negative will go accross the front of the engine and then into this 'bound bundle'. In the bundle it changes colour .. just to make life interesting and becomes white / blue, and splits into two halves, one goes to the rev counter .. the other is the rpm feed to the ecu.
or
2) There is a black / white wire coming off the coil that runs into a loom and then across the front of the engine, is usually cable tied onto the inlet hose, then connects on a spade terminal to a wire coming out of the Air Flow meter connector.

Whichever version you have .. if this wire is not connected then the pump will not fire up as the engine starts spinning.

I am guessing you have checked for a spark already? if not then check for that as well .. it is really easy to get the two pins on the dissy the wrong way around.

Landyslim said:

Hi All,


The engine loom has a seven pin plug rectangular plug by the gearbox. Does anybody know what each terminal should be? None of the colours match up with the diagrams available on the web. I have a rogue Black/Brown wire coming out of this connector which I need to trace.
Slim

Click to expand...

If this is the 'Brown' connector it should have the fuel pump relay power feed (white / purple) , starter solenoid (colour varies but often black), fuel pump power (from the relay .. white / purple) , RISTS relay feed (black / red) (no idea what this does .. I have never connected it!) , white / green - 12v ignition live from barrel, brown / green - permanent 12V live.

That is the only 7 pin connector I can think of to be honest .. hope it is the right one!

Do check your ignition switch. As has already been said, you need power while cranking and my series 3 had to be rewired to provide that when I put the 3.9 in - took me a while to figure it out

Did you sort this? Funny enough I have just wired in Efi and have exactly same problemAAA

Hi guys - We have sorted out the wiring issue -= thanks very much for your help! Now the problem is that when I start the car (having sorted out the timing issues) the car revs its nuts off top the point that i have to turn it off. Are there any ideas on what could be causing this??

Cheers again in advance

PS - no the black/brown problem wire is still not connected, the other thing that has come to mind is that the car was an auto and is now on a manual box - dont know if this makes a difference??

An air leak or stuck idle stepper?

Car should adjust its own idle. If air gets in the it will over rev.

Get it running then cover up intake before MAF and see if it stalls or keeps running from another air source.

I have changed the Stepper motor - but that hasnt sorted iyt - does anyoine have any other ideas at all???

OK -

I have sorted this out - the problem occured due to some idiot thinking it would be a good idea to use the flapper throttle linkage and not the hotwire one -

They may look the same and fit but the replacement stops the butterfly from closing properly - about 10 mins with a file and job is a goodun!!

Thanks for all of your help on the build so far

James

Hi Guys,

I thought I'd add my 2p worth as it really annoys me when I read these and there doesn't seem to be any conclusion, and you never know whether what was suggested worked for the original poster!!

MattMatt and Crazydave were indeed spot on with their diagnosis on the wiring. It seems there are two ignition live terminals on the ignition barrel: both give you +12v when you turn the ignition on, BUT only one remains live when you turn the key to the start position. We connected the ECU feed to the same terminal as the main loom for the vehicle presuming that this stayed live. A simple test with the multimeter revealed that it did not. It would therefore appear that the vehicle loom is cut off when the engine cranks over. Attaching the ECU feed to the other terminal on the barrel achieved the desired results with the fuel pump staying live whilst the engine was cranking.

Thanks again for all of the help with the wiring issues.

Slim

OK Guys - just a final update

Have got the car running, and apart from the small teething issues - rad isnt any cop etc... I will be taking the car for MOT tomorrow. After a new rad is aquired from Island 4x4 in the am.

Many thanks for your help

Conebonce