RRC Starting Problem

[CAPP0]

Thought I'd try and pick the brains of the RRC experts here

You might recall, I bought a 3.9 Vogue a month or so back, knowing that it had a starting problem. The issue is, sometimes it will start immediately, but other times it just churns and churns over, occasionally catching a single fire but not starting. A further symptom is that often, when this happens, it will fire when you release the key.

So, basics first, I replaced the dist cap and rotor arm. Cap says it is Lucas but I remember something about Lucas-branded stuff now being some Italian import? Anyway, either the original or replacement items have made no difference.

It has had all manner of possibly-related parts replaced before I bought it (including airflow sensor, stepper motor and throttle position sensor, it has also had a new distributor, which is free and moves under vacuum, and new plugs and leads although from looking at receipts I'm not sure the plugs are premium-quality). I have also put a brand-new battery on (because on a cold day, inching the original one out of the battery well with my fingertips, it slipped and fell to the floor with obvious consequences )

Then I wondered about vacuum leaks. Have checked all over the place and also sprayed carb cleaner all around the vacuum system but nothing from that.

Next thing was engine earths. I stuck a jump lead from the battery to the water pump and lo, it started instantly. Bingo, I thought, but then it went back to doing the same thing even with the jump lead in place.

Then I wondered whether the ignition switch was faulty and was cutting the coil feed when you turn to the start position. Jumped a 12v live straight onto the coil and lo, it started instantly. Bingo, I thought, but then it went back to doing the same thing even with the jump lead in place.

It has to be something ridiculous and simple, because sometimes it will start fine, and once it's running, it runs fine (although does seem a little down on power, but we can come back to that another day!).

I'm wondering about ECU earth, since that is under the seat and the floor in the driver's footwell is poorly. I'll have a look at that.

Failing that I guess I'm into a full diagnostic of all the injection system, but as I said, I sense it may be simple. Anyone got any other ideas/had anything similar?

TIA.

[foreverme]

I been going through a similar issue with my Defender 3.5 V8, not efi so its a bit easier, replaced all the easy parts (dizzy, plugs, leads, new electronic ignition etc) had the wiring all cleaned up etc.. Most of the time no problem at all, but sometime i go to start and nothing just a clicking underneath the stereo/above the fuse box, take the key out wait, and then all is fine again, very random

[CAPP0]

Ah, well mine churns over happily enough, so it's not the starter or any part of the starting circuit. it just won't actually fire enough to run under it's own steam.

[paintman]

ECU is earthed by wire in the loom, not through its casing.
Have a look at this, includes a couple of links:
http://forum.lro.com/viewtopic.php?f=65&t=9450...

[CAPP0]

paintman said:

ECU is earthed by wire in the loom, not through its casing.
Have a look at this, includes a couple of links:
http://forum.lro.com/viewtopic.php?f=65&t=9450...

Cheers paintman, just heading out now, I'll have a read when I'm back.

[V8 Fettler]

CAPP0 said:

Thought I'd try and pick the brains of the RRC experts here

You might recall, I bought a 3.9 Vogue a month or so back, knowing that it had a starting problem. The issue is, sometimes it will start immediately, but other times it just churns and churns over, occasionally catching a single fire but not starting. A further symptom is that often, when this happens, it will fire when you release the key.

So, basics first, I replaced the dist cap and rotor arm. Cap says it is Lucas but I remember something about Lucas-branded stuff now being some Italian import? Anyway, either the original or replacement items have made no difference.

It has had all manner of possibly-related parts replaced before I bought it (including airflow sensor, stepper motor and throttle position sensor, it has also had a new distributor, which is free and moves under vacuum, and new plugs and leads although from looking at receipts I'm not sure the plugs are premium-quality). I have also put a brand-new battery on (because on a cold day, inching the original one out of the battery well with my fingertips, it slipped and fell to the floor with obvious consequences )

Then I wondered about vacuum leaks. Have checked all over the place and also sprayed carb cleaner all around the vacuum system but nothing from that.

Next thing was engine earths. I stuck a jump lead from the battery to the water pump and lo, it started instantly. Bingo, I thought, but then it went back to doing the same thing even with the jump lead in place.

Then I wondered whether the ignition switch was faulty and was cutting the coil feed when you turn to the start position. Jumped a 12v live straight onto the coil and lo, it started instantly. Bingo, I thought, but then it went back to doing the same thing even with the jump lead in place.

It has to be something ridiculous and simple, because sometimes it will start fine, and once it's running, it runs fine (although does seem a little down on power, but we can come back to that another day!).

I'm wondering about ECU earth, since that is under the seat and the floor in the driver's footwell is poorly. I'll have a look at that.

Failing that I guess I'm into a full diagnostic of all the injection system, but as I said, I sense it may be simple. Anyone got any other ideas/had anything similar?

TIA.

Firing when you release the key can be related to no operation of the fuel pump when cranking. Fuel pump operates when the key is turned back to the "run" position, engine fires but doesn't have enough rpm to continue running.

Go back to the basics: spark and fuel?

[paintman]

Connect a live feed to the fuel pump & see if that makes any difference.
I resolved a connection issue with mine that way by disconnecting the pump at the tank & connecting a spare battery to it. I knew mine wasn't an ignition problem as it ran perfectly on LPG & with the battery connected ran without issue.
The vehicle loom part of the connector was the problem - corrosion to the pins & water ingress.

ETA. Had been a bit of a head scratcher, as a multimeter said 12v present. Penny dropped when I tried a test bulb & it didn't light - should have used the bulb from the outset!

Edited by paintman on Saturday 7th February 10:50

[CAPP0]

Thanks all, with this and the links posted I have a ton of stuff to work through - will report back!

[CAPP0]

Had a hectic couple of weeks and finally got a few minutes to look at this again today.

So, with the ignition on, I can't hear the fuel pump running (bear in mind that once started the car runs fine!). It looks as if the pump has been replaced at some point, it looks new and clean and the pipe unions are shiny. it also has some weird lashed-up connection; originally 3 wires (black blue and green) spliced into a little extra harness with 4 wires (2 black, 1 blue, 1 green).

Disconnected this and found that with the ignition on and the pump disconnected, I only had about 5v at the connector. I then tried putting 12v across the pump and still couldn't hear it running (bear in mind that once started the car runs fine! ). If I start the car and then pull the pump connector, the engine dies in <1 second. So, somehow the pump must be running (maybe it was replaced with the new silent-running version ) Picture of the pump and connectors below.

I still have a suspicion about the ignition switch. Does anyone know how it is supposed to deliver power when turned to the start position as opposed to the run position? The reason I say this is that if I turn the key hard over to the start position, the engine turns but doesn't start. If I carefully, gradually, back the key off towards the run position, when it gets to the point where it is just about to stop turning the starter, the car often fires into life. I could of course be completely imagining all that and it may be coincidence! For the sake of £18 I might try replacing it though.

Your thoughts and expertise welcome as ever!

[paintman]

The key issue is interesting.
The fuel pump is energised during cranking and continues to be energised whilst the engine is running.
Have a look at this, scroll down to 'ECU Initial start up sequence'
http://www.g33.co.uk/fuel_injection.htm.
What's happening at the pump during cranking?

[CAPP0]

I'll have to wait until MrsC is home to check the pump during cranking (or make up some long meter leads!). I'll see where I can break in tot he wiring to get a reading.

[CAPP0]

Had another go at this and here's the latest.

I connected a voltmeter across the blue & black to the pump and got the following readings:

1. Ignition off: 0v
2. Ignition on: Initial volt spike as expected to prime the pump (approx 10.5v, but a digital meter doesn't catch up that quickly) then drops away to something like 3-4v
3. Ignition cranking: 7-8v. This doesn't seem enough. From the g33.co.uk page which paintman listed above (great site, thanks!) there should now be 12v at the pump, as the ECU should turn the pump on
4. Using my "backing the key off" technique above, which strangely seems to be the most reliable way of actually getting the car to start, once it's running the voltage at the pump is 12v or thereabouts, as it should be.

So, I'm not sure what's happening in step 3 above. Somehow the ECU is not delivering the full 12v to the pump. Anyone got any thoughts on that? Despite my ignition switch theory, it seems that the ECU, and not the ign switch direct, should be powering the pump, so the ign switch is not a factor?? Or perhaps is the switch not delivering 12v somewhere it should be and that's the issue? I don't want to throw new parts at it willy-nilly but I'm tempted to go for a switch at £18 if only to rule that out?

Actually I think I next need to power up the pump directly (as was suggested above) to see if I get an instant start. If I do that with everything connected (by baring back a section of the insulation on the wiring harness as I have done to take voltage readings), is that going to back-feed the ECU and nuke it? Or should I just disconnect the pump completely and power it up that way?

Thanks for sticking with this! It's quite interesting for me and I sense I'm closing in on it.

[V8 Fettler]

Do you have a wiring diagram?

[paintman]

When mine played up it was the light bulb that showed the voltage was too low - digital meter just said 12v. Wonder if an analogue would be better?

I disconnected the fuel pump from the loom altogether & powered it from a spare battery. Bear in mind mine's a flapper, so slightly different.

If you can work out what wire does what in the ignition switch then you could try connecting them to see if it works - I'm assuming you'd need to touch one wire to the others to simulate the 'start' position. Can't help with which should be connected I'm afraid.

[CAPP0]

Weirdly even if I power the fuel pump direct, I can't hear it running; would have thought I would. But it obviously runs because the car can be driven.

If I disconnect the pump from the loom, put power to it, and try and start the car, nothing happens, but if I reconnect it then with my key technique it starts. It's almost as if the ECU knows the pump is missing, but I didn't think it was that intelligent.

I've got access to a wiring diag but only a copy in front of me. I'll pore through it.

Edited by CAPP0 on Monday 23 February 22:55

[paintman]

An intelligent Range Rover?

[CAPP0]

Well exactly!

Have any of you chaps had your ECU tested? Or do you go the route of just measuring voltages at all the pins?

Any recommendations (and prices) for testers, if I end up down that route?

[V8 Fettler]

CAPP0 said:

Weirdly even if I power the fuel pump direct, I can't hear it running; would have thought I would. But it obviously runs because the car can be driven.

If I disconnect the pump from the loom, put power to it, and try and start the car, nothing happens, but if I reconnect it then with my key technique it starts. It's almost as if the ECU knows the pump is missing, but I didn't think it was that intelligent.

I've got access to a wiring diag but only a copy in front of me. I'll pore through it.

Edited by CAPP0 on Monday 23 February 22:55

You have a 3.9i and you've mentioned the stepper motor, therefore you probably have a hotwire EFi (14CUX), does your wiring diagram look something like this?

http://www.gomog.com/allmorgan/HotWireEfiWiring.jp...

Fuel pump is 8

[CAPP0]

V8 Fettler said:

You have a 3.9i and you've mentioned the stepper motor, therefore you probably have a hotwire EFi (14CUX), does your wiring diagram look something like this?

http://www.gomog.com/allmorgan/HotWireEfiWiring.jp...

Fuel pump is 8

Yep, that's the one

However, it looks like the fuel pump relay is solely responsible for fuel pump power regardless of the engine state? In which case the relay is either going to be in or out, which doesn't account for the difference in voltage at the pump when cranking or running?

[V8 Fettler]

There could be several reasons for measuring voltage fluctuations. I generally use a flying lead back to the battery earth terminal to eliminate earth issues at the voltage probe when checking voltages on mature vehicles. To prove fuel pump operation and go around any control system issues, I would try running a pair of wires from a battery to the pump as a temporary measure, and run the pump in electrical isolation from the rest of the car. There are risks associated with this, you need to be confident of your own ability.

Fuel pressure gauge would be useful.