Range rover classic problem starting up

[ct21]

Hi i was wondering if anybody could shed some light on the problem i am having with my classic 3.9 efi auto petrol/ lpg , if it has been stood for more than say 8 hours i have to turn it over for what seams like ages
(probably 15 to 20 seconds) then it will fire up, so i bought an in-line spark tester which goes on top of the spark plug and i have noticed that there is no spark for the 15 to 20 seconds that it has been turned over and the second i see a spark it fires up straight away, any help would be appreciated

 

[ukadamwest]

are you shutting it off from running on LPG ?


try switching it back to petrol and let it idle till the fuel runs back into the fuel rail before switching it off and see if that makes a difference when starting the next time. try it and let me know.

 

[ct21]

I haven't tried that, but i will do it and let you know if it works,
thank you

 

[Ratae]

Worth a try, but if you have no spark at all for the 15 to 20 seconds you say then that should make no difference.

 

[ct21]

That,s what i thought but i am willing to try anything to get it to start normally

 

[Ratae]

Mine's on dual fuel with the changeover being switched so I control when it changes - it's a 3.5EFi & I replaced the gas ring with a BLOS some years ago.

Starting switched to petrol is usually pretty much instant. It's a flapper so the fuel pump runs either on cranking OR when the flap is open. Any issues in the fuel line that could allow fuel drain back are likely to give a delayed start. I believe yours is a hotwire & that runs the fuel pump for a few seconds on turning the key?

If I start on LPG I usually wait a few seconds after turning ignition on - I can hear the 'click' as the solenoids open - & that also gives pretty much instant start. If I don't & just go straight to cranking then it does take a few seconds, but nowhere hear the amount of time yours is.

 

[ct21]

Hi
Ratae
Thank you for the advice, I have noticed that if i turn the ignition on for about 5 seconds i hear the pump run but only for about 3 or 4 seconds, so what i have found now is if i turn the ignition on for 5 seconds and off, do this 3 times she starts instantly, so i think i will put a none return valve in the fuel pipe and see if that does the trick, thanks once again for your advice regards Chris

 

[Ratae]

The hotwire should run the pump for a few seconds & then stop until cranking.

I suggest you need to check the LR manual - IIRC yours will be covered by the RAVE disc - & carry out the fuel pressure tests given.
I only have the manual that covers up to 1989 & I don't know what differences - if any - there may be between the hotwire tests in that & the 3.9.

 

[ct21]

The hotwire should run the pump for a few seconds & then stop until cranking.

I suggest you need to check the LR manual - IIRC yours will be covered by the RAVE disc - & carry out the fuel pressure tests given.
I only have the manual that covers up to 1989 & I don't know what differences - if any - there may be between the hotwire tests in that & the 3.9.

This was going to be my next test to see what the fuel pressure is like. I have also looked in to replacing the fuel pressure regulator but have you seen the price of them lately iv also been looking at the ECU mate it's a shame they don't seam to make them anymore seamslike a nice bit of kit

 

[Ratae]

Would any of the other diagnostic tools work? Not something I have any knowledge of as I don't do computery stuff!

The flapper 4CU ECU was problematic. I've had mine since 1994 & I'm on my 4th. To be fair, they were all used & I keep a spare in the car! I can say that they either work fine or they don't I've never had an intermittent problem with one. I've tried various different part numbers & can't say I've noticed any difference between them.
I did speak to Lucas & gave them the numbers I had & the reply was:
"PRC4764 with 84477B is the OE unit fitted at the factory made under license
LRZ149 with 84477 was a recon unit
84477D looks like it’s a later number
I think that they are all interchangeable with each other"

AIUI the hotwire is more reliable.

For me the LPG is a useful diagnostic tool, if it plays up on petrol & runs fine on LPG then it's a petrol delivery problem but if it runs rough on both it's ignition & it's been a plug on two occasions & a pattern dizzy cap on the other. The cap was an intermittent miss at speed & under load on both fuels & worse when wet.
Apart from the ECU failures (detected by substituting a spare as a first test) fuel delivery problem has been one fuel pump failure & one defective wiring at the pump connector. The latter was corrosion in the wiring, something of a headscratcher as a multimeter said there was battery voltage at the connector & the pump ran perfectly connected to a battery. Wasn't until I tried a 12v bulb that the penny dropped. The bulb didn't light. Pin on a wire pushed through the insulation for a couple of cm put the bulb on. Turned out to be the wire at the connector on the loom was down to a couple of strands - enough to show on a digital meter but not enough to carry the current necessary. I'm given to understand that an analogue meter would have shown the low voltage.