Diagnosing 3.9 Engine Problems - Where to Start

Hi Folks,

Apologies for my first post asking for help, but I will reciprocate in due course.

Just bought a 1994 3.9 Auto knowing it had a problem which the previous owner thought might be an ecu issue, or more likely head gasket.

Got her running today eventually, turns over coughs, catches, splutters dies.
Turn her over again and nothing. This happened several times, until with foot off the accelerator fired up.

Sounds fine, no nasty noises etc, but if you press the acclerator quickly splutters and dies. Press it gently sounds lovely.

Before it came fully upto temp, cut out and wouldn't start again. Battery now dead and on charge.

There is no water in the oil, and no oil in the water, but there is a bit of white foam/bubbles in the reservoir.

Before I remove the heads does anyone have any suggestions please.
I love these engines but don't know anything about them. Would hate to still have the problem afterwards.

Cheers

Andy

Check air flow meter, check throttle potentiometer, check ignition timing, check mechanical and vac advance on dizzy.

Also check for air leak in plenum and air inlet pipe.

Do a compression test.

Might also be worth checking the coolant thermistor.

Thanks for the advice, going to order a haynes manual tomorrow to get the settings and find out where the bits are.
Air leaks etc no problem, but no idea how to check the rest. Did my training long before electronics were involved.
Will search the forum for the parts mentioned, and see if I can find anything.

Cheers

Andy

I agree with kev.

I had simlar problem and the timing was a tooth out!

Sounds like HT leakage to me!
Would be a lot worse under load, rev engine from under bonnet at night with no light and see if you can see any arking particually around the coil and remove the rubber cover if fitted and also have a good look around the dizzy cap and king lead when accelerating!

Update Folks

Got the haynes manual, but also have another problem now, turn the key and nothing happens.
Have checked all the fuses on the centre console, all ok.

Read up on the starter and apparently there should be a main fuse box and starter relay on the rear bulkhead, but I can't see them.
Also tried to find ecu under drivers seat without success, manual is quite informative about how to test this so keen to have a go.

Are there alternative locations?, do I need new glasses?.
The manual only goes up to 1992 and mines a 1994.

Engine bay is a bit crowded due to lpg system, and I don't want to disturb anything unless I need to.

Thanks for any advice.

Andy

are you sure its in N or P, you wouldnt be the first to make that mistake.

Or a flat battery or immobiliser fault?

Tried both mate, N and P.
Battery isn't flat, got a spare even.
Immobiliser seems to be ok, light goes off when doors are unlocked etc.
Pretty handy with a spanner but electrics....

Take the ignition switch out and check it hasn't fallen to bits. No really, check your ignition switch.

is it a disco or a range rover helps
could be spider on the disco
fuel pump no fuel,cap leads and rotor use gen only
coolant temp sensor
what codes are in the ecu

Its a Range Rover, thought I'd put that at the top - Oops.
Changed the plugs, got a new dizzy to fit etc but it wouldn't turn over after changing the plugs. Rotor arm looks good.

Can't even find the ecu and its not OBDII so no error codes unless the ecu has a 4pin plug, in which case I can get a code reader made for £100.

You can hear what I assume is the fuel pump when you turn the key and there are a few lights on the panel, but no idea what should be lit etc.
Got fuel, when it did turn over old plugs were soaking and I've put more in just in case.

Totally baffled on this one.

It's time to check the basics then.

Remove plugs and check for good spark.

Check for live at coil.

Remove injectors and check for fuel spray. Remove fuel feed and check good fuel pressure. Check for live at ECU.

Short starter solenoid to force turnover. Check for live at coil when turning over.

Search '14cux' on google and go to first result: britishv8.com, it's a great help for efi troubleshooting.

Then try to establish if things are happening in time. Check igntion timing, check ECU is getting engine speed pulse (see pin-outs on Britishv8 page)

Check resistance for everything. Britishv8 page has info for all the vital parts, bar vehicle speed sense, which won't cause bad starting anyway.

Good luck

Oh and theres a purpose made 14cux code reader on eBay all the time, have a look

Thanks for the reply, appreciate any help as I don't have a clue what the problem is, suspect ecu etc. But at the moment won't turn over at all.

I've read that if there are problems with the ecu and becm and if they won't handshake this can happen.

Trouble is I've no idea where the components are located. Haynes manual states the ecu is under the r/h seat, checked both but again can't see it.

Local garage isn't interested, but hopefully I've got a mobile guy booked for Friday.

If he can't sort it or doesn't turn up, then all I can think of if getting it recovered to a specialist. Trouble is I don't know one.

Will have a browse of the V8 link and see what I can come up with.

Cheers

Andy

if its a classic it doesnt have a becm

and the ECU wont control start, only gearbox switch (if auto) or starter relay

It is an auto so potentially there could be a problem with the switch, I'm assuming it detects N&P. I've been underneath and tapped the starter just in case, but even when the engine was turning over it still wouldn't start. Tries to but....

Going to wait and see if the guy turns up tommorow, if not then probably going to recover it to a specialist for diagnosis.
If there are any recommendations locally then it would be most appreciated.

I know a guy who will come to you. he is excellent but busy.

He fixed mine in the snow last year, I had a moble and a garage first try it for 3 weeks with no luck and then he turned up and fixed it in half an hour. He doesnt charge alot for the travelling either.

PM me if you want his details.

Hi Folks,

Thanks for all your help.

Had "Rover" recovered to Lewis 4 * 4 in Neath, S Wales, and they have replaced a relay and got him running but I need a new distributor.

Done a bit of googling and the cheapest option seems to be a recon unit with a 2 year warranty from ignitioncarparts.co.uk @ £130+vat. This price also includes a new coil.

Going to buy one unless anyone knows a cheaper supplier.

Cheers

Andy

Find out how much a land rover dealer are charging as these engines don't like pattern parts at all.