Land Rover / Rover V8 Poor Running HELP PLEASE

Disco_V8_LPG · Post by **Disco_V8_LPG** » Sat Nov 10, 2007 12:39 am

Hi all

I am in Need of a bit of HELP

I have a Land Rover Discovery with a 3.5 V8 on carbs and it keeps running Rough, Lumpy, Irratic Idle, Very High Hydrocarbons (10,000 HC )(when i get them down they get to about 3000 HC and then she wont run), Wont start up without Choke (wether hot or cold), timing keeps going out (get it right according to My AutoData Manual and then 2 months later it is out again) and one of the HT leads on the Dizzy Cap keeps coming out of the Hole and turning Blue (it ARC's across it to create a spark

It has Electronic Ignition (I.E No Points)

What am I not Doing?
What am I Doing that I should not be?
What Can I Do to Check it?
What Can I Do to Resolve it?

ALL HINTS, TIPS and HELP are Deffinatly Appreciated

THANKS in ADVANCE

kiwicar · Post by **kiwicar** » Sat Nov 10, 2007 7:19 am

Hi
I'd start by changing distributer cap and HT leads and rotor arm, all for lucas parts, not patten. With leads falling out you are not going to get too far fault finding.
Then one thing at a time....
Check for play on the distributor shaft (you will not believe how warn these can be and it just run rough) if thats OK.
Check the fuel side, check supply from pump and pressure, renew filters.
Take the top off the carbs and check the pistons are not sticking, check the pistons for wear (if they are leaking air around the piston this will give you unsteady readings). Check the needles for wear and flat spots and the jets. (if these are Strombergs check for tears in the diaphram).
Check the float needles for wear and replace if in any doubt, make sure the bowl levels are stable.
Check for airleaks around the inlet manifold and the vac advance pipe.
Carb type and engine milage would be usefull.
Mike

Disco_V8_LPG · Post by **Disco_V8_LPG** » Sat Nov 10, 2007 11:32 am

Hi cheers I replaced Rotor arm, Leads, Plugs and Dizzy all with the Proper ones (i never Use patern parts on my own vehicles)

the Carbs are SU's
and the Milege of the engine is 190,000 Miles
but the Engine was rebuilt by one of the previous owners at around 100,000 miles Due to Reciepts in the service history

Also what is the Thickest oil i can put in her? or What Oil Shoud i be running in her?

kiwicar · Post by **kiwicar** » Sat Nov 10, 2007 1:50 pm

Hi
at 90K your cam will be pretty worn out, I suspect the timing chain is pretty loose by now so this will "scatter" the sparks. If the distributor is original then I would think the shaft bearings have gone, if the cam was renewed at 100k and the distributor gear not done then that will be pretty shot aswell. A 190k distributor is old!

.
Bores will probably be good if they were redone at 100k.
The SUs will be tired, it depends on what emissions gubbins they have on them though, I would do the checks sugested earlier.
If it were mine I would renew the cam, lifters, distributor and timing set, clean and check the carbs (find some lower milage ones if I could) and strip out all the emisions junk off them (especially the poppet valves) and check the rockers and shafts.
If you have a bit more budget then do a full rebuild, if the bores were done at 100k then just a hone and re ring would be enough (measure the bores) and new bottom end bearings (doubt the crank needs a grind) but it all depends on what was done at 100k.
20w/50 is the best oil for the rover
good luck
Mike

kiwicar · Post by **kiwicar** » Sat Nov 10, 2007 2:01 pm

Just thought
is this running on LPG?
if so, check the state of the exhaust valves, thet are probably burnt badly if the timing has been late at any point, also the Su carbs will have suffered and the needles will probably be stepped where they are held open when on gas.
Even if it is purly petrol it would be worth a new set of needles and jets by 190k even if the rest of the carbs are working OK.
Mike

Disco_V8_LPG · Post by **Disco_V8_LPG** » Sat Nov 10, 2007 9:30 pm

I Have not put any LPG in for over 2 months as i want it running right on petrol which should then sort out the LPG problems (but i know what they are)

Just a note it was about 8 years ago the engine was rebuilt,

I will definatly putting a new Distributor on, new valves, Pistons, Rings, shells and new camshaft in but should i be putting a new Crank in because it is so old?

kiwicar · Post by **kiwicar** » Sun Nov 11, 2007 7:48 am

If you only do the cam, timing chain set, distributor and rocker gear you can do it with the engine in the car (radiator out

)
if you decide to do a full rebuild the crank may need a grind (measure it up when you strip it down) and check the bearing shells, if it was ground at 100k then it will probably only need new shells.
As a very rough guide on a rover engine with the right oil changed at the right time.
Cam wear will effect performance at 45-60k getting significant by 90K and needs replacing 110k.
Bearing shells last to about 120 to 140 k and will start to damage the crank about 140Kto 160k (but alot of this is actually down to a worn out oil pump).
Piston rings are good for 150 to 180k but if they were changed at about 90 to 100k then the bores will go on and on, especially if you give it a light hone each time, pistons are good for at least two sets of rings.
Oil pump this is good for 70 to 80k or so before it starts to wear enough to reduce presure and flow by 120k it is getting pretty poor (tappets rattle and the pressure light is slow to go out) and will be accellerating the wear on the bottom end.
Working from this a timing set rebuild now, and a rebuilt/ renewed oil pump should give you at least another 50k on the engine (probably a bit more). However it all depends on what was done on the last rebuild and if you want to tune it, as if you do then I would pull it out and do a basic rebuild.
Best of luck
Mike

Disco_V8_LPG · Post by **Disco_V8_LPG** » Sun Nov 11, 2007 12:41 pm

i have an engine sat in a spares vehicle at the moment so i will strip that one down and rebuild it then replace the one in the vehicle and then rebuild the first one si i got a spare if it does play up

kiwicar · Post by **kiwicar** » Sun Nov 11, 2007 1:04 pm

Is you plan to run this on LPG?
just if you are it would make sense to build it to start and run on LPG only, my experiance of "dual fuel" is that it is very difficult to build a reliable engine that works on both, LPG is slow burning and very high octaine rating compared to petrol and what works for one tends to bring out the worst in the other.
I am going to get shot down here as there are many on this site who love the stuff but my experiance with LPG wasn't good.
For an LPG engine you want to be running high compression (minimum 11.5:1 really about 12.5or 13:1 with lots of turbulance in the combustion chamber and inlet port, with a very compact chamber (very un rover

)

. You also want Late opening and early closing of the inlet valve and relativly very late opening of the exhaust valve and really twin plugs and quite alot of advance. In the rover this isn't easy and with this set up on petrol the engine would self distruct.
If you could find a way of very high pressure port injecting the stuff right behind the inlet valve then I think life would be better, but you still need to get it to burn before the exhaust valve opens. The other thing with it is it seems to be a very poor lubricant compared to petrol and quickly strips the oil out of the valve guides just making the problem worse.
Have fun
Mike

Disco_V8_LPG · Post by **Disco_V8_LPG** » Sun Nov 11, 2007 1:08 pm

Hi Yes the plan it to use the LPG for Road use But use petrol off road (i feel safer having it running on petrol) i want it running nice on both if possible

diamond dave · Post by **diamond dave** » Sun Nov 11, 2007 2:22 pm

Disco_V8_LPG wrote:Hi Yes the plan it to use the LPG for Road use But use petrol off road (i feel safer having it running on petrol) i want it running nice on both if possible

Might be a tad difficult, as it's a bit of a trade-off settings wise.
Basically, to have it running well on gas, you have it running a tad lumpy on petrol & vice versa, due to different plug gaps etc.
Que someone telling me different

My 3.9 is set up for petrol & idles lumpy on gas, needs sorting as gas is my "primary" fuel.
As for the lube issues, just use petrol for a mile or two at the start & end of your journeys.

Sussed who you are now

Did you get in touch with Jim ?

Disco_V8_LPG · Post by **Disco_V8_LPG** » Sun Nov 11, 2007 6:48 pm

diamond dave wrote:
Disco_V8_LPG wrote:Hi Yes the plan it to use the LPG for Road use But use petrol off road (i feel safer having it running on petrol) i want it running nice on both if possible
Might be a tad difficult, as it's a bit of a trade-off settings wise.
Basically, to have it running well on gas, you have it running a tad lumpy on petrol & vice versa, due to different plug gaps etc.
Que someone telling me different

My 3.9 is set up for petrol & idles lumpy on gas, needs sorting as gas is my "primary" fuel.
As for the lube issues, just use petrol for a mile or two at the start & end of your journeys.

thats what i will have then must remember a bit lumpy on petrol

Sussed who you are now
Did you get in touch with Jim ?

Sorry??

Slothie · Post by **Slothie** » Mon Nov 12, 2007 1:11 am

Might be worth checking the vacuum advance diaphragm is working - I've had a couple of car run like a pig because the diaphragm is holed, impossible to get the mixture right, idling all over the place, stalling whenever it felt like it!

Disco_V8_LPG · Post by **Disco_V8_LPG** » Mon Nov 12, 2007 2:00 am

Slothie wrote:Might be worth checking the vacuum advance diaphragm is working - I've had a couple of car run like a pig because the diaphragm is holed, impossible to get the mixture right, idling all over the place, stalling whenever it felt like it!

Ahh that sounds like my problem will check that

cheers