Topic: Running Like a Dog ... HELP !!!! (Read 4759 times)

Greybeard · « **on:** February 16, 2006, 20:09:44 »

These words were posted yesterday in Modified under the heading LPG .....

I have a 1999 3.9 Disco on LPG and have just this week finished converting my 1990 3.9 RRC with an OMVL kit.

I have absolutely no problems at all with either vehicle. My dad runs a carb V8 on lpg and his actually starts on gas and runs very nicely. There is a minor power drop but running a V8 it isnt that noticeable. Do it, you wont regret it.

Well famous last words ... My RRC started misfiring on the way home from work and initially i thought it was running out of gas, albeit a bit too soon. It cut out at a set of traffic lights so i switched to petrol and with a little coaxing it fired up. Drove home with a little bit of a misfire but seemed to clear when i wound it up so to speak. Some time after getting home i had to go out again to pick up my daughter, car fired up ok seemed to be running fine, switched to gas, all seemed fine. As the engine reached operating temp it started to misfire again and then cutting out although it was doing the same on petrol and i had previously verified that it wasnt out of gas.
To me this seems like an electrical / fuel injection issue.
Came home tonight and checked connections , vacuum hoses etc fired her up and at first she was lumpy but then she cleared and i went for a test run thinking all was well. As the engine warmed up , the misfire got worse till i was back to cutting out again. If i keep the revs up she seems ok if they drop i have to almost feathjer the throttle in the same manner i would if it was a twin choke carb running out of fuel.
This has occurred since the sump was removed to check bottom end bearing sizes although i cannot see how it is related. For now it has me stumped , do any of you far more knowledgeable people have any ideas.
I was maybe thinking ignition amplifier or coil. one thing i have just remembered is that when i was running it on petrol it was horrendous on fuel and very rich but seeing as it was going to be run on gas i didnt bother with it , possible cold start issue which maybe why it is worse when hot ....................

HELP

thanks in advance

Steve

500bhp · « **Reply #1 on:** February 16, 2006, 20:31:42 »

Hi Steve, I run on gas out here in Portugal, things to consider.
The spark at the plugs has to work harder on gas as it is a "dryer" fuel then petrol, this will often highlight any problems in the HT circuit, I run with my plug gaps slightly smaller than recommended for petrol, give that a try, then give the HT circuit a good check, a trick you can try is, running the engine till it missfires then put a radio next to the engine tuned off station and listen to the static and listen out fo the tell tale clicks of a spark going to earth, or park somewhere pitch black peer in the engine bay while its mis firing and look for the little flashes on the HT circuit going to earth :D

Greybeard · « **Reply #2 on:** February 16, 2006, 20:39:35 »

Hi Phill ,
done all that except the radio thing, thing is it does it slightly worse on petrol but is easier to keep running at low revs on petrol. Also seems smoother on gas when it was running correctly as though the engine preferred it and it was quieter.

Steve

500bhp · « **Reply #3 on:** February 16, 2006, 20:49:48 »

Mine runs smoother on gas, it due to it being a slower burn, hence why the ignition has to be advanced on gas. I still think it sounds like a HT problem as the petol side is all off when running on gas.........also recheck any vacume, breather, hoses as when the engine is cold its running richer, when its hot it will lean off, then if there is an air leak it becomes to lean. I have the auto data cd if you want all the settings, readings, for your engine, i will need model, year engine size etc

Greybeard · « **Reply #4 on:** February 16, 2006, 21:06:13 »

Phil

I have given it all a look see but nothing was glaringly obvious. I seem to remember there was something you could spray on your pipes and the engine revs would increase if you had a leak,cant remember any ideas ? btw i dont think it was petrol lol. I had made the mistake of fitting my coil upside down on the bulkhead forgetting they are oil filled but that was a week ago and until last night it was running superbly.
I also suspect HT side of things and if it wasnt electronic i would have said condenser.

Steve

500bhp · « **Reply #5 on:** February 16, 2006, 21:19:23 »

If you want to PM me your email address I will send you the things that the AutoData CD says to check.

Range Rover Blues · « **Reply #6 on:** February 17, 2006, 01:23:48 »

Sounds like the ignition amplifier then. take a lead off and lok for the quality of the spark on a spare plug. Wearing rubber gloves check the distance the spark will jump to earth too as this tell you how strong the spark is.

500bhp · « **Reply #7 on:** February 17, 2006, 17:47:40 »

Hi Steve, I sent you an email did you get it ok ?

Greybeard · « **Reply #8 on:** February 17, 2006, 17:55:46 »

Hi Phill , yeah thanks very much, will try and get the details for you. Definately worse as it gets hotter. The only doubt to it being HT circuits is that it runs better on gas and as far as i understand it, lpg will find any weakness in your ht circuits. So how come it runs better on lpg when it gets rough than it does on petrol. Surely if it was an ignition problem it would run worse on lpg as it would magnify the problem.

I am leaning more to the side of vacuum , hose , leak unless more light can be shed on my meagre brain by someone far more informed than i.

Thanks folks

Steve

500bhp · « **Reply #9 on:** February 17, 2006, 18:09:54 »

One of the things the CD says to check is the water Temp sensor for the ecu if its faulty it will get worse as the engine warms up, the ecu thinks the engine is still stone cold. The cd gives the resistance readings it should have as the engine warms up, when you have the engine details I will send them to you as it differs from cat, no cat and lo compression............running on gas is not as sensitive to temp as running on petrol would be, so may be on the right trail....but still give the hoses a good check, try spraying with wd40 that will make a difference if it gets sucked in instead of just air at a leak.

clairedave · « **Reply #10 on:** February 18, 2006, 21:17:47 »

hi went out today for run out to wales with kids ,and all was well till we got to worcester. when engine lost power and started to miss fire, so called rac man who come out,rev up ok but under load no good he did lots of checks and said it was fuel starvation.and said it was airflow meter .last week we had a blow back and did not run too good afterwards, but sorted it self out after run on motorway,so i will watch this with interest.

way2deep · « **Reply #11 on:** February 18, 2006, 23:27:16 »

check the hoses that run from air flow meter to engine ..a mate of mine had his collapse internally that caused power loss now and then ....just a thought

Greybeard · « **Reply #12 on:** February 18, 2006, 23:29:40 »

Update,

currently the engine is in bits, fitting new heads new mains and big ends. Will be trying to get her back on the road for tommorrow. Incidently, last night checked voltage from Ignition amp , ignition off and it gave battery reading, Should have been zero so will be rplacing the ignition amp also. When i came to strip engine, found the breather pipe that comes from the filter on left bank rocker box was blocked solid as was the small bore brass insert in the t piece near the airflow meter. These can not have helped much so will see tommorrow. If nothing else she should run quieter and the previous owner 's didnt know how to change oil by the look of the insides of mine. Disgraceful but a tirbute to the inherent good design that the engine is as good as it is when as full of crap as it was.

Cheers

Steve.

H · « **Reply #13 on:** February 18, 2006, 23:30:54 »

also check the airflow meter isnt earthed as this will give a faulty reading to the ecu.

H

clairedave · « **Reply #14 on:** February 19, 2006, 18:19:42 »

have checked ht coil leads in dark, and lead from coil earthing out to body. so will replace asap and try that, but have to wait for new air flow meter from thrasher,as mine has damaged wire broken, after big blow back when it had ran out of gas. and i forgot then when i tryed to start on cold day in garage,there was the biggest bang ever ,and things in garage jump of shelves.i was just unlucky that day,had runing problems since then

Greybeard · « **Reply #15 on:** March 15, 2006, 14:25:49 »

Well 3 weeks later i finally fired her up. The [!Expletive Deleted!] would fire and almost run, but then stop. I had strobed the timing and set to 4 degrees BTDC.I had petrol and spark, new ignition amp fitted , replaced the plugs which were soaked btw.
Eventually i decided the only thing i hadnt done was move the distributor. Moved it to about 14 degrees BTDC and away she went. 2 minutes later she stopped. Would not restart. Realised after more head scratching the distributor had rotated again as i had not nipped it up. moved it back, away she went.

Anybody know why it wont run set at the correct timing ??? Runs very nicely at 14 degrees.

Steve.

iianorthants · « **Reply #16 on:** March 16, 2006, 13:23:18 »

not sure if ok to plug http://www.v-8.org.uk/forum/ on here, but worth a look. they have a few bits on there about setting TDC as can be out on the RV8. will just take a bit of time to find but some interesting info.

Range Rover Blues · « **Reply #17 on:** March 17, 2006, 01:44:07 »

It's not unheard of for the timing mark to be in the wrong place, particulary if the engine's been stripped. Anyway, one method of measuring TDC is to measure the piston travel to a know deapth at either side of TDC using a probe of some sort down the plug hole. This gives you 2 marks, one either side of TDC and by finding the halfway point, you find TDC.

Greybeard · « **Reply #18 on:** March 24, 2006, 12:58:54 »

WOW dont these things backfire !!!! :shock:
Frightened me to death, totally unexpected and my ear was almost next to the airbox when she spat back. I was deaf for 20 minutes. Anyway , i digress, the darn thing is still not running correctly but the interesting thing is, i dont have a revcounter at below about 800 rpm and the timing needs to be at about 14 degrees btdc. If i disconnect the Temperature thermistor for the ecu i get revcounter and the timing will sit nearer to standard. I am now thinking it is this little jobby as it only starts to misfire when hot. If it was a carburettor i would definately say it was a blocked pilot jet as it is the initial throttle opening that is causing the problem, once past that it runs like a gem. This is only when HOT. I am thinking of a bonfire now so someone please help me, oh and i have checked hoses btw.

Thanks in advance

Steve

Range Rover Blues · « **Reply #19 on:** March 25, 2006, 01:51:41 »

The idle jet (or more correctly the progresion jet) is replecated by a stepper motor on the back of the plenum, the throttle valve shuts completely at idle, which is why the throttle response from idle is not as good on LPG.

Greybeard · « **Reply #20 on:** March 25, 2006, 07:14:59 »

It is the same whether on petrol or gas. The engine does seem to run better on LPG incidently until we get to the problematic misfire. Then it doesnt matter which fuel. The improvement is in smoothness.

Range Rover Blues · « **Reply #21 on:** March 25, 2006, 14:59:05 »

If the problem is there both on petrol and gas then it's not a fuel problem as such.

I'd suggest you concentrate on getting it running on petrol first and ignore the gas conversion for now.

clairedave · « **Reply #22 on:** March 25, 2006, 22:14:39 »

had same problem taken me allday to sort mine out .when you refitted dizzy did you set oil pump lug so when dizzy put in at tdc ,it was set at number one,mine was one touth out and would fire up but not run for very long ,plus back fire on gas as could not turn dizzy too correct timing,now running sweet as a nut ,set at 6 btdc

Greybeard · « **Reply #23 on:** March 25, 2006, 22:20:55 »

Thanks for that i will try it, although it was doing all this before the engine was stripped.

clairedave · « **Reply #24 on:** March 29, 2006, 22:46:19 »

hi there my range keeped jumping one back after setting timing found problem was rockers,when you fit rockers back to engine make sure oil ways are in line,as it is a four mil hole and there is three mill play in bolts so if there not in line .engine will jump back one on dizzy,common error on rebuilds ,my range running fine now, i have found problem , :lol:

Greybeard · « **Reply #25 on:** April 03, 2006, 21:25:13 »

Just in case anyone is interested, i have replaced the ht leads, the fuel temp sensor and the ecu temp thermistor. Thought it was cured then it reached operating temp and went onto 6 1/2 cylinders. It is still driving me nuts. I am now looking at coil perhaps being faulty as i fitted it to my bulkhead out of the way and it is oil filled. Trouble was, it was upside down and i think maybe it got hot. Anybody cast any doubt on this or have any more really good ideas.
Thanks
Steve

Greybeard · « **Reply #26 on:** April 07, 2006, 23:41:38 »

Well i sorted the problem. Replaced dizzycap and rotor arm ( pattern part ) with a Lucas item i had already. Away she went and no cutting out when hot.

One thing that did happen tho was the plastic filler plug in the radiator decided to split in two and i still havent found the top part. Lovely hot shower , infact it was boiling hot, fortunately had just turned her off when it went.

Anybody got a spare one ???

Regards
Steve

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AuthorTopic: Running Like a Dog ... HELP !!!! (Read 4759 times)