GQ Patrol 88 on LPG

Submitted: Saturday, Mar 31, 2007 at 01:08
ThreadID: 43830 Views:3887 Replies:3 FollowUps:2
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Hi All

Does anyone have any insight into why my patrol won't idle on petrol. It has a gas conversion that was pre existing but over the last 6 months it has stopped idling on petrol and hesitates before picking up, I have changed the fuel filter to no effect, the guys at the garage reckon the Carby may be warped and need machining. I was wondering if anyone has experienced this problem and might be able to give me a bit more insight.

Cheers
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Reply By: Member - 'Lucy' - Saturday, Mar 31, 2007 at 13:38

Saturday, Mar 31, 2007 at 13:38
Well Godlike, the Archangel Gabriel is here to help (LOL)

Mate I have a 1981 Datsun(Nissan) bluebird which I purchased new and converted to LPG in 1986.

Have done all sorts of R & D projects on it re the LPG, and since around 1988 it has been 100% LPG. Why - because of too much playing around to make it work equally as well on both fuels.

Don't despair at my solution because you obviously need dual fuel where I didn't.

In the earlier days of LPG dual fuel (1980's) the engines were produced with valves and seats designed for petrol only.

As an alternate fuel LPG has a few nasty qualities in that it burns hotter, has no lubricate in it and requires a colder spark plug set at a higher gap.

When all this is combined with a petrol set up something has to 'give' and after the initial tune to get both fuels to run at their best, the usual ( repeat usual) practice in the 1980's was to start on petrol and run on LPG (as it was cheaper) and switch to petrol before shutting down for the day. Plus maybe pump a tank of petrol through the engine whenever for lube purposes.

Also a 'lean' mix on the LPG to air ration can exacerbate the valve degradation.

ACCUMULATIVE AFFECT:

(1) In a nutshell the valve faces, valve seats and valve stem guides used to deteriorate much quicker leading to valve recession and then burnt out valves or seats (Exhaust).

The valve recession gives the symptoms that you describe both on petrol and LPG.

(2) I take it your set-up has a 'mixer ring' on top of the Carburettor. Over time where the user/s have elected to use LPG as the fuel of choice then the engine heat and 'dry fuel' absolutely wreck all of the Carby seals and make the Carby do strange things.

You won't notice it on LPG as it goes straight through, however on petrol it can be a real bitch.

CONCLUSION:

These are the two main sources of problems with this this type of setup and the first thing I would be doing is to check the valve clearances (Costs nothing)

Then make sure the carby is work correctly - See if it is filling up with petrol, pumping/squirting when the accelerator is activated.

Also check if it is a dual barrel carby (bet it is) and if so there are two jets underneath that people inevitable put back in back to front when they turn the carby upside down to work on it. (Has happened to Moi)

Air/vacuum leakages, will affect the smooth running of the LPG way before it shows on the petrol side of things. So I wouldn't be considering the warped carby just yet,

Hopefully this will give you something to look at.
AnswerID: 230851

Follow Up By: Godlike Chef - Saturday, Mar 31, 2007 at 20:10

Saturday, Mar 31, 2007 at 20:10
Thanks Archangel for the insight hopefully with some playing around I can get the problem fixed.
It's all a bit of a learning curve at the moment (but thats half the fun) fingers crossed I can fix it.
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FollowupID: 491757

Follow Up By: Member - 'Lucy' - Sunday, Apr 01, 2007 at 00:35

Sunday, Apr 01, 2007 at 00:35
Good luck.

Remember.

(1) Valve clearances

(2) Carby

(3) Vaccuum (sucking air)

(4) Spark plugs and settings
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FollowupID: 491793

Reply By: Dallas from Team Green Autogas - Monday, Apr 09, 2007 at 12:51

Monday, Apr 09, 2007 at 12:51
Hey Chef,
I wouldn't take much notice of the guys at your garage if i were you. They've suggested to machine the carby base to get rid of any vacuum leaks BUT the fact that it runs on lpg suggests that it's not vacuum leaks you're chasing as lpg is really sensitive to vacuum leaks & would give you grief before petrol in those circumstances.
Your flat spot just above idle could be as a result of hardening diaphragms in the lpg converter (not responding as quickly & accurately as it should)(not relevent to petrol problem).
By the same token the flat spot could be from retarded ignition timing too. Either way it sounds like a petrol supply problem. It'd be good to know if it'll continue to run if changed over @ revs. This would at least tell you whether you have petrol getting to the carby itself. (showing fuel pump operational????). If the problem is only @ idle then maybe it's as simple as good old needle & seat sticking open. All the best mate, keep us informed.
AnswerID: 232374

Reply By: Brew69(SA) - Monday, Apr 09, 2007 at 16:14

Monday, Apr 09, 2007 at 16:14
Overhaul the carby mate.
Mine runs a lot better on gas but thats because it's tuned on gas.
Another tip...........have you changed over to electronic ignition???
AnswerID: 232395

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