FJ60 problems on LPG/petrol !

Submitted: Monday, Oct 13, 2003 at 19:19
ThreadID: 7793 Views:2427 Replies:2 FollowUps:2
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Howdy all!

Um, just a quick one.
My old Tojo bus ( love the 60!) is not running that well & I'm looking for some advice.
On gas, its backfiring ( comes & goes ) reasonably often & then on petrol it suffers a significant lag ( a few seconds or so ). I had it recently tuned & it seems quite responsive (power wise) & tuned but still suffering the above probs. Its also not idling to well?

Was the tuning a bad job? Mixture too strong? Pump not operating correctly?

Thanks in advance!
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Reply By: Member - Ken - Monday, Oct 13, 2003 at 20:08

Monday, Oct 13, 2003 at 20:08

I have a Datsun Bluebird (the 4 cylinder limosine- don't laugh) that I have had from new since early 1982.

I converted it to LPG in 1986 and have conducted a lot of R & D on it since.

One of the biggest problems that I had was valve recession into the seats.

Why am I telling you this, well this causes rough idling like you wouldn't believe and no amount of 'tuning' will get rid of it.

I know you said you had yours tuned, but did they adjust the valve clearances.

I ended up having a special 'head job' done on it which included stelite exhaust valves and (I think they call them ) Serta seats put in. That Serta is spelt phonetically. It might have been Sertia of Certa, whatever, they are Italian and come in three grades A,B, & C for the most appropriate aplication.

Never had a problem with that again and as a matter of fact it has run on LPG only since 1987 when I had that special head thingy done. I just took off the petrol pump and blanked the port, adjusted the timing for LPG only ( It has a series II electronic igition) and it is still running A-OK at 330,000Km.

Also get this, I replaced the exhaust system in 1986 when the LPG was fitted and that whole, yes the same whole exhaust system is still on it today and it trundles around Melbourne like the geriatric that it is every day.

Power wise, wouldn't pull the skin off a bannana. Who cares, costs me sweet F/A.

And those cootas of the 'flat earth society' (Canberra) intend taking the so called LPG excise concession off in 2008. I think the rust battle will have beaten her by then though.

Speaking from a lot of experience with LPG I would definitely say its something to do with the head.

The other thing is that LPG setups are extremely sensitive to leaking Vacuum hoses and/or Vacuum air into and around whatever throttle body you are using or the inlet manifold.

This can give you rough idling as well and is not as noticeable when switched petrol.

Thats about it, hope it gives you an idea or 2 towards fixing it.


Ken Robinson

AnswerID: 33647

Follow Up By: Rowen - Tuesday, Oct 14, 2003 at 23:47

Tuesday, Oct 14, 2003 at 23:47
Cheers Ken!

I appreciate the time you've put into this response. If u type as slow as me, you wouldve heard the paper boy's squeaky brakes as you finished typing.

I need to better 'process' what youve said & consider it. Anyone else have the same problems out there?


FollowupID: 24317

Follow Up By: Member - Ken - Wednesday, Oct 15, 2003 at 19:31

Wednesday, Oct 15, 2003 at 19:31

I forgot to mention one other thing that I should have and just because I was having a 'senior moment' at the time, didn't.

Another post jogged my foggy memory.

Do you have a EGR (Exhaust Gas Return) valve on your machine. If you do, these cootas can play havoc with the LPG. You really have to blank them off, because all they do is bleep a heap of exhaust gas into the throttle body when it opens and can upset the preset gas mix.

What tends to happen is that the tune up guy either gets it right for when its open (Hot) then everything is good, however when cold or warming up it either won't run, or runs like a dog.

Or vice versa, if he tunes the mix when cool or warming up and that valve hasn't opened then you are in the bleep .

All of the EGR'S I've seen operate on vacuum via heat sensors in the anti polution system. However it depends on what ever system has been installed in your machine

I blanked mine off when the fuel pump was removed.

Another thing you can do is connect a vacuum guage to your manifold and see whats going on.

When I was having the problems the needle was only lifting about a third of the way around at idle and was jumping all over the place. i.e poor vacuum from the valve seating.

Now at idle it goes around to the max and sits steady.

Feel free to use my email site.


Ken Robinson

FollowupID: 24424

Reply By: Rowen - Friday, Oct 17, 2003 at 22:33

Friday, Oct 17, 2003 at 22:33
Ken, your a good man!

thanks heaps for the goss. Much appreciated.

Um, I'm only a 'pleb' w/e mechanic, learning as i 'play' with the old girl.
I'd love to dawdle over the car & work on what u say, but unfortunately that will take weeks & im workn 24/7 with some weekend driving missions comin up. The good thing is that I work @ a school camp near Licola & I have occassional time 2 use the large array of tools & poke around the FJ.

So, Im thinkn, I'll get it looked at again ( with more guidance/ questions from me )
I hoped that Valve clearances are a standard procedure 2 check when tuning?
so, um, obviously your specail valves prevented valve recession eh? Mayb I should consider the same thing. I reckon your on the money tho with gettn the valves checkd out.

whats your opinion on electronic over mechanical ignition? How much would mechanical 'lag' & get outta tune over time? Even the advantage of electronic fuel pump over mechanical?

Yep, the 60's got EGR. When u say blank them off, you just blocked it out right? 2 easy? How much do these emission systems block power out at all ? Its illegal 2 pull these systems off right?

My bus tends 2 start alright & then gets noticeably worse ( backfire & stuttery ) over a long drive.

I was thinking mayb the carby needed a clean? they tend 2 get 'dirty' dont they with the dual fuel configuration.

sorry 2 peg at your brain/ knowledge Ken ( or any1 else ) !

looking forward 2 any more responses!
AnswerID: 34224

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