Hydraulic lock in petrol FJ75 TRoopy
Submitted: Saturday, Nov 25, 2006 at 18:07
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Member - John and Val W (ACT)
Anyone met this one?
Dual
tank petrol Troopy parked nose down on a slope. Petrol, presumably vented from the tank/s into the carburetter as liquid rather than gas, overflows carby through inlet manifold into no 1 cylinder (the lowest). (The tanks are vented through the carby as an antipolution measure?) Try to start the engine - big bang, no 1 con rod shaped like banana, lots of $$$$. That happened to me a few years ago. Couldn't find anything wrong or anyone who'd ever had this sort of problem, Toyota was no help. No problems since, until today.
Now to the present
After a couple of hot days parked nose up
hill this time. Try to start - obvious hydraulic lock. Open both petrol tanks - lots of pressure in them. Remove all spark plugs and disable ignition. Hit starter - spit out lots of petrol from no 6 cylinder (now the lowest) through plug hole. Put it all back together and drive away. After 10km open petrol tanks and find a lot of pressure in both.
Somehow I've got to stop this happening again - last time cost about half the cost of a replacement engine. (Lucky the crankshaft survived or it would have been twice as bad!)
Any one experienced this? Any (constructive!) suggestions would be most welcome.
TIA
John
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Reply By: 666toy - Saturday, Nov 25, 2006 at 19:02
Saturday, Nov 25, 2006 at 19:02
Well i have not come up against this problem but for fuel to get into the manifold in the first place it must get past the needle &
seat it is the only way it can get into the manifold unless you have a fracture in the carb itself & then it would be a problem all the time . extremely unlikely too. do you run a standard Toyota 2brl carb or a holley 2 brl carb ?? as for pressure in the tanks that is fairly normal in most Toyota petrol's . my own Sahara get pressure however you should not have extreme pressure unlikely to be the problem . you mention it has happened on upward & downward slopes ? check the float levels & the floats themselves .i am nearly sure your problem is within the carb either needle &
seat or float levels or (depending what carb you have) pinholes in the float itself . if you have any probs post your email & i will send you a tear down of the Toyota carb if you want to try tackle it yourself. also you can eliminate fuel
tank pressure by drilling a 1/8 drill hole in the fuel cap to allow it to vent naturally. please let me know how you get on ...666toy
AnswerID:
206869
Follow Up By: Member - John and Val W (ACT) - Saturday, Nov 25, 2006 at 20:58
Saturday, Nov 25, 2006 at 20:58
Thank you for your thoughts.
If the float valve wasn't closing properly and there was pressure in the tanks, it could account for liquid fuel reaching the cylinders. (If it could force it's way through the mechanical pump, which it probably can.)
The two tanks actually vent through a carbon filter into the base of the carby below the ventury. I'd been thinking of this as the probable source of fuel, but a sticky float valve is certainly an obvious option, and one which can be monitored easily since the float chamber has a window in it. I can also disconnect the vent line, block off its carby port and vent to atmosphere, which will prevent it getting involved.
Carby is the standard Toyota one. Think I'll have a look inside the float chamber and free up the float and valve. Thank you for
clearing my mental block!
John
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Reply By: 666toy - Saturday, Nov 25, 2006 at 21:08
Saturday, Nov 25, 2006 at 21:08
no worries but i still would vent the fuel
tank cap this ensures proper venting but only if you think fuel
tank pressure is really excessive...hope i helped out...666toy
AnswerID:
206884
Follow Up By: 666toy - Saturday, Nov 25, 2006 at 21:17
Saturday, Nov 25, 2006 at 21:17
sorry ment to say aswell fuel can run through the fuel pump without any probs but it has a one way valve in so it cannot return...666toy
FollowupID:
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Reply By: ross - Saturday, Nov 25, 2006 at 21:56
Saturday, Nov 25, 2006 at 21:56
Are these factory dual tanks?
On the subject of venting,the tanks vent off a charcoal canister before the fuel pump.
The charcoal canister then lets excess pressure out via a hose inside the front RH chassis rail.
The carburettor vents off it own canister on the LH side of the engine bay.
There is also metal tube thats on the side of the filler tube that should help equalise pressure.
Ive had a petrol landcruiser and cannot remember ever getting pressure in the fuel
tank.
The valves on the charcoal canister could be blocked. The test is to blow air through them to see if the valve opens .
AnswerID:
206891
Follow Up By: Member - John and Val W (ACT) - Saturday, Nov 25, 2006 at 22:28
Saturday, Nov 25, 2006 at 22:28
Yes - original factory fitted tanks. Seems there are several configurations for the charcoal filters - one description I've seen says they are used to capture fuel vapour from the tank/s and then release it to the carby when the engine is running. I was actually offered a second hand filter once which simply discharged into a chassis channel as you describe.
Mine vents into the base of the carby which led me to see it as a possible source of liquid fuel. I also have the filter you refer to on the LHS of the engine bay - I understand this one vents the float chamber.
Interesting that you've never experienced pressure in your tanks. From what I've heard, it's quite common. In my case air/vapour will sometimes pour out for several seconds when the filler cap is removed.
Thank you for your thoughts. I've now got lots of things to follow up!
John
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Reply By: Kiwi Ray - Sunday, Nov 26, 2006 at 08:29
Sunday, Nov 26, 2006 at 08:29
hi John
Have you fitted after market fuel
tank caps, they may not have the correct valves in them, common problem on earlier cars.
if not , check the vales in the caps you are using
You will get a pressure increase in fuuel tanks but it should not be high enough to unseat the needle vales
AnswerID:
206921
Follow Up By: Member - John and Val W (ACT) - Sunday, Nov 26, 2006 at 10:48
Sunday, Nov 26, 2006 at 10:48
Hi Ray,
I think the caps have been replaced at some stage, but with the introduction of antipollution gear I don't know that they are permited to vent to atmospere the way they used to in the "good old days". Pretty sure my caps are not suppoosed to pass anything when closed, regardless of pressure.
From suggestions made here, I'm inclined to think I simply have a sticky valve in the float chamber which is not closing properly, allowing fuel through from the tanks when they heat up and become pressurised. I wouldn't expect
tank pressure to unseat the valve - it's not that high!
Another symptom I haven't mentioned is that in the last few hot days the engine tends to run on after the ignition is turned off. I'd put it down to heat ( and of course the inbred willingness of troopys to work!), but excess fuel in the float chamber might
well be involved here too, again pointing to a dicky float valve. Today I've noted carefully the fuel level in the float chamber and left the Troopy in the sun to pressurise the tanks - if the level rises in the float chamber - got it!
Thank you for you input.
John
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Reply By: Max - Sydney - Monday, Nov 27, 2006 at 09:29
Monday, Nov 27, 2006 at 09:29
John
You may be describing a worn carby. After thousands of kms of service, the float needle, jets etc all wear, and gaskets get soft and collapse, and deposits gum things up. You might need to try and find someone who is expert at overhauling carbys - probably a rare commodity these days. In the meantime, a dose of carburettor cleaner might help out, plus the obvious of having a look at the float and the needle valve as mentioned above.
But - it takes an expert - an enthusiastic trier can immobilise a car, believe me!
Max
AnswerID:
207066
Reply By: Member - John and Val W (ACT) - Monday, Nov 27, 2006 at 11:38
Monday, Nov 27, 2006 at 11:38
Final Wrap-up
First, thank you all for your valued comments. Very much appreciated and right on the ball.
Yesterday, I parked Troopy in the sun and released any pressure in the fuel tanks by removing and then replacing the filler caps. Noted the level of fuel in the float chamber. Two hours later the fuel in the float chamber had risen out of sight. It seems pretty definite that pressure in the heated tanks forced fuel through the pump up to the carby where the float valve failed to stop it getting into the carby.
Two factors need attention - the sticky float valve and the excess pressure.
Tomorrow Troopy spends the day with a competent carby specialist. (Yes Max, I've been inside the carby before and agree it's an easy way to convert a sick vehicle into a dead one!) He also pointed out the obvious - excessive pressure buildup in the tanks MUST come from a blockage in the venting system, usually a u/s carbon canister.
I'll spend a few dollars buying expertise, but probably cheaper than buying fuel to pour into the engine to create a really serious problem.
Again, thank you everyone. I'll report any interesting unexpected issues, but I think we've already covered everything.
John
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