3f major running & driving issues.

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Junior62
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3f major running & driving issues.

Unread post by Junior62 » December 28th, 2014, 6:29 pm

Hey guys
Having some issues with my Toyota FJ62 3f carby fed motor. It sputters & struggles to get around I've tried every style of driving from heavy hard footed to slower & steadier then your nan, & there's no change. I recently deleted the LPG system & went full time petrol on it, & installed dual tanks. I install a solenoid switch to switch from main to aux tanks, I also split the return line between the tanks. I also had it tuned to suit the petrol.
I took it for a 4wheel the other day & struggled to drive up an obstacle I've driven before when I had the LPG. The car would sputter & die in 2low driving uphill off the main tank (standard tank) I changesd down to 1low & drove a little further before it really struggled to even turn the engine over. I then stopped & changed to the full auxiliary tank letting it run for about 2mins, then had the same issues again.
Today I checked the spark plugs all the gaps were good but the plugs were quite black (running rich) I carby cleaned the carby & did a general once over the engine. Took it for a drive still having the same issues. It also backfires from the idle circuit to driving almost everytime.
Has anyone ever had these issues or could help me problem solve mine.
Cheers
Thomas

typhoeus
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Re: 3f major running & driving issues.

Unread post by typhoeus » December 28th, 2014, 7:43 pm

does the carb have a pumper circuit? if that jet is blocked, the carb will kind of stutter when it goes from idle to acceleration. It certainly sounds like a carb problem. When you got it tuned, did they check out the vacuum advance in the distributor?

Jimmy Wood
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Re: 3f major running & driving issues.

Unread post by Jimmy Wood » December 28th, 2014, 10:06 pm

X2 on the carb

Did it run well once you got it tuned?
Did the problem suddenly come on or was it as soon as you removed the gas system? Maybe some crap has been sucked into the system and has blocked the jets in the carby. Do you have a filter?

Is it better if you change tanks, I mean, does it momentarily get better? It kind of sounded like it did by your last post.

Maybe describe the symptons and the onset in lots of detail.

Also, check the timing and vac advance as typhoeus said. The factory timing mark will be pretty meaningless with lower octane fuel these days.

80Butts
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Re: 3f major running & driving issues.

Unread post by 80Butts » December 30th, 2014, 9:11 pm

Rebuild the carby. If its backfiring off idle its sucking air from where it isnt meant to suck air. If youve been running gas, fair chance its all a bit dry. At the least change the base gasket between the carb and manifold and check all the vacuum hoses. Guarantee thats where your dramas lie.
bit of love and she'll run sweet and fight another day

Boof mk triton
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Re: 3f major running & driving issues.

Unread post by Boof mk triton » January 10th, 2015, 6:02 pm

Carb i reckon is on the money as well. I am going to go out on a limb and say your accelarator pump isnt operating as it should hence you get no change or difference whether grandma or race car driving it - it may be dry like the others said meaning instead of pumping the fuel into the carb its just running back through the seals. Maybe look out for a 350 holley and modify the floats to suit climbing and fourbying - much easier to get bits for and dirt cheap too. Good luck.
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Jimmy Wood
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Re: 3f major running & driving issues.

Unread post by Jimmy Wood » January 10th, 2015, 6:26 pm

I wouldn't go for a holley over the finely engineered Aisin carby. They are good if serviced. Holley will probably starve on slopes and use a lot more fuel. Prolly easier to tune but.

Boof mk triton
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Re: 3f major running & driving issues.

Unread post by Boof mk triton » January 12th, 2015, 8:39 am

Plenty of bits to mod your holley for fourbying these days. Definitely easier to tune, more readily available. Both have a case o be a good thing.
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Junior62
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Re: 3f major running & driving issues.

Unread post by Junior62 » January 20th, 2015, 7:24 pm

hi guys!
sorry about the late reply had a busy chrissy & new years!

I managed to get the car to my mechanic last Friday, he started at the carby as I stated the backfiring issue & hard/long starting, & found no issues he's stated.
But has the looked to the dizzy (points dizzy, convert to pertronix electronic ignition) & found that turning it clockwise & letting it spring back on the advance was normal, but also found it could be clicked backwards & get stuck retarded, he said that the governer shaft is damage & not retaining the rotor properly anymore & possibly that there may be a tooth broken off on the cam gear of the dizzy.
So were going to start by replacing that, & retiming the engine. if I continue to have issues were going to start looking at the carby more in depth.
Cheers
Thomas

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Re: 3f major running & driving issues.

Unread post by mydmax » January 21st, 2015, 7:38 am

The idea there is a tooth off the drive gear is rubbish.
There is no "governor" shaft in a distributor.

The mechanicals of a distributor has to be in good working order for it to meter sparks out at regular intervals.
It either IS ok or it isn't.

A stuck retarded distibutor cam/ trigger (now with electronic) will make the vehicle sluggish as it will be retarded.

A retarded engine forced to/made to run while retarded WILL most likely then burn an exhaust valve.
Next check is a compression test to see how many ex valves are stuffed. Then it will run properly.
They burn because much f the heat value of the fuel isn't used as heat in the cylinder and it is still burning as it leaves the cylinder and grossly overheats the exhaust valves. A half decent mechanic will know that immediately you start speaking.
Of course first check the valve clearances as gas running as well as petrol running will cause the valve seats to wear and decrease the valve clearances on ALL valves.

Jimmy Wood
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Re: 3f major running & driving issues.

Unread post by Jimmy Wood » January 21st, 2015, 9:58 am

Did the problem come on straight after you removed the LPG? Did it run well at all after you got it tuned?

The fact that it appeared to run ok when you switched tanks, (what I think your first post says), makes me think its the carby, as the dizzy would not be effected by that.

If you put a timing light on the engine, you would pretty quickly see any issue with the dizzy or timing. Just retime it and see if all good. Should take a mechanic 2 mins to retime the motor. Rev it up a bit and see if the timing goes all wonky or it just advances like it should as it revs up. Id look at that before buying a new dizzy. It could be the issue, but Id put my money on the carby. They should have timed it when they tuned it for petrol anyway, so it should be spot on, unless they didn't tighten it up and the dizzy has moved a bit. That can happen. Good idea to check the timing every service anyway.

Either way, just pull the dizzy and see if the drive gear is ok, its a 2 min job to pull it I think, just loosen the holding bolt and pull it out (but mark it so you can get it back in with the same timing). I think it there was a tooth missing, it would not run at all, as the timing would get a tooth out each revolution and would end up being 180 degrees out of time very quickly.

You shouldn't have to get a new dizzy to diagnose any of the faults your mechanic has mentioned.

As for the governor, I think that you may be mistaken Mydmax, the 2F and 3F diszzys do have a centrifugal governor. I remember reading it once in a factory service manual. It may be what they call the advance weights, but being a low revving engine, it would make sense to have the governor there.

Junior62
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Re: 3f major running & driving issues.

Unread post by Junior62 » February 25th, 2015, 7:17 pm

Hey All
finally got the car back to my mechanics, we replaced the distributor & timed it right & to suit 98octane fuel. Makes a massive difference, no more struggling off idle, starts first time every time, idles easily, fuel economy has improved greatly. it really was a distributor issue, we narrowed it down to either broken vacuum advance unit or buggered shaft, shaft had enough play to warrant replacement I think.
but on a side note, we noticed a bit of a stutter under heavy acceleration, we tired tuning it out of the carby but couldn't, we then removed carby hat form carby, test drove it & the stutter is gone, put hat back on & remove snorkel & it returns, there are no blockages in the air intake line, & the air filter is only 2500km old & still quite clean, any ideas??

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Re: 3f major running & driving issues.

Unread post by mydmax » February 25th, 2015, 7:45 pm

On many engines there is a sonic wave of air, unseen but there anyway. because of the nature of the induction, the intake flow can be experiencing a return wave which bounces off the internals of the intake manifold system especially where there is a restriction, ie, carby venturi narrowwng.
That means at certain speeds there is actually LESS air available for the intake at some frequencies of that airflow.

Fitting a BOOST botle as seen on earlier 2 stroke engine can help withabsrorbing the wave and allowing a realatively constant flow according to engine requirements instead of a deficiency at some rev range.

I would imaging a blanked off T form or Y form of 70mm to 90mm dia (approx piping) ie, plumbers fitting, could be fitted to the intake before the carby but after the airbox and it may assist with eliminating the dead spot.
Bottom of Y to face engine.

4 litre, 4 cylinder, Isuzu engines suffered a similar situation around 80kmh in top gear and went sluggish until the speed crept past the point where the wave and became non cancelling as is normal. While it nearly cancelled the intake flow it was a dead feeling flat spot.

All probably caused by the alteration of fitting a snorkel as it's length will have altered the "tuned' length of the intake system.

All engines especially 2 stroke rely on beneficial intake and exhaust wave forms for power and speed ability.

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