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Toyota 4Y Gas performance?

Number of messages: 6

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resteast
Maryland, United States

Hello,

      I have several Toyota 7FGU20 gas trucks with the 4Y engine that I'm having performance problems with;
Symptom,
        While operating at full throttle especially up a grade the engine will start to stumble and sputter and until it stalls,sometimes when you go to restart it sounds like it has no compression at first.
    We have cleaned the fuel system (tank,filter,lines,etc...) we have set the engine speeds and timing according to the manual. we have replaced governors, we have replaced the distributor and this problem still shows up!!! Anybody have any suggestions?

Thanks in advance

-------------------------
Thanks, J.L.

Posted 7 Jun 2007 01:01 AM

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genjohn
NB, Netherlands

I think your intake manifold are full off black slutge end he get now air A nof
That symptom I got to in the Netherlands
End what is mounted more on the engine have you monted A lamba sonde on the exhaust
than the problem can be in the balance line of the converter.

And the carburator what's mounted A ca 55 look fot the spring of piston inside

John.
Netherlands

Posted 8 Jun 2007 01:36 AM

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dave_b
South Australia, Australia

check your inlet manifold first. 4ys have a habit of "coking up" the manifold.Ive seen some to the point where you cant even stick your finger in them. Also valve spring and lifter issues are common also.

Posted 8 Jun 2007 07:51 AM

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Surfing
New South Wales, Australia

Mate,

Check your valve springs, I have come across this quit a bit where they loos there tension. This was a big issue here in Oz when the first 7FG’s came out. We were fitting springs from the 5 series 4Y but I believe that Toyota have over come this issue in the parts department.
The symptom is like you are running out of fuel and the engine will cut out. But will re start and operate fine for 2-5 minutes and then cut out again.
You can change the valve springs with out taking the head off.

Cheers,

The big wave surfer

Posted 8 Jun 2007 09:33 AM

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DaveUK
BERKSHIRE, United Kingdom

Has anybody found a cure for this problem of inlet manifolds clogging up on the 4Y? It seeems to happen on an engine that is starting to get a little bit tired! My theory is that it is oil mist created by piston ring or bore wear coming down the PCV valve and building up on what is the hot spot between the inlet and exhaust manifolds. It is interesting what surfing says about valve springs...........I have not experienced that in the UK, but have had problems with hydraulic tappets sticking if the engine has not been serviced to schedule

-------------------------
Who bravely dares must sometimes risk a fall.

Posted 31 Jul 2007 06:10 PM

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Alabama
Illinois, United States

Make sure fuel mixtures are set, check manifold for build up, dependent on what carb you have on it, make sure there are no loose or defective parts in carb. Adjust valves if needed. I also think that using HD5 propane rather than the all purpose propane will reduce coking, or build up in manifolds. you should have this problem fixed by now, i hope this can be some help for other techs.

Posted 11 Oct 2007 10:31 PM

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