Power Problems - part 2

Mike G.

Guest
Well - another weekend spent working on the cruiser with no positive results gained (other than learning a :-X load about about cruiser mechanical systems and diagonostics). My problem of power surging under load conditions continues. I think I am finally gaining a handle on the problem - but haven't cured it yet.

Distributor can be ruled out. Completely disassembled, checked for wear, lubed baseplate, mechanical adv. and vac. adv. checked out good. Dwell rock steady at 40, timing is steady on the mark @ 650rpm.

Fuel delivery is good. New fuel filter, clear screen at carb inlet, float level perfect in the sight glass. Haven't checked fuel pressure, but new Napa elec. fuel pump is running strong.

Continued looking for vacum leaks, but havn't found any. Haven't hooked up a vacum gauge yet - that's next on my 'to do' list.

Pulled the plugs and replaced them. Noticed the plugs were burning lean except for #2. Advanced the timing, retard the timing, timing right on the mark - makes no difference in the misfiring. Tail pipe is showing a lean burn. Fuel economy sucks.

I am thinking the problem is in the carburator. The engine idles perfectly smooth at 650rpm. No problems with mis-fire untill about 2000 rpm under load. Then there is a huge dead zone and all hell breaks loose. I have found to ways to avoid the misfire - either stomp on the gas and power through the dead zone (secondary is kicking in) or pull out the choke.
I messed with the idle mixture screw (richer, leaner, back to original setting) - no cure. The carb was rebuilt by Jim C., so I am having a hard time believing the carb is the problem. But - the carb was a huge basket case before being rebuilt - so maybe it is time to retire it??? Hate to waste money on a new carb if that is not the problem.

Any more suggestions - what should I do next??????

mike g
tlca #134456
 
P

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Oh! Oh! If I read you, your engine is misfiring over 2,000 rpm except when flooring gaz pedal, right?

Theoritically, only distributor's centrifugal advance components are effective when flooring gaz pedal. When you are cruising, distributor's vacuum components are also effective for fuel efficiency issue. Stucked mechanism or diaphragm leak may cause problem.

Did you check cylinder compression? #2 is OK?
 
Pin_Head

Pin_Head

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If it goes away when you give it the choke, it is a carb problem: Running too lean.

Here is a link about troubleshooting running problems that may help:

http://www.recarbco.com/technical/newtrouble.html

The possibilities are:
Primary jet too small (not likely if it the original one)
Power valve (aka Economizer jet) stuck closed (not terribly likely)
Primary fuel passage partially obstructed (not likely in a Jim C. rebuild)
Accleator pump not working (not likely for same reason)
Vaccum leak above the throttle plate. The reason it is above the throttle plate is that it idles fine. (For FJ40s this would likely be the EGR valve. FJ60 EGR lines enter at the manifold.)

If it was me, I would check the EGR valve (if it is a 40) by plugging the large hose and if that doesn't do it, call Jim C. and see what he thinks.
 

Mike G.

Guest
Thanks for the replies and information. I think I am getting closer to the source of the problem.

I just hooked up a vacuum gauge and it dosn't look good....... The needle was dancing back and forth between 17 and 9 at 650rpm. Increased idle to 2000 and the needle sweep became shorter amd more rapid.
I sprayed carb cleaner all around the base of the carb, top and bottom of the intake manifold, pluged the pvc port on the carb insulator. No difference in the reading. Are there any other ways to check the intake manifold for leaks?

I guess a valve adjustment is next on the list. That or it's back to a faulty distributor. Any other suggestions???
 
Pin_Head

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[quote author=mike g. link=board=1;threadid=10309;start=msg92586#msg92586 date=1074578674]
Any other suggestions???
[/quote]

Yes. The dancing needle is often a sign of a dead cylinder. Check the compression. It may be a bad valve, rings or head gasket. Remove one spark plug wire at at time and see if the RPM drops. If you pull a wire and nothing happens, the cylinder isn't firing.
 
Tooth Fairy

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Mike G. said, "I sprayed carb cleaner all around the base of the carb, top and bottom of the intake manifold, pluged the pvc port on the carb insulator. No difference in the reading. Are there any other ways to check the intake manifold for leaks?"

If you still wanna look for vacuum leaks use starting fluid not carb cleaner, you won't get the same results. and spray it all around the entire engine compartment , basically anywhere there is a vacuum line. Just a little at a time though and even in places like by the brake booster and on the pas. side of the motor. Spray wait and listen... etc. Any increase in rpm could, repeat could, be a leak but it might also just be drifting in through an open element filter. Definitely do the comp. check too. Intake leaks are usually a lot cheaper to fix :).
 

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