Engine troubles.

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usmcruiser

usmcruiser

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Oct 6, 2004
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Longmont, CO
Okay I'm no master mechanic and I have a ton more to learn about Cruisers so please bear with me here.

I have a '76 FJ55 with 2F that is having some engine issues. The engine idles just fine and runs well at low RPMs. But when I get into 3rd and 4th gears driving down the road, the engine will start to stumble and eventually backfire. While it is stumbling it's like the engine isn't even running. Almost as if I let off the gas so that it is coasting and engine braking, but it isn’t firing. If I push in the clutch and give it some gas the engine will rev back to life like nothing happened. But the second I let the clutch out to maintain speed it will stumble and backfire again. Because of this I cannot get above 45-50 MPH.

The odd thing I have noticed about this is it only happens when it is warmer than say 60 degrees out. At 4:30 in the stinking morning when it is cool out I have no issues with the engine. It runs fine. And I didn't have any problems all winter. It just started doing it this last month when it started warming up.

Its seemed that as this past month has gone on and the days get warmer it starts doing this at a lower and lower RPM.

So I was wondering what could be causing this stumble then backfire? Do the valves need adjusting? Or could it be my dizzy? What could the problem be? This is my DD so could really use some info ASAP!

Thanks guys,
 
Have you upgraded to electronic ignition?

Does it still have points and condensor?

Your timing could be off because the vacum advance is not working. It will advance the timing depending on the load or RPM of the engine.

Just a thought. I asuming that you already replaced the fuel filter and made sure you did not have a pinched line causing a flow issue.
 
Maybe check your ignition coil? Mine went bad awhile back, it first started as some random stalling. Now that you mention it, it got worse as the weather warmed up... It's worth a shot anyway...
 
Maybe your fuel filter is clogged? (or fuel pump failing?) Maybe starving at high fuel demand...? Try re-creating the stumble in your driveway with the hood up and watch the little porthole window in the float bowl.
 
Since it varies with the temperature, I would assume that it is fuel related. The first thing that I would do it change the fuel filter. If that's not it work your way up to the carb from there. Vapor lock is possible but it generally happens after the vehicle is shut off and sitting still getting hot.
 
Awsome I will try all these things when I get off work. I am hoping it is simply a fuel supply demand. I did have the tank boiled but not lined so it may be clogging the fuel filter and restricting it when it needs some extra fuel.

But why would it only affect it in the afternoons when it is warmer?

This temp thing is what is killing me.
 
surfpig said:
Maybe check your ignition coil? Mine went bad awhile back, it first started as some random stalling. Now that you mention it, it got worse as the weather warmed up... It's worth a shot anyway...
Click to expand...

How do you go about checking to see if you have a bad ignition coil?
 
what type of carb?

I had an issue with the choke closing up when it throdels up ...a floppy choke lol

it wasn't attached corectly...my bad when i did a rebuild.

just to throw out a blanently obviouse...the air cleaner isn't cloged right?

sorry about my spelling...not a good day for typing :)
 
The FSM has the procedure and readings for checking the coil. Might be here in FAQ too. Or I can read to you from my engine manual. Requires an ohmeter. I just throw on another one 'cause I've got spares...


usmcruiser said:
How do you go about checking to see if you have a bad ignition coil?
Click to expand...
 
JohnnyC said:
what type of carb?

I had an issue with the choke closing up when it throdels up ...a floppy choke lol

it wasn't attached corectly...my bad when i did a rebuild.

just to throw out a blanently obviouse...the air cleaner isn't cloged right?

sorry about my spelling...not a good day for typing :)
Click to expand...

I seriously doubt it is the carb. I had Jim C rebuild it about 6 months ago.
 
Nick - sounds like you have plenty of things to check... but, one other thing would be the accelerator pump. Make sure you are getting a squirt in the primary when you give it the gas (engine off or you may get a BIG surprise... like backfire thru the carb).

Try going full throttle on the way home and see if it smooths out (the secondary should provide sufficient fuel) when the carb is wide open. If the stuttering stops, then you definitely want to check the AP.

EDIT: Just noticed that the carb was recently rebuilt. Nevermind.
 
Crazy thought...check your air filter too. (though I can't imagine such a big aircleaner getting clogged)
 
Right. Increasing fuel demand does not help a fuel starvation problem...

usmcruiser said:
I have tried flooring it on the way home hoping to power through the stumble but it just makes it worse.
Click to expand...
 
99% of the time with symptoms like yours it is a fuel delivery insufficiency. Confirm by putting the tranny in N and shuttingoff the engine when it starts stubmling, coast to a stop and check the fuel level in the carb window. If there is no fuel in the bowl, check the usual suspects.
 
Well as of what you guys have said so far, I am currently searching the crappy parts stores (i.e Napa, Checker, Autozone) to see if they have an air cleaner, and a coil. I figure they are cheap enough I will just replace both weither they need to be replaced or not.
 
Pin_Head said:
99% of the time with symptoms like yours it is a fuel delivery insufficiency. Confirm by putting the tranny in N and shuttingoff the engine when it starts stubmling, coast to a stop and check the fuel level in the carb window. If there is no fuel in the bowl, check the usual suspects.
Click to expand...

Very nice I will try this on the way home.
 
these symptoms sound like fuel starvation to me as well.

there is sometimes a filter under the banjo bolt on the carb, check that out. dont rule out the idle selenoid either, typically not what your describing but it does control a fuel circuit. fuel pump could be on its way out and can be heat related. make sure your gas tank is venting, remove the cap for your commute tommorow and see what happens.

next step, coil and/or resistor could be bad, they can most definietly be heat affected.

what emmisions do you have installed?
 
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