Stumbles and dies in 3rd (1 Viewer)

[zerbit]

I have a '72 FJ40 with a stock motor. I just recently replaced the fuel pump and filter. The car started dieseling when I'd turn it off, it never did that before. Now, when I get into 3rd gear, it will stumble and stall out. Lower gears and low speed it is fine. I have checked for vac leaks, cleaned the carb, checked wires. It has new plugs, new rotor and cap, it was running fine until the new pump and filter... Help!

Thanks in advance,

Mike L
Sparks, NV

 

[Pighead]

it was running fine until the new pump and filter...

Then I would suspect something wrong with the new pump or filter...certainly sounds like a fuel delivery problem.

 

[65swb45]

1. IF you can rev it out in 1st and 2nd without stumble and stall, it makes a fuel delivery issue less likely.

2. 3rd gear has the most 'lug' on the motor, lowest vacuum on acceleration, where, if something's not right in the carb, more likely to show up.

3. Perhaps shellac in the line dislodged from the jolting and jerking of the fuel lines during pump and filter install. That would explain the timing of the problem coinciding with the parts replacement.

4. Dieseling=fuel, so again, maybe dirt has interefered with keeping fuel 'in check' in the carb at shutdown.

Clean the carb again and report back.

Best

Mark A.

 

[zerbit]

Just a thought I had this morning: I ALWAYS use premium gas due to the age of the truck. My son put a full tank of regular in it on the last fill up... Think it could be ping due to the lower grade gas? I'm going to try some octane booster and see if it clears it up...

 

[rockcrawler]

When replacing any parts on the fuel system always check/re-adjust float afterward.

 

[zerbit]

OK, I have been through the fuel system and the ignition, all seems to check out. Does anybody from Battle Born Cruisers in Reno / Sparks have recommendations on a shop that does good work on stock 6 cylinder Cruisers motors? I'm stumped. Rebuilding my carb would be my next step and I'm not even sure if that is the real problem... Help! Still starts to buck and backfire over 45 mph in third. Runs like a champ until that point. Thanks,

Mike L
Spanish Springs NV

 

[jcj_78FJ40]

Did you check to make sure the filter is in correctly?

You might try swapping back to the old filter, then the old pump to rule out that there are no issues with your new parts.

Good luck.

 

[zerbit]

Filter is facing in direction of arrow. I removed the fuel line to the carb and cranked the motor, plenty of fuel. The Crusier runs like a champ until I hit 3rd gear and about 45 mph, then it starts bucking and wanting to cut out. Push in the clutch and rev and the motor runs fine, back in gear it wants to stall out. Anything over 45 mph is when the problem starts.

 

[Pin_Head]

It sounds like a fuel delivery problem to me. Bucking and spitting back through the carb are classic fuel starvation symptoms. The engine needs the most fuel under high load, like going up a grade in high gear with the pedal to the metal. Either the fuel pump is installed improperly (like using a spacer with a non-spacer pump) or the filter is clogged, or the lines or tank is clogged with junk. Measure how much fuel the pump can put out in 15 seconds of cranking with the coil wire pulled. It should be at least 4 oz or half a cup. If the pump is putting out OK, then maybe the carb inlet is plugged.

 

[zerbit]

The mesh filter in the carb was filled with some real funky fiber and some chunks of clear silicone... I also rebuilt the carb replaced the float and now it runs like a champ!

 

[nspctr1]

I think pinhead is on the right trail. as usual, Maybe you have the wrong pump. there are two kinds , one with a space and one without. Get them mixed up and you have problems.