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Ran out of gas, bogs/dies down at high speeds


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#1 ianmc54

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Posted 13 June 2017 - 08:34 PM

I just bought my first Datsun about 2 months ago. It was running great until I ran it out of gas and it sucked up crap from the fuel tank. 
 
So now it bogs down and hesitates with a quick throttle blip and dies at high rpms usually over 25mph. It idles fine. 
 
I have L16, weber 32/36, matchbox dizzy
 
I've replaced two fuel filters, replaced the fuel pump, replaced the spark plugs, taken apart the carb and cleaned all the jets and the fuel screen in the front of the Weber. 
 
Where should I look next? I am by no means a mechanic but totally willing to learn, this is my first time with a carburated car and I don't know where to look next. Check fuel pressure? Look further into the Carb? Please help I want to drive this thing.

 

Also my first post and getting frustrated because I can't figure out how to directly post pictures from my computer. 



#2 Crashtd420

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Posted 14 June 2017 - 06:38 AM

From what I am reading the only place you haven't looked is the gas tank....
Maybe something got stuck in the pickup tube.....
A fuel pressure gauge won't hurt...
Maybe try a little compressed air into the pickup tube and see if it clears anything....
Another trick is rig a seperate gravity gas feed to the carb....
Start the engine with the fuel pump output going to a separate container and see if your fuel pump gas a good consistent flow....
Can you access your fuel cell for a look?
What the vehicle model?
My 521 gas tank had a drain, maybe the tanks needs to be flushed? Had the vehicle been sitting for a while before you bought it?...
And no idea on posting picks on the computer... I use my phone but there should be some writes on posting pics here...

#3 Draker

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Posted 14 June 2017 - 07:42 AM

Did you pull the last chance filter on the carb it self?


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#4 ianmc54

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Posted 14 June 2017 - 08:46 AM

1970 Datsun 510

Also when these symptoms occur, there is occasional backfire and soot buildup in the exhaust.

Crash-kinda what I was thinking thanks for the gravity fed idea. Can a fuel sender get clogged?

Draker-I only pulled the fuel screen where the fuel comes in to the carb in the front. Can't seem to find where this "last chance filter" is on the 32/36.

#5 ]2eDeYe

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Posted 14 June 2017 - 08:54 AM

Disconnect the fuel line before the filter and pump. Blast some compressed air through the line to the tank, this should dislodge any debris clogging the tank.
If it runs good  your tank needs to be cleaned out. Sooner rather than later. 


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Whenever I think that I'm out of my mind for putting this much time and money into an old Datsun, all I have to do is look some of your threads to know that I'm not nearly as whack as you are.

You're going to skin a few knuckles, stand up too fast and bump your head, hunt around the floor for the nuts and bolts you dropped, invent a few new cuss words and when you're finished you'll say "That wasn't so hard after all!"


#6 Draker

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Posted 14 June 2017 - 09:06 AM

Draker-I only pulled the fuel screen where the fuel comes in to the carb in the front. Can't seem to find where this "last chance filter" is on the 32/36.

 

 

Sounds like you found it. On the inlet of the carb, unthread the fitting, there is a round metal fuel screen. Also known as the last chance filter. It's the last chance for debris to be caught before it ruins your day.


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#7 racerx

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Posted 14 June 2017 - 10:24 AM

Take out gas tank and do a looksee

#8 ianmc54

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Posted 14 June 2017 - 11:52 AM

Ok sounds like I gotta check everything from the fuel filter back. I'm sure the tank still has debris in it based on how bad my fuel filter got and knowing it was a garaged for the majority of its life.
Wouldn't I see more crap in my new filter if the problem was behind the filter? The filter has run clear now for 2 weeks on all my test drives after refueling.

#9 datzenmike

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Posted 14 June 2017 - 11:53 AM

I just bought my first Datsun about 2 months ago. It was running great until I ran it out of gas and it sucked up crap from the fuel tank. 
 
So now it bogs down and hesitates with a quick throttle blip and dies at high rpms usually over 25mph. It idles fine. 
 
I have L16, weber 32/36, matchbox dizzy
 
I've replaced two fuel filters, replaced the fuel pump, replaced the spark plugs, taken apart the carb and cleaned all the jets and the fuel screen in the front of the Weber. 
 
Where should I look next? I am by no means a mechanic but totally willing to learn, this is my first time with a carburated car and I don't know where to look next. Check fuel pressure? Look further into the Carb? Please help I want to drive this thing.

 

Also my first post and getting frustrated because I can't figure out how to directly post pictures from my computer. 

 

The fuel bowl should be full to at least half way so a part clogged line or filter won't affect a quick blip of the throttle. It won't affect idle or low speed, low demand driving. What a restriction like a clog will do is limit how fast the gas gan get into the carb to keep it filled. When the demand is higher than the supply rate the engine simply 'runs out of gas' and will behave like it. Usually bogging and bucking but when you pull over it naturally idles and drive just fine. 

 

The fuel pick up tube does not actually empty the tank but is about 1/2" short of the bottom.  Anything in the tank has a chance of being picked up at any time. This is what the fuel filter is for, to catch it and be replaced. Unlikely water, as todays gas is 10% ethanol and it readily binds with gas and water and can't build up in the tank. If water (unlikely today with 10% ethanol blends) it will pass through the filters.

 

 

If the fuel filter was changed after the problem started, it is likely that some obstruction is already in one of the jets.

 

 

 

Two months of ownership isn't a long enough base line to say for sure this was caused by running out of gas. This may be something else that crops up every now and then. Maybe the points are bad, maybe the spark is jumping to the coil negative terminal under sudden load. Maybe the plugs need cleaning replacing. Maybe the cap or rotor are worn or cracked. A cracked or burnt valve? Not trying to alarm you, just saying that armchair diagnosises is difficult at best.


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#10 ]2eDeYe

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Posted 14 June 2017 - 01:01 PM

Ok sounds like I gotta check everything from the fuel filter back. I'm sure the tank still has debris in it based on how bad my fuel filter got and knowing it was a garaged for the majority of its life.
Wouldn't I see more crap in my new filter if the problem was behind the filter? The filter has run clear now for 2 weeks on all my test drives after refueling.

 

 

Not if debris is in the tank outlet. 

 

 

 

 

 

If the fuel filter was changed after the problem started, it is likely that some obstruction is already in one of the jets.

 

 

 

This is also a possibility, 


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Whenever I think that I'm out of my mind for putting this much time and money into an old Datsun, all I have to do is look some of your threads to know that I'm not nearly as whack as you are.

You're going to skin a few knuckles, stand up too fast and bump your head, hunt around the floor for the nuts and bolts you dropped, invent a few new cuss words and when you're finished you'll say "That wasn't so hard after all!"


#11 ianmc54

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Posted 14 June 2017 - 09:29 PM

Thanks everyone, I understand its hard to diagnose from the computer I was just making sure I didn't overlook something "easy." After all this was my first time ever opening up a carb and cleaning the jets. I'll be sure to post pictures and let you know what I find when I make some time. 

 

And yes, there was debris clogged all around the last chance filter in the carb and some in the bowl. It's a new carb otherwise and looked pretty good after I cleaned it. I took the whole carb out today and will give it one more thorough cleaning. If I'm not mistaken, there are the two idle jets, the main jet in the middle of the bowl, the primary and secondary jets, the emulsion tubes, and the other jet that sits in the middle with a tube going to each chamber. Is there anything else I need to open up? 

If thats not it, I'll go look in the tank, use compressed air, pressure check to see if its getting enough fuel at higher fuel bands. Can I stick the tube that goes from the filter to the pump in a container of gas and start the car? If that doesn't change the symptoms then its not clogged behind the filter right? 



#12 Crashtd420

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Posted 14 June 2017 - 11:00 PM

Well you have a game plan...
And yes where ever you put the new tank becomes a cut in half info point for you... if No difference then that location forward is where you need to look... if ran better then whats rear of the add on gas tank has to be where the problem is...
And the way I read the end of what your saying... you can bypass that tank anywhere you like.. start back at the tank even.... disconnect the stock tank and run with aux tank.....
Might be a good idea to blow some air through the metal lines while your disconnecting things and back into the tank...
I was gonna say you should probably drop the tank and atleast rinse it out and inspect, but one step you could do that might give you some insight is get a small flexable cameras down the filler neck and take a look that way... I even think autoparts stores may loan it out.....

#13 distributorguy

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Posted 15 June 2017 - 04:01 AM

Ok sounds like I gotta check everything from the fuel filter back. I'm sure the tank still has debris in it based on how bad my fuel filter got and knowing it was a garaged for the majority of its life.
Wouldn't I see more crap in my new filter if the problem was behind the filter? The filter has run clear now for 2 weeks on all my test drives after refueling.

Actually, you need to check everything from the carb base gasket back to the fuel fill cap.  No stone unturned.  

 

The biggest likelyhood is that the float got bent a bit when you put the carb back together.  What you describe sounds like an emulsion tube problem, brought on from an improper fuel level in the carb.  Reset the float height and float drop to factory specs, and while you have the lid off, flush the emulsion tubes again with brake cleaner since its stronger than carb cleaner and leaves less residue.  



#14 2LittleTime

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Posted 16 June 2017 - 06:10 PM

If all else fails to resolve your issue make sure you check your flexible fuel lines. You just disturbed a lot of them changing the filter and working on the carb. I've seen the interior of older fuel lines collapse and cause partial restrictions. Same thing that happens with flexible brake hoses. Its a long shot but if nothing else pans out to be the problem check it out. When the filter clogged you may have collapsed one of the suction lines and compromised it internally. I've chased that ghost before.

#15 distributorguy

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Posted 18 June 2017 - 04:42 AM

With the matchbox, what's your timing set at?  Try 16 BTDC.