Help...Cranks but won't start

[brnco_luvr]

So I was driving on a nice sunny afternoon with my wife. As I was driving up a hill at about 45mph, the engine started stuttering and shut down. It then cranked but wouldnt start. No smell of gas. Had to tow it back home. I think it may be the fuel pump, but would appreciate any suggestions on where to start and how to diagnose the problem. I am a novice mechanically, but would love to try to fix it myself if possible.
'74, 302, C4, 4 barrel carb.
Thanks ya'll
Shane

 

[75MIKE]

Have you tried starting it once it cooled down?

 

[ared77]

1) Look down into carb (air cleaner off) wile you move the throttle by hand - see streams of liquid gas shooting in? Answer is probably "no" since you don't smell any gasoline.

2) If no, pour a thimble sized amount of gas into carb and quickly try to start it. Could also use a shot of starting fluid if you want. If it starts, or you notice it try to start, you probably have figured out it is in fact a fuel problem.

3) Once you are convinced it's a fuel issue you can try to decide bad pump, or clogged fuel line, plugged up gas tank, etc.
A) remove fuel line at carb, put a container over end (in case gas comes out) and crank engine for just a second. If no gas -
B) remove line that feeds the fuel pump, gas come out there? If so it's probably the pump. If no gas there, try removing the gas cap and while someone has their ear to the gas tank put a slight shot of compressed air to the line. Other person should hear a slight gurgle from the tank. If not it may be a clogged up fuel line...and that may mean a rusty tank.
C) Also be sure to eliminate any inline fuel filter(s) as one of those could be plugged up causing the problem.

Good luck!

Norm

 

[brnco_luvr]

Thank you. Will do today. Could it be vapor lock since I was kinda pushing it up the hill and it was hot and humid yesterday? I read a bunch of threads on CB.com that talks about that.

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[SHX669]

Start with the simplest - do you have gas in that tank -? -
How much - do you have 2 tanks ? - running off the correct one ? - are you trusting the factory fuel gage ? - do you have a mechanical fuel pump or an electric fuel pump ? If electric how is it plumbed ?- if so which fuel pump is it .

 

[SHX669]

Start with the simplest - do you have gas in that tank -? -
How much - do you have 2 tanks ? - running off the correct one ? - are you trusting the factory fuel gage ? - do you have a mechanical fuel pump or an electric fuel pump ? If electric how is it plumbed ?- if so which fuel pump is it .

 

[B RON CO]

Hi, since it sputtered and died it probably is fuel related, but everyone should have a $10 spark tester for a quick check, just so you know you have spark. Good luck

 

[brnco_luvr]

Thank you all for your suggestions. Will follow all suggestions as soon as I get home and followup. Starting with checking my tanks, putting in some gas, and then the rest.
She has a mechanical pump.

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[brnco_luvr]

1) Look down into carb (air cleaner off) wile you move the throttle by hand - see streams of liquid gas shooting in? Answer is probably "no" since you don't smell any gasoline.

2) If no, pour a thimble sized amount of gas into carb and quickly try to start it. Could also use a shot of starting fluid if you want. If it starts, or you notice it try to start, you probably have figured out it is in fact a fuel problem.

3) Once you are convinced it's a fuel issue you can try to decide bad pump, or clogged fuel line, plugged up gas tank, etc.
A) remove fuel line at carb, put a container over end (in case gas comes out) and crank engine for just a second. If no gas -
B) remove line that feeds the fuel pump, gas come out there? If so it's probably the pump. If no gas there, try removing the gas cap and while someone has their ear to the gas tank put a slight shot of compressed air to the line. Other person should hear a slight gurgle from the tank. If not it may be a clogged up fuel line...and that may mean a rusty tank.
C) Also be sure to eliminate any inline fuel filter(s) as one of those could be plugged up causing the problem.

Good luck!

Norm

Hi Norm,

Squirting fuel into carb started the engine. Then, took fuel line off the carb, started car, and fuel came out of the line. So it looked like it was a carb issue. Then I put the line back on and she started right up and stayed on! Not sure why! Could vapor lock happen inside the carb?

Thank you for your suggestions and advice. It was great to resolve the issue myself with ya'lls help.

Look forward to fixing more problems in future!

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[brnco_luvr]

As a followup, should I do anything with the carb now?

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[DirtDonk]

Well, if it's not too far away from home I would go up that same hill at the same air temps if you can. But without the wife! Instead, either by yourself or with someone ready for the adventure of pushing and roadside fixing and such adventurous stuff.;D

See what happens.

Paul

 

[brnco_luvr]

Lol... it'll be a while before she rides with me again! She got all dolled up to go to a friend's house, and got stranded on the side of the road! She'll come around.

I will try some other hills little closer first.

Any reason the service the carb? Clean it, etc?

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[DirtDonk]

Always. It's a carburetor and that's what you do with them!%);D
I generally run a can of fuel system cleaner in the tank at least once a year in every vehicle I own.
Nothing but good things in a can basically.

A deeper cleaning is not out of the question either, if you have never done so. You could have crap in the float bowl that was clogging things up temporarily when you were on the hill.
Or you could have a weak and tired old fuel pump that only works when it's cooler, but starts to act up when it gets hotter.

Still hard to say at this point unfortunately.
What you learn with old vehicles is that: "99% of carburetor problems are the electrical system. And 99% of electrical problems are the carburetor!" and we just get to deal with it all each time!

Paul

 

[brnco_luvr]

Thanks Paul.

Just got back from a drive. She drove strong, even up a couple of hills. Just out half a bottle STP fuel treatment in the main tank and filled it just more than half. Will repeat another time in that tank and then do same in the aux tank.

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[ared77]

Glad you got it going...and you fixed it yourself! Always a good feeling.

Norm

 

[brnco_luvr]

Thanks Norm!

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[nvrstuk]

So ALL you did was wait till it was completely cooled off and it started correct?

More than likely it was vapor lock. It goes away by itself.

Carb doesn't need cleaning unless the fuel is dirty. Keep the tank clean and an excellent high quality filter and you will never need to clean the carb...never. (20 yrs is never). So long as it doesn't sit for a month at a time or have the same crappy gas in the tank for months. IF SO then you need to treat it regularly and todays gas doesn't last long compared to the old days. In a 2 stroke an engine will barely start with 6 month old gas and you can notice a HUGE power difference...everybody can notice it.

4 stroke isn't as critical but still, every couple months it should have new gas or be treated. I run boats and no problems IF you keep treated and fresh gas in them.

How close is your fuel line to your exhaust and or exh manifold?

Just asking because you didn't have to do a thing to restart... correct?

 

[brnco_luvr]

So ALL you did was wait till it was completely cooled off and it started correct?

More than likely it was vapor lock. It goes away by itself.

Carb doesn't need cleaning unless the fuel is dirty. Keep the tank clean and an excellent high quality filter and you will never need to clean the carb...never. (20 yrs is never). So long as it doesn't sit for a month at a time or have the same crappy gas in the tank for months. IF SO then you need to treat it regularly and todays gas doesn't last long compared to the old days. In a 2 stroke an engine will barely start with 6 month old gas and you can notice a HUGE power difference...everybody can notice it.

4 stroke isn't as critical but still, every couple months it should have new gas or be treated. I run boats and no problems IF you keep treated and fresh gas in them.

How close is your fuel line to your exhaust and or exh manifold?

Just asking because you didn't have to do a thing to restart... correct?

Thanks nvrstuk!

I drive it at 5 to 6 times per week and put in about 6 to 8 gallons of gas every 1 to 2 weeks.

I did try to cold start first before troubleshooting, and after putting some gas in main tank. It wouldn't start. Thats when I started to troubleshoot as Norm suggested. It basically started up after disconnecting and reconnecting the line from the carburetor. My own novice minded theory is that there was vapor lock somewhere in or after the fuel filter. Go figure. Sure would've costed me several hundred dollars if I had taken it in and probably ended up with a new pump, filter and who knows what else. The whole problem happened suddenly which points more toward either a vapor lock or debris clog which cleared up. No other symptoms before as one would expect from bad filter or pump. Its working strong now. Hopefully I'm right, not to say I don't anticipate full filter or pump issues in the future. I consider that part of the whole experience!

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[nvrstuk]

Great news.

How far away is the line from the exhaust?

Easy to shield it.

Have fun and keep driving it!

 

[brnco_luvr]

Great news.

How far away is the line from the exhaust?

Easy to shield it.

Have fun and keep driving it!

The rubber hose from the pump to filter to carb run pretty close to the manifold. Ill look for some ways to shield the line without comprising the cosmetic appearance of the engine bay. I have dual exhaust. Will look at the lines closer to the tanks and see if the driver side line is inside or outside the frame and make adjustments/shielding as needed.

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