345 fuel issues

R

Ralphy4life

New member
I have a 77 Scout 345 5.6l I just changed over from mechanical to an electric fuel pump to fix what I thought was a vapor lock issue. Rode great for a couple of days. But then at about 45 mph she stutter and turns off you have to wait a couple of minutes and she will turn on again and give you a few more minutes and repeat. I noticed that there was a small leak in the pump so I changed it today but same deal still happens. What should I do!!!!
 
Go back to the mechanical pump. This is sounding more like an electrical/ignition issue rather than a fuel problem. A '77 would have been originally equipped with a Holley electronic ignition commonly known as a "gold box" because of the amplifier module fastened to the firewall which is often gold in color. Check your battery connections, your main chassis ground, your connections at the starter solenoid, the bulkhead connectors, the gold box, (amplifier module) and ignition coil.
 
Id also add a few things to try if that doesnt pan out.

1) dont use those crappy inline 40$ fuel pumps.
2) make sure you dont have a leak elsewhere. A hole in the fuel line.
3) vacuum advance line.
4) carb
5) I actually had this problem before with my 76 terra. I had a multitude of problems at the time. My float was sticking on my carb. My accel pump was leaking. My gold box was bad. The wires coming out of my dizzy had a short. My wires were cracked. My spark plugs were caked in an unmentionable substance. I had a hole in my gas line. I had crap in my fuel filter. My timing was off. My life was in shambles.....ok that one is irrevelant. The wires leading to my firewall had melted together. My alternator went kaputt.

While thats probably not your problem its just an example of how the little things really piss you off in the long run
 
Next time it dies pull the air cleaner off and look down the carb throat while working the throttle. You will have a shot of fuel or you won't. If there is a good shot of fuel it's an electrical problem. If a weak bubbly shot it's running out of fuel. Let us know what you find.
 
Well all my connections look good it's possible tht it's time for a new starter because it seems to stumble at times. It seems though that I'm still not getting enough gas so I think I'm goin to go back to the mechanical pump. How do I test the golden box? And when I do change back to the mechanical pump how would I avoid the issues I had before with the vapor lock?
 
The mech fuel pumps are calibrated to deliver between 5-7 psi fuel pressure. Without having a fuel pressure gauge connected downstream from your pump all one can do is speculate about what your electric pump of unknown parentage is doing. Folks commonly jump to the "vapor lock" conclusion whenever any performance issue is encountered, very rarely with any concrete evidence. More often than not, upon further investigation, the real culprit turns out to be something altogether different and usually centered around an improper state of tune or lack of routine maintenance. Now, you May indeed have a vapor lock issue, or you just as likely May not. Again, all I have to go on at this point is your speculation.
The testing procedure for the gb system is fairly involved, but is explained in detail within the pages of the factory service manual. A digital multimeter is but one of several basic diagnostic tools required to work through it.
Did you happen to try chappie's suggestion about checking your fuel squirt inside the carb immediately after the engine dies without starter cranking or pumping the gas pedal? If not, you should do so. That is one simple yet effective way of ruling which direction to focus with the diagnostics. If you get two strong streams the first time you blip the throttle, then this isn't a fuel starvation issue. If it dribbles and piddles hardly any visible fuel, then it is a fuel delivery problem. So try that and report back.
 
I did the jet check and I'm getting nothing that is why I think my pump is not working. I hear it moving but I don't think it is effective. So I will change it out. I figured it was vapor lock before because I had no issues until it got hot out.
 
Okay sounds good. Drive around and do the same test once you've gone back to your old pump. Make note of any similarities and differences. How's your fuel line routed? You need to keep it away from and insulated from heat sources as best as you can. Is your carb base gasket roughly a quarter inch thick and does it have any provision for shielding your fuel bowl from the intake manifold? If not, you should look into getting a thick base gasket with fuel bowl insulator to help minimize any potential vapor lock issue you May be having.
 
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