I've been trying to figure out why the truck has been running so irradically......vapor lock. It runs fine when you initially start it but as soon as it heats up I notice that there's no fuel coming through the filter and barely runs. The fuel pump is brand new so I ruled that out. I'm looking into an electric unit with a low pressure switch to see if that will help. Any other suggestions?
Robert, I'm not so sure that vapor lock is your problem. Vapor lock was a problem on 40's and some 50's carby set-ups, but is almost unheard of in relatively modern systems. IIRC, you're running a 70's or 80's V8, right? My first thought was distributor cap. I had a '72 Nova 350 back in the day (you might have seen it in '75-it was the red and white blurr on I-55 between Sardis and Horn Lake). I had to replace the dizzy cap twice because it would have a hair line crack in it. Check your cap and also the plug wires, as they can be problematic too! Also check the routing of your fuel line. Vapor lock can be caused by routing the fuel line too close to a source of high heat such as the exhaust manifold, engine block etc. Food for thought! Ken
You might want to check your gas cap to see if it's vented properly too. When it starts running bad, pull the cap off and see if it runs better.
It's a late 60's 327 & the distributer is new. Installed a rollover vent valve in the tank and it appears to be working fine.
Fuel Flow Well ; If it's vapor locking you'll know my simply touhing the steel fuel line , it'll be too hot to keep your fingers on it . I'm also thinking of maybe fuel starvation caused by kinked hose / pipe or crud in the tank causing poor siphon , did you ever test the siphon ? it's a simple thing and will either be yes or no . Try driving it sans filler cap for a quick venting test , yes you installed a vent but K.I.S.S. remember ? . If you go with the E-pump , be sure to only use the 2 ~ 3 # one and mount it back by the tank , NOT up under the hood .
I forgot to mention that I'm getting some strange readings from the fuel pressure guage. Sometimes the needle bounces around wildly and then at times it holds steady at about 5-6 psi. Any thoughts?
is it running good at 5-6#?What is the running temp when your taking this reading? as mentioned before Check for vented gas cap,kink in gas line(under cab at gas tank)and fuel pump. good luck Bobby
pick up pipe have you checked the pipe tank side of the pump? if you have a small leak you could be drawing in air instead of fuel, also the same for pick up pipe in tank, is it bent/cracked so its not picking up fuel consistently as you drive down the road, does the problem happen if you sit in the drive and run it for a while, rev it occasionally, or is it only while driving, have you got sludge/object in the tank, when you switch off it drops to bottom of tank but as you drive it shifts and restricts the pick up pipe. Another idea, when its hot and miss firing shut it off and whack the dizzy cap off, moisture in cap, when cold moisture can sit hidden in the base of dizzy until it heats up and causes chaos with the firing order. jus my 2 bob
rubber line Robert I had a old F##d pickup years ago that acted the same way.It had a short rubber line that connected the suction side of the fuel pump to the steel line from the tank that would collapse when you got down on it.It ran fine at idle and if you drove it easy.Don't know if you have the same setup ,but if you do, it is something to check. Good luck!
wasted weekend I replaced the mechanical pump with an electrical one and most of the rubber lines with steel ones. Started and ran fine, Pressure guage held rock steady @ 5 psi. headed out for a test drive and it did the same thing...ran like @($% & on top of that the brakes started locking up agsin!. The only other alternative is to check the carb. I'll see if one of my buds will let me borrow one just to test this theory. I'm getting pretty tired of this!!!!!!!
Before you get yourself worked up too much try these 2 things....First take your gas cap off and go for a ride, see if that helps with the fuel problem. Second pull the pin on your brake pedal rod that go's to the power booster and shorten the adjustment a little and see if that helps with the brakes. We've suggested this before but you have never indicated to us that you have tried it. Then let us know.....Big Tim
Hang on! You have a misfire and probs with the brakes, are you running a servo on the brakes? could that be the cause of both probs! brakes sticking and air leak through the vacuum line Jus my 2 bob
I'm outta ideas. I swapped the carb and it's still running lousy. The tank is vented and clean. New fuel lines, filters, fuel pump, distributer & coil. Using fresh fuel.
Check your dizzy, and electrical connections. Sometimes the tractor has problems and the spark plugs and or distribitor are the problem, or the ing. switch but that is on the 8 or 9 N's Front Dist.. Also, take off the gas pressure gismo gauge and see if it runs with out it.
You need to get back to the basics here. It only takes air, fuel and spark to make an engine run. Try disconnecting your fuel system from the fuel pump to the gas tank. run a fuel line from the pump in to a gas can and see how it runs. This will tell you which direction to go. If it runs good then your problem is before the pump, if it runs bad then its from the pump forward. That is if it's a fuel problem and not electrical.....Big Tim
One thing you may want to check that can be heat related would be the condensor. I know this is a part that either works or doesn't work. It maybe worth a look.Another thought that just popped in is the ballast resistor. good luck Bobby
http://www.ytmag.com/cgi-bin/viewit.cgi?bd=nboard&th=780252 Nate gives a Very good way to trouble shoot the problems and has posted it many times, it does not change no matter what the engine is in be it a Car, Truck or Tractor, here is a link to a site that talks about a "N" that will not start. Almost the same as Nates posts, but for the tractor not our AD's, problem still applies. http://www.ytmag.com/cgi-bin/viewit.cgi?bd=nboard&th=780252 Also, do check that pressure gizmo, you stated it was acting strange before this started.
