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Engine temp / fuel delivery

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B

BobS76

Senior Member
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1976 1500.
Webber carb. Stock fuel pump. I have worked on neither.

I have had enough success with this car to be able to get some road time - but not a lot. I have been having some fuel system problems after rebuilding the cooling system.

The cooling system - the fan ate a hole in the radiator. That plus some previous work has resuluted in a new radiator, fan clutch, all hoses, and water pump - pretty much every thing but the thermostat. Prior to that work, the temp gauge was reading 160-170 degrees. Following the work it is reading 180-190. The outside air temp has gone from around 80 to around 100 (SE Arizona), which might account for a shift in the coolant temp.

Simultaneous with the coolant system repairs, a problem has occurred with the fuel system. Once the engine has heated up, my idle drops below stall speed and if in gear the engine acts as if it being starved for gas - I get major surges in power, several seconds on and several seconds off.

I might add that I have not yet taken it far from home and as soon as this starts to happen, I return home. AS SUCH, I cannot be certain that the engine temp has stabilized out to the 180-190 mark. However, the temp rise looks normal, slow and steady all the way from 'cold', with a slow down as it goes higher.

Is the temp rise likely a problem, or linked to the outside air temp? If a problem, what might it be?

And what might be causing the fuel problem?

Hoping for an answer,
Bob
 
operating temp in 100 degree weather of 180 to 190 degrees is actually very good.

Press on. Up your idle just a bit.
 
Thanks. I appreciate the info. What sort of temp would you expect? This car is new to me - bailed out my son. Drove a B for 25 years, but there seem to be differences.

I have tried upping the idle a bit, but that will result in a considerably higher idle during warm up. Am I making a problem out of something that I normal? And that probably does not address the prom of surging power, which happens only after engine warm-up.
 
You might be having a fuel boil or vapor lock problem. Mine does that once the underhood temp gets hot. Been working on it on and off with little success so far. I just ease off the gas and let it recover and drive easy until I decide to stop somewhere. It is very annoying.
 
Kim,
Thanks! After reading the Wikipedia article on vapor lock, that sounds like it might be the problem. Besides temperature, I am also dealing with altitude. Maybe the electric fuel pump will help.
Bob
 
I thought about changing my fuel pump but it seems to work well. I took it off and tested it and cleaned it out and it filled a quart jar on a high shelf in 40 seconds, should be plenty of fuel. I made an aluminum guard and put over the carb to try and get the protection from the heat from the radiator and then took an old air horn and put it behind the grill and ran a hose from it to behind the gaurd. That way, cool clean air is blown on the carb while the radiator heat is deflected. mine seems to cut out in a long hard steady pull after it had gotten hot under the hood after at least 30 min of driving.
 
On a 100 degree day anything less than 200 is great.
 
Some of the reason we have problems with fuel this time of year and newer cars dont are fuel injected cars fuel is under higher presure and kept cooler by recirc to the tank. our fuel sits in the fuel line baking 5-6" inches from the 100+ asphalt only to be further heat soaked by the slow dilivery rate of the small amount being used. Then we cook it till its boiling some more by having it inches away from a hot engine. then we store it in the float bowel till we need it were it kept nice and warm.

Vapor lock: An engine performance problem due to high vapor pressure in fuel. While ethanol increases the vapor pressure of fuel, state and federal standards continue to lower vapor pressure levels—virtually eliminating vapor lock problems. Additionally, all major auto manufacturers now use in-tank fuel pumps, which are not subject to the vapor lock problems seen in older in-line fuel pumps.
Great.. what about the rest of us... time to look into a fuel cooler.
 
pielter cooler!
Maybe some trials with one of these units bonded to a aluminum sandwich block. fuel passing thru it maybe some thing to try. heck with the flow rates we work with 400 watts may be over kill.
ebay item no. 310059627720
 
I am working on the solution still guys. One simple idea is a spacer to get the carb farther away from the intake to prevent heat transfer that way. 400 watts is around 30 amps, way took much load on an alternator. Been talking to a buddy who familiar with the dgv on air cooled vws. The get real hot some times. He said that they used to make a loop of copper tubing and put it in a coffee can and fill the can with ice and then insulate the heck out of the can. Bug starts acting up stop somewhere and have a coke and then dump the ice in the can and off you go with ice cold fuel and better performance to boot. That is desperation right there :lol:
 
Your rite about the amp draw. consider it a deep cycle batt. test :laugh:
I know the drag guys kind of do the same as the cool can you referred to More ponies
 
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