Surging when hot

[Steve_bigD]

I have been plagued by intermittent surging and what feels like fuel starvation. I have an electric fuel pump mounted under the rear door with an inline filter between it and the gas tank. The tank was cleaned out and coated about 25 years ago. Recently I replaced the filter, cleaned out the fuel bowl and screen on the mechanical fuel pump, and cleaned the needle and seat and reset the float level in the carb. The choke is working well and the heat riser is blocked open. Also I rechecked and adjusted the timing and dwell.

It runs great until it gets hot then it surges and can barely maintain 50MPH. If I feather the gas for a few minutes it will smooth out for a bit and pick up power. I don't think it is vapor lock since I run the electric pump all the time which should have enough power to push through vapor lock. However if I turn the pump off the problem gets worse. I have the mechanical pump still in series with the electric pump.

My worry is that if the 25 year old gas tank sealer is partially dissolved by the ethanol in today's gas it clogs the inlet filter screen in the gas tank which causes this problem. However wouldn't that occur all the time and not just when hot? The engine never runs more than 180 degrees.

Any suggestions would be appreciated.

Steve D

[packick]

Steve D:

I had this problem with my '36. I replaced the fuel pump, fuel filter, etc. but the problem was still there. In my case it didn't matter whether the car was hot or cold. I would get down the block a bit and the car would start surging. I eased up on the gas pedal and it would sputter but I could make it back home.

As you suspect, what was causing the problem was that the gas tank sealer came "undone." In my case, I pulled the gas tank, removed the senting unit, and there was a glob of sealant visible. I got some needle nose pliers and pulled out what I thought was a bit of sealant. It turned out it was ALL of the sealant in one big glob. My mistake was that I purchased a can of sealant at a swap meet that was not ethanol-proof. After removing this blockage the car ran great. I ended up taking the tank to a professional shop to have it sealed where they bake the sealant on.

Live and learn.

Edited August 31, 2012 by packick (see edit history)

[FLYER15015]

Steve,

I too had a "pokey" car this summer, and it turned out to be the vacuum advance diaphram was gone.

Pull the line to the carb and apply vacuum. to check the tubing AND the diaphram.

No advance yields a pokey car.

Just my $ ,02

Mike in Colorado

[Steve_bigD]

Thanks for the fast replies. When I sealed my gas tank 25 years ago ethanol proof gas tank sealers were not available so it very well could be that. I was also suspicious of the vacuum advance and I will check that first. If it is not that then another winter project along with rebuilding the steering linkage (6" free play in the steering wheel) and front brakes (severe pull to the right under hard braking) is awaiting me.

Steve D

[trp3141592]

Hi,

In my experience, you can have the vacuum advance unit rebuilt by Terrill Machine Co, Deleon, TX, and the gas tank refurbished with baked-on sealants at Gas Tank Renu, which has outlets around the country. Of course, there are other sources as well.

--Tom

Edited August 31, 2012 by trp3141592
Corrected spelling (see edit history)

[packick]

Steve D:

I also have severe brake pulling on my Packard which I can't figure out. All of the mechanical parts are working fine, there is no oil on the shoes, and I had the drums turned. My mechanic told me that he has had a few instances where only one shoe was engaging when braking. So that is the next thing I am going to check out. He said even though the wheel cylinder may not be leaking, one of the the aluminum pistons in the cylinder could be hanging up and not working. Of course there could be other culprits, but I thought I'd pass this along in case you too are at a loss as to what could be causing the pulling.

[Steve_bigD]

Thanks, packick. You know this is not a obvious problem since the brakes always pulled to the right from the day I bought the car in 1978. About 10 years ago I completely rebuilt the brake system replacing everything including the hard brake lines, all hardware and rebuilding the master and all wheel cylinders. The shoes were replaced along with turning the drums and new wheel bearings, and I switched to silicone brake fluid. I had also completely rebuilt the suspension about 10 years earlier. It still pulled to the right under hard braking. By the way that silicone fluid is still as crystal clear as the day I installed it. Just the purple color has faded.

I am wondering if the loose steering could be a factor in the brake pulling although it is funny that it always pulled to the right. If I brake very hard the right front wheel will lock up and it takes all my strength on the steering wheel to prevent it from veering off the road. I plan to re-inspect the right brake very closely as my assumption is that the brake that locks up is the one at fault?

Thanks,

Steve D

[Guest Grant Magrath]

Had the same problem with the coupe, and it had us stumped. The car was owned by a guy who had a brake shop before the guy that sold it to us, so we had no reason to think it was anything but needing new cylinders up front and a bit of adjustment. But when our very clever friend came over to help adjust the brakes, he noticed the brake shoes on one side were round the wrong way! So maybe pull the drums and check the brake shoes to see if the sizes are the same front and back on both sides. It sure caught us out!

Cheers

Grant