Skip to main content

I just replaced my 780 dual feed carb with a new 600 single feed carb because my mechanic said it will help eliminate the poor performance at low speeds.The motor seemed to be starving for more fuel when I drove it home. I didn't drive the car for a couple of weeks and when I tried to start the car it turns over but won't start.That I was 3 months ago and I've tried to poor fuel in the carb and it will start but then die.Fuel pump?Fuel filter? I am not a mechanic and have little knowledge about mechanical stuff
Original Post

Replies sorted oldest to newest

It could be fine rust particles from the stock steel tank clogging the system. Replacing and cutting open the filter would help determine that. Or it could be the pump, which he could help test with some extra hose and a fuel pressure gauge added temporarily inline after the pump and hung somewhere you can read it under load through the rear glass. I assume he set the float levels on the new carb. I have also basically burned out fuel pumps from the rust issue before I had discovered the rust, where one pump failed during, another soon thereafter. If you have to pull or replace the fuel tank, that requires pulling the entire engine/transaxle on a Pantera, so hopefully not that, but not all that hard even if so, just would need to find fellow enthusiasts willing to help do it for pizza and beer instead of shop hourly rates. Stainless tanks are available for around $1,300 last time I looked, or the stock tank can be coated inside much more cheaply but probably a less permanent solution if you have tank rust. But hopefully it's just the pump (or an old clogged filter that never got replaced in the conversion). Or inconsistent voltage to the pump, easy to check with a voltmeter (if you have an electric pump). I suppose there could be an obstruction elsewhere (I think there was a mesh sock on the sending unit's fuel pickup tube in the tank as well that you could remove if still there, but you'd have to pull that 1/4 glass above the fuel tank to get the sending unit out to check it, and that glass is not always easy to get back in), but these are the most likely sources. I had that issue with the same symptoms on a 928 years ago that shops could never find, and a friend who encountered the same on a 968, found his problem there as well, but those have a plastic housing that if/when that assembly pops off, will intermittently obstruct fuel flow at the pickup tube in the tank. But I doubt any "sock" is your issue here.
You might want to give Tommy Hodges a call 1-562-301-0583 Tommy's shop is in Paramount Ca. not to far from you!
Tommy did a lot of work to my Car recently, some up grades and (Correct/repair Shoody work done in the past) which included a new Holley 750 carb. (took off a Demon carb. which Never worked right) My Car runs great and I got 18 mpg on the drive back Modesto Ca.
Tommy worked for Hall Pantera for years and is very knowledgeable and fair!
Give Tommy a Call.
Curt
FWIW- Holley, Carter/Edelbrock and Rochester carbs all come with some sort of built-in filter- usually a sintered bronze thimble- in the carb body behind the brass adapter fitting for the fuel line. If as was said, you have a rusty tank or lines, the bronze filter will plug almost instantly upon starting the engine, and there is no bypass. The engine may run but be extremely lean, or it may not start at all. Replacing the filter with another identical will quickly plug that one, too. Add a good paper filter but be careful- most fuel fires come from poor craftsmanship in additions like this. Steer clear of the aftermarket glass see-thru filters- they disassemble themselves from vibration and really won't flow enough fuel for high power engines anyway. Also be careful NOT to get a filter made for EFI- that doesn't work well with carburetors.
Vincent if I understand the problem started immediately when the new carb was installed, "when I drove it home". If so, dirt in the tank is unlikely, what is likely is that the new (proper size) carb is not well adjusted. I would immediately have turned back to the mechanic, he should have done a better job.

Most likely incorrectly adjusted float level(s) and or idle screws. Have a good mechanic try that first. I would call Tommy and explain.
One other thing important in cold start cranking is the choke. If you take off your air filter, when you've done everything (switched the key on and/or floored the gas pedal once) to set the choke and are about to turn the switch to "ignition," you should find that oval choke butterfly on top of the carb closed, meaning flat. The choke can be adjusted, but it should start in closed position. The earlier symptoms you described are probably not choke related, but sheer cranking could be that.
I am inclined to agree with Mikael in that the carb wasn't set up properly to begin with. And then after not driving it the fuel in the bowls dried up. When they are totally dry you can sometimes have to put fuel down the carb a second time after starting it on the first, as the fuel pump did not have time to get the fuel to the bowl. I have had to do this quite a few times.

Add Reply

Post
×
×
×
×
Link copied to your clipboard.
×