Bucks in third after hard accel

[eugenel]

Another weird question...

1979 spider with the carb'ed 2000 and an unknown gearbox?

My fuel pump failed a few weeks ago and I went to electric. As it was failing, hard acceleration and shift into 3rd would cause insane power loss and bucking for a few seconds before power was available again. Fuel pump pretty much died and I had to push it to a gas station, with enough fuel in the tank I drove home. Everything made sense, hard accel fuel retreats down the fuel line due to failing fuel pump and power available again after the engine sucks in some more gas. It was a stretch to get it to hit 80...

For a few days engine ran like a complete champ, grinning like a teenager after his first lap dance. Was pushing it exactly like I used to and realized I was going way faster and doing 95!??!?

Except after a few days it started doing the same thing with the electric fuel pump... Other then that it seems to run fine, oil is clean and oil consumption is low, a couple very slow leaks on the valve covers. Averaged 27 mpg on the trip I took this weekend over 550 miles.

I have a brand spankin new weber 32/36 dfev sitting on a brand new single plane 1800 manifold. Need a complete overhaul on the exhaust but could that cause the problem?

[btoran]

what about fuel filters?

[eugenel]

Replaced with the new fuel pump as long as new lines. Oreilly's was nice and threw the lines in for free.

Filter is one of those washable ones, saw a lot of gunk fill it up for a while and cleaned it once. Filter totally clean at this point. Fuel is nice and clear, way better then the brown crap that came out of the old one. Still no clue how the thing even ran when I bought it, amazes me beyond belief.

[vandor]

Well, the Oreilly electric pumps are pretty low quality, but they usually last about a year, so likely it's not that. I would check that the pickup in the tank is not blocked and that all the hoses are in good shape and not kinked. Clamps tight so pump does not suck air.
Where id you mount the pump, in the engine compartment or the trunk? Pumps push fuel better, so mounting it in the trunk would be better.

[JEEPER]

I have a 79 that did the same thing since new. Thanks to this forum after 36 years the problem is gone. I had an electric fuel pump that FIAT put in mine back in 82 under warranty. MY FUEL PUMP was only putting out 1 1/2 PSI and in 3rd went to 0. I now have a 4 1/2 PSI pump and in third the pressure is only down to 3PSI. I got it from ROCK auto and it is mounted in the trunk.

[btoran]

the pump that csaba sells fixed a similar issue in my 1975 (carbed) recently. also gave the car a noticeable boost in power.

[johnsje6]

I fought a similar problem with my '79, was rust in the gas tank. Would run great then every once in a while would buck like crazy and act like it was running out of fuel. I cleaned out the rust and coated the inside of the tank, problem is gone. I had replaced the fuel pump with one from AR, but still had the problem till I cleaned and coated the tank.

[eugenel]

I put the fuel pump in the engine compartment. I will try moving it to the back, where would I get switched power back there for it?

[JEEPER]

I put the fuel pump in the engine compartment. I will try moving it to the back, where would I get switched power back there for it?

The lead is already back there for the electric fuel pump. It is blue with a red tracer.

[vandor]

> The lead is already back there for the electric fuel pump. It is blue with a red tracer

Not on a '79. He'll have to run his own wire.

[JEEPER]

> The lead is already back there for the electric fuel pump. It is blue with a red tracer

Not on a '79. He'll have to run his own wire.

It is on my 79 with the harness for to gas guuage float. It has a white nylon female spaid connector on it.

[vandor]

I don't know what your car has, these cars are 35 years old and most have gone through way too many creative POs.
'79s had a mechanical pump from the factory, thus had no wire in the trunk for an electric fuel pump. There were 2 wires for the sender, one for the gauge, the other for the light in the gauge.

[JEEPER]

I don't know what your car has, these cars are 35 years old and most have gone through way too many creative POs.
'79s had a mechanical pump from the factory, thus had no wire in the trunk for an electric fuel pump. There were 2 wires for the sender, one for the gauge, the other for the light in the gauge.

I bought this car new with a mechanical fuel pump. Fiat USA put an electric fuel pump on it in the early 80's under warranty because it bucked from the day I took delivery. They said they suspoected vapor lock so the installed the electric in the trunk with the factory wireing . My 79 has a build date of AUG 78 and I took delivery in SEPT of 78. Where the harness comes out in my car is a bundle of wires. fuel sending unit, fuel light, trunk light, and a ignition switched electric fuelk pump blue with red tracer.

[Auspider]

So it seems the bucking is a common problem?

I've got a 78 with a warm 2 litre and a 34mds carb. Its got a Mechanical pump that I took off an 1800 and it bucks terribly when giving it the beans. Weird thing is, when I had twin 40 IDF's on it it never did it! Are there different types of mechanical pumps? Filter is clean and doesn't collect rust from the lines.

[majicwrench]

Really really need to test some things here. "T" a fuel pressure gauge into line, tape gauge to windshield, make it buck, what is fuel pressure doing?? All this guessing is ...........well, guessing. Pressure should never go down on accell.

Electric pump should always be mounted as close to tank and as low as possible.