Engine cuts out after 3 to 4 seconds of medium acceration

[Zymurgy]

This problem has got me baffled. This all started before I did any of the current work on the car. This is what I have done so far.

1. Mechanic fuel pump push rod 3/8 short, replaced new one, it is stuck in block, so I added electric fuel pump.

2. Rebuilt AFB again (3 year old rebuild), by a professional he saw no problems, replaced accelerator pump.

3. Electrical fuel pump has built in regulator added a pressure gauge. Regulator reading 5 psi near engine could not get the pump to adjust, replaced with another new pump, set it at 6 psi

I still have the problem. It starts and idles fine I can drive it up to about 40-50 mph under easy acceleration and then it cuts out. If I punch it after it is warmed up I have 3 to 4 seconds until it cuts out. It will kick in the 4 barrel and sounds great until it dies.

I can take my foot off the gas and it will always come back to life after coasting for a couple of seconds. I can always limp it home driving about 30-40 mph.

Fuel pump installation. Mounted below the lowest point of the tank (recommended location). There is about 12 inches of rubber hose from sending unit to pump with a clear fuel filter in between. I have an unobstructed flow from the tank, I can remove the inlet line from the pump and it flows out freely.

One note the fuel pump is suppose to be adjustable from 5 psi to 10 psi. The second one I got to go up to 6 psi (which is what I was told to set the pressure) Is this correct? I don't think it will go to the 10psi level. I already have it adjusted nearly the whole way in.

It is acting exactly the same way as it was before I did any of the current work, no change at all.

 

[68plymouth383]

Your sending unit could be restricted. Your tank vents could be restricted. How's your gas cap? Its supposed to be non vented, and your tanks vent lines are vented.

 

[Zymurgy]

Your sending unit could be restricted. Your tank vents could be restricted. How's your gas cap? Its supposed to be non vented, and your tanks vent lines are vented.

New non vented gas cap, replaced last year. Vent lines have new rubber, installed last year. When I disconnect connect the fuel line at the pump, the gas flows smoothly out of the tank on it's own. Sending unit replaced 3 years ago.

 

[commando1]

Mike, remove the cap and try it anyway. Just for giggles...

 

[Zymurgy]

I needed to step away for a while and ask for advice. I will double check what you guys have recommended. I will try your idea first Stan.

 

[68plymouth383]

It'll act differently under load then it will in the driveway. I've heard about new sending units being restricted at the sock.

 

[Zymurgy]

My tank has only been reconditioned with Red Kote, 3 years ago and the guy did say this is only a temporary fix. My tank is not in the best shape.

 

[70bigblockdodge]

Sounds like a restriction in the fuel line somewhere.

 

[Zymurgy]

Sounds like a restriction in the fuel line somewhere.

I will add that to the list too, that might explain 2 different fuel pump that won't adjust.

 

[70bigblockdodge]

My Challenger had two problems the line was restricted tank to pump and my sending unit had a pinhole about 2/3 of a tank, above was fine below would suck enough air to cause problems. Then on top of all that my ecu was not grounded well enough and the car would sputter above 4500 rpm, took a while to sort out these stacked up problems good luck and one thing at a time.

 

[Wollfen]

Since the electric pump is built for pushing gas more than pulling, having the fuel filter between the sender unit and the pump may be causing an issue too. Temporarily eliminate it and test to see if there is any difference.

 

[Fury440]

Maybe not your problem, but food for thought.

A friend of mine was driving his 4x4 on the highway and found he couldn't get the silly truck to run faster than about 25 mph. We pulled into a country garage and the mechanic said "fuel filter" and replaced the in-line filter. This however didn't fix the problem. Further examination uncovered a second in-line filter mounted out of sight and mind below the alternator. This filter didn't appear to have ever been changed. In fact 90psi shop air couldn't blow through.

With 2 new filters his 4x4 ran like a new truck!

Some carbs have an internal filter. Not sure about Mopar but a lot of Chev's do.

A thought on your problem, tank vents plugged? Run without the fuel cap to find out.

 

[Zymurgy]

Since the electric pump is built for pushing gas more than pulling, having the fuel filter between the sender unit and the pump may be causing an issue too. Temporarily eliminate it and test to see if there is any difference.

Thanks for the suggestion. I had it first set up with just the original filter which was new. Then added the one before the pump, per the manufacturers recommendation. I then removed the original and put in the pressure gauge in its place.

 

[Landyacht]

Vapor lock? Thicker carb gasket.

 

[Big_John]

My tank has only been reconditioned with Red Kote, 3 years ago and the guy did say this is only a temporary fix. My tank is not in the best shape.

It's time to full the sender. Ethanol spiked gas is really tough on those gas tank coatings.

I'll bet the sender is gummed up with the coating.

 

[Zymurgy]

It's time to full the sender. Ethanol spiked gas is really tough on those gas tank coatings.

I'll bet the sender is gummed up with the coating.

I hope this is it. It makes the most sense to me that something is clogging the sending unit. Thanks everyone for the input. I feel better about going back tomorrow investigating everything you guys have suggested.

I was out of ideas, feeling more positive again.

 

[detmatt]

I've been reading along since you started and was willing to put money on something ethanol related. I hope you get it figured out quickly and don't miss too much seat time because of it.

 

[68plymouth383]

I've had guys with 66 c bodys use 67 c body gas tank because there more readily available. If you're tank is questionable, and is plugging up the sending unit I'd change them.

 

[Zymurgy]

I've had guys with 66 c bodys use 67 c body gas tank because there more readily available. If you're tank is questionable, and is plugging up the sending unit I'd change them.

It will not fit at least on my car, I measure one from a 67 it is too long. I don't remember the exact number but the floor unibody supports on my '66 2 door, are directly on the front and back of where the tank is mounted, so the 67 tank won't fit. I see a restored tank in my future.

 

[rexus31]

A shot in the dark here, but have you had the coil tested? Have you pulled any of the plugs? What do they look like? Vacuum advance checked out?