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Fuel delivery problem?

Started by racertb, March 04, 2013, 11:47:34 AM

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racertb

Good Morning:

I took the Plymouth to a show this past Saturday that made for a 90+ mile round trip.  The car ran great on the way down, but on the way back, it seemed to "stumble" a little every few miles...

After several miles at my cruising speed of 40 mph, the car would start to buck a little and decelerate.  I would "play" with the choke a little to see if that would help and it seemed to sometimes, even though that might have been phsycological if anything.  What got the car "normal" again was by letting off the throttle until it "gathered" itself up (at the same time, the speed decreasing to 32-33 mph) and then I could slowly work my way back up to speed.  Then, it would do it again...sometimes after a few miles, sometimes after about a mile.

Again, it did not do this on the way down at all.  Also, it never did this at slower speeds and in stop and go traffic; ONLY during sustained 40 mph driving.  Filiing up the tank on the way home didn't seem to help things either.

I plan on replacing the fuel filter first to see if that helps, since that would be the easiest thing to do first for trial and error purposes.

Any thoughts or other things I should consider at this point?  Thanks!

frankp

Racertb,

Your description does sound like it is not getting enough fuel at that rpm, even though intermittent.  Can you replicate symptom in the garage?  I think you're on track with cleaning filter first. Can you verify vac tank/fuel pump is functioning properly?  My next step would be to remove carb and clean all jets, as much as I dislike doing this.

I hope someone can give you better info, like a quirk in the distributor??  Please keep us posted and good luck.

frank

frank p

imoore

Just a thought. Take the air cleaner off. And bring the rev up with one hand and cover the air intake with the other for a split second. This will suck fuel from every posable jet and clean anything that might be blocked. Then take it for a drive.
I have done this and it works a treat Every time.
Defiantly easier then pulling carby apart.

Ian
1928 Q tourer (Holden bodied)
Several vintage stationary engine

chetbrz

My guess would be fuel flow not keeping up with the demand at the higher speed.  Do you have the vacuum fuel canister and are all the vacuum lines tight.  If you use a vacuum pump is the vacuum line connected to the oil pump or the manifold.  The Oil pump will give you a more consistent vacuum return then the manifold.   I use an electric pump and some guys have one wired in just to replenish the fuel canister after heavy usage or long periods of inactivity.   Clogged fuel filter and items of this nature my second thought.   I would try adding some gas to the canister?  You may be using a tad more than can be replaced at a sustained speed of 40 mph over a long period of time.   

Good luck,  Chet...
http://www.1948Plymouth.info           Web Master - Forum Administrator - AACA member

racertb

Thanks for the replies...I will try Ian's method to see how that does as well as replacing the fuel filter; for what it's worth, the filter is between the tank and the fuel pump.

Chet - The car has a Carter 6v fuel pump with an in-line dial-type pressure regulator.

Ted

Doug

Check the pressure regulator. those things can be a problem

Old Man

Plan A:Disconnect your fuel system at the last piece of fuel line going to the tank. Take off the gas cap and put a dust blower gun on your air compressor and blow air back into the gas tank through the fuel line. You should hear a lot of bubbling. Put everything back together,with a new inline filter, and drive it. If the problem is 'cured' then you will have to remove the tank and clean it out. Which is another post altogether,Plan B. (You may want to start by unscrewing the drain plug on the bottom of the tank but they are usually 'age welded' in place. However if you get it off it should produce a 3/8" wide free flowing 'tube' of gasoline. If you have to stick something into the hole to start it running then you will have to move on to Plan B.)   

frankp

Re: Plan A.  Brings back laughable memories.

After I got vac tank functioning, my engine would quit running from time to time, regardless of speed/rpm, due to lack of gas.  I would disconnect the fuel line at the vac tank, put a lip-lock on the line and blow until you could hear the bubbles in the tank.  Cured symptom for a bit, and I was  never stranded.  My experience was, when my fuel line was plugged, the engine did not run at all.  There was no filter on that line, just a glass sediment bowl between vac tank and carb.  (I never left home without that wrench and still carry it to this day!)

For what it's worth,
frank
frank p

1929luv

fuel regulator is your problem I have had this problem to the diaphragm goes bad and causes restriction.  Good luck If mine I would put original pump on it Craig