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Discussion Starter #1
I am wondering if the fuel pump in my 72 D200 is going out. It has a mechanical fuel pump on the lower front right of the LA360, under cylinder number 2. The last two times i have driven it, it has left me temporarily stranded for an hour each. It also runs very rough at idle, which is very low. The engine also shakes noticeably (almost 1 inch of travel). I noticed that the in-line fuel filter is nearly empty, with only about a quarter inch of yellowish gas going through it. It used to be completely full when i first installed it. It has bad hesitation under light acceleration and the last two days it dies when it gets hot, somewhat like vapor lock. How do i test the fuel pump? How hard is it to convert to an electric fuel pump, and how much would it cost?

According to my records, the fuel pump was last replaced in 1998, and it sat from 06-08, and was run periodically but not road legal from 08-12.

specs:
Truck: 1972 Dodge D200 adventurer sport
Engine: 5.9 L 360 CU LA360
Carb: Carter AFB 9636SA
 

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KOG
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I long ago put electric pumps on all my 360s. $30-50, bypass the mechanical pump as you do not want gas being pumped into the crankcase through a defective mechanical pump.
 

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KOG
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Very
 

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Best mounted near the fuel tank. Reliable but do not lift high in most cases. Pump high, not lift high on suction.
 

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ok, well I just had to throw my 2 cents in here....while I dont disagree that electric fuel pumps have there place ( newer fuel injected cars where high pressure is required and racing applications)these older carbed engines run just fine on mechanical pumps the way they were designed to by the factory, I have run only Chrysler powered cars and trucks for over 34 years with about half of those carbed engines and I have only replaced one mechanical pump due to a externally leaking diaphram, maybe the pump that was replaced in 1998 was a poor quality off shore made one, I would say by a good quality replacement mechanical pump and save your self the time and hassel of the modification then it should last for years, just my opinion.
 

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The advantages of electric pumps are many. Constant pressure and volume, good reliability, and no chance of filling the crankcase with fuel from broken diaphrams. I run 3/8 line from a Carter pump located at the tank. Filters at both ends.
 

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Electric pumps are very reliable, and yes, mount them near the tank, place a piece of rubber between the pump mounting bracket and the frame when you mount it so it isn't as loud.

As far as your issue goes, check your electronic ignition for gap and condition of the distributor cap. When the electronic ignition starts to wear out, the heat is what affects them the most, dying for several minutes after they are warmed up and running fine, usually less than an hour then they die, start back up about half an hour later. Fuel filters don't have to be full to operate and work, my 6pac has three filters and all three of them maintain air pockets and have for 25 years of driving her. I imagine it would be a different story if they stood straight up and down.
 

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Once horizontally mounted filters amass air that comes in with the fuel, (low fuel in the tank, some boiling of the fuel in the lines, etc.) they have a tendency to keep the air coontained within. Fuel actually does continue to flow but at idle it is such a small amount being pumped that you do not actually see much fuel in the filter itself. Vertical mounts will usually pass the air into the carb and it is no longer empty. Hopefully you do not have a slight leak in the lines between the tank and the pump. Some of those leaks only occur while fuel is being drawn from the tank and will not show external leakage. From your symptoms, I would expect that you may have electrical issues as described above. Have you disconnected the line at the carb and spun the engine over to see the actual output of the pump? (make sure you hae a safe containment for the pumped fuel - Fires suck). Another possibility is vapor lock which usually comes from overheat on the vacuum side of the pump. Make sure that you have no exhaust leaks, lines running close to the exhaust and that the heat riser is not frozen.
 

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Discussion Starter #10
I don't have a plug tester, but I've checked that several times and replaced two wires to the ignition coil, the cap and rotor are about 3 years old and have maybe 100 miles on them max. I just replaced the fuel pump today, but i need to get some bugs worked out with the line first before its up and running. Also, it cranks and cranks and tries to start but wont, i think i may check ignition again, although I've had much more trouble with carburetion issues and fuel than ignition(Right now, there is a healthy layer of varnish on the inside of the carb... I just put in half a can of B-12). Also, our 73 Dodge Motor home with a 318 had a nearly identical problem, and that was fixed by replacing the fuel pump.

One more thing that worries me, the Pump was rated at 5.5-7 PSI, i have read that my carter shouldn't go above 4 PSI. Is this something to be worried about or not?
 

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Factory style pumps are usually good, but you are right, it should be lower pressure, 6-7psi is max.
 

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Discussion Starter #12
So am i in the clear, or do i need to get a regulator? I tried cranking it over but it was acting like it was nearly flooded, and wouldn't start. It might be pushing the floats down and flooding the carb. Last time i rebuilt it(early march) it was right after a small carb fire, and the floats were jammed way up, like they would be if it was pushing too hard. It ran fine after i reset the floats. Maybe i should start stocking up on carb gaskets...
 

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Only a high performance fuel pump could have high enough psi to give you pressure issues. 5-5-1/2 should not be too much. How would high psi jam a float UP? it would push a float down away from the needle. More likely to find a piece of debris that does not allow the needle to fully seat causing a too full issue.
 

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Discussion Starter #14
It would push the float arm down, and if it bottomed out, it would then push the float up, because the float would hit the bottom and the middle (back of float) would be pushed down. It would be like if you put a board in between two bricks and pushed the middle down. If it stuck, the end would be "pushed up"

Anyways, I finally got the fuel pump installation all fixed, and tried to start it. It was immediately flooding(it seemed) and i had to hold the throttle down to get it to start, then it ran very poorly, no power, ran rough, barely able to move itself at idle without dying. It ran for about 5 minutes then died, so i left it. Back to the drawing board i guess. I did check spark and vacuum leaks with a can of carb spray. Nothing out of the ordinary. It also hesitated VERY bad at about 1000 RPM, and i had a difficult time getting it above that, but once it was above, it was fine, but still ran rough.

Edit: Could it be timing? Where are the timing marks?

Edit 2: Two more things, one, the carb puts off whispy bits off fuel vapor when i first shut it off and take off the air filter, sorta like smoke, but there is no fire. Also, several of the carb screws that hold the top on were stripped when i rebuilt it.
 

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KOG
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You can buy electric pump in 2 or 3 different pressure ranges. Get one rated for 4-5 psi.
 

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Discussion Starter #16
I doubt that will solve the problem, maybe, i have no plans of buying a third fuel pump. I'll get a regulator before i do that.
 

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rcnesneg said:
It would push the float arm down, and if it bottomed out, it would then push the float up, because the float would hit the bottom and the middle (back of float) would be pushed down. It would be like if you put a board in between two bricks and pushed the middle down. If it stuck, the end would be "pushed up"

Anyways, I finally got the fuel pump installation all fixed, and tried to start it. It was immediately flooding(it seemed) and i had to hold the throttle down to get it to start, then it ran very poorly, no power, ran rough, barely able to move itself at idle without dying. It ran for about 5 minutes then died, so i left it. Back to the drawing board i guess. I did check spark and vacuum leaks with a can of carb spray. Nothing out of the ordinary. It also hesitated VERY bad at about 1000 RPM, and i had a difficult time getting it above that, but once it was above, it was fine, but still ran rough.

Edit: Could it be timing? Where are the timing marks?

If it pushed the arm down, then fuel would fill the chamber and fill it to flood stage and over the top into the venturi or outside on some older carbs. It would never push to the bottom.

Edit 2: Two more things, one, the carb puts off whispy bits off fuel vapor when i first shut it off and take off the air filter, sorta like smoke, but there is no fire. Also, several of the carb screws that hold the top on were stripped when i rebuilt it.
 

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Discussion Starter #18
Well i'm at a loss to know what to do. I took the top of the carb off, the floats were in their normal position, this thing is driving me nuts. I'm almost tempted to buy another carb. Suggestions?

:frusty: :frustrated: :pullhair: :cry:
 

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after re-reading all the post the one thing that stuck out for me was post 10, "right now there is a healthy layer of varnish inside the carb", there should never be any!, when this happens, jets and passages plug, the motor will run poor at low end untill it gets past that threshold where it can start to more efectively burn off the fuel as the engine consumes more, therefore some what smoothing out past that 1000 rpm mark, as you mentioned some screws being damaged from the last rebuild and as carb throttle shafts do where out I would lean towards a different carb, the edlebrock performer is based off the same design as the afb and they are very reasonable brand new.
 

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Discussion Starter #20
Well, i cleaned most of the varnish off today with some carb cleaner before i ran it, i also added half a can of B-12 to the fuel tank a few days ago. That should help.

So here is the story for today:

So i figured i didn't have too much time to work on it this evening, so i just took a can of carb cleaner spray and one of those computer-duster cans of compressed air. I took off the air filter, and sprayed both down in the metering rod holes (with them removed), the air bleed vents on either side that stick up, and two holes i found on the side that apparently cause fuel to come out of the secondaries when you put air down them. I also sprayed it around the carb barrels in general.. After that, i tried starting it, and after 30 seconds of coaxing or so, it fired up and ran for about two minutes. Then it died. So i repeated the process but didn't bother with removing the metering rods. Another 15 seconds of coaxing or so, and it fired up. It idled a bit rough so i brought it up to 2000 RPM. It ran fine there, so i just held it there. Then i started watching my watch. I figured i'd just leave it there for a few minutes, then i figured i'd leave it there for five minutes. After five, i figured i'd leave it there for ten. Ten became 15, and 15 became 20. It ran perfectly smooth at 2000 RPM for 20 minutes, then i let it back to idle. It idled a bit rough, but not as much as before. Then i drove it 200+ feet to the back of the lot and back, and it ran fine, but slightly rough. It didn't lack any power though. Sounds like there must be something in the idle circuit that's causing trouble. I let it sit for about 20 minutes and i'm going back out now to see if it runs fine again after sitting.


Edit: Well, i tried it again after sitting about 25-30 minutes, and after a few seconds of coaxing, it lit right up, and ran fine. Idle is barely rough enough to notice, but otherwise its great. It smells good again too.
 
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