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1972 F250 4x4, 78 d60/d60, 3.55, np205, 200hp 4bt nv4500 superHX30w
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The U shape tube delivers boost positive pressure to the top of the diaphragm in the AFC housing, wouldn’t want to lubricate in there. I was referring to the lower side of the diaphragm which is vented to the atmosphere through the rubber boot below the afc line.


The AFC is the diaphram thing with four screws? I see the tube from the intake and the small vent tube. Hard to spray in that little tube. (I didn’t try yet) I’ve been fixing other unrelated stuff on the truck from the trip. I need to do some baseline driving on a select road to make sure what happens when I make a change.
The AFC is the diaphram thing with four screws? I see the tube from the intake and the small vent tube. Hard to spray in that little tube. (I didn’t try yet) I’ve been fixing other unrelated stuff on the truck from the trip. I need to do some baseline driving on a select road to make sure what happens when I make a change.
 

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Discussion Starter · #22 ·
So I looked at my fuel pressure gauge and found the neadle broke off. I knew mounting it to the engine was bad. I’m going to get another and mount it with a short hose before I do anything else.

I did some calculations and figured there was about 15 gallons in my 50 gallon tank when it was running horrible. I put 30 gallons in and it definitely got better in the next couple minutes. I have previously run the tank down to one gallon before it started running bad. So a clogged filter is high on my list. I have two filters. One is the stock one on the engine And the other is a summit racing in line filter.

I replaced the engine filter along time ago (10 years) when I was building the truck. Not much fuel was run through it, but I was using a five gallon plastic tank that probably was not too clean. Once I got the new tank in, I added the summit filter. It is designed for gas and I think it only filters to 100 microns. I read recently that diesel likes 10 microns or smaller. So it maybe passing some stuff on to the engine filter.

I’m going to order a new engine filter. Any suggestions where to get?
 

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Discussion Starter · #23 ·
So I got a new fuel filter. It is a Wix FF 5052. I found the part number in the sticky’s and they had one in stock at my local auto parts. It looks like a metal spin on oil filter. The one on my truck looks like a plastic housing. Do I got the right filter?

If this will work, what problems am I going to have? Do I just fill it up with diesel, thread it on and start the truck? Is it going to run bad for a couple minutes while the air gets worked out? Or do I need to crack injectors?
 

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1972 F250 4x4, 78 d60/d60, 3.55, np205, 200hp 4bt nv4500 superHX30w
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Here is some what I believe to be good information on bleeding the fuel system. The fuel filter is pretty far up stream.

First try the lift pump prime lever and see if there is any resistance. If not you need to bump the engine over to get the cam in the right position. After you have the lift pump ready to prime crack the fuel filter 1 turn. prime till you get fuel out of the filter then tighten it. Next crack the fuel inlet line on the Inj. pump. Prime some more till you get fuel there and then tighten the inlet line. Next loosen the injector line at the farthest injector from the inj. pump. Crank the engine till you get fuel squirting, tighten the line. Then do the same to the next farthest injector. etc.,etc. After 3 or 4 cyls the engine should start. Let it idle a minute or so. If it still has a miss, go back and bleed each inj. one at a time while it is idling.
 

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Discussion Starter · #25 ·
Are you saying it won’t work itself out after it starts? I have a 3 cylinder tractor. Ive run it out of gas many times. if I can get it started, it will bleed itself in a minute or two. Sometimes starting it can be a chor, but after that, all’s good. I’ve never had to crack all three injectors.
 

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With a VE IP so long as you do not touch the injection lines and just pump the fuel through filter with the lift pump is should start just fine. The air will bleed through the IP via the return line.
 

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Discussion Starter · #27 ·
Ok, to day I pulled off my fuel pressure gauge. (the needle was broke off.) I didn’t have another gauge with a 0-15 scale, so I put a 10-60 one I had. I installed it with a flex tube so it wouldn’t vibrate. I didn’t have the tube tight enough and when I started the truck, fuel poured out at the fitting. It took me a minute to realize what was going on and the engine stalled.

After fooling around a bit, I got it started again with no leaks. The gauge showed no pressure. How is this possible? It seemed to run fine. (Didn’t drive it) I’m going to order a new gauge with the proper scale, but I’m still wondering why it doesn’t show anything. How low of pressure can the engine run on? I suppose if it only had 3 psi, it might not show on this scale. But I would think the needle would move slightly.
 

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Ok, to day I pulled off my fuel pressure gauge. (the needle was broke off.) I didn’t have another gauge with a 0-15 scale, so I put a 10-60 one I had. I installed it with a flex tube so it wouldn’t vibrate. I didn’t have the tube tight enough and when I started the truck, fuel poured out at the fitting. It took me a minute to realize what was going on and the engine stalled.

After fooling around a bit, I got it started again with no leaks. The gauge showed no pressure. How is this possible? It seemed to run fine. (Didn’t drive it) I’m going to order a new gauge with the proper scale, but I’m still wondering why it doesn’t show anything. How low of pressure can the engine run on? I suppose if it only had 3 psi, it might not show on this scale. But I would think the needle would move slightly.
I found these FWIW
"
Here are the fuel pressure requirements for a 1st Generation Dodge Cummins with a Bosch VE injection pump.

Maximum Inlet restriction ............................... 4 In Hg

Maximum Return line Restriction ................ 20.4 In Hg

Maximum pressure drop across fuel filter ............ 5 PSI

Maximum pressure at the injection pump .......... 10 PSI

Minimum pressure at the injection pump ............. 3 PSI

Volume of fuel pumped in 30 seconds ........ 0.79 Quarts

The maximum inlet and return line restriction is measured using a vacuum pump against the lines looking for flow restrictions. Minimum and maximum fuel pressure are measured between both idle and WOT operation looking for the performance of the fuel pump are with the specification. The measured fuel pressure should be measured near the injection pump. The volume of fuel is measured by disconnection the fuel line and disconnecting the fuel shutoff solenoid and cranking the engine for 30 seconds.

WARNING! Don't crank the engine for more than 30 seconds or starter damage could occur. If you need to repeat the test allow the starter to cool for at least 2-3 minutes before testing again."
 

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After looking at the specs I posted earlier it got me thinking about the physics of moving fuel, in my rig the fuel tanks bottom is well above the lift pump say10" and tank has 18" standing fuel when full so when full the IP and filter are nearly the same level as full tank. This has by dumb luck has made it nearly "self bleeding", so full tank just crack bleeder at the filter and it will start to drip in a short time or worst case 3-4 strokes on lift pump lever. I recalled when a Kid we had an early '70's dodge motor home that we used for fishing/camping, it had bad issues with spending too much time at lower engine speeds with a nose high attitude think boat ramp engine would quickly die due to lac of fuel in carb bowl. After many hours of trouble shooting spread out over months it was discovered that the lift pump could not make the head pressure needed to feed carb when vehicle was pointed up hill more than 20*-30* as pump was required to make a 5 or 6 foot lift we fixed this with an old AC electric pump at the tank used to boost fuel to the factory fuel pump.
So long story short you might need to look at the system as a whole using the above data to find the cause or causes, hell enough lift, filter restriction, return restriction and plumbing restrictions could well be adding up to where it is struggling. This will also affect IP life as the VE is lubed and cooled by the fuel flow....$.02
 
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Discussion Starter · #30 ·
That is interesting. I wonder if I had jacked up the rear with the airbags, I could have made the truck run better.

The specs you quoted are for a 6BT? (Mine is a 4BT) Maybe there the same.

I do know that I have previously run the tank down to 1 gallon and it ran OK. So something changed when it started running terrible with 15 gallons still remaining. And it definitely got better quickly after putting 30 more gallons in. But it still wouldn’t go over 52 mph. I just drove it again and 52 seems to be the magic number it won’t pass unless a serious hill. My lift pump is a relatively new piston pump.
 

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That is interesting. I wonder if I had jacked up the rear with the airbags, I could have made the truck run better.

The specs you quoted are for a 6BT? (Mine is a 4BT) Maybe there the same.

I do know that I have previously run the tank down to 1 gallon and it ran OK. So something changed when it started running terrible with 15 gallons still remaining. And it definitely got better quickly after putting 30 more gallons in. But it still wouldn’t go over 52 mph. I just drove it again and 52 seems to be the magic number it won’t pass unless a serious hill. My lift pump is a relatively new piston pump.
The feed requirements between the 2 "should" be the same, I am running the same lift pump.
IMO your gonna need to look at component by component and verify that each stands muster until a pattern appears, I do not see it being a big issue to come on like this but.......
I'm totally OCD and will NOT lose to any mechanical issue to the point where I dream about the issue I'm dealing with but I also spent over 40 years as a machinist/millwright so it's in my blood and i have learned that it any issue can be overcame IF you approach it this way. It must be fueling related so starting at the fuel source and working to the IP is the path to take.
 

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The piston lift pump you have should have a screen in the suction side, check it is clean. What pressure was the lift pump putting out before your gauge failed?
 

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You say you can't get over a certain speed. Will the engine rev up when sitting still? If not, you possibly have a governor issue. I assume you have a 3200 RPM spring.
True Charles, never thought of that...But I should have.. :oops:
 
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Discussion Starter · #36 ·
You say you can't get over a certain speed. Will the engine rev up when sitting still? If not, you possibly have a governor issue. I assume you have a 3200 RPM spring.
Yes, I have a “higher than stock” governor spring. (Can’t remember which) I think it was only one step up because I didn’t want to put valve springs in.

I thought of the governor possibility, but I keep coming back to the trip where it wouldn’t go faster than 40 until I put more fuel in. That really tells me the pump needs the extra help from the fuel “head pressure”. That help is either making up for a weak pump or clogged fuel filter. When I rule those out, I will be looking at the governor and AFC.

On that note, I’m going to post a pic of my fuel filter. The one on the truck really doesn’t look like the same thing as what I got. Now maybe I can remove the old one and the new one will go on in its place. I would kind of like someone on here to confirm this before I try to remove the current one. It is very tight and is made of plastic. I’m afraid that if I put a channel lock on it, I will break it. I don’t want to find out then I can’t put the new one on. (At least I can move the truck now)
 

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Discussion Starter · #37 ·
So here’s a pic of my current fuel filter.

Motor vehicle Gas Auto part Machine Nut


Unfortunetly, I can’t read the part number beyond FF42. But it is obviously plastic and appears to separate about 2” down from the metal. At the parts store, they came up with this.

Fluid Drinkware Material property Adhesive tape Shipping box


I could possibly believe the plastic one could be removed completely up to the metal and this one thread on. I would like that as I prefer this version to the plastic. Can anyone confirm this will work. If not, doyou have a part number of a filter that will work with this base?
 

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So here’s a pic of my current fuel filter.

View attachment 134955

Unfortunetly, I can’t read the part number beyond FF42. But it is obviously plastic and appears to separate about 2” down from the metal. At the parts store, they came up with this.

View attachment 134956

I could possibly believe the plastic one could be removed completely up to the metal and this one thread on. I would like that as I prefer this version to the plastic. Can anyone confirm this will work. If not, doyou have a part number of a filter that will work with this base?
I'm running a Wix 33472 fuel/water separator, it does not cross to the Doge 6bt though IIRC I cane upon this PN sa fitting the Chevy P-30 with the 4BT however last time I looked it up that listing could no longer be found. It does "Look" the same.
 

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Fuel filter shouldn't be made of plastic. Fuel filter is steel and has a water drain at the bottom. Standard fuel filter on VE pump engines was Cummins part 3931062 which is Fleetguard FS1251, That was changed to a Cummins 3286503 which is still the FS1251. Not sure why they had 2 part numbers for the same filter. That plastic one you have on there is Fleetguard FF42000. Don't believe that one has the water drain. It is not listed as a replacement for the FS1251. It replaces the FF5052 and several others. That filter is one of the two piece set used in the dual filter system on a 4bt. Not the single design filter you want on an older 4bt. The Wix number Steve mentioned is a direct replacement.
Tableware Camera accessory Automotive tire Drinkware Cylinder
 

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Discussion Starter · #40 ·
Thanks for the info, Charley. So do you know if that plastic one will come off and the 1251 go right on? Or do I have to source a different base?

I found another picture of mine before installing the body.

Automotive tire Motor vehicle Bicycle tire Bicycle fork Bicycle part


You see there’s no place for two filters.

PS, I would really like a water drain.
 
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