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You like creating problems for youself. If you had an accurate gauge you would know the condition of the pump. Testing is always better than guessing. What was the inlet filter on the LP like?
 

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Discussion Starter · #62 ·
You like creating problems for youself. If you had an accurate gauge you would know the condition of the pump. Testing is always better than guessing. What was the inlet filter on the LP like?
I got my accurate gauge yesterday and it indicates the same thing as the inaccurate gauge. (a vacuum when running) I didn’t take the inlet filter out. Is it just a screen? It would appear that it can pump scrap oil easily, so I doubt it is clogged.

I got the FS1251 and it appears it will work fine. So now I’m just waiting for the pump.
 

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Discussion Starter · #64 ·
Just an oil filled 0 to 15 psi gauge from Summit. I have it on the end of a flexible line now, so it shouldn’t get destroyed by vibration. I checked and I did have a snubber on the old one, but it was solid mounted and not oil filled. I guess the vibes caught up with it.

Edit, I’m curious if anyone has solid mounted an oil filled gauge. I really don’t like the hose. Maybe the oil would cushion the vibrations?
 

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Yeah, sounds like a multitude of problems and all associated with the lift pump. Be sure an put the correct filter on with the new one. Might inspect the input filter screen on the old lift pump a see if any trash had collected there. If so you might have gotten some bad fuel. Happened to a friend of mine. We were traveling together on vacation. My truck was diesel his gas. We fueled up at the same time, but at two different stations. We drove about a mile and his died right in the middle of the interstate. We got him towed to a shop and they found muddy water in his gas tank. Stuff like that does happen.
 

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OK, if the pump does pump and you have vacuum showing then you have a restriction in the system. What do you have for fuel lines? Tank pick up? Side mounted, sump or pick up tube? Tank vent? Which banjo bolt is the gauge on?
 

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Discussion Starter · #68 ·
Yeah, sounds like a multitude of problems and all associated with the lift pump. Be sure an put the correct filter on with the new one. Might inspect the input filter screen on the old lift pump a see if any trash had collected there. If so you might have gotten some bad fuel. Happened to a friend of mine. We were traveling together on vacation. My truck was diesel his gas. We fueled up at the same time, but at two different stations. We drove about a mile and his died right in the middle of the interstate. We got him towed to a shop and they found muddy water in his gas tank. Stuff like that does happen.
It’s kind of hard to check that screen because I pumped scrap oil through it. (It did pump easy though)

Did you say that you have an in-line filter before the pump? If so, I would give that a look, Very difficult for the pump to draw through a filter.
If the lift pump couldn’t suck through the inline filter enough to make any pressure, how could the injection pump suck enough to run?

OK, if the pump does pump and you have vacuum showing then you have a restriction in the system. What do you have for fuel lines? Tank pick up? Side mounted, sump or pick up tube? Tank vent? Which banjo bolt is the gauge on?
Tank is all brand new stainless. (I welded it up) Fuel lines are all stainless hard lines except for about 6” of flex at the motor. Tank has a pick up tube. The vent line goes to one of those little cone air filters Tucked up inside the body. I happened to be in the access panel right before this trip and it looked brand new. I have the gauge on the outlet side of the filter. So if that filter was clogged, it could be the whole problem.

I could pump the prime button easily and make fuel come out of the hole where the gauge mounts. When I cracked the banjo on the inlet side of the filter, it appeared to pump fuel just as easy. But remember, I’m pumping different piston than the motor does. I just thought of a good test that I could have done. Start the motor and crack the banjo before the filter. If the filter was clogged, it would gushing fuel. Hind sight is 20-20.

At this point, I would say it has to be the filter was clogged or the pump was stuck. I’m leaning to the latter.

I will say that I thought I had changed that filter ten years ago when I “went over” the engine. Now I don’t believe I did. So that would mean it is from the bread truck the motor came out of.
 

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Is the pick up tube angle cut at the inlet? Have seen straight cut tubes that grab the bottom of the tank when low on fuel.
 

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That FF42000 filter you had on there would not likely have been used on a bread truck. That is a special filter only used on the dual filter setup which not used on road engines. Now the previous owner could have stuck that on there but the engine specifies one with a water separator. That filter could be used on other brands of engines but wasn't specified on the 4bt.
 

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Discussion Starter · #71 ·
Is the pick up tube angle cut at the inlet? Have seen straight cut tubes that grab the bottom of the tank when low on fuel.
Not slant cut, but when it was giving me trouble, I still had 15 gallons. Also, my tank design has a 5 gallon drop out where the pickup and float go. That section of tank is very sturdy.

That FF42000 filter you had on there would not likely have been used on a bread truck. That is a special filter only used on the dual filter setup which not used on road engines. Now the previous owner could have stuck that on there but the engine specifies one with a water separator. That filter could be used on other brands of engines but wasn't specified on the 4bt.
I got this motor from longtime member on here. Something like “crucab deisel” in TN. He said he got it right from a truck scrapper. He seemed to be a “straight arrow“ kind of guy. I don’t believe he would lie to me. Of course, anyone could have changed out the filter before he got it.
 

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Just a word of advise on mounting the lift pump. Another member gave me this idea, he suggested getting longer than stock bolts then what OEM uses. Cut them into studs and walk those lift pumps on slowly with the nuts and washers. I did the stud idea and it worked great.
Sorry to here this is still running bad, just putting my .02 cents in for the swap of the lift pump.
 

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Discussion Starter · #74 ·
Still haven’t got the new pump. Going on a trip now. (Different vehicle) why do I want studs instead of bolts?
 

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When one mounts the pump, one is compressing the spring, surface is slanted, hard to reach and see. Studs provide guided route to start with, much easier to start nuts when unit already guided by studs, not have to hold against the spring, find threaded, off angle hole with bolts.
Everyone’s choice, for $10. worth it to me!

Ed in CO
 

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When one mounts the pump, one is compressing the spring, surface is slanted, hard to reach and see. Studs provide guided route to start with, much easier to start nuts when unit already guided by studs, not have to hold against the spring, find threaded, off angle hole with bolts.
Everyone’s choice, for $10. worth it to me!

You left out the bit about the gaskets and spacer sitting on the studs instead of trying to
keep them all together on the bolts.
Ed in CO
 

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Discussion Starter · #77 ·
I wish you guys would have brought this up before. I’ll order a kit, but if the pump shows up, I probably won’t wait. I don’t remember having a big issue when I bolted the old one on. Right now the spacer and one gasket is still stuck on the block, so I only have to deal with one gasket.
 

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Discussion Starter · #78 ·
Got the new pump. Bigger and laid out different. Note the prime pump is below the main pump.

Automotive tire Gas Automotive wheel system Auto part Space


Stud kit would have been nice, but not too big a deal. The gaskets with the new kit are tight on the bolts which helps a lot. The tube/banjo line does not fit at all, but my old one does.

Installed the new pump and the new filter. primed it till the filter was full and fuel was coming out the snubber. Tightened the gauge and primed till 12 psi. (It would fall off slowly)

Started the truck and it slowly went to 6 psi. After a couple minutes, I reved it and it went down to 3 psi. I reved it a lot and it went down to 0. Let it idle and it maybe came up to 1 psi.

Damb

I guess I will take apart the inline filter.
 

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Your old lift pump is a Delphi model which one of the less expensive replacements for the original Cummins low pressure. They don't have a bad reputation for failure. Your new one is like the standard Cummins model. Now, something else is going on with your system. Highly unlikely to have two bad lift pumps. You're loosing you pressure some where. Another bad thought is there's something wrong with your camshaft. That isn't very likely. Might try a test. Connect a hose to the outlet side of the pump and put it in a jug. Spin the engine a little to see whether you're getting fuel. Your gauge gave a reading when you manually pumped it so the gauge seem to be working. Other possible problem is the injection pump. There is an overflow valve on the pump that vents excess fuel back to the tank. If it is bad then most of your fuel is being sent back to the tank and not allowing the lift pump to build pressure. It's a very inexpensive part and could well be your problem. The valve and a couple banjo washers might be had for around $20. Here's listing showing that valve and washers. Believe I'd try that first. Dodge Diesel OEM VE Pump Return Overflow Valve - 1463456303
 

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Thought he had a VE IP. If so there is no overflow valve, just a restrictor in the return banjo bolt.
Still sounds like a restriction in the suction side.
 
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