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Generators & Electric Motors General Discussion

2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?


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  #1  
Old 08-21-2011, 06:40:14 PM
Walter J. Walter J. is offline
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Default 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

I pulled my Detroit 2-71 out of the garage to run it in anticipation of Irene hitting West Palm Beach on Thursday. It is hard to start as I think fuel drained back into tank. I have a marine type primer bulb with internal check valve that I use to prime the fuel filters. Eventually it will start running. It will run for about 15 minutes and then die unless I squeeze the bulb and replenish the fuel. This went on for about an hour. When I shut it off and came back in about 15 minutes the primer bulb had swollen to about twice its side from back pressure. I assume I need a check valve between the engine and secondary filter to prevent the back pressure. Why is engine starved for fuel when running after about 15 min? Weak fuel pump? I have all new filters and hoses with no leaks so I am not sure what problem is. I need to know soon so I can fix it before the storm. Any thoughts would be appreciated.



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Old 08-21-2011, 06:43:32 PM
Walter J. Walter J. is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

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  #3  
Old 08-21-2011, 08:19:00 PM
Arkie Arkie is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

Can you rig a pressure gauge to test the fuel pump output pressure when it's running? (sounds like your fuel pump is bad and a pressure test will confirm)

Nice rig!
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Old 08-21-2011, 09:18:22 PM
Walter J. Walter J. is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

I will try but I suspect you are correct. How hard is it to rebuild the fuel pump? I can buy a rebuild kit or a remanufactured pump. I have never had much luck rebuilding fuel pumps on cars.
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Old 08-21-2011, 09:30:58 PM
Arkie Arkie is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

Quote:
Originally Posted by Walter J. View Post
I will try but I suspect you are correct. How hard is it to rebuild the fuel pump? I can buy a rebuild kit or a remanufactured pump. I have never had much luck rebuilding fuel pumps on cars.
If hurricane is headed your direction, might be easier to immediately replace and play with the old pump later! Once you get it primed and running you can temporarily remove the rubber bulb (before the storm) and splice the line if it keeps swelling up. I've seen the rubber bulbs swell(expand) when subjected to full of fuel and heat from hot sunshine, but never seen one burst, but get swelled up like a big toad frog.

Good Luck to Ya!
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Old 08-22-2011, 12:33:46 AM
SoTexRattler SoTexRattler is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

That's one very nice looking DD genset you've got there! I'm impressed!

Not sure but seeing the weather cracking in the close-up pic of that rubber bulb, you had better have another if a hurricane is coming your way.
By the way, most every one of those primer bulbs I've ever seen has check valves that leak back slightly. I almost believe they did that on purpose to prevent them from turning into "footballs" like yours tried to do.

I can't see from the pics but is that bulb sucking THROUGH the prefilter from the tank?

Keith
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Old 08-22-2011, 05:41:41 AM
Walter J. Walter J. is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

Thanks. I do have another one I can put on as I noticed that one is cracking. It is in line between tank and primary filter. I have a brass check valve that I will put between bulb and primary filter as that is location shown for original check valve in DD parts manual for 2-71. My set up never had one as I went back and checked the original canister filters and fittings that I saved looking for check valve and none exists. Any thoughts on why fuel quits after about 15 minutes? Fuel pump? I am headed to Miami this morning to DieselPro.com to get pump and or kit just in case. Hurricane Irene is coming our way according to 5am update. Anything over 50 mph and we will lose power.
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Old 08-22-2011, 09:01:40 AM
Jim Rankin Jim Rankin is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

Make sure the tank cap is venting properly.

Also need to ensure there is good flow from the tank. You may have to siphon it and let it run into a bucket for a while. I'm wondering if there might be some kind of foreign material in the tank which will find it's way to the outlet after a while. It may take draining the whole tank and looking in with a flashlight to find it.

Have you considered it may be a clogged return line instead of a clogged feed line. Frequently will have the same symptoms from that, but I'm not sure on a DD system.

Change out the bulb first. Could be something caught in its valves.

Blow some rain to the west when it comes by!

Good luck!
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Old 08-22-2011, 10:41:51 AM
Arkie Arkie is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

Quote:
Originally Posted by Jim Rankin View Post
Make sure the tank cap is venting properly.

Also need to ensure there is good flow from the tank. You may have to siphon it and let it run into a bucket for a while. I'm wondering if there might be some kind of foreign material in the tank which will find it's way to the outlet after a while. It may take draining the whole tank and looking in with a flashlight to find it.

Have you considered it may be a clogged return line instead of a clogged feed line. Frequently will have the same symptoms from that, but I'm not sure on a DD system.

Change out the bulb first. Could be something caught in its valves.

Blow some rain to the west when it comes by!

Good luck!
Jim wrote: I'm wondering if there might be some kind of foreign material in the tank which will find it's way to the outlet after a while. It may take draining the whole tank and looking in with a flashlight to find it. Keep this one in mind!
I found a small tree leaf in a gas tank few years ago after replacing a fuel pump, re-building a carb, and pull several wads of hair, 2 cases of beer and 3 bottles of whiskey, several bottles of aspirin, lost sleep, etc. The engine was intermittent, might run day or two, sopmetimes a week then quit. Let it sit few minuites and it would run again. (the leaf would lift away from the tank outlet line when at rest, then eventually return and block the outlet.
I finally installed a permanent pressure gauge on the output of the new fuel pump to help isolate the problem. Had to remove the tank and dump the tank contents.

Moral of story: When you do something the HARD WAY first time, you usually will not forget it the next time around!
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Old 08-22-2011, 02:04:29 PM
Richard L Richard L is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

I guess the first question would be was this running befor, or is this a new unit you built up.
The detroit 71 have a gear driven pump that feeds the injectors and circulates fuel back to the tank,there is usually a check valve in the supply system to keep the fuel draining back, the outboard bulb you have installed will not work, in this kind of systen, you need a brass gate check to do the job.
If this is a new assy, are you sure that you have your fuel lines connected to the correct ports on the engine? I have seen these run with the fuel hoses switched, but not well.
Each cylinder has its own injection pump/injector that is one piece, and it takes fuel from the gallery as the pumps circulates it.
I would get rid of the bulb and check that the lines are running to the right connections,also your return line cannot go back to the filter but must go back to the tank directly.
To check if the fuel pump is moving fuel, disconnect the return line at the tank and see if your moving fuel you can use a pail.
Also is your fuel tank vented ,try removing the fuel filler cap.
Give me a holler, if you want
206-284-1848
Rick
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Old 08-22-2011, 07:14:54 PM
Walter J. Walter J. is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

I bought the unit from DieselPro.com in Miami that had rebuilt it. I added the trailer, tank, air filter, new spin on filters, control panel from Emerson Matkin etc. I replaced the fuel hoses. The return from the head goes straight to the tank. I really never ran it more that 10 minutes until the electrical disconnect was installed. It died when my electrician was testing it and we thought it was out of fuel as we had only added a couple of gallons. I put 55 gallons of off road diesel in yesterday and fired it up to really test it for 30-40 minutes with a load on it. It was then I noticed the starving of fuel and back pressure problem. The flow of fuel matches what I replaced as well as my 2-71 parts manual which has a good picture of the piping. There was no check valve when I got it yet the parts manual shows one on the primary fuel filter intake. I put one on today and that should take care of back pressure. i will have fuel pump in morning and will replace it as the one on there is probably original. Might as well as I have let fuel run out of various areas. The tank has a pressure cap that is not vented. I will put everything back together tomorrow and then test it with cap on and off. Thanks for your help.
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Old 08-22-2011, 09:01:32 PM
RSCurtis RSCurtis is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

There are two things you can check. First, remove the fuel pump and make sure the drive coupling is in tact. The coupling is designed to fail if the pump inhales a foreign object. Second, make sure the fuel return like is hooked up to the restricted fitting on the head. If the lines are backwards, the engine will run but the injectors will be running at less than adequate fuel rail pressure.
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Old 08-22-2011, 09:05:00 PM
K D Redd K D Redd is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

Your fuel tank cap needs a vent. One of the things that many people Do Not know about a DD is that the fuel flow through the injector/pump assembly COOLS the injector/pump. If your fuel tank is not vented and the run time is enough to heat the fuel it will expand creating pressure in a non vented tank that could cause things to swell. With a long enough run time the return fuel is near the engine's operating temperature.

Kent
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Old 08-23-2011, 12:22:12 AM
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Talking Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

I would point out that the x-71 DD has no Injection Pump as such, but a Gear Driven Fuel Pump that Feeds a common Fuel Rack Header, which then feeds each, and all Injectors in Parallel. Injection Timing is accomplished off a Cam Lobe and and Rocker Adjustments to each Injector. Totally different system than the modern Injector Pump/High Pressure Injector Lines/Injectors of todays Diesel Engines.
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Old 08-23-2011, 09:22:08 PM
Walter J. Walter J. is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

Problem Solved for now. I received rebuilt fuel pump from DieselPro today. I switched it and upgraded the fuel lines coming off of block. Even though I had several fuel leaks when installing hoses and fittings she fired right up on first crank. I was only able to run it for about 5 minutes as it was getting late and neighbors probably do not want to hear the old 2-71 running. I will let it run longer on Saturday morning. Thanks for all the help. It looks like North Carolina will get brunt of storm as Florida was lucky this time.
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Old 08-23-2011, 10:20:39 PM
Isaac-1 Isaac-1 is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

Good to know you have it going, one suggestion get some good chains and locks to secure that thing. DD 2-71's don't tend to grow legs a much as smaller generators do, but this one is already on wheels.

Ike
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Old 08-24-2011, 06:54:52 AM
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

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Originally Posted by Isaac-1 View Post
Good to know you have it going, one suggestion get some good chains and locks to secure that thing. DD 2-71's don't tend to grow legs a much as smaller generators do, but this one is already on wheels.

Ike
Very true! The gennys sometimes evaporate or get carried away by the high winds right during the storm.
Tie chain it down good and install a good tongue lock also.
Weatherman says it could still very easily shift the 100 miles in your direction real easy!

You still need to vent the tank?

Good Luck to Ya!
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Old 08-24-2011, 07:13:24 AM
Walter J. Walter J. is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

I have a removable tongue on trailer so cannot be towed with out it. You won't be lifting it into back of pick up. I do have vented cap that will relieve any pressure from fuel flowing back to tank. I will let it run this weekend for an extended period just to make sure everything is working ok. Thanks again for all the suggestions.
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Old 08-24-2011, 09:22:40 AM
Jim Rankin Jim Rankin is offline
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Default Re: 2-71 loss of fuel pressure from fuel tank-check valve? or bad fuel pump?

Looking at that cap, I believe it has a vacuum relief as well as a pressure relief. We have something that looks similar on a tank in the back of a pickup. Unlike the older tank we had, it doesn't have to be removed to pump fuel out into something. Made sort of like a radiator cap inside.
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