Fuel problem on 751

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bobbie-g

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1995 751C, ser 514711004, 1100 hours. Peugeot Diesel XUD9 engine. 50 hours on the fuel filter, no water in it. --- I have a starting problem, the engine runs fine once it’s running, even under heavy load. When the engine is shut off and sits for 15 minutes, then I attempt a start, it begins to run then stops just as if the key were shut off. Fuel cap is new and vented (verified by sucking air through it) so we’re not pulling a vacuum on the fuel tank. 12V always present at the fuel cut-off solenoid when key is on, so that does not seem to be the problem. The primer squeeze bulb feels like it has air in it. After several pumps, it feels like the air has been expelled from the bulb, and the engine usually can then be started, although it usually runs rough for a minute or so (air in the fuel line?). Or, while holding pressure on the primer bulb I can crack the air bleed valve on the injector pump and I get a few seconds of sputtering air before I get a solid stream of fuel. Shut the bleed valve, then the engine will start promptly and runs fine until it’s shut off again. I had the primer bulb, the pickup line in the tank and the screen/check valve replaced, with no noticeable change (except to the contents of my wallet). I unhooked the fuel line at the output of the primer bulb (before the fuel filter) and hooked up a vacuum tester to the line continuing on to the filter/injector pump, noting that it held a 10 psi vacuum perfectly, so the line is not leaking between the primer bulb and the injector pump. Now I’m told by the Bobcat dealer that I have a weak pickup pump (located inside the injector pump housing), verified as weak because when the engine is running, it will speed up slightly when the primer bulb is squeezed. Cost to rework quoted at $1000 or more. In my mind, the dealer has not yet explained how there comes to be air in the fuel line. I still suspect an air leak between the pickup line in the tank and the primer bulb (those parts are conveniently located under/behind the engine). Any ideas out there? ---Bob
 

Tazza

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It sounds to me like a split/loose hose in your fuel line. But as you said, you did a check on this. If the lift pump was weak i would expect it to blow air bubbles when you crack the bleed screw, but not air back in the priming bulb, but i guess it could happen. Good luck in finding your problem!
 

JustAwrench

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Since your lines are new, I would guess that you're sucking air through your fuel pump, like your dealer said. He's estimating to pull and probably send out your injection pump for service. I don't like that lift pump integral to the injection pump on the peugot, but that's what you got. It will pull air after you shut off and you'll lose your prime. Don't be tempted to put an electric fuel pump in-line, though. It will fill your crankcase with fuel and your engine will run away to destruction.
 

bobbie-g

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Since your lines are new, I would guess that you're sucking air through your fuel pump, like your dealer said. He's estimating to pull and probably send out your injection pump for service. I don't like that lift pump integral to the injection pump on the peugot, but that's what you got. It will pull air after you shut off and you'll lose your prime. Don't be tempted to put an electric fuel pump in-line, though. It will fill your crankcase with fuel and your engine will run away to destruction.
Shane, many thanks for the advice. I was contemplating adding the electric pump! Do you know how the air gets in the line? Does it come back in the bypass/return lines to the tank? I assumed there was no way for air to enter through the fuel pump. Tnx again for the words. I'll get the Bobcat back on Monday with new fuel lines and we'll see if that makes any difference. I did run it today at the dealer's and pumped the primer bulb myself and heard the engine speed up. Now, the next question is, where do I find a pump? Bobcat wants $1400 for a new one, local shop will swap for a rebuilt one for $1000. Anyone have ideas? ---Bob
 

JustAwrench

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Shane, many thanks for the advice. I was contemplating adding the electric pump! Do you know how the air gets in the line? Does it come back in the bypass/return lines to the tank? I assumed there was no way for air to enter through the fuel pump. Tnx again for the words. I'll get the Bobcat back on Monday with new fuel lines and we'll see if that makes any difference. I did run it today at the dealer's and pumped the primer bulb myself and heard the engine speed up. Now, the next question is, where do I find a pump? Bobcat wants $1400 for a new one, local shop will swap for a rebuilt one for $1000. Anyone have ideas? ---Bob
The air enters from your leaking(internally)lift pump, which is part of your injection pump. It's pulling air from the top down when your engine is off, and you lose prime. When your engine is running, you may have fuel leaking into your crankcase. Better check your oil, if it's overfull, it may have a lot of fuel in it, which could wash your bearings. If the local injection shop will also remove and install, I'd call that a decent deal, though all this stuff is out of my financial league. Good luck.
 

bobbie-g

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The air enters from your leaking(internally)lift pump, which is part of your injection pump. It's pulling air from the top down when your engine is off, and you lose prime. When your engine is running, you may have fuel leaking into your crankcase. Better check your oil, if it's overfull, it may have a lot of fuel in it, which could wash your bearings. If the local injection shop will also remove and install, I'd call that a decent deal, though all this stuff is out of my financial league. Good luck.
I had all the fuel line components replaced, from inside the tank clear up to the injector pump. But I still get air in the line when I shut down for a few minutes (ranges from 3 minutes to 15 minutes). Looks like that clearly puts the problem in the injector pump. Shane, how does the air get in? It must come back through the overflow line? I remember overflow lines on each of the injectors, and I think I remember one on the pump itself. Thanks for the warning about not putting an electric pump in line. I don’t see how fuel would get to the crankcase, since the injector pump is not physically connected to the crankcase. It’s bolted to a flange with two bolts, and the drive gear is driven by the timing belt. Could I get away with an electric pump with a momentary switch, so I could just bring up the pressure (4 or 5 psi) as I try to start it? ---- And does anyone have a clue where I can get an injector pump for less than $1000? -------------------------- Tnx, ---Bob
 

Tazza

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I had all the fuel line components replaced, from inside the tank clear up to the injector pump. But I still get air in the line when I shut down for a few minutes (ranges from 3 minutes to 15 minutes). Looks like that clearly puts the problem in the injector pump. Shane, how does the air get in? It must come back through the overflow line? I remember overflow lines on each of the injectors, and I think I remember one on the pump itself. Thanks for the warning about not putting an electric pump in line. I don’t see how fuel would get to the crankcase, since the injector pump is not physically connected to the crankcase. It’s bolted to a flange with two bolts, and the drive gear is driven by the timing belt. Could I get away with an electric pump with a momentary switch, so I could just bring up the pressure (4 or 5 psi) as I try to start it? ---- And does anyone have a clue where I can get an injector pump for less than $1000? -------------------------- Tnx, ---Bob
The lift pump will have a rubber/neoprene diaphragm that gets pushed backwards and forwards by a cam that creates pressure/vacuum that pressurizes the fuel much like a car fuel pump does. Air will get into the fuel line through and splits/cracks in the diaphragm, the air will get in from your engines breather, as where the cam pushes a plunger that connects to the diaphragm will not be air tight as the rubber diaphragm *should* make it air tight when it is not damaged. Now, *IF* the diaphragm is damaged and you put an electric fuel pump in line with a damaged fuel pump you will push fuel through the cracks in the diaphragm which will pass through where the plunger goes into the engine or injector. The injector pump will most likley be fed by your engines oil system and any fuel that makes it past the plunger will enter your engines oil. I am not sure if leaving it *patched* with a pump will be a good idea, You will still get diesel entering your engine oil. I think running your injector dry can cause damage, as you will never get all the air out of the lines using that method. Surely you can get a new diaphragm for the pump and install it yourself if you are mechanically minded. Good luck!
 

JustAwrench

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Yeah-what Taz said. I may have been premature about the warning of filling the crank with fuel. If the fuel pump is isolated from the crankcase, as may be with the belt-driven Peugot(going on momory here) in which case you would have an external fuel leak. That is, if the fuel was leaking at all. Some failures will leak one way(drawing air)but not the other(leaking fuel.) And, filling the crankcase with fuel will water down the oil, which will trash the bearings, but the more immediate and physical danger is once you get to a certain level of fuel/oil(mostly fuel) mix in your crankcase, it comes over the top of the pistons and then your engine runs away. Now after reading what you said I'm not sure if the Peugot will do this , but I wouldn't chance it. This probably dosen't help, but Bobcat has a Kubota conversion kit for the contemptable peugot 751, which turns it into a decent machine, IMO. Sorry for your troubles, Bob.
 

bobbie-g

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Yeah-what Taz said. I may have been premature about the warning of filling the crank with fuel. If the fuel pump is isolated from the crankcase, as may be with the belt-driven Peugot(going on momory here) in which case you would have an external fuel leak. That is, if the fuel was leaking at all. Some failures will leak one way(drawing air)but not the other(leaking fuel.) And, filling the crankcase with fuel will water down the oil, which will trash the bearings, but the more immediate and physical danger is once you get to a certain level of fuel/oil(mostly fuel) mix in your crankcase, it comes over the top of the pistons and then your engine runs away. Now after reading what you said I'm not sure if the Peugot will do this , but I wouldn't chance it. This probably dosen't help, but Bobcat has a Kubota conversion kit for the contemptable peugot 751, which turns it into a decent machine, IMO. Sorry for your troubles, Bob.
Shane, Taz, others: Many tnx for the advice and descriptions. I've been using the 751 as is, and it finally gave up the ghost. Had to keep pumping the primer bulb to keep it running at all. Goes into the shop now for a rebuilt ($1000) injector pump, plus some labor to swap it out, and might just ask them to do the timing belt while it's exposed. More later on how this chapter plays out.... ---Bob
 

JustAwrench

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Shane, Taz, others: Many tnx for the advice and descriptions. I've been using the 751 as is, and it finally gave up the ghost. Had to keep pumping the primer bulb to keep it running at all. Goes into the shop now for a rebuilt ($1000) injector pump, plus some labor to swap it out, and might just ask them to do the timing belt while it's exposed. More later on how this chapter plays out.... ---Bob
Sorry, man. Soemtimes a guy just has to suck it up and slap leather.
 

bobbie-g

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Sorry, man. Soemtimes a guy just has to suck it up and slap leather.
OK, gang. Problem resolved with lots of money. Needed a new fuel injection pump, $1400 new from the dealer plus several hours to install it. Runs fine now, starts every time. I believe the old one only needs the pickup pump repaired, there never did seem to be a problem with the high pressure injection system. Anyone out there who would be interested in the old one? --- Tnx for all the advice. ---Bob
 

Lavorn

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OK, gang. Problem resolved with lots of money. Needed a new fuel injection pump, $1400 new from the dealer plus several hours to install it. Runs fine now, starts every time. I believe the old one only needs the pickup pump repaired, there never did seem to be a problem with the high pressure injection system. Anyone out there who would be interested in the old one? --- Tnx for all the advice. ---Bob
I also have a pugeot 751 that is having similar problems. It was running fine until we changed out the filters and then it began to have the symptoms that you describe? We can make it run if we keep pumping the bulb, but it runs out of fuel when we quit pumping. Ours sounds like it might be a fuel line or something easy as it was running fine until we changed the filters? I assume I will be told to replace the fuel lines and check the cap? I was gong to just put an online elect fuel pump to resolve the problem? Now I won't! Hopefully I don't need a new injector pump. Any suggestions?
 

Lavorn

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I also have a pugeot 751 that is having similar problems. It was running fine until we changed out the filters and then it began to have the symptoms that you describe? We can make it run if we keep pumping the bulb, but it runs out of fuel when we quit pumping. Ours sounds like it might be a fuel line or something easy as it was running fine until we changed the filters? I assume I will be told to replace the fuel lines and check the cap? I was gong to just put an online elect fuel pump to resolve the problem? Now I won't! Hopefully I don't need a new injector pump. Any suggestions?
I should have been more clear: the machine starts just fine, but runs out of fuel after running a minute unless someone continues to pump the primer bulb. That is the only way to keep it running. Any new ideas?
 

Lavorn

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I should have been more clear: the machine starts just fine, but runs out of fuel after running a minute unless someone continues to pump the primer bulb. That is the only way to keep it running. Any new ideas?
A more specific question is how do I clean out the fuel tank as we have reason to believe it might be a dirty tank problem? Not positive, but a good place to start if we can get some ideas on how to clean it. Any help will be appreciated as this looks like a major deal to have to remove the tank and there is bound to be an easier way to clean it out. Thanks
 

OldMachinist

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A more specific question is how do I clean out the fuel tank as we have reason to believe it might be a dirty tank problem? Not positive, but a good place to start if we can get some ideas on how to clean it. Any help will be appreciated as this looks like a major deal to have to remove the tank and there is bound to be an easier way to clean it out. Thanks
There's a fuel drain under the machine.
FuelDrain.jpg


Make sure you only open the plug shown the other plug is for the chaincase. Flush the tank with mineal spirits. Flush it until it drains clear. Install plug, put in a couple of gallons of fuel and check the plug for leaks before filling the tank up.
To remove the tank the engine/pump assembly has to be removed so hopefully you can get it clean out by flushing.
 

Tazza

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There's a fuel drain under the machine.


Make sure you only open the plug shown the other plug is for the chaincase. Flush the tank with mineal spirits. Flush it until it drains clear. Install plug, put in a couple of gallons of fuel and check the plug for leaks before filling the tank up.
To remove the tank the engine/pump assembly has to be removed so hopefully you can get it clean out by flushing.
If you need to pump the hand primer, you may have a bad lift pump..... If the hand primer is being sucked flat, the problem is the pickup tube, if not it is very possible the lift pump is not giving the pump enough pressure.
The lift pump is aprt of the injector pump. Check your engine oil. Does ti smell of un-burnt diesel? is the level higher than it should be? I believe when these pumps go, they can leak fuel into the engine and dilute the oil.
 
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