What happens when the rack sticks or hangs up?
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Topic: What happens when the rack sticks or hangs up?
Posted By: DougG
Subject: What happens when the rack sticks or hangs up?
Date Posted: 16 Mar 2013 at 9:40pm
| What causes a P series pump rack to stick open? Or i guess a pump to cause an engine to run away at open rpm,s ; got an A pump on a 180 and a fella said to keep the in fuel pressure around 20 psi to avoid rack or plunger sticking ;; heard of horror stories so what causes it to happen? |
Replies:
Posted By: O.P.S. Heads
Date Posted: 16 Mar 2013 at 10:17pm
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An injection pump guy can explain this better than me, but I will try. Think of any inline pump as an engine. The plungers go up and down inside of the barrels just like pistons go up and down in an engine. The plungers also act as a control valve of sorts and rotate within each barrel. The rotation of all six plungers is what dictates the fuel delivery amount and is controled by a common rail type gear which is the rack. The rack is controled by the governor. When a plunger seizes inside of its barrel it will no longer go up and down or rotate. When one can't rotate neither can the remaining five since they are all controled by a common rack. What then happens is that the heathy five plungers keep pumping fuel to the engine. They are usually stuck in a position of high fuel delivery so the engine runs nuts on the healthy five cylinders. The tell tail sign is a miss in the engine. This of course is due to the cylinder with the stuck plunger being dead as no fuel is being supplied to it. Every pump is different and every pump builder has a different idea, but 20 lbs sounds like a low number for supply pressure. 60 - 90 lbs sounds more like it on a pulling pump.
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Posted By: SteveM C/IL
Date Posted: 17 Mar 2013 at 4:48pm
| Don't quote me,but my understanding is that it's forien material in fuel system that scores a plunger causing the sticking situation. Barrels and plungers have no room for swelling from a scratch. Farmer built fuel supply systems aren't known for being "sterile". |
Posted By: wi50
Date Posted: 18 Mar 2013 at 2:08pm
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I have some take out plungers and barrels I should take a picture of and post so you can visualize what happens..
The plunger has a notch in the top and a helix cut in the side of it. There's a hole in the barrel or (sleve). As the plunger comes up to pressureize the fuel, the port is closed off in the barrel by the helix. Depending on where the plunger is rotated, this changes the point of port closure and controlls the amount of fuel sent to the injector. At idle the plunger port allignment stays open for a good share of it's stroke and bleeds the fuel off, at wide open fuel delivery the plunger is rotated to close the port off much earlier, pumping more fuel. All the plungers are hooked togather on the rack. One plunger sticks, they are all held in that position, usually wide open. ------------- "see what happens when you have no practical experience doing something...... you end up playing with calculators and looking stupid on the internet" |
Posted By: Larry(OH)
Date Posted: 19 Mar 2013 at 5:48am
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I just heard..and this is through the pulling grapevine that Adam Biehl, running the "Mule Deere" John Deere LSS ws just killed testing a pump on a new engine. The story is they think the rack stuck and ran off and the cast flywheel came apart. WI...you may be able to find out more from the SS world, not sure. Left behind a wife and 2 daughters
http://www.mariettatimes.com/page/content.detail/id/550536/Tractor-repair-work-turns-deadly.html?nav=5002" rel="nofollow - http://www.mariettatimes.com/page/content.detail/id/550536/Tractor-repair-work-turns-deadly.html?nav=5002
------------- '40 WC puller,'50 WD puller,'50 M puller '65 770 Ollie *ALLIS EXPRESS contact* I can explain it to you, BUT I cannot understand it for you!! |
Posted By: injpumpEd
Date Posted: 19 Mar 2013 at 12:31pm
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OPS, & WI nailed it. I've seen plungers seize due to dirt or foreign material getting run through, but another thing causes it is injectors that are too small to flow what pump is pushing out. The whole Adam Biehl story is just a terrible thing to have happen, anywhere! ------------- 210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers! |
Posted By: DonDittmar
Date Posted: 19 Mar 2013 at 1:39pm
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Saw that about Adam on the NTPA facebook page earlier. Bad deal........ ------------- Experience is a fancy name for past mistakes. "Great moments are born from great opportunity" 1968 D15D,1962 D19D Also 1965 Cub Loboy and 1958 JD 720 Diesel Pony Start |
Posted By: Butch(OH)
Date Posted: 19 Mar 2013 at 5:45pm
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I too am very sorry to hear about Adam. I dint know him other than watching him at the pulls, a tough competitor he was. Here are the pump pieces the guys are referring too. This is a Bosch pump for one of my antique diesels but same operation only for one cylinder. Ed can likely explain them much better than me but in the foreground to the left is a plunger. To the right is a barrel. You can see the helix that OPS and Marty referred to. Also see the hole in the right side of the barrel. The stroke of the plunger is fixed. what controls the fuel flow is the relationship of the helix to the hole in the side of the barrel. The more stroke prior to the hole being lined up with the helix cut the more fuel to the injector that stroke. At the top of the plunger is the no fuel slot for killing the fuel flow. When you hear people say a "13mm pump" 17MM or whatever they are referring to the diameter of the plunger which in this case is 8MM. The fit of the plunger to the barrel is both precise and critical. The rack and pinion that turns the plunger as behind it along with the body of the pump. An interesting aside is this style pump was invented by Benz and perfected by Bosch in the early 20s and still in use.  |
Posted By: DougG
Date Posted: 19 Mar 2013 at 7:16pm
| Thanks for the info ! |
Posted By: bmartin55
Date Posted: 20 Mar 2013 at 11:27pm
| hi im bob from vincent ohio ..it was a mess hear sunday because of the accident..it was just a year a go on the same farm with marks accident. the flywheel& clutch parts thrue the roor of the building.. |