My brace was tight. I don't think that would affect this gasket either way though.
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7520 fuel pump problems
- Thread starter jrchafin
- Start date
- Views: 17008
My brace was tight. I don't think that would affect this gasket either way though.
So finally got time to put the new gasket in my fuel pump and re-install. It doesn't leak any more, but unfortunately doesn't run right either. I think there may be something wrong with the pump, but before I take it for a rebuild, I want to make sure I'm not missing something I can fix.
It's a VE type injection pump, which runs off a pump gear with a woodruff key. I did not crank the engine or move the location of the pump gear while the pump was off, and did not rotate the pump either. I was careful to align the key with the pump gear when I put the pump back on, and I've aligned the timing marks between the pump housing and the engine block. The engine runs, but very rough and has some strange behavior.
It starts and idles fairly well, but when I give it fuel, it doesn't do anything at first. Then, once I add enough throttle, the engine takes off and jumps up RPM, running fairly well, but still rough. It smokes gray intermittently, and even back fires some.
Controlling the throttle on the pump itself with my hand, the first inch or so of rotation doesn't have any effect in the engine, and then it suddenly takes off, jumping to 2000RPM or so. If I release the throttle it returns to a rough idle. So is something stuck inside the pump? I can't see any other explanation for why the throttle would be doing this.
Any advice on troubleshooting would be much appreciated.
It's a VE type injection pump, which runs off a pump gear with a woodruff key. I did not crank the engine or move the location of the pump gear while the pump was off, and did not rotate the pump either. I was careful to align the key with the pump gear when I put the pump back on, and I've aligned the timing marks between the pump housing and the engine block. The engine runs, but very rough and has some strange behavior.
It starts and idles fairly well, but when I give it fuel, it doesn't do anything at first. Then, once I add enough throttle, the engine takes off and jumps up RPM, running fairly well, but still rough. It smokes gray intermittently, and even back fires some.
Controlling the throttle on the pump itself with my hand, the first inch or so of rotation doesn't have any effect in the engine, and then it suddenly takes off, jumping to 2000RPM or so. If I release the throttle it returns to a rough idle. So is something stuck inside the pump? I can't see any other explanation for why the throttle would be doing this.
Any advice on troubleshooting would be much appreciated.
Try rolling the pump... loosen the bolts then turn it clockwise as much as possible then tighten back down.. it wont move much but should help
Doesn't that change the timing? I'd love to understand this system better. What do you think is going on? Why would moving it clockwise help?
SPYDERLK
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Try rolling the pump... loosen the bolts then turn it clockwise as much as possible then tighten back down.. it wont move much but should help
Yes it does, but I think theres not much range of movement so you cant change it much. Is sounds like your injection timing is out. Could that gear you extracted the pump from have possibly skipped a tooth while it was not being held engaged firmly by the pump shaft? ... That would do it I think - and theres not enuf rotational adjustment to make up for it AFAIK.Doesn't that change the timing? I'd love to understand this system better. What do you think is going on? Why would moving it clockwise help?
larry
Yes it does, but I think theres not much range of movement so you cant change it much. Is sounds like your injection timing is out. Could that gear you extracted the pump from have possibly skipped a tooth while it was not being held engaged firmly by the pump shaft? ... That would do it I think - and theres not enuf rotational adjustment to make up for it AFAIK.
larry
It does seem like that could be the problem Larry, but I can't imagine how that gear could skip a tooth. Any experienced folks out there know if that is possible on this engine? I rotated the pump clockwise as Nav suggested, and it did help, but is still not running right.
Jon
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Ok. I'm waving the white flag. I got a day off today and pulled the pump back off, and the story just keeps getting worse. The nut that holds the pump shaft somehow worked it's way loose and was all the way off, but still sitting there when I took the front cover off. Unfortunately, the lock washer is nowhere to be seen. :ashamed:
I have determined there is no way to make the pump gear shift a tooth while it's still in it's housing, even with the pump off. Even went so far as to make a shaft that I bolted to the gear so I could shift it in every possible direction, and there is not enough play to disengage the teeth and shift them.
So I guess my problem must be the pump, which I will have rebuilt.
How much do I need to worry about that darn lockwasher??!! :duh:
I have determined there is no way to make the pump gear shift a tooth while it's still in it's housing, even with the pump off. Even went so far as to make a shaft that I bolted to the gear so I could shift it in every possible direction, and there is not enough play to disengage the teeth and shift them.
So I guess my problem must be the pump, which I will have rebuilt.
How much do I need to worry about that darn lockwasher??!! :duh:
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SPYDERLK
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There probably is nothing wrong with the pump. Any chance that loose/ missing nut caused enuf timing disruption to explain the ruf running? -- There is thrust due to drive on that helical gear that could cock it a little and change timing more than is intuitive. You could try reinstalling and see if its fixed. ... I would worry about the lockwasher, but probably irrationally. It likely fell out of the way and will stay there.
larry
larry
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I think the problem was air somewhere in the system. I pulled the pump again, replaced the fuel filters, checked all the fuel lines. i also used a boroscope to look inside the engine for that washer, and it's not in there. It's quite a large washer, and since it's a lock washer, it's pretty thick when not compressed, so there wasn't room for it to fall past the idler gear. Thankfully it's not in there. I just misplaced it somewhere. So I reinstalled everything, very carefully bled the lines and the pump. My plan was to do this and then bring it to a mechanic when it didn't run. But when I went to crank it, it fired up just like new. :cool2: