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  #1  
Old 08-28-2017, 12:19 PM
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rblackley rblackley is offline
 
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Default Mechanical Fuel Pump Issue

I either have a bad mechanical fuel pump or I didn't allign the push arm and flange correctly when installing pump. How do I tell which problem I have?
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  #2  
Old 08-28-2017, 12:27 PM
YellowJacket RV9 YellowJacket RV9 is offline
 
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If you pull the pump, I would imagine the wear pattern on the end of the arm could indicate if it is making contact properly with the pushrod. If you are unsure I would definitely want to pull it and check. I believe at least one fatal accident has been attributed to an incorrectly installed mechanical pump that led to catastrophic engine failure.

Chris
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  #3  
Old 08-28-2017, 12:41 PM
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Default The wear mark is correct from the previous instal.

if it's not aligned correctly now and I start the motor I assume that it will leave a mark on the side of the flange. Is the is there a way to bench test a bad fuel pump visually or otherwise?
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Old 08-28-2017, 02:18 PM
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Quote:
Originally Posted by rblackley View Post
if it's not aligned correctly now and I start the motor I assume that it will leave a mark on the side of the flange. Is the is there a way to bench test a bad fuel pump visually or otherwise?
I don't think it would leave a mark, as the cam follower would not be moving. It would be in the "down" position, just sitting there. The pump pushes it up, the cam pushes it down, IIRC.
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Old 08-28-2017, 03:00 PM
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I thought if it wasn't aligned right, and then torqued down, it breaks the plunger off?
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Old 08-28-2017, 04:19 PM
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Pull the drain plug at the back of the sump and send a bore-scope up the back side of the engine. You should be able to see if it is aligned. Pulling the pump might be just as easy, though.
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Old 08-28-2017, 05:05 PM
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What makes you think the fuel pump isn't working? No full pressure? Engine will run only on the boost pump? Loud banging noises from teh accessory case when you crank it over?

If you want to look with a borescope, I think the left mag hole will give you the quickest access.
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  #8  
Old 09-06-2017, 11:15 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by rv6builder View Post
I thought if it wasn't aligned right, and then torqued down, it breaks the plunger off?
This would me my assumption. Either the rod would bend or the shroud in the casting would crack off. I suppose the fuel pump arms pivot pin could also crack. I think Paul has the best idea. Pull the left mag and use an automotive inspection mirrror. You will be able to see the pump arm and pushrod. You could also just pull the pump, inspect the parts and reassemble. It's pretty easy to tell if you have done it correctly if you take your time and follow good procedure. You can keep angling the pump (up and down) after a turn or two on the bolts. It is a feel thing, but generally If you feel the spring tension in both directions, it is aligned. When you are not on the pushrod, the pump doesn't want to tip up. The key is not to let the side to side angle deviate from 90* during the entire process. However, slight deviations left and right will also let you feel if the plunger arm in hanging up on the side of the pushrod or not. If your inexperienced, force the arm to one side while installing (without bolts of course) and see how it feels. Sometimes it helps to know exactly how it feels when it is wrong.

Larry
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Last edited by lr172 : 09-06-2017 at 11:28 PM.
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