Retz Posted February 9, 2019 Report Posted February 9, 2019 I'm having an issue that despite all of our tries, we can't seem to isolate. The low electric boost pump setting in my 252 is not working. I'm out of ideas, and anything you guys have to offer would be grand. Here is the what we have tried: 1. New Electric fuel pump (old pump had same problem, so we had it overhauled) 2. Pump works fine with switch in Hi 3. Pump inop with switch in low 4. With 12V battery connected directly to pump, it operated normally in low 5. Voltage checked at pump cannon plug. Hi produced 24V and low produced 12V 6. Rewired cannon plug and ground, no fix 7. Power across switch is normal I'm out of ideas to approach. I took out the fuel pump regulator and inspected, it looked fine. Besides, the power is correct at the cannon plug. Is it possible that the boost pump regulator isn't putting out enough amps? How would I test that if it isn't at a load? Thank you for any ideas, Joe Quote
ArtVandelay Posted February 9, 2019 Report Posted February 9, 2019 Connect the 12v battery to the cannon plug. BTW, checking voltage on a open connection doesn’t necessarily mean it’s good, a corroded connector may provide too much resistance to allow enough current to pass, but enough to show a voltage.Tom Quote
carusoam Posted February 9, 2019 Report Posted February 9, 2019 Some continental fuel pump controllers... (IO550s) Have reported issues of the Lo boost control failing... See if you have a pump controller connected to the Hi/Lo boost switches? A search around here should find additional detail. PP thoughts only. Not a mechanic. Best regards, -a- Quote
N231BN Posted February 9, 2019 Report Posted February 9, 2019 Find a way to measure voltage with the pump connected, I bet it doesn't stay at 12v. Your regulator is either bad or like mentioned above, you have a dirty connection somewhere. Quote
Retz Posted February 9, 2019 Author Report Posted February 9, 2019 My thought was the regulator b/c I completely rebuilt the connector, and it still doesn't work. Prior to this I also pinned in a 12V battery through the connector and it worked. It does have the regulator. I have previously removed and inspected it. It is a very simple circuit with just a transistor and a few resistors. My guess is that the transistor failed, it is the most likely culprit. Does that match with any of y'alls thoughts? Thanks for the help Quote
Cody Stallings Posted February 9, 2019 Report Posted February 9, 2019 Had the same issue with my 252. Don Maxwell fixed it over the phone. Just above the co-pilot left knee up under the panel is a step down resistor that’s used for the low/fuel pump, fortunately mine just had a bad ground so it was a easy fix. If the high side of the pump is still working, I would bet your problem is in that area. Quote
squeaky.stow Posted February 9, 2019 Report Posted February 9, 2019 Had exactly the same problem. It was the regulator. Sent it to Don Maxwell for repair. They fix these all the time and it cost around $300 if memory serves. A new one from Lasar is $1800. Some older Ks had just a resistor instead of the regulator. Quote
Retz Posted February 10, 2019 Author Report Posted February 10, 2019 9 hours ago, Cody Stallings said: Had the same issue with my 252. Don Maxwell fixed it over the phone. Just above the co-pilot left knee up under the panel is a step down resistor that’s used for the low/fuel pump, fortunately mine just had a bad ground so it was a easy fix. If the high side of the pump is still working, I would bet your problem is in that area. Cody, Do you have the contact data for Don Maxwell? How did you fix the ground? Cheers Joe Quote
Retz Posted February 10, 2019 Author Report Posted February 10, 2019 6 minutes ago, Retz said: Cody, Do you have the contact data for Don Maxwell? How did you fix the ground? Cheers Joe I have his contact info, but how did you fix the ground. Quote
Cody Stallings Posted February 10, 2019 Report Posted February 10, 2019 The resistor was grounded to the panel that it was screwed to. Took the acre out an cleaned the mating surfaces with scotch bright an put it back together. works great now Quote
carusoam Posted February 10, 2019 Report Posted February 10, 2019 http://donmaxwell.com/ Somebody looking for DMax? Around here, it is possible to find @Pmaxwell Paul can be pretty helpful as well... Best regards, -a- Quote
JRam Posted February 10, 2019 Report Posted February 10, 2019 I had this problem when I first picked up my plane. Mechanic struggled to find the problem. @DanM20C had the guy pull the step down box out and they drilled out the rivets to find a broken weld. Turned out to be a simple fix. He could wiggle the wires and it would intermittently work. Quote
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