I guess I get to be first with an Apache specific thread on this new forum. I hope some of you can help me trouble shoot a fuel pressure problem that has just cropped up in my Geronimo.

A couple of weeks ago a passenger pointed out to me that, during takeoff and climbout, one of the fuel pressure guages kept dropping to zero, but he couldn't remember which one. During the cruising portion of the flight everything read normal, so I dismissed it as nothing. Yesterday during run up I noticed that the right side FP wavered from normal (around 4-5) to zero, whether or not the aux pumps were on. At one point When the pressure dropped I opened the crossfeed and noticed that the pressure came right back up. Because the engine seemed to perform okay, and there had been no other problems to this point, I proceeded with the takeoff. At about 50 feet in the air the right engine lost partial power and the plane began to veer to the right. Of course, this all happened just as I pulled the gear handle up! As I was recognizing that this was going to be an aborted takeoff, (which took about one half of a second), I glanced at the FP guages and, sure enough, the right side registered zero.

I quickly added left rudder to realign with the runway, pulled power back, threw the gear lever back down and landed just as the third green light winked on. During all the excitement of executing my very first aborted multi-engined takeoff at the worst possible moment (that wasn't initiated by my instructor), I completely forgot to try switching the fuel selector to crossfeed to see if that would've restored FP to the right side. (I'm kidding, of course!). Actually, it all happened so fast that my training took over and I didn't even have time to panic or do any troubleshooting- I just did the drill and made a nice, safe landing. Because I hadn't reached my "we're flying" point yet, the decision to abort was, in effect, already made when I started the takeoff roll.

So, before I go over to the airport and try to recreate the problem, I thought I'd submit it to the collective wisdom of this group and see if we can all learn something together. Here is some pertinent information: 1958 PA 23 with full Geronimo mods in 1978. Both Lycoming 0-360s have about 60smoh on engines and props. New mechanical fuel pumps, new carb on the left, same old carb on right. Both electric fuel pumps are less than 100 hours old. I had the crossfeed valve rebuilt and replaced at the last annual in December. During cold weather the right side fuel sump leaked, so I removed it, straightened the top flange, added a new gasket and reinstalled it- maybe 20 hours ago. The FP lines to the guages come off of the crossfeed lines at a fitting near the wing roots, so any pressure generated by either side's pump pressurizes the entire system on it's respective side of the crossfeed valve, until that valve is opened, then the side with pressure pushes fuel across to the other side.

That's all the pertinent info I can think of to help us slueth this pesky problem. Any ideas?

Mike Beard
N3285P

Here's an update on the missing fuel pressure caper...
I spoke with two former Apache owners who suggested the culprit may be aux fuel valves that don't seal tight, along with aux fuel tanks that are completely dry. This creates a situation in which the engines, while at run up power settings, do okay, but when at take off power and calling for way more fuel, the fuel pumps suck air through the leaky aux valve and cause low fuel pressure and partial power loss. I checked my aux tanks- I thought I had two or three gallons in each- and sure enough, they are bone dry. I duplicated the problem with the dry tanks, then added a few gallons to each tip tank and tried it again, and it seems that the problem is solved, sort of. I guess I need to have the aux tank valve o-rings replaced.
blue skies!
Mike

ZT,
THanks for the comments. I should update this post to report that the fuel valves were indeed the culprit, but not because aux tank valves were leaking. The main fuel valves weren't opening up all the way because the fuel cable linkages were stiff and a little out of adjustment. Repeatedly pushing the right side selector handle forward would eventually open the main valve all the way, but a thorough cleaning and relubricating the cables and adjusting the linkages at the valve bodies solved the problem.
Mike
N3285P