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I am having a problem the fuel system air compressor on my 1928 Series 36. When starting the engine cold, I pump up the fuel pressure with the hand pump to “2”. After starting, for the first 5 minutes the fuel pressure gradually drops. After 5 minutes or so the needle starts “wiggling” a little and the pressure rises to 3 and remains there. It seems that the air compressor doesn’t make pressure for the first 5 minutes of running until it gets warm. In talking to some other dual valve 6 owners, they say the needle on their pressure gauge starts wiggling from the time the engine starts. This problem only occurs on a cold start and once the compressor starts making pressure it seems to continue to run fine. With the engine not running, the system holds pressure, so no leaks. Before I take the compressor apart, anyone have any ideas on what the problem might be?
I only noticed the problem recently because I filled the car with some of that good non-ethanol gas at the end of the Kerrville meet, so there is not much air space in the tank and the engine started stalling because of low fuel pressure. I suspect if the fuel were lower, the pressure would hold long enough for the compressor to kick in.
Thanks,
Dave
It is not unusual for the pressure regulator mechanism to develop a bit of sludge which causes to ball in the regulator to stick. Loosen the jam nut and remove the center mechanism. With this out use a small pencil like magnet to remove the ball. Clean these parts with a little WD-40. Squirt a bit of WD-40 down in the hole. Reassemble being careful not to change the position of the jam nut. If you need to adjust the pressure, turn the center piece out to increase the pressure or in to decrease the pressure.
Thanks Paul. It sounds pretty simple. I’ll let you know how it works out.
Dave
Success. I didn’t have a magnet that would fit into the compressor body, but putting a piece of 1/4″ I.D. soft plastic tubing down the hole and sucking lightly on it brought the ball out. I did not notice any crud inside and everything that came out was oily but otherwise clean. I flushed the housing with WD 40, ran a pipe cleaner(remember those)down it (again no crud) and reassembled. The pressure built up immediately upon start and held at just over 3.
When I took the outer lock nut off, it was loose, not even hand tight. I am wondering if pressure was leaking past the nut gasket so it was just taking a long time to build pressure. I would have thought that the tank pressure would have bled off when I let the car sit for 2 hours, but maybe there is a check valve somewhere downstream that prevents pressure from bleeding back out the compressor when the engine is not running.
Dave
Thanks for the update Dave, good to here you’re back in the saddle!
Hi John, Donna told me she wasn’t going to keep pumping the hand pump while we drove, so I had no choice but to fix it.
ha, good stuff!
When I drove Nate’s (yours) car at the Tahoe meet it had that problem and I learned to drive and pump the fuel at the same time until it would maintain some pressure after some five minutes, JUST like you described. I’m glad that you’ve fixed it.
Bill
Well, I haven’t taken it on a lengthy drive yet, so we’ll see how it holds up. We had no problems with it in Kerrville, but I usually let it warm up for at least 5 minutes, so I may not have noticed it. It made all of tours, over 300 miles, with the only minor issue being a leaky water pump, since repaired by repacking.
Dave