Have any of you guys seen a fuel pump lobe wear out on a small block Chev? I think that's what's causing my driveability concerns.......I've got fuel pressure, but no volume. Truck's been sittiing for a while, carbs are empty and they won't fill when cranking for an extended period of time........developed a valve tic too. Cam's probably on it way out...... Thanks!! JS
I have seen the arm extending from the fuel pump that contacts the lobe lose its tension or not return all the way to properly contact the camshaft lobe therefore resulting in loss of volume and or pressure.....this is easy to check by pulling the pump and bench checking it's operation...just my 2 cents worth
The arm on the fuel pump doesn't contact the cam on a SBC. You could have a check valve problem. New pumps are relatively inexpensive.
Sheepdip, there is a special pushrod that actually rides or follows the cam lobe in between the cam and the fuel pump actuating arm.
I have seen some fuel pump pushrod worn down,but ck the fuel filter and fuel to the pump,if ok test the fuel pump
last time I went thru this on an old truck with a 283, I finally got it going again after running a piece wire thru the fuel line that feeds the pump....could be lots of things causing the problem. Use a systematic approach, make sure that fuel runs out of the pump inlet line when you disconnect it from the pump, then make sure the pump is pumping it, then make sure it's getting into the carb.
I've had a SBC with a cheapy fuel pump that just had a roll pin for an arm pivot point. It wore quickly and got a noise like a lifter tick. Was still pumping OK when I changed it to get rid of the noise. Maybe yours is a little farther gone?
If it has been sitting, the valve tic you hear might just be a lifter not pumping up(you didn't say hydraulic or solid lifter cam) I find that a quart of Rislone or a quart of Marvel Mystery oil added during an oil change will help loosen sticky lifters and remedy valve tics
The lines are new ( rubber fuel injector hose/steel ), filters have been replaced, pump's been replaced. I put a new tank and sender in it 2 years ago. Fuel sample is clean. checked for vacuum leaks, I checked the rod, it fell right out of the hole when the plate was removed. It's running so lean now to the point of running hot, even overheated on me the last time I had it on the highway ( trying to make it home ). It got progressively worse over time ( think AC comp cycling rapidly while at speed, or a later model veh that can't decide if it wants to go into lockup or not ), then a couple rockers started tapping on the right side bank. Carbs have been taken apart and meticulously cleaned. I'm thinking of taking an elec. pump I have laying around and see if that makes it better. I was just curious to see if anyone has experienced the pump lobe wearing out......thanks for the input fellas!
contemplating what you said,, "then a couple rockers started tapping on the right side bank",, makes me think is there an oil pressure problem? first you have rockers tapping, now a blown fuel pump eccentric,, maybe your cam is goin flat,, how much oil pressure you got? if your pressure is ok, and your cam is ok, but your eccentric is gone bad, then yea an electric pump and a regulator could put you back in business.. suggestion,, change your engine oil and filter, check it out closely in the drain pan, check for metallic particles and if you really are curious (like me) cut the oil filter open and see what goodies lurk inside.. let me know if you go that route,,
Actually, the driveability concern started before the valve noise ( lean condition....ran better partially choked ), oil pressure is good. I do suspect the cam is going flat.......just not too happy about it! I will be dropping the oil, will let you know what I find.........
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