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Idleing, fuel pressure is good (8). Straightaway is good(8). But in apex of turn and off, fuel pressure drops to bobbling between 2-3. Car stumbles off corner until fuel pressure picks back up, then everything is fine until next corner. Has new inline fuel filter. And guage line is in the log, so can't be carburetor issue. Car didn't have this problem last year, but we've seen it before in a different car or two. I would really appreciate any advice on what to check first.
Last fuel cell I bought had too short of a pick up tube, was doing the same.Quote:
Originally Posted by lucky 13
Is this a mechanical pump on the block? If so, I had the same issue and it was the fuel pump itself. Fought it for a couple weeks. Changed regulator, inline fuel filter etc. Still had issues. Ordered a new pump and it took care of it. Good Luck.
There was 17 gallons in the cell. I hate to have to take apart the cell. Especially, when we didn't have this issue with the car last year. Yes on the mechanical pump. I guess I'll try that first. But why would the pump work all the time except for when the g's are highest through the turn?(I'm not that mechanically intelligent). Thanks for the advice.
I had the same stumbling issues but my fuel pressure wasn't the problem. I extended the vents on the carb and the stumble went away. If your pressure is dropping it has to be the pump or regulator.
Might check how far the fuel pump pushrod is moving.Took a motor apart that was running fine, but the fuel pump lobe on the cam was going flat.
might also check the fuel pickup tube in fuel cell. if it is a rubber line, it could have curled up inside tank, exposing the end of the pickup line to suck air.
What kind of fuel pump and how old is it?
RCJ, I'm not smart enough to figure out the pump rod movement. But I can't understand, if there was a lobe, or rod problem, why wouldn't it act the same way all the time? Problem only during turn doesn't make sense to me how it could be that problem. As for pump brand, I'll check tonight, probably less than three years old. Once again, I appreciate the help from everybody.
It probably has less to do with the forces of the turn and more to do with the demand for fuel that you're putting on the carb coming off the corner. We had a very similar issue last season. It only occurred when the track was hammer down coming off the corner. As soon as I had to "manage" the throttle, the problem went away. A new pump fixed it and I'll never use another cheap pump again. We went with a CV pump and I consider it money well spent. The motor runs like a scalded dog compared to even a new cheap pump with the same ratings. Another thing to consider is regulator. If you're going to run a regulator, do it right and use a return style and do NOT put the regulator between the pump and the carb. Put it on the back of the fuel log so that the regulator regulates pressure without restricting FLOW. This is another common problem.
Was using a procam pump years ago and was having the same problem you are having. I adjusted the bowls way above where it should be and fixed the problem... for that night anyway.. problem came back again the next week. It ended up being the pump. Those things dont last more than 1 season. the springs get weak and everything inside dont last.. the pump cant keep up with the demand of fuel.. Worn out pump, 100%
Have you checked to make sure the fuel filter is going the right direction? Its worth double checking
measured a fuel pump cam lobe .300 to .350
Pump problem or pickup problem more than likely. The pump either can't pickup the fuel required to maintain pressure or the pump can't move enough volume to create pressure.
Check the O-rings in the fuel log. They will dry out and crack causing the pump to syphon air.