Engine Starves for Fuel When I Hit Second Gear

[Old Yeller 1970]

Originally Posted by Marv D

The one question no one has asked yet,, what fuel pressure gauge are you using that says it's only 2psi? The one common denominator here and I didn't see anything saying the gauge was verified.
So... I again say. BORROW A GOOD WORKING HOLLEY CARB and watch your 2nd gear problem magically disappear.

I thought about the gauge and tested it but didn't post the results. What I have is an adjustable Summit fuel line with the gauge on the filter. All my readings are from under the hood right off the gauge. I took it off and drained my air compressor down to nearly nothing and used the rubber tip of my air gun to blow into it. As far as I can tell the gauge is working accurately. It will swing up to the max at 15PSI and looked to be the same as the gauge on my compressor below that.

I thought about throwing another carb on the the truck, specifically a Holley 750 VS but I can't afford to buy one except with my credit card. I asked the local drag racing guru if he had an extra one and he didn't. Keep in mind I live in a county of 900 sq mi with less than 8000 people in it so there's not to many people to go to around here. [Edit: Notice in the picture above there is absolutely nothing in the back ground. That's not some photoshop wizardry. There really is nothing here. ]

If it's the carb and not the fuel pump, then tell me why the carb ran great when it was on the engine when it was stock. It made a huge difference over the QJ. I didn't change anything in the carb (other than turning in the four corner idle screws) when I put it on the new engine. What is different is way bigger heads, way bigger cam and way bigger HP. This engine definitely want's way bigger gas and it's not getting it.

Curiously I noticed after I parked it that the fuel in the bowls was slightly below the bottom line. I had set it at the middle line. After cranking the engine it came back up to the middle line.

Originally Posted by 383Ram

So i guess my next question is to the OP, what are your next steps to figure this out?

I guess I'm going to buy a $60 pump or a $260 750 Holley if Marv talks me out of the pump.

One last thing. I was looking at a different brand pump last night and read through the installation instructions for that pump. After repositioning the body it said: "Before fully tightening these screws, the rocker arm must be actuated to and held in the “full stroke” position. This is done to ensure that the diaphragm will be pulled to and held in its maximum working (flexed) position while the retaining screws are torqued tight (20-25 in/lbs.). This procedure will ensure against premature diaphragm wear and subsequent failure due to over-stretching of the diaphragm material when in the full stroke position. Another by-product of an improperly set diaphragm is erratic fuel flow and pressure. NOTE: This procedure can be assisted by holding the fuel pump in a vise or appropriate fixture, and holding the rocker arm down with a pipe or similar tool."

I thought what the heck, pumps are pumps I'll try it on mine and see what happens. After re-installing it on the truck my PSI nearly went through the floor whereas it had been 2 1/2-3 it was now no better than 1 1/2.