tqracer

i posted about a problem last week about 97 motor that would miss out and the throttle would stick. i took out the over flow valve. spring was fine and i pulled it out just a little. drilled and tapped bango bolt. i show 24psi and 30psi at wot. i know it said to check volume at the top of fuel filter but i checked it at the injection pump. not sure of cranking rpm but the flow chart said about 11oz for 30 sec cranking . i tried this 2 times and got 6 oz. this motor is in a 85 chevy truck witch has been in there about 2 1/2 years. pulled tank and replaced all the rubber hoses with new ones 3/8 ths size. retried flow test and came up with about 5 1/2 oz. got a different lift pump today to try it. fittins were differnt so i took the old ones out to use. the fitting on the suct. side had a foot valve in the old one with a spring that held it in place. it would not work the new pump so i did not use it. the fitting in the new pump just had a piece on screen in it no foot valve. started truck it fired right up. it did not run as good as before. checked the flow rate and only had about 2 1/2 oz. if i put an elec. pump on it what on do you recommend. or should i find the right man. lift pump to put on it. if i block off return line pressure goes up to 60 psi but did not seem to make it run much better. the pump on it now had 24 psi at idle mid rpm drop down to 19 or 20 and would go back to 30 psi at wot. thanks for your help

Partsman

Just a shot in the dark but on a 97 12v did you check the pre-screen next to the pump?

RCW

Put the original lift pump back on the truck and do a pressure and flow test. At idle you should have 17-22 psi, and at 2500 rpm it should be 25-30 psi.

The fuel volume test is difficult, as you must disconnect the shut down solenoid and run the injection pump dry before you do this test. Then insert a special fitting where the banjo bolt is attached to the fuel water separator at the rear line, then attach a rubber hose to that special fitting and into a graduated container. Be real careful you do disconnect any lines to the injection pump and let it suck any air. Leave the fuel shut down solenoid disconnected during the test. Then you need a very accurate tachometer that will read your cranking speed. You will crank exactly 30 seconds, no more and no less, then measure the fuel. Here is a table that will tell you how much fuel to expect, first number is cranking rpm and the second is ounces of fuel to expect:
200, 10.2; 225, 11.9; 250, 12.7; 275, 13.6; 300,15.3; 400, 20.3. If you do any other type of flow test, you will be wasting your time.

One other thing. Chevy uses a screen on the fuel pick-up in the tank. Pull and clean that before you test. It is also a good idea to pressure test the lines from the engine to the tank to be sure you do not have any leaks.

If you do not get the volume, or get the minimum pressure, replace the pump. Be careful you do not end up with the first generation diaphram pump on the second generation engine. It is a much less expensive pump, and will simply not work because it produces both low pressure and low volume. You want the piston type pump made for this engine. Take the CPL from the front driver's side of the timing cover and use that when ordering your new transfer pump.

The only electrical pump I would ever recommend as a replacement for the mechanical transfer/lift pump is the FASS unit. The others will overheat and fail.

tqracer

i do not have a tach to what rpms i'm turning. i have a new starter and 2 900 ca battery. motor spins over pretty fast so i say it is at least 200 rpm. i used the fitting in the banjo bolt suppling fuel to the inj. pump. might be just a little restriction. the old pump put out about 6oz. the pump i put on yesterday was new but would only put out about 4 oz. went to dodge today and got another new pump. put it on and started it did not sound much better. checked the flow of it and it only put out about 4 oz. not sure why i checked it but if i push the primer button it pumps out 16 or 17 oz in the 30 sec time frame. do you think the cam shaft lobe is wore down and not pushing the piston the right amount. i took the screen off the tank. i cleaned the pre filter screen. yes it was a piston style that i tried yesterday. talked to a guy that rebuilds inj. pumps and he said the fuel might be flow thru the inj pump with the motor turning . i crimped the return line off but still only got 4 oz.