low fuel pressure

Yes did u try hooking up in the threaded hookup I have never tryed using the quick connect. I thought that was for priming the fuel system. Use liquid filled gauge it wont flutter near as much. Ive never seen any info on using the quick connection for pressure test and I have alot of cat manuals. Im not sayin your wrong I just have never herd of using the quick fitting.

 

yeah i use the threaded hook up at the front top of base. like i said i figure where it vibrates the highest is the pressure. i only put one washer in to shim it. i dont want to shim it anymore until i figure whats causing this.

 

where exactly on the filter head are you testing the pressure?
Usually there is a test port along side the Fuel temperature sender. This will show the Transfer Pump pressure best and the jumping needle is an indication the Safety relief valve in the pump is cracking off and closing continuously.

There is another plug that can be removed from the front left of the filter head and this is After the filter and you will not see as much fluctuation in the gauge at this port. What you can look for is the pressure difference between the pump side of the filter head and the Head side of the filter head by putting a gauge in both these test ports.

 

thats where im hooking up the gauge on the front top of base. could a pressure line cause this by swelling shut? the only rubber line on the pressure side runs from the filter base to the connector for the steel line that goes to the front of head.

 

Test the fuel pressure at both sides of the filter head. If there was a hose blocked the restriction would cause a Higher pressure and from what you have posted you have a low pressure problem. Mind you if the restriction was before the port that you are taking the pressure from then you would see very little evidence of the Safety relief valve in the pump cracking off and this is not the case as your needle is jumping.

An example of this is you may have 120 PSI before the filter and 70 PSI after and when under full load 130PSI before and 30 PSI after which I recently witnessed on one truck with low power and vibration complaints under load.

 

ok could an injector be causing this? im inclined to think not because i dont get any smoke at startup and im not making oil and water if it was going in through a cup.

 

ok switched to other port same readings. needle still vibrates some i think it's the gauge im using its for testing automatic transmissions.

 

an Injector???
I thought the complaint was Low fuel pressure? I get the impression from your posts the needle is jumping when you test the fuel pressure. This would indicate some sort of relief cracking off... if it was fuel leaking internally then the fuel pressure would be low due to leakage and not making the relief valve crack.
I would suggest you start from scratch and take your first fuel reading from the test port to the right side of the Fuel temp sender. then record this at low Idle. Mid RPM range say 1400 and then at Hight Idle.. noting the movement of the needle.. then put the gauge after the filter on the test port on the front where the fuel exits the filter head. record and not this movement also.

 

Your gauge could also be 10 PSI out so maybe find another gauge to back up your readings. If the pressures are the same either side and the characteristics of the needle movement the same its indicating to me the Safety relief valve is cracking off and it would appear to be premature pending the accuracy of your gauge. I use a Dual Needle gauge and test both at the same time.

 

ok i moved to other port same readings bounces between 95 and 80 lbs. im just at a loss here just throwing out the possability of an injector causing this. like i said in a previose post i have changed the trans pump and check valve and suction lines and return line from head to filter base. popped the buttons out of primer pump and it seamed to help a little. at 700 rpm it's bouncing between 65 and 75 lbs. at 1400 it's at 80 to 88 lbs and at 1900 rpm at 80 to 95 lbs. with one washer shim in pump. before i took the buttons out of primer pump it would stay between 70 and 80 give or take a couple of lbs.