Alright so ive got a 1990 cherokee, died on me it the woods about a month ago. Got it home crank but no start, basic diagnostic lead to no power to fuel pump. replaced the starter relay and cleaned up any related conection. Was able to get it to run and drive around the yard, almost stalled a few times, ran a pressure test and am getting about 10 psi in the fuel rail. Looking for tips and what direction to take to get the fuel pressure to where it needs to be.

 

Fuel filter costs something like seven bux. I'd start there.

Why did you change your starter relay to get power to the fuel pump?

 

31 PSI at idle and it should jump to 39 psi when you remove the vacuum line from the fuel pressure regulator on the front of the fuel rail.

 

Watch the pressure gauge as you prime the key a couple times. Does it build pressure? Does it hold or does it fall?

 

I replaced the filter and pump yesterday, get about 20 psi on start, after a few seconds it drops to 10 and dies out. could it be teh cps or maybe the ballast resister

 

Honestly not sure how or why that helped i have a fused link just off the starter relay in the ornage/black wire. When cracking the fuse would pop. Replaced the relay and now the fuse stays good and it starts.

 

CPS doesnt have anything to do with your fuel pressure.

 

The ballast resistor was installed to quiet down the fuel pump... owners were whining about them being too noisy.

A quick test would be to splice the two ballast resistor wires together and see if there is any change.

 

Ive tried that as well didnt make a differance, just checked and am getting about 8.5 volts to the pump while running.

 

8.5V at the orange wire? How is your ground from the pump?

Have you got the wiring schematic on hand?

 

At the connection off the pump its a purple wire that has 8.5V. As far as i can tell the pump is grouned. Yes i have the schematic.
Just started it and the pressure jumped to 31 for about half a second then down to 20 and slowly droped from there.

 

Pull the vacuum line off the regulator with the engine running (if it lets you get that far) and see if theres any fuel in the line. You shouldnt see or smell any fuel.

 

That's interesting... the schematic I have for the 90 shows the + wire to be orange and the - to be black.

Make sure your ground from the pump is clean and tight.

 

Just tried that seems clear put my nose to it and no smell.

 

It seems like someone may have rewired it at some point, an orange wire comes out of the frame then is spliced into a green wire that connects to the purple off the pump.