Hello y'all

so I am having an issue with my fuel pressure as I I have the beast running and its only giving me 26PSI. but lets start from the top; I hooked up the fuel gauge and turned the key to the "on" position and it reads 0PSI I go to crank it and it slowly climbs to 26PSI than when I remove the vacuum line on the regulater do-dad(right next to the fuel press. test port) nothing happens no rise or drop in press. when I turn her off the press. drops to 10 than down to 0. also when I drive it it likes to die after about half mile it also cranks for about 4-5 secs on start ups even when hot. any ideas?

1990 cherokee 4.0l

thanks

 

pressure should be 31, 39 with vacuum disconected. change fuel filter just because, but the problem sounds like the pressure regulator. that's the dodad with the vacuum line on it.

 

Just did the filter and the fuel pump is only a fee mo old kinda looked small when I put it in. But I was thinking the same that it was the fuel Pres. Reg.

 

I think you can pinch off the return line, alittle, for a second. See if the pressure shoots up.

 

With the key in the on position, the pump should run for 2 seconds and you should see some pressure. The Pressure Regulator could still be bad, but if sounds like a pump/filter issue as well.

 

When the key is in the "on" position I have no fuel Pres. Only when I crack it will it start to slowly build pressure. It also dies when driving. Might it be both these things?

 

There may be an issue with the fuel pump ballest resistor on the left fenderwell.

 

it may sound stupid, but go back and double check all the hose clamps on the fuel pump. i burned through a decent amount of money just to find out that my fuel pressure problem was a hose clamp that came loose on the fuel pump, it would run and drive but die underload.

 

^ that will be my next step tomorrow. After making sure that the balst thing had clean wires to it it still keeps a low pressure and only builds pressure when cranking so maybe it is a lose fitting

thanks again all

 

Checking for clean wires to the ballast resistor is not the way to troubleshoot this component. Here are the only two ways.

1. Measure it with a meter. If it fails, replace it. They're cheap

2. Bypass it with a short piece of wire. The ballast resistor is there only to reduce noise on the fuel pump circuit, so you can safely bypass it. Starting in 1994, Jeep actually eliminated this resistor

By design, the ballast resistor is bypassed when the key is in the full right START position. But when you let off the key and it goes back to the ON position, the ballast resistor is back in circuit.

 

What kind of fuel pump did you put in it?

Fuel pressure should be a consistent 31 PSI with the vac hose connected and 39 with it disconnected. If you disconnect the vac hose while running is it leaking any fuel out of the vac line? If it is then the regulator is bad and needs to be replaced. Also with the key in the on position can you hear your fuel pump cut on?

 

What should the reading be when using a volt meter?

I used the one auto zone supplied http://www.autozone.com/autozone/par...86870_27854_0_

also I can not hear the pump come on at all when the key is put in the run position and when the vac line is disconnected there is not change in pressure and no leaks

 

ive heard lots of bad things about airtex fuel pumps being flaky.

heres some better ones
http://www.rockauto.com/catalog/x,ca...,parttype,6256

 

Great news! After deciding to buy and replace the fuel pump all is fine in the jeep world and she is running and driving like a champ! I would like to say I didn't think size mattered, But after pulling the old one out I found the thing was tiny! no wonder it couldn't keep up with my gas guzzling needs. The new one fits great and when in the 'On" position shoots the psi to 35 and holds 32 when running and when shut off holds at 20.

Thank you all who helped out on this one