OK so my truck has been misfiring like crazy lately and i think its ether the fuel pump or fuel pressure regulator. the truck is hard to start now and it used to start right up. I dont have the valve on my fuel rail to check fuel pressure or the adapter house to check the fuel pressure so i just undid the fuel line on the frame and stuck my fp gauge on it and turned the pump on and the pressure went up to 48 psi then went off and held at 45 psi. I believe the psi should be 35-40psi right? I left the gauge on and checked the pressure 15 min later and it went down 10psi. I think it should stay constant wright? there is also a really gasy smell to the exhaust. Plus my gas gauge has been going crazy for about a year now witch ive been told its the sending unit. So i think its time for a new fuel pump.

So assuming i do need a new one , i was think about trying to put a external fp and regulator in. has anyone ever put a external fp and regulator on our trucks? If not do you guys think it would be hard to do?

 

psi should be 49 +/- 5, so yours is on the money. its also normal to bleed off a little in 15 minutes.

if running rich/poor mpg, i'd suspect front O2 sensor, or one cylinder not firing (and passing gas)

 

Would that cause the truck to be hard to start? I am sure the O2 censor needs to be replaced ether way i just want to make sure i know what it is before i spend money on something i don't need to.

 

you could just have some dirty fuel injectors.....the are very easy to remove and inspect. i would give that a shot....and be sure to put new o-rings on injectors if you do remove them, dont use the original

 

i removed the injectors a few months back when i did the plenum. i cleaned them and put new o rings back in so i don't think it would be that but i could be wrong, have been be for lol. ill check though just to be sure.

Ive also all ready replaced cap, rotor, plugs, wires and coil.also have checked the asd relay to. if that helps narrow things down.

 

If you cycle the key a time or two before you try and start the truck, will it fire right up?

 

No it still wont fire right up. itll only fire right up if i start the truck right after i turn it off.

 

Would be interesting to see what the PCM thinks engine temp is at cold start.... (the gauge uses a separate sensor than the PCM)

Usually, long crank times are associated with low fuel pressure.... but, yours seems ok, at the pump..... and if it runs good once started.... throws another wrench into the thought process.

 

so do you have any ideas to what it could be?


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When we the last time the truck had a tuneup? (cap, rotor, wires, plugs)

Unfortunately, there is a whole host of things that could be the problem.....