Engine/Transmission (1998.5 - 2002) Fuel pressure Question

[GeneralMachine]

Ive noticed when the key is first turned on the fuel gage don't move, also doing the starter bump the fuel PSI only reaches 5psi, on engine start up instant 15 psi, wot not less than 10psi, I feel these are good number's, running but im use to seeing 5psi just turning on the key, and the starter bump reaching 15 psi, something has changed. I was woundering if anyone else has had this ordeal and if so wasupppppppp? TIA Harv

 

[Bfoot17]

Where is your pressure gauge located at? Before or after the filter?

 

[Huff N Puff]

You need to check power to the pump

If you have power and ground to the pump when you turn the key on and no pressure. Replace the lift pump. Remember the PCM controls power to the lift pump might be one reason the lift pumps fail alot. If this is the case you could use the PCM power source to the lift pump to turn on a relay which in turn powers up your new lift pump. May make it last longer. Merv

 

[Steve St.Laurent]

You are fine. There was a reflash and there may be some later trucks that had the flash that only run the lift pump for a VERY short period of time (I've heard 2 seconds in some cases) when you turn the key on before cranking. Fuel pressure may not build that fast especially in cold weather with thick fuel. When you are cranking your ECM pulses power to the lift pump for a lower PSI for startup as well. High pressures (> 7 psi) during cranking can create a hard start condition with the VP44. The hard start condition was the reason for the reflash. As long as you are seeing good pressures (which you are) once the truck is running you are fine.



Just noticed you mentioned you only see 5 psi on a start bump. My bet is that it's because the heater grids are cycling in combination with thicker fuel being it's cold. The heater grids pull a LOT of juice. Now that it's winter your grids are coming on when you turn your key on and come on again at a starter bump. The next time you drive your truck on a warmer day after you've driven it for a while and it's fully up to temperature shut it down and do the starter bump and see what happens. I bet you'll see the same as you saw in summer.

 

[GeneralMachine]

Thank's for the reply's, I didn't think about it being cold im gona try that today ill bet that's it, for our morning's here are in the twenty's and all summer just turning on the key gave me the 5 psi, and a starter bump would give me 15psi, im gona driver to work today and give that a try. Thank's again for the input. Harv

 

[GeneralMachine]

Originally posted by Bfoot17

Where is your pressure gauge located at? Before or after the filter?

I have the gage right on the pump, put the tapped banjo there, fuel filter is new only 500 miles on it, it has always showed the pressures i posted, Stve may be on to something with the grid heaters and cold weather im gona give it a 18 mile run to work today let the 12 valve rest and see what it does all nice and warm. Harv

 

[vaicase]

you should always put your gauge reading after the filter because a plugged filter will cause a lower reading and keep you informed of your filter maybe getting plugged if you think your lower reading is not caused by the filter just put it before the filter with a bajo bolt from genos garage or wherever thanks

 

[GeneralMachine]

Hey guys' All's well Steve hit the nail on the head, must have been the grid's and the temp of the fuel for after all was warmed up to normal operating temp all reading's were back to normal, thank's for the input, Harv