My truck is chugging again during prolonged acceleration and I am wondering how I can tell what is wrong. I have had both the lift pump and the OPS cause this in the past. I don't have access to a pressure gauge that will measure fuel pressure.


Thanks


Slapshot

Open the fuel bleed with the engine idling. If it shoots out fuel, ok, if it dies no supply pressure. You can jump the fuel pump relay and hear it run. It's in the fuse block under the hood.

I have a surging problem i just replaced the lift pump...


Where is the OPS and how much will that cost me????

The OPS is mounted justbehind and below the fuel filter.


Before you just replace the OPS test to see if that is a problem.


If you jumper the orange and grey wire coming off the OPS the fuel pump should run as long as the ign. is on. Put the jumper in place and take a ride. If you still have the stumble it is not the OPS that is causing the problem.


If you switch is OK consider relaying across the switch to prolong it's life. Details on my web site.

In addition to checking power, a test that works for me, is to put a long hose on the filter drain connected (Brass valve with chrome tee handle dead center front of engine) to a temporary gage in the cab and read pressure while driving, make sure to route it so hose isn't pinched which will give false readings.


At idle should have 4-6 psi on gage, on hard acceleration like in a hill climb may drop to 1-2 psi, should recover to about 4 psi during steady cruise speed, if it doesn't may have a weak lift pump. Do the power tests as Howie suggests, then do the gage check if you still are stumbling.


All of this is going on assumption you have already checked/replaced fuel filter, even a "just changed one" can be suspect if you have gotten fuel from a "new place"; had that happen to me once, a "just changed" filter <5K mi got some crud and partially blocked filt could run empty but not towing.


Swap fuel filt should be 1st step, they are not that expensive, if it doesn't fix it, if you are strapped for $$$ drain fuel from removed filt and save as a used but good filt for later. (remember to make sure plastic screen that fits in center says in the bowl and does not get stuck in the removed filter).


One last delivery test you can do, run pump with same filt bowl drain open to a collection bottle, with 3 psi minimum delivery is 15 gph, so run pump for 15 sec you should collect with a healthy pump .24 Litre or 1/2 pint.


I prefer the gage method as you are checking with a real load demand of the engine and IP.

I just purchased this truck the lift pump is brand new the injection pump has about 10 k on it. I know the guy i purchased it from real well. the truck was well maintained. I will jumper the system and see if that solves my problem.





Thanks for the info guys