Looking for some info to compare with my truck trying to figure out a problem.

Trying to find out if you turn you5 key to the on position, but DO NOT start your truck what FP do you read on the guage? Then does the truck hold the FP, or does it fall off slowly/quickly?

 

Mine stays around 31psi, never changes unless I hit the gas.

 

30, stays there.

 

With the motor not running?

 

Well I can tell you one thing right now.. The pumps will prime and there will be fuel in the system when you turn the key. The pressure should stay in the system for a while. It will evventually drop but it should take a long time to do that.

Let me go hop in the truck right now and see what what pressure it hits.

 

Mine stays at 30 with the engine off and the key on and hitting the gas many times.
Mark

 

Casey, when you cycle the key to run, you should see base fuel pressure, which should be 39 psi. It should hold that pressure for some time. If it's not,then you have a leak somewhere causing the pressure to bleed back. I have seen this with the 255s before. It's not really a problem, as long as it IS actually the pump.

 

Mine ALWAYS seem to stay where it was last before the motor was turned off.

 

This bleads down instantly. It reads about mid 20's when the guage gets sorted out(never gets a chance to get out of it's test pattern really) and instantly drops fast. And goes to nothing. But, the truck will still start; which it seems like when you start cranking the pumps turn back on.

I have no "external" leaks anywhere at all. It's either pumps or injectors. Once I did notice a black like puff at startup; maybe injectors. I just can't decide which way to go.

I really think and hold to a fuel system problem. Guess I'm about to drop the tank. Maybe I'll stick the pumps in a bucket and see what happens.

 

How would hitting the gas with the engine off affect the pressure?? I alway's have operator's at my work pump the fuel pedal on a diesel engine while trying to start, I try and teach them that it's a fuel injected vehicle and doesn't have a choke!!(not a slam, just an observation!! )

I usually see close to 40 psig with the engine off, I adjusted the regulator down to 34#'s(running)because I was having a miss fire problem (seemed to take care of it, except when it's hot. Hope one of my pump's aren't going bad!!) Just as soon as the boost come's in the pressure jump's to 50 and rises with boost to 60+.
Bryan

 

Well mine went to 32 and then crept up to 33 psi and stayed there. I went to turn the sprinklers on and left the key in and when I came back 3 minutes later it was still at 33psi.

Good luck bro.

 

Sal you sure about that 39 psi? I see 32-33 psi? And it seem that the couple of people who posted here see low 30's as well. I may see 39 when I actually start the truck and its at idle... or maybe a bit more than 39.. I cant recall.
,Jason

 

If you unplug the vacuum line on the regulator and start the truck you should see close to 39#'s which is base FP. I'm not sure if it would do the same on the prime cycle or not.

 

On my 01L, with stock pumps, my Autometer electric gauge stays at about 32psi when I shut it down at idle speed (about 700rpm). When I start it up - and with the key in "start" position, engine cranking, guage shows 0 - but as soon as engine fires, jumps right up to about 32 again.

 

Should be about the same because there's no vacuum (engine not running). Should be about 39 psi with the key on but not started. When it starts the vacuum will pull it down to near 30 psi.

Jody