I installed a fuel pressure gauge (oil-filled, 100psi, pre-filter). When I start the truck in the mornings (5:30 a.m.), the pressure reads about 58 psi. I drive down the road about 30 minutes, and it works its way to about 60. (62 is the highest i've seen it-once). My truck stays parked all day while i'm at work til about 3pm. When i get in and crank it then, the pressure only reads about 40 psi. At the end of my drive home, it only gets up to about 48-52 psi. My wife also noticed the same changes in readings when she drove it on a sat. before and after shopping. Also, if we make a trip in the evenings, (even if we have only parked the truck for a couple hours) the pressure is starting at the higher numbers like in the mornings.

So, the only thing we can think of is that the temperature outside is somehow affecting the readings. I live in LA and the heat index has been over 100 for the past few weeks pretty much every day. When we get better numbers in the evenings, it is always after it is startin to cool off some.

Just some ideas: Would it be possible that the heat is weakening the FPR spring? Or could it be the pump? I don't think it's the pump b/c when the system is pressured up, no matter how i drive it, regardless of what the pressure is, the most it will lose is 3-4 psi when i accelerate. I'm trying to rule out one or the other without having to replace both. All this trouble-shooting, etc, adds up $ fast.

 

Are you having performance issues with the truck or just curious about the readings? Is the gauge installed such that you can see the pressure while driving under load or under hood idle only?

 

Alittle of both. It started with a mechanic saying I needed 8 new injectors when my truck didnt seem to have the power it should of. So after discussing it on here we started trouble shooting. The first step I took was mounting A fuel pressure guage on filter housing pre filter mounted by wiper blades. Clay with Riffraf saw the troubles and said to start working on a problem till it was fixed then move on. I still have the power issue just trying to knock this out first.

 

Hey David. I don't know much about the fuel system on our trucks because I have the stock system. Saturday we can do test with the AE to try and figure what is going on with the injectors, if anything.

 

Some fluctuation is normal, but steady pressures below 50 aren't good. On a stock truck, it shouldn't drop too much when getting on it. Could have a pump issue, regulator issue, pickup issue, or combination. The regulator is in the fuel bowl return (line on driver's side of the bowl, near the top). I'd start by doing the in-tank mods, which will allow you to inspect the screens in the tank, then go from there...

 

Thanks Izzy,
Ive done the in tank mod. And cleaned out the screen onthe back side of fuelpump. I think I'm gonna change the regulator with a factory one that way it is set already and if I still have the flucuations I will see about changing the pump.

 

Good deal. Only thing left is the FPR or pump now then... Good luck!!

 

Do the FPR shim to increase your pressure to around 60 psi. Does not take much time and almost no money. Just be careful with the regulator housing, it is fragile-pot metal.

 

I'm not sure how to shim it whith the different pressures and I dont want to boost the pressure too much. By the way do any of you have the write up on shimming the regulator.

 

This is a good link to a FPR shim write up. Enjoy!

http://www.puredieselpower.com/Tech/...tor%20Shim.pdf

 

How high can you safely go on boosting your fuel pressure with the shims? I did the mechanical fuel gauge install on the lower port on the back of the fuel bowl the other day and am getting between 56-61 approx.

 

I have an RR, and I have it set around 65 at idle. That seems to be the "sweet spot"...

 

I think you should not exceed 70. Consider staying where you are at.
The fuel bowl filter becomes increasingly difficult to seal as the pressure increases.

 

Thanks for that. What a good write up. the pictures make it look so easy. Im getting together with Miller today so im going to wait on shimming the reg in case this would change any varibles on my power loss issue.But I'll have the sscrew ready when my truck is back up to snuff.