draining my rail

[dwax]

My lbz is not holding rail pressure at full throttle. The desired rail pressure stays between 26800-27500 and the rail pressure stays about 22000. I took my factory fuel filter and assy off and put a line in its place. My air dog filter is new. I have the shim kit. It does not throw the 0087 code. What else should i check? I have a spare engine with a known good cp3 on it but would like to avoid changing it.

 

[1lowdiesel]

Check your fuel psi to make sure you're not dropping too much. Also you may want to look into bumping up your fuel psi if it's down around 8.

 

[dwax]

Are you talking about the psi of my lift pump? How would i check the psi and how would i bump it up?

 

[Jscherbs]

i believe you would need the other spring to adjust the AD150

 

[1lowdiesel]

Yes. There is a port on top of the AD base that you can tap an 1/8" sender into. If you needed to go up in pressure you'd have to either purchase a new spring or try and stretch that one out a bit. On the LBZ it's hit or miss on above 11 psi causing issues with loping. But you can try it, it's not gonna hurt.

 

[dwax]

i looked at my air dog and definately dont see a way to adjust it

 

[dwax]

ok thanks alot. ill check the pressure, see if i can adjust it and go from there

 

[coker6303]

Check your fuel psi to make sure you're not dropping too much. Also you may want to look into bumping up your fuel psi if it's down around 8.

You can Put a gauge in where you bypassed the stock filter. Mine is around 14 psi and drops to 7-8 psi on the big tune.

1low has all the info on the AD itself

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[Burn Down]

Make sure it can command full rail pressure at idle, use a tech 2 or efi live. Do a bottle test just to eliminate the rail relief valve. Bad injectors can cause this as well, if balance rates are good they still can be returning to much fuel. Do a injector return rate test. Henry posted the test for all engines.

How big is your tune? With 40 overs you might be at the limit of the stock pump...

 

[Kspen90]

Yes. There is a port on top of the AD base that you can tap an 1/8" sender into. If you needed to go up in pressure you'd have to either purchase a new spring or try and stretch that one out a bit. On the LBZ it's hit or miss on above 11 psi causing issues with loping. But you can try it, it's not gonna hurt.

whar psi is good on an lb7?

 

[1lowdiesel]

8-11. Sometimes 11 is pushing it. Those trucks are very finikey.

 

[Kspen90]

I ask because a guy has that 260 gph fass but he says its set to 18 and idk if i could turn it down enough for my truck.

 

[dwax]

This is some good info. I checked balance rates and my #1 is at 11.00 at idle but zeros out with some throttle. I have some spare inj. So I will swap over the nozzle and install a new one. The bottle test passed. And the tune is a big one from Rob

 

[Burn Down]

They go to zero once throttle is applied. #1 is no good, however I would do a compression test on that cylinder before you do the injector... Low compression can cause numbers like that also.

 

[gmduramax]

How much pulse width are you running?

 

[x MadMAX DIESEL]

Check your fuel psi to make sure you're not dropping too much. Also you may want to look into bumping up your fuel psi if it's down around 8.

Whats wrong with 8? Aslong as there is pressure that should be enough??

 

[dwax]

They go to zero once throttle is applied. #1 is no good, however I would do a compression test on that cylinder before you do the injector... Low compression can cause numbers like that also.

I cant easily get my hands on a compression tester but i have a few lbz injectors laying around so ill swap #1 out. If i can get a tester, how much pressure should i see?

 

[dwax]

How much pulse width are you running?

looking at my log, my max pulse time is 2500 but fluxuates between 2400 and 2450

 

[Burn Down]

I would want to see more than 400 ish? give or take. Lots of variables, like how you do the test, mileage on the engine etc. I would just do all 8 or at lest one bank and compare them. Being you have the injector and not the compression tester just swap it.

 

[dwax]

Well i finally got around to changing my Bad inj with a known good one and the known good inj now looks bad. It is at 10mm. I will start searching for a compression tester tomorrow.