Losing prime

[RENODMAX]

Hey all long time no see. My old LB7 is losing prime when it sits. It will start initially but die a few seconds after starting. If I prime by hand starts and runs just fine. I replaced the filter head and lines to FICM, going to replace hoses at CP3 tomorrow. Any other idears?

 

[catman3126]

replace the rest of them and done forget the little one going to the test port. oh and get a rebuilt kit for the primer pump. should fix you up.

 

[Burn Down]

Not that this is your issue Jordan but I have an LB7 at the house waiting for a set of injectors that acts similar, balance rates are bad on several holes. Ck them lately?

 

[catman3126]

balance rates wouldn't really cause a hard start though. bypassing too much fuel will and this will be worse and start harder when hot then cold if its his injectors.

 

[Burn Down]

balance rates wouldn't really cause a hard start though. bypassing too much fuel will and this will be worse and start harder when hot then cold if its his injectors.

Tell that to the LB7 sitting in the driveway... Starts hard cold or has to be primed, once warm it's fine, balance rates are ugly. No need to do a return rate test

 

[catman3126]

Tell that to the LB7 sitting in the driveway... Starts hard cold or has to be primed, once warm it's fine, balance rates are ugly. No need to do a return rate test

Out of curiosity can you explain how a bad balance rate injector would cause this? are all the glow plugs working is the compression good? and if it has to be primed due to hard starts when cold its losing prime. Ive seen some really jacked up balance rates and no hard start issue. like 10 +/- on some and still start fine. the balance rate does even always mean the injector is bad it could be low compression, bent rod causing low compression valve not sealing correctly.

 

[Burn Down]

Out of curiosity can you explain how a bad balance rate injector would cause this? are all the glow plugs working is the compression good? and if it has to be primed due to hard starts when cold its losing prime. Ive seen some really jacked up balance rates and no hard start issue. like 10 +/- on some and still start fine. the balance rate does even always mean the injector is bad it could be low compression, bent rod causing low compression valve not sealing correctly.

Lol would you like to come up here and have a look for yourself?

All 8 420-440 compression, 8 new glow plugs and one glow plug rail. Last winter the owner was hand priming once in awhile to get it started, I have never had to but it does crank a bit longer to start. 218k on the engine and to my knowledge the injectors and pump haven't been done in at least 130K. Deductive reasoning tells me that good compression, bad balance rates and high mileage equals bad injectors. Are they returning to much fuel, probably, do I need to do a return rate test, um no...

I never said the balance rates could cause his hard starting issue... It's just a quick way to ck the health of the fuel system. Are you going to tell me that if you had bad balance rates on LB7 injectors and a hard starting issue you wouldn't suspect injectors knowing what he has already replaced?

 

[juddski88]

I've had a few cp3's leak over to the return circuit while sitting and cause this. Can watch it happen with the mityvac. Most recent was a 78k mile lmm that has been babied.

 

[catman3126]

Lol would you like to come up here and have a look for yourself?

All 8 420-440 compression, 8 new glow plugs and one glow plug rail. Last winter the owner was hand priming once in awhile to get it started, I have never had to but it does crank a bit longer to start. 218k on the engine and to my knowledge the injectors and pump haven't been done in at least 130K. Deductive reasoning tells me that good compression, bad balance rates and high mileage equals bad injectors. Are they returning to much fuel, probably, do I need to do a return rate test, um no...

I never said the balance rates could cause his hard starting issue... It's just a quick way to ck the health of the fuel system. Are you going to tell me that if you had bad balance rates on LB7 injectors and a hard starting issue you wouldn't suspect injectors knowing what he has already replaced?

What does rail pressure do when cranking and hard start? Also if rail was good and it hard starts you'd still have smoke when it's cranking and not starting, How long is it cranking before it starts when it cranks an extended amount of time. Sounds like a combo of issues to me.

 

[RENODMAX]

Catman if you read my post you would know I out a brand new fuel filter housing on so that's not it. Albert I figure if it were returning too much fuel it wouldn't start then die probably just wouldn't start. It doesn't matter if it's hot or cold. After the fuel filter housing today it runs for 20 sec or so then dies. Pretty odd.

 

[RENODMAX]

Judski where did you pressurize? Through the tank? Did you have to replace the cp3 on the aforementioned vehicles?

 

[catman3126]

Catman if you read my post you would know I out a brand new fuel filter housing on so that's not it. Albert I figure if it were returning too much fuel it wouldn't start then die probably just wouldn't start. It doesn't matter if it's hot or cold. After the fuel filter housing today it runs for 20 sec or so then dies. Pretty odd.

I read your post did you replace every rubber fuel line in the valley too?

 

[Slowmax]

Merchant Auto bleeder screw by chance?

 

[Burn Down]

What does rail pressure do when cranking and hard start? Also if rail was good and it hard starts you'd still have smoke when it's cranking and not starting, How long is it cranking before it starts when it cranks an extended amount of time. Sounds like a combo of issues to me.

I have it figured out thanks. I'm not going to list out every thing I checked on this truck in Jordan's thread. If you really want all T/S info, PM me

 

[Burn Down]

Catman if you read my post you would know I out a brand new fuel filter housing on so that's not it. Albert I figure if it were returning too much fuel it wouldn't start then die probably just wouldn't start. It doesn't matter if it's hot or cold. After the fuel filter housing today it runs for 20 sec or so then dies. Pretty odd.

Jordan you have a lift pump correct? Are you sure it's working?

 

[RENODMAX]

No lift pump anymore Albert. I'm an old man.

 

[juddski88]

Judski where did you pressurize? Through the tank? Did you have to replace the cp3 on the aforementioned vehicles?

I did replace the cp3s. I pressurized the cp3 fuel supply and it wouldn't hold 2psi. Plugged the return hose and was able to hold 20 (I just stopped the test there, no particular reason)

 

[Burn Down]

No lift pump anymore Albert. I'm an old man.

lol you and me both brother:hug:

Any chance some doucher dropped something in your tank that is getting sucked into the pick up tube? Maybe try a gallon of fuel right at the filter head if Tim's test turns out ok on the CP3.

 

[RENODMAX]

Maybe fiddle with it tomorrow. Gotta tear some crap off to get to cp3. Replace lines first and see what happens