No way to prime it.
But am gonna try a jug of fuel to the filter head directly before I pull the bed.
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LB7 Fuel System Issues - Wagers?
- Thread starter kidturbo
- Start date
But am gonna try a jug of fuel to the filter head directly before I pull the bed.
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This sure brings back memories. "dead bugs" i remember the exact same thing pulling the filter head apart. Down came the tank and the pick up was plugged solid with those little black bastards, boy did seeing that make me happy.
Picked up a fuel line quick release tool from Autozone last week. And grabbed the wrong one.. Note: Is the larger of the 2 scissor tools when comparing. >> 3/8-1/2".
This tool did allow me disconnect the return at engine, which I ran into a small bleeder kit bottle. All of my good glass beakers from the bioD days, are Not being used for proofing moonshine.. No idea where they went, but are all gone... So the total system return after 15 seconds cranking, is only about 32-35ml. Well below the 100ml most of the YouTubers say when checked at cooler. To accumulate some fuel in a jug, fired it up and let the return go for 10 minutes. Quick reference check, at idle shes returning about 60-65mil in 15 sec, while holding 40,000kpa rail.
Only changes since last post, fresh oil and filters.. Another new fuel filter just to be safe. Vac still creeping at idle.. So next test will watching this one.
Luckily we cut the main line and spliced in a section above last time was searching. So am gonna pipe a 1/2" line straight into my jug, strap it to this deer slayer front bumper, and see how does on the highway. Vac gauge in play, betting we find our answers right shortly.
I'm still saying weak pump, but my GM techie friend has his money on the fuel tank or line still due to the vac reading. An old washer fluid jug might solve this one for us..
This tool did allow me disconnect the return at engine, which I ran into a small bleeder kit bottle. All of my good glass beakers from the bioD days, are Not being used for proofing moonshine.. No idea where they went, but are all gone... So the total system return after 15 seconds cranking, is only about 32-35ml. Well below the 100ml most of the YouTubers say when checked at cooler. To accumulate some fuel in a jug, fired it up and let the return go for 10 minutes. Quick reference check, at idle shes returning about 60-65mil in 15 sec, while holding 40,000kpa rail.
Only changes since last post, fresh oil and filters.. Another new fuel filter just to be safe. Vac still creeping at idle.. So next test will watching this one.
Luckily we cut the main line and spliced in a section above last time was searching. So am gonna pipe a 1/2" line straight into my jug, strap it to this deer slayer front bumper, and see how does on the highway. Vac gauge in play, betting we find our answers right shortly.
I'm still saying weak pump, but my GM techie friend has his money on the fuel tank or line still due to the vac reading. An old washer fluid jug might solve this one for us..
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Your pulling too much vac. Im with your guy. It aint the pump lol.
Ok, the jug answered some questions.
Vac reading with bottle plumbed directly to the engine, never hit 3" at WOT.
Even I was leaning hard towards a tank restriction, until I rolled out on the road and into the throttle. Still can't keep up, so lines or tank not the issue. Road drive tells the tale, but here is a good stall up I snapped when returned to the shop.
After a short test drive, I'll possibly agree to calling this a draw.. Cause pumps shot either way..
Vac reading with bottle plumbed directly to the engine, never hit 3" at WOT.
Even I was leaning hard towards a tank restriction, until I rolled out on the road and into the throttle. Still can't keep up, so lines or tank not the issue. Road drive tells the tale, but here is a good stall up I snapped when returned to the shop.
Sure looks like your returning a lot of fuel with the pump not keeping up. Did you test each bank and CP3 yet for return?Ok, the jug answered some questions.
After a short test drive, I'll possibly agree to calling this a draw.. Cause pumps shot either way..
Vac reading with bottle plumbed directly to the engine, never hit 3" at WOT.
View attachment 129788
View attachment 129789
Even I was leaning hard towards a tank restriction, until I rolled out on the road and into the throttle. Still can't keep up, so lines or tank not the issue. Road drive tells the tale, but here is a good stall up I snapped when returned to the shop.
View attachment 129790
Ok, the jug answered some questions.
After a short test drive, I'll possibly agree to calling this a draw.. Cause pumps shot either way..
Vac reading with bottle plumbed directly to the engine, never hit 3" at WOT.
View attachment 129788
View attachment 129789
Even I was leaning hard towards a tank restriction, until I rolled out on the road and into the throttle. Still can't keep up, so lines or tank not the issue. Road drive tells the tale, but here is a good stall up I snapped when returned to the shop.
View attachment 129790
Eh, im still holding out for that pump lol. So clearly you have a restriction somewhere between CP three and fuel tank if the truck’s not getting over 3 inches at wide open throttle.
What’s the main injection rate at idle along with the balance rates while keeping that bottle hooked up to the CP three?
He's got a hose from a jug right into the pump. So rules out the tank and lines
Unless im completely missing it. Jug connected directly to the back of the cp3, truck does not see over 3in/hg under WOT (this is good). Fuel system hooked up like stock will slowly increase vac beyond 3 at idle and go over 10 at wot (thats bad)
So that means that something between the cp3 and fuel tank is causing the restriction. This is completely separate from the fact he cant hold rail pressure with the cp3 pulling fuel from the jug.
What why i asked what the main rate and balance rates are while bottle is attached is to see if the worn injectors will show themselves via main rate.
Basically, we have 2 separate issues causing the low rail pressure. You could fix whats causing it while the bottle is hooked up but once you hook the stock fuel lines back to it, you will have the high vac issue again and rail will fall
You been chatting with my GM buddy?
He thinks the restriction wore out the mechanical lift.. I said, help me change the cp3, and you can tear it apart.
Took the bottle off and put it back to stock to move stuff around. Should have checked those balance rates again on the bottle. It's so clean and smooth, I'm guessing someone put injectors in it previous. One thing I have mastered playing with these things, is smelling an unhappy stick.. lol
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He thinks the restriction wore out the mechanical lift.. I said, help me change the cp3, and you can tear it apart.
Took the bottle off and put it back to stock to move stuff around. Should have checked those balance rates again on the bottle. It's so clean and smooth, I'm guessing someone put injectors in it previous. One thing I have mastered playing with these things, is smelling an unhappy stick.. lol
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Lol nope but ive been around them enough, thats for sure. I like that guy though!
Those injectors wont just wear out to the point they smoke/haze or cause a lope. We get alot of trucks at our shop that no one else can fix or they half ass a fixed. The amount of off the wall issues ive seen that have not been on this site is crazy. Few months back we had a lly that came in because he got bad fuel from a fuel station. Low rail after fresh fuel and filter. We didnt bother testing if it was pump or injectors, fuel station paid to have pump and all 8 injectors replaced. No more issues. He never had a restriction issue like this. Ive had filter heads fight us but thats the worse of it.
That said, i still have hope for the pump but its still very possible shes tired. I have a cp3 only return cranking spec written down. Ill find it for you. I wanna say its 15ml in 15 sec. Could be wrong.
The mechanical lift pump just bolts on the back of the cp3. Industrial injection use to have “bag of bolts” or something like that which was an upgraded pump with some bigger feed holes.
I wore out the lift side of my cp3. I just put a lift pump on it and rolled on with it.
Surprised thats still around lol
Going off memory here, I want to say the spec for inlet restriction is 12 in of vacuum. If you're only getting up to 10, I don't see that as a problem. What I do see as a problem is not being able to build rail at idle. There isn't much fuel quantity at idle, so restriction and low pressure pump performance don't really play much of a role in this test. It is purely a test of the CP3's ability to build pressure. I've never seen anything except a bad pump cause this test to fail.
On my LB7, it would have a hard time building pressure at idle when the injectors had high return. Exceeding what the pump was capable of producing at idle. But if you kept the RPM up, it ran. New injectors fixed it
In my experience, bad injectors will cause a loss of rail under load, but I haven't seen them cause a pump to not build pressure at idle unless they were so bad the truck couldn't even build enough pressure to start without some help (as in ether or a gas soaked rag over the intake).
Yeah, mine did need assistance to start