It runs, but.

[72mike]

Fired my swap today for the first time.
Runs good once its running, but takes a couple try's at cranking it before it will run.
I am thinking air in the fuel rails, how can i bleed air out?
Has anyone have anything like this, and what did you do, or did it just work itself out?

2000 4.8/4l60E
thanks Mike

[TR65]

72,

There is a schrader valve on the fuel rail you can bleed air out of, at least on my LS2. Mine wouldn't start until I did that.

Injectors might be sticking if the engine hasn't been run in a long time. It took mine a while but they straightened themselves out without having them cleaned.

TR

[usmcchevy]

What TR65 said, it should have a black cap on it. Who did you tune? Reason I ask is I had a junk *cough*Wait for me*cough* tune in my 00 silverado that would need to re-learn idle every time I disconnected the battery, among many other things. A good tune fixed all of that.

This is the first start on mine.

YouTube - '07 Chevy 4.8 in a '72 pickup,...

[72mike]

I though that might be it.
Question, key on pumped up then hit the schrader valve?
thanks Mike

[y5mgisi]

Yes, just have a rag over it or something and watch your eyes! Can spray out pretty hard.

[Shon]

Does it back fire any? if so, check Cam Position Sensor.
Check Fuel Pressure, this will also bleed out the air when installing the gauge, we have not had air issues that did not clear up quickly.

[72mike]

No back firing, and i didn't run a fuel pressure regulator. It's a motor out of a 2000, i was under the assumption if the fuel system had a return line it was self regulated.
The hard to start has gotten better but hasn't cleared all the way up yet. Granted i have only run it about 10 times now and only put 20 miles on it. Today i am going to run it about 100.
Thanks for all the advise...
Mike

[ls1nova71]

If you've driven it 20 miles, there should be no air left in it. Are you running an internal or external fuel pump? It almost sounds like you're losing the fuel prime and the long cranking is giving the pump time to re-pressurize the system. I would put a fuel pressure gauge on it and make sure that the pressure doesn't fall back off instantly. It should hold pressure, if it doesn't you most likley have a leak, if it's an intank pump, it could leak pressure but you'd never see it leak any fuel. I've seen fuel pumps that wouldn't hold pressure too, and the only fix I know of for them is replacement.

You're correct, a 2000 should have a return and the fuel pressure regulator is on the fuel rail, I think what the other poster was refering to was a fuel pressure gauge that screws onto the schrader valve on the rail, which is what you need to get to make sure your pressure is good and steady. You need about 58 PSI, less it will usually run but won't runn as good as it should.

Hope this helps.

[usmcchevy]

Could be a bad regulator. Pull the vac hose off the regulator on the fuel rail. If there is gas, the regulator is bad.

[Shon]

U have to have a FEED and RETURN.
Even if regulator is on the rail, you have a return off that rail. if not on the rail then you have to have one in-line b/c the pump should be putting way more than 58PSI thru it.

You are flooding the motor with fuel, check the oil see if its gassy.

Also, if all that is in working order, and you are loosing pressure after prime or run, could be a leak injector.

[Clyde65]

Take your rails off (where the fuel line hooks up to), and look into them, mine had all kinds or junk caked in there, making starting difficult due to fuel starvation, especially when I gunned the foot feed. when I cleaned all that out with wire brush and carb cleaner, engine ran like a new penny looks.

[72mike]

I have an external pump, walbro 255.
I will look into all of the things that were recommended by everyone.
Starting with bleeding off the fuel rail at the schrader valve. Also see if it can find a gauge for the fuel rail to check pressure...
I will let you guys know what i find later today.
Thanks
Mike

[72mike]

I had a couple small issues today, so i have not been able to do all the testing i wanted to do.
But i did notice the other day that my gas tank is being pressurized, when i screw off the cap its releasing air. So after trying and trying to get it running i though to try without the gas cap on it. What do you know, it fires on the second try. Not that it fixed the problem but atleast i realize i need to vent my tank.
This could have something to do with the air never getting out of the system.
I will hook up an gas pressure gauge tomorrow to see what its running at.
Mike

[BR3W CITY]

Originally Posted by 72mike

I had a couple small issues today, so i have not been able to do all the testing i wanted to do.
But i did notice the other day that my gas tank is being pressurized, when i screw off the cap its releasing air. So after trying and trying to get it running i though to try without the gas cap on it. What do you know, it fires on the second try. Not that it fixed the problem but atleast i realize i need to vent my tank.
This could have something to do with the air never getting out of the system.
I will hook up an gas pressure gauge tomorrow to see what its running at.
Mike

Even if you do replace your fuel pump, make sure to still get a vented cap. Since most of us have no evap setup, I'm assuming we still need a vent/bleed point for the gasses. Plenty of cars have vented caps, hopefully you can find something that fits.

[Clyde65]

sounds like you may have found your issue, I would go ahead and check the items mentioned here, just to be safe and by all means find a vent for your tank, what is the vehicle? stock or aftermarket tank?

[72mike]

1972 c-10 lwb.
4.8L 4L60E (2000)
Blazer tank with an external walbro 255 pump. I have the pump mounted low with 2 different bungs welded in 1 in front 1 in rear to feed the pump, gravity feed so i wont burn it up.

I am going to find a vented cap, hopefully that works.
Thanks Mike

[Clyde65]

I have basically the same motor, only difference is mine is a 2005 but it has the DBC top end.

[72mike]

So what i have found is that the Walbro 255 fuel pump I installed is not creating enough fuel pressure to start the engine. I guess it needs a minimum of 62lbs to start it and needs 58 while running. I have 52lbs while its running and if i unplug the FPR it jump to 60lbs max. As well as the pump bleeds back pressure in a matter of seconds. I am guessing i received a bad pump from the get go. Now time to see if the guy i bought it from is going to be difficult or not.
Is there any other inline fuel pumps that work as well? just in case i have to buy something else?
Thanks Mike

[Shon]

I am using a $40 ebay "E2000" pump

[Clyde65]

I have a Pierburg I got from Turnkey Engine supply, they are not cheap, but they do supply 75+psi and are real good units, so I am told. Mercedes and other exotic supposedly use them.

[72mike]

So new fuel pump installed and same starting problem, it wont.
I know need to start looking at other things.
Remove fuel rail, new FPR, maybe even another FPR before the fuel to up the PSI.
Any other suggestions on what to check that might make it hard to start?
Mike

[ls1nova71]

So is the pressure still falling off quickly? If it is and you have no visible leaks, I would pull the fuel rail off of the intake, but leave the fuel lines connected. Then while holding the fuel rail up away from the intake, have someone turn the key to the run position to prime the fuel pump. DON'T START IT. then with pressure in the rails make sure no gas is leaking out of any of the injectors. If there is that will cause a hard start because its flooding the engine. If they're not leaking, while you have the rail off, it wouldn't hurt to go ahead and remove all the injectors and soak them over night in some Seafoam, just in case they may be sticking.
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[ls1nova71]

Also as usmcchevy said earlier, did you pull off the vacuum hose at the pressure regulator and make sure there was no gas coming out of it? That wasn't an uncommon problem with the earlier engines.
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[72mike]

is it possible that the FPR is bad even if there is no gas coming from it?
Second, would a sticking injector make the truck run funny? when it is running it runs smooth with a very good idle. I am going to switch the FPR tomorrow regardless, seems to me a cheap insurance.
mike

[72mike]

Problem solved.
I had a bad connection on my fuse panel, causing my constant power to be lost while cranking.
Funny how a seeming fuel issue ends up being an electrical problem...
Thanks for everyones input and help...
Mike