need some LS help

[hubdawg]

Transplanted a strong running and driving 2004 tahoe 5.3 out of a 72 k10 into my 72 blazer and running into some problems with the transplant. I did a frame off resto on the 72 and installed a painless harness. When I try and start it it runs super rough at high idle and quits within 5 seconds.. I ran the same inline pump from the k10. If i run an OBD it only shows O and OH flashing with a solid yellow light. Any ideas on where to start

[ls1nova71]

Originally Posted by hubdawg

If i run an OBD it only shows O and OH flashing with a solid yellow light.

What exact do you mean by this? Do you have something that will read codes?

[mongocanfly]

Is the maf hooked up...minus the codes, mine did the same thing with it unhooked..

[hubdawg]

I'll double check the MAF sensor connection. Is there a way to check fuel pressure at the engine to eliminate a low pressure from the inline pump?

[mongocanfly]

I have a fuel pressure gauge hooked to the Schrader valve on my fuel rail..

[ls1nova71]

Originally Posted by hubdawg

I ran the same inline pump from the k10.

What pump is this? Also, high idle won't be caused by low fuel pressure, but it will cause other issues. Is it a carb pump? Sounds like you have a massive vacuum leak. Still don't understand what you meant about running the diagnostic and getting O and OH and a solid yellow light?

[hubdawg]

I think I've narrowed it down to a fuel pressure problem with my inline pump. Tested pressure at the shrader valve and it's pretty much non existent. I'm using an OBD 2 to read codes. I'll try some different things tonight after work.

[hubdawg]

pressure at the shrader valve on the intake reads 54lbs so i dont think thats the problem and my MAF is plugged in. Does the screen on the MAF unit go out or towards the motor.
Still running rough and occasionally popping ant ideas?

[ls1nova71]

Originally Posted by hubdawg

pressure at the shrader valve on the intake reads 54lbs so i dont think thats the problem and my MAF is plugged in. Does the screen on the MAF unit go out or towards the motor.
Still running rough and occasionally popping ant ideas?

Screen goes towards the air cleaner. There is an arrow on it that shows air flow direction. How long has the engine run for? Does it always shut down after a few seconds? Has the VATS been turned off?

[hubdawg]

VATS is off, It used to be in a 72 K10 I bought and drove for a while then transplanted into my frame off 72 Blazer. In the K10 it ran on a modified stock harness then I changed to a new painless. I'm still wondering if the 54lbs of fuel pressure is enough. It starts and runs rough for 5 or 6 seconds and maybe a little longer if I pedal it. It has an occasional pop to it as well. Can a bad MAF cause this and can you test them.

[hubdawg]

Originally Posted by ls1nova71

Screen goes towards the air cleaner. There is an arrow on it that shows air flow direction. How long has the engine run for? Does it always shut down after a few seconds? Has the VATS been turned off?

Posted via Mobile Device

[hubdawg]

Originally Posted by hubdawg

VATS is off, It used to be in a 72 K10 I bought and drove for a while then transplanted into my frame off 72 Blazer. In the K10 it ran on a modified stock harness then I changed to a new painless. I'm still wondering if the 54lbs of fuel pressure is enough. It starts and runs rough for 5 or 6 seconds and maybe a little longer if I pedal it. It has an occasional pop to it as well. Can a bad MAF cause this and can you test them.

Posted via Mobile Device

[ls1nova71]

Should be 58psi, but I wouldn't think you would notice much of a difference at 54. Is the vacuum hose to your pressure regulator hooked up? In that pic it doesn't look like it. Still though, it doesn't seem fuel related to me. Maybe the IAC isn't working? Does it have any codes at all?

[hubdawg]

The vacuum regulator hose was not connected so I connected it. When I turn the key on I get power to the fuel pump relay but only for a few seconds then it clicks off. Do I have to go through that relay or can I direct wire the pump to a circuit that comes on with the ignition

[paul mora]

When you turn the key it the pump should go on to build pressure It will shutoff till you start cranking and then keep pumping till you turn the key off and shut down the engine

[hubdawg]

Thanks I finally figured that out but still have the rough running issue and knowing where the different hoses go on top of the plenum

[ls1nova71]

In your second pic, the fitting with the short piece of hose going straight up should go to the fuel pressure regulator. There is a larger fitting on the very top of the intake near the center, that is the PCV line that goes to the left valve cover and then there's the brake booster fitting at the rear on the driver's side. Make sure none of them are left open. That could cause it to run at high idle and die.

[Rich84]

If it sat for a long time before you got it running again you could have gummed up injectors which causes all kinds of problems.

[hubdawg]

LS, There are two connections on the top driver side of the plenum the small one closest to the front I have connected to the fuel pressure regulator and the other which has a short piece of tubing on it is open. There is one more connection in the middle of the intake which I currently have to the new brake booster. The pcv valve on the rear drivers valve cover is not connected to anything either

[hubdawg]

Sorry forgot to mention the motor ran fine 3 months ago and I installed new plugs and wires when I installed it in the blazer frame. I double check all those connections as well.

[ls1nova71]

Originally Posted by hubdawg

LS, There are two connections on the top driver side of the plenum the small one closest to the front I have connected to the fuel pressure regulator and the other which has a short piece of tubing on it is open. There is one more connection in the middle of the intake which I currently have to the new brake booster. The pcv valve on the rear drivers valve cover is not connected to anything either

So if I'm reading this right, you don't have anything hooked up to the factory brake booster connection? If so, that's your massive vacuum leak causing your high idle and dying issue. Hook the brake booster to the rear most fitting, the one with the red ring around it, then hook the middle of the top intake fitting to the driver's side valve cover and see how it runs. It should smooth out with no big vacuum leaks.

[hubdawg]

Thanks for the help I’ll try it when I get back from fishing
Posted via Mobile Device

[hubdawg]

Well I connected all the hoses and still have the same result. It starts and runs or 5 or 6 seconds then dies, if I pedal it it'll run longer. The small hose to the fuel pressure regulator is hooked up but I noticed the connection on the intake looks like it's just a post no hole in it. Any other ideas...getting frustrated

[hubdawg]

re did some of the vacuum lines and need help on some of the connections. I noticed there is nothing in the very back of the intake, is there supposed to a nipple of some sort there and is that where the brake booster is supposed to be connected. I think some of the problem is that the exhaust is open headers causing it to run rich and maybe shut the fuel down? How would i get it to the exhaust shop without trailering it, is there a bypass. The engine starts right up and runs for a few seconds still and shuts off

[ls1nova71]

There is a hole in the back of the intake, that is what the brake booster hose hooks to. If it is open, then plug it. It really should go to the booster and the middle hose on top of the intake should go to the PCV valve on the left valve cover.