Engine/Transmission (1994 - 1998) Fuel Pump Pressure

[TAchterberg]

I am helping a friend troubleshoot a fuel delivery problem with his '94 12v. It's a freshly rebuilt engine, with a new lift pump.

We had it running for about 2 minutes, but it would miss when brought off idle. So we cracked an injector line to bleed the system, then the truck died and hasn't restarted since.

We can get fuel by hand-priming the pump, but when cranking the engine we get none, and it won't fire.

We're considering an electric pump for the frame rail to by-pass the factory lift pump. What GPH and PSI pump ratings should we look for?

Thanks in advance.

 

[BigPapa]

You said freshly rebuilt. Did it get a cam? Is it the original '94 engine?

 

[Big Red 94Ram]

The cam I used is a Hamilton Cam, the towing/economy version. And it is an original 94 engine.
I've already talked to Hamilton asking them if that cam das the lobe on it for the pump, they said yes. But the engine still isn't getting fuel, like we mentioned above.

 

[BigPapa]

If it worked before the cam install and doesn't now, I suspect the wrong cam.

I would pull the lift pump and feel the cam to make sure it has the "lobe" for the pump. You'll probably need to get someone to turn the engine over while you hold your finger on it. It's not really a "lobe" but more of an eccentric.

I know Hamilton said it has it, but we've all made mistakes and it may have been packed or pulled wrong.

If it's the correct cam I'd say you need to replace the lift pump again.

 

[Big Red 94Ram]

We're going to install an electric pump. Just in case I have the wrong cam. The shut off solenoid does work, so that's been ruled out.

 

[BigPapa]

Whatever floats your boat, but an electric pump is not nearly as simple or reliable as the factory lift pump. It's easy to check the cam and replace the pump if it's bad.

The shut-off solenoid has nothing to do with fuel supply to the injector pump.

 

[Big Red 94Ram]

My mech mentioned that he does get fuel when he activates the fuel pump arm manually, but doesn't get fuel when it's in the mounted. Thus suspecting that the cam doesn't have the lobe.

 

[crabman]

The best explanation of the 12 valve fuel system.
http://www.cumminsforum.com/forum/94-98-engine/58777-joe-gs-fuel-system-writeup.html

 

[BigPapa]

Not trying to be argumentative, but there is no arm. There is a push-rod that rides against the cam that pushes a piston, just like the primer button. It would be difficult to manually operate the pump sufficiently to test functionality while connected to the fuel supply.

I just hate to see you needlessly go with something that's going to be a lot more trouble in the future when you can be certain of the issue by pulling the pump and checking the cam.

 

[Big Red 94Ram]

No problem BigPapa. Any advice is welcome.
I'm not the mech doing the work. I'm the customer and i'm just trying to help out my Mech diagnose this issue. He's had my truck for 4 months now, due to delays (engine builder is the main one).

 

[Big Red 94Ram]

Lift pump will prime by hand, but doesn't pump when cranking engine.

 

[Big Red 94Ram]

Problem solved. We bypassed the fuel heater and the truck started up without any more problems.

 

[Bob4x4]

The fuel heater is a known possible air leak point

 

[Big Red 94Ram]

Unfortunately, the truck is back in the shop. This time it's a warranty issue with the engine. She's leaking oil. So she's at the engine builders shop now. Let's see how long this will take to get fixed.
This truck has been out of my hands since Dec 3rd 2015. I'm getting impatient on all the excuses and setbacks these guys keep throwing at me.