The 396-6.2 swap project

[jeeper]

How long has it run total since you have had it in your truck?

Is it sucking/leaking air into the fuel supply? I recall last spring I was having a hard time getting a 6.2 to start and stay running and found a loose fitting on the lift pump.

[Barrman]

Total in the truck is maybe 3 minutes.

[jeeper]

Is it possible you still have air in the lines after three minutes?

Or maybe a loose line?

[Barrman]

Yes it is. I know at least one of the lines on the bottom of the IP is leaking fuel which means air is also getting sucked in. Good point.

I have done several IP swaps in the past and never had bad idle problems. Even though bleeding the lines is something I don't normally do.

Thanks for another idea of the cause.

[Barrman]

We started this morning by getting all the ag diesel out of the tank. I used the electric pump to push about 8 gallons out. Then when it was just sucking air in the tank, I removed the tank drain. Even though I had drained all the gasoline out back in the summer before adding diesel. I got a gold colored mixture out of the tank that smelled more like gasoline than diesel. I couldn't even see the red from the ag diesel. We pulled the screw on filter, found it about 1/3 full of red diesel smelling fuel, dumped it out and put it back on.

I am more confident my problems are fuel related more than anything else. I was sure there was no gasoline left or at least not enough to matter. Now, it seems there might have been a lot. We left the spin on filter loose and I filled it with the primer pump until clean diesel came out the top. Tightened that back up and we tried to make it run. It took a lot of cranking to get it to fire. I had to wind it up like last week, but once started, it ran better and even idled on its own. Of course, as soon as I got out to look for the line leak it died and wouldn't start again.

We also spent a lot of time making the fan shroud fit better and not hit the fan. Sure was nice to hear it run with just engine noises.

I have the muffler in my class, but we have to move the truck to another lift before we can weld it in. Can't move the truck until is starts again. I added another 2 gallons of coolant and am pretty sure I will be left with a 5 gallon system. The power steering fluid seems to be leveled off now too.

I am letting the batteries charge and the starter cool down over lunch and then will get it running again. This time, I am going to hold it at a pretty fast idle for at least 5 mintues before I even try to let it run on its own. That should work out any air and bad fuel. Then, I will try to drive it to the lift near the 220 plug for exhaust welding.

They are still using the camera, so no pictures again today.

[Barrman]

While the batteries where charging and the starter cooling, I pulled the intake. We must have never put a wrench to the #2 cylinder line at the HH. It wasn't even hand tight. All 8 are tight now and the intake went back on.

It took forever to start it up again, but when it did things were a lot smoother. I had it at high idle until the motor just stopped running at 2 minutes and 12 seconds by my stop watch. Fuel pressure was never below 6 psi.

The valley was dry, no leaks at the mechanical lift pump and as I wrote. 8 psi with the electric pump on and 6 psi with it off. I pulled the spin on filter and got fuel blowing out when I screwed it off. However, it was only about 1/3 full again. The base for it does not have a bleeder screw. That doesn't bother me because it is the exact same base and filter I have on the bomber. I just fill the filter all the up, screw it on and drive.

I tried filling it up today but had to let a little out. Basically, below the threads so I could tilt it over to screw on. Lots of cranking later and the engine was running great. I started my stop watch, put it in 2 wheel low and backed the truck off the lift. It pulled great as I climbed onto the other lift. I let it keep running and was playing with the throttle when it burped once, then died. 2 minutes and 38 seconds is now my longest run time.

I pulled the spin on filter and it was less than 1/4 full again. I am stumped. Here is my fuel system:

-M715 in tank pick up
-12 volt electric pump that was used as the only fuel pump with the gas engine.
-Metal line to the back of the engine at the firewall.
-Neoprene flex fuel rated line to the stock 6.2 metal line to the mechanical 6.2 lift pump.
-Hose from the pump about 1 inch to a metal line I bent and put there to carry the fuel back to the rear of the engine.
-Fuel psi adaptor.
-Neoprene line to the spin on filter base.
-NAPA 3123 fuel water seperator.
-Neoprene line to the IP inlet.
-IP return line to the stock M715 fuel tank vent line back to the tank.

The only thing I can think of is the filter base isn't vented so I can't bleed it all the way. Along with my fuel cap on the truck is the non vented type. I will pull a vent fitting off a M35 tonight, drill and tap it into the filter base tomorrow. I will also try running the truck with the fuel cap off.

Anybody else see something I am missing?

Thanks.

[randyscycle]

I'm thinking that you have an air leak from the tank to the filter. Sounds like its running on what you put in the filter then running out after 2-3 minutes. Maybe a pinhole in the tank pickup that didn't make much difference on a carbureted gasser.

[osut362]

is this the same fuel tank and in tank filter that you had to keep blowing through the fuel line to keep the old engine running? just a thought.....al

[jeeper]

I'm thinking Randy may be right.

Have you tested flow from the mechanical lift pump? Pressure doesn't guarantee flow. Is the filter after that I'm assuming?

Is the electric fuel pump running while the engine is running?

[Barrman]

No flow test on the mechanical pump. The electric pump flows about 1 to 2 gallons per minute based on how fast it emptied the tank this morning.

Al, my in tank pick up sock is what used to clog up every six months to a year no matter how much I did or didn't drive. It was a gradual thing that I could pick up normally on my psi gauge. Pulling a load up a hill would drop down less than 1. Back flowing the line into the tank with air would clear it up. I did that a few weeks ago as part of my change over prep. Good idea though. I will look at it some more.

You and Randy both are telling me to look at the suction side of the system while I have been looking at the positive side. I am going to install a bleeder for the filter base while students weld underneath on the muffler. Once we are done with fire under the truck, I will look at that side of things.

Thanks.