I bought the battery in January 2022 so it is around 2.5 years old. It was able to crank the engine before I installed the new fuel pump so its strange that it wont crank anymore. But I will most likely just replace it since the starter is less than a year old and hopefully still good.

 

The fuel pump cannot draw enough current to cause the start voltage to drop that much unless it is defective or there is a short but then it would blow the fuse. 2.5 years is an early battery failure unless it’s a budget brand or it’s been allowed to sit depleted, this reduces the useful life by causing sulfation on the lead plates.

Before you do any further testing make sure that you have a known good battery charged to 12.6 volts with the surface charge knocked off after charging ( headlights on for 15 sec). The voltage during cranking should not drop below 10v. A battery load test simulates the 100a ish current draw of a typical start sequence to see how well the voltage holds up.

George

 

I just put a brand new battery in it but had the same result when I tried to crank.

 

then, either the terminal connections at the battery are not clean and tight or there’s a problem with the starter. does it sound like the starter throws the Bendix gear into the fly wheel? If you have an amp clamp meter capable of reading, DC amps, put it on the positive battery cable by the battery and tell me what amperage rating you get when you try to start the truck and the battery voltage drops to 6 V.

George

 

Turns out the engine was hydrolocked. I took out the spark plugs and fuel poured out of the cylinders. I took off the upper intake but did not see any leaks.

 

Fuel or water?

George

 

It was fuel

 

What is the result of the 10 min fuel pressure leak down test now?

George

 

Leaking fuel pressure regulator and/or 'nut kit' (interal fuel lines), both of which are inside the intake plenum. Time to pull the upper plenum off and have a look inside. You can remove the upper plenum leaving the fuel system intact which will allow you to pressurize the system and inspect for leaks.

Once you find the leak and get it repaired, you'll have some cleanup to do before you can fire it up again. I would pull all of the plugs and spin the engine over with the starter after disabling the fuel pump. Then squirt a little engine oil into each cylinder and spin it over again to relubricate the rings. After that, change the oil to remove any chance of fuel contamination and reinstall the plugs. After all that you should be good to actually start the engine.

 

I turned the fuel pump on while the upper plenum was off but I did not see any leaks in the nut kit or regulator. Is there a way to test if the fuel injector itself is leaking? I pulled the poppet valves out and turned the fuel pump on and they all sprayed fuel.
Thank you for your advice, I will be sure to do all that cleanup before I try to actually run it again. Should I replace the spark plugs as well? The current ones are brand new, I just removed them in order to drain the fuel out of the cylinders. The oil and oil filter are pretty much new as well but I will change those just to be safe.