Long crank issue with 5.3LS

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badsamaritan

badsamaritan

10 Year 15 Year
Joined
Feb 16, 2011
Threads
139
Messages
1,262
Location
San Diego, CA
My truck has been sitting for a little over a month while I worked on the guage cluster and a few other items. I got everything wrapped up and went to start the truck and it cranked but no start. After charging the battery and checking fuel pressure on the rail, I can get it to start, but only with the vacuum line for the fuel pressure regulator removed. I'm replacing the fuel filter because it's ancient, but I also ordered a fuel pressure regulator and a new fuel pump. Is there anything else I should look at?

  1. Fuel pressure is 62psi with key on engine off
  2. Cranking pressure is 58psi
  3. No fuel in the vac line from the pressure regulator which was a sign it had failed.
  4. No codes in PCM
  5. Battery is ~2.5yrs old has 12.8V at rest
 
Batteries today aren't as good as they were. Load test it. Make sure connections are clean and tight. I use NAPA terminal spray and the corrosion felt washers. Large diameter copper wire is good - I'm running 2/O now - way better than the #2 size I had before. I like the cast on terminals, much better than the bolt on units. I used the old #2 ground wire to go from the block connection to the starter.

Paper elements in filters have a hard time passing fuel if it gets wet with water. Yellow bottle fuel dryer is the ticket for warm days/cold nights that condense water right out of the air into your gas tank. Keeping the tank full helps cut condensation.
 
I had a similar issue with my 5.3 when I first started it. The two fuel lines on the left side of the engine are for pressure and return. I looked them up to see which was which and set mine up that way. That’s when I had the problem you described.
I reversed them and it started right up and has been working fine for the last year. I thought it might have something to do with that vacuum shutoff right in front of it.
 
This setup has been in this truck for about 15yrs and until now has been pretty solid. This is a pretty recent issue after sitting.

I did swap in my optima red top from my Chevelle and it behaved exactly the same. Wouldn't start until I took off the vacuum line from the fuel pressure regulator. Once it catches it seems to run fine
 
I found a spot where my feed line looked a little pinched and I got excited. I removed the pinch and rechecked everything but no change in behavior really outside the mechanical fuel pressure gauge needle is now bouncing very rapidly between 68-70psi with the vacuum line disconnected from the FPR
 
update: for grins I wired up the old switch and the rig fired right up no issues. I recently went from a generic autoparts store unit to a toyota switch from Ebay. After some more testing, The switch stopped working altogether. I'm not sure if it was just a defective switch or if there is something with my painless harness that is causing that.

Pink - Ignition Coil
Orange - Ignition Switched Fuse Panel
Purple - Starter
Red - Battery
Brown - Acc Fuse Panel (unused)

Here's the old but working switch was wired:

Orange to ACC
Pink to IGN
Purple to ST
Red to BATT

PXL_20250927_185235985.PORTRAIT.webp
 
I figured it out, and it's a screwup on my part. Thankfully I took pictures of the old switch before I took it apart so I could see where the colors are supposed to go. Once I mapped it all the same as the old switch, everything fired up and ran great.
 
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