Hard Start

[usmcdevildog73]

Good evening everyone. I have a 2004 Suburban. 5.3l. I recently replaced upper manifold gasket. All connections appear good. New knock sensors, new oil pressure sender, new camshaft sensor. Cleaned injectors, tested to see if they ran well. Put everything together, started her up and boom....hard start. Took 3 cranks to start. Primed fuel pump, started right up. Tested fuel pressure...read 36psi. No drop in pressure after a few hours. Replaced fuel pump ( integrated fuel pressure regulator and filter). Started up...hard start...one crank only this time. Baffled. Checked fuel pressure again...46psi. Not as low as before but still low. Thinking bad ground or defective pump. Thoughts.... it's a Delphi pump

[CamGTP]

Is that 46 psi key on engine off or is that with it running?

 

Does it get higher with rpm/driving?

[usmcdevildog73]

10 minutes ago, CamGTP said:

Is that 46 psi key on engine off or is that with it running?

 

Does it get higher with rpm/driving?

engine off.  goes up to 52 when running

[usmcdevildog73]

my understanding it should be around 55-62 without engine running

 

[CamGTP]

Does the pressure get up any higher if you double prime the fuel system?

 

The 52psi while running is fine though. I've seen those trucks vary from 52-60psi depending on idle or heavy load.

[usmcdevildog73]

No it doesnt go up higher 

[CamGTP]

Could be a bad regulator/check valve on that new pump then. Just a guess though.

[usmcdevildog73]

that really sucks if it is.  I was going to drop the tank again to check for voltage...figured I would wait for replacement pump before doing it.  Had a defective alternator a few months ago and that one was a delco.  Guess new parts arent what they use to even with reputable brands

[usmcdevildog73]

On 4/23/2022 at 9:50 PM, CamGTP said:

Could be a bad regulator/check valve on that new pump then. Just a guess though.

So I think I'm getting to the issue.  I'm thinking it might be a bad Cam shaft sensor. I replaced I replaced the old one with a new 1 since I already had the intake off.. My understanding is is a faulty faulty camshaft sensor and/or crank shaft sensor can Show itself like a bad fuel pump.  Your thoughts?