5.7 starting issues

[exp500]

Thanks for update. Keep them coming!

 

[woody367]

I have spark, and fuel pressure is 58 psi and drops to 52 when relay clicks off. I will pull the cap and rotor in a day or two just to check it. It is suppose to rain tomarrow.

 

[exp500]

Woody367- I have been following both of your threads, so to not confuse me or anyone else, do not start any more and we will get you going and finish any other questions here.
What I need from you is All your vehicle specifics, maintenence history and results of prior work.
For fuel pressure, 1) test at key on engine off, 2)cycle key 3-4 times to on to see if pressure rises above 1).
3) engine idling 4) driving 5) time on leak down when key off. Asking for more because I've seen only one of this vintage runs at 58#, One wouldn't run at #61.(same guage).

 

[woody367]

Woody367- I have been following both of your threads, so to not confuse me or anyone else, do not start any more and we will get you going and finish any other questions here.
What I need from you is All your vehicle specifics, maintenence history and results of prior work.
For fuel pressure, 1) test at key on engine off, 2)cycle key 3-4 times to on to see if pressure rises above 1).3) engine idling 4) driving 5) time on leak down when key off. Asking for more because I've seen only one of this vintage runs at 58#, One wouldn't run at #61.(same guage).

I only have one post going about this. It will not run now so that is the only fuel pressures I can get.Today iy backfired out the TBI with lots of smoke. I sure sounds like timing is off. I pulled the cap and rotor and they look almost new. I have a new set on the shelf so I will just change it. Mot that I want to throw money at it I think I will replace the cam sensor while the cap is off. I like to use OE parts but can not get a ACDELCO sensor for a few days so I will just pick on up from advanced auto. The truck has 180K on it. Always maintained but have never do a cam or crank sensor. I have put 2 fuel pumps in it in the past. I rechecked and there are no code found.

 

[OR VietVet]

Smart move while you are in there.

 

[exp500]

Woody367- your present situation with backfireing with no codes sounds like distributor cap. Check wires inside dist. they sometimes wear rubbing on dist deck.
Does your tach needle bounce around while cranking/backfiring? (meaning outside of range expected/not stable). Usually bad cam sensor shows as P1351 or others.
What are you using as scanner? Also check plug wires at correct cylinder.

 

[woody367]

I am going to change cap, rotor and cam sensor while it is apart. I will check all the wires also. No sure about the tack, I was not looking. I have a ACTRON CP9175 code reader. Thanks

 

[1BADI5]

I had this same problem back in '18 with my 99 Yukon

It was the crank sensor

 

[woody367]

That will be my next try. I need this thing back on the road.

 

[exp500]

Yes you can test crank sensor- but you have spark so no test. Thats why I asked about Tach bouncing.. Sometimes the pigtail for the crank sensor gets wonky, just like the one for ICM. Usually test those on a missing/sometimes dies engine with engine running.
Next step after cap/rotor if no start is spark test at Dist coil term/ then at coil. A 5 second crank is good if you can see it well. Report if uneven or weak spark.